The concept of “Heat exchanger efficiency” with heat exchanger efficiency related several facts will be summarize. Depending on the performance of the ideal system heat exchanger efficiency will be determined.
The term of Heat exchanger efficiency can be explain as the relationship between the amount of heat which is transfer in the physical heat exchanger to the amount of heat which is transfer in the ideal heat exchanger. With the help of heat exchanger efficiency we can analysis and design of the heat exchanger.
What is heat exchanger efficiency?
The process of heat exchanger is happened between two fluids which are containing different temperature and the fluids can be classified by any solid wall or the fluids can be touched position to each other.
The term of heat exchanger efficiency explain as, the proportion between the quantity of heat transfer through heat exchanger that is the actual one which one works as a input of the system and the quantity of heat transfer through heat exchanger that is the practical one which one works as a out of the system.
The term heat exchanger efficiency can be written as,
η = Qact/Qideal
Where,
η = Heat exchanger efficiency
Qact = The amount of heat which is transfer in the physical heat exchanger
Qideal = The amount of heat which is transfer in the ideal heat exchanger
Q̇= The amount of heat flow through the heat exchangers and its unit is Watt
U = Heat transfer coefficient and its unit is Watt per meter square degree centigrade
A = The area from where heat is floe and its unit is square meter
ΔT= Temperature difference and its unit is Kelvin.
Image – Partial view into inlet plenum of shell and tube heat exchanger of a refrigerant based chiller for providing air-conditioning to a building; Image Credit – Wikipedia
How to calculate heat exchanger efficiency?
For the system of heat exchanger the efficiency can be calculating by comparing the factors of actual performance with practical performance.
Heat exchanger efficiency = Actual output / Output of the practical system ….eqn (1)
But where the practical heat exchanger is not available for that case eqn (1) is not applicable. In that case we can use the product of heat transfer coefficient and the surface area from where the heat is flowing which is express as UA to express the best rate of the heat transfer that can be easily can get by the given process condition ΔT. So, the equation we are used in that case is given below,
Q = UA(FΔTLM) ….eqn (2)
Where,
Q = The amount of heat flow through the heat exchangers and its unit is Watt
U = Heat transfer coefficient and its unit is Watt per meter square degree centigrade
A = The area from where heat is floe and its unit is square meter
FΔTLM = Log mean temperature difference and its unit is Kelvin
The LMTD approach is applied when input and output temperature is given but the size of the heat exchanger is not selected. The alternative approach for the LMTD the thermal effectiveness method is applied which is calculating the practical world heat transfer amount and the inside of a heat exchanger heat transfer amount. The expression is given below,
E = Q/Qmax ...eqn (3)
Typical heat exchanger efficiency:
The term typical heat exchanger efficiency explain as, the relationship between the amount of heat which is transfer in the physical heat exchanger to the amount of heat which is transfer in the ideal heat exchanger is gives the flow rate near about 90 percentage.
Typical heat exchanger efficiency value is more than the shell and tube, spiral, kettle and tubular heat exchanger.
How to improve heat exchanger efficiency?
Improving the efficiency of heat exchanger is given below,
Online cleaning helps to prevent the scaling and fouling without interrupting the operation of the heat exchanger or without stopping the operation of the heat exchanger. Online cleaning including the basket, brush and ball type system. Online cleaning treat a chemical conjunction arrangement and standalone approach.
Offline:-
The offline cleaning another name is pigging. Offline cleaning is very useful to improve the efficiency of heat exchanger. In this process a equipment which is use looks like a bullet which is placed in every tube of the heat exchanger and pushed down with air high pressure. Chemical cleaning, hydro lancing and hydro blasting are common methods to use offline cleaning.
Periodic cleaning:-
The most useful methods to clean the dirt and debris from the heat exchanger are periodic cleaning. After a certain time lots of unwanted dirt will gather into the system which decreases the working efficiency thus after a time periodic cleaning is very essential.
Maintaining heat exchanger:-
To boost the efficiency of the heat exchanger regular maintenance is very important. The maintaining of heat exchanger helps to prevent blockage, leakage and fouling of the system.
Cleaning of the PHE manually:-
Manual cleaning is important to follow the instruction of the manufacturer’s. When PHE is installed when prefer to clean the plates of the system without isolate them from the frame of the system.
How to calculate plate heat exchanger efficiency?
For the system of heat exchanger the efficiency can be calculating by comparing the factors of actual performance with practical performance.
Heat exchanger efficiency = Actual output / Output of the practical system ….eqn (1)
But where the practical heat exchanger is not available for that case eqn (1) is not applicable. In that case we can use the product of heat transfer coefficient and the surface area from where the heat is flowing which is express as UA to express the best rate of the heat transfer that can be easily can get by the given process condition ΔT. So, the equation we are used in that case is given below,
Q = UA(FΔTLM) ….eqn (2)
Where,
Q = The amount of heat flow through the heat exchangers and its unit is Watt
U = Heat transfer coefficient and its unit is Watt per meter square degree centigrade
A = The area from where heat is floe and its unit is square meter
FΔTLM = Log mean temperature difference and its unit is Kelvin
The LMTD approach is applied when input and output temperature is given but the size of the heat exchanger is not selected. The alternative approach for the LMTD the thermal effectiveness method is applied which is calculating the practical world heat transfer amount and the inside of a heat exchanger heat transfer amount. The expression is given below,
E = Q/Qmax …eqn (3)
How to improve efficiency of plate heat exchanger?
The way the improve efficiency of plate heat exchanger is listed below,
The design of the plate thickness is not depend on the corrosion resistance. The plate design thickness is depending on the pressure bearing capacity. The plate thickness the heat exchanger can be increases by the pressure bearing capacity.
Plate should be choosing:-
Choosing the plate for the heat exchanger plays a very role. The materials which have thermal conductivity such as copper alloy, stainless steel, titanium steel are selected. The thermal conductivity for the stainless steel is about 14.4 watt per meter Kelvin.
Decreasing the thermal resistance:-
The thermal resistance is of heat exchanger of fouling layer is reduce just because of to avoid scaling from the plate. The fouling thickness is when about 1 mm that time the amount of heat transfer coefficient is reduces about 10 percentages. For this reason it is important to control the quantity of water on the both portions of the heat exchanger.
Image – An interchangeable plate heat exchanger directly applied to the system of a swimming pool; Image Credit – Wikipedia
How to calculate shell and tube heat exchanger efficiency?
For the system of heat exchanger the efficiency can be calculating by comparing the factors of actual performance with practical performance.
Heat exchanger efficiency = Actual output / Output of the practical system ….eqn (1)
But where the practical heat exchanger is not available for that case eqn (1) is not applicable.
So, the equation we are used in that case is given below,
Q = UA(FΔTLM) ….eqn (2)
Where,
Q = The amount of heat flow through the heat exchangers and its unit is Watt
U = Heat transfer coefficient and its unit is Watt per meter square degree centigrade
A = The area from where heat is floe and its unit is square meter
FΔTLM = Log mean temperature difference and its unit is Kelvin
The LMTD approach is applied when input and output temperature is given but the size of the heat exchanger is not selected. The alternative approach for the LMTD the thermal effectiveness method is applied which is calculating the practical world heat transfer amount and the inside of a heat exchanger heat transfer amount. The expression is given below,
E = Q/Qmax …eqn (3)
How to increase efficiency of shell and tube heat exchanger?
The process of the increases efficiency of shell and tube heat exchanger is listed below,
Online cleaning
Offline
Periodic cleaning
Reduce the thickness of the plate
Plate should be choose
Decreasing the thermal resistance
Maintaining heat exchanger
Cleaning of the PHE manually
Heat exchanger efficiency vs. effectiveness:
The major difference between heat exchanger efficiency and effectiveness is discuss below,
Parameter
Heat exchanger efficiency
Heat exchanger effectiveness
Definition
Heat exchanger efficiency is the quality or state of being suitable in performance.
Heat exchanger effectiveness is a degree which defines the success story of something which creates desired result.
Focus
Heat exchanger efficiency focuses on the resources and process.
Heat exchanger effectiveness focuses onGoal of the result.
Thinking
Heat exchanger efficiency is only applied for present state.
Heat exchanger effectiveness applied in long term.
Belief’s
To do things correct in process.
To do correct things in process.
Heat exchanger efficiency vs. flow rate:
The major difference between heat exchanger efficiency and flow rate is discuss below,
Parameter
Heat exchanger efficiency
Flow rate
Definition
The relationship between the amount of heat which is transfer in the physical heat exchanger to the amount of heat which is transfer in the ideal heat exchanger
A fluid is flow in a particular time volume of per rate time.
Formula
Q̇= UAΔT
Q = vA
Advantages of Fireplace heat exchanger efficiency:
Advantages of Fireplace heat exchanger efficiency is listed below,
Smoke is not produced
Efficient energy
Economical
Maintenance is low
Long lifespan
Availability
Water to water heat exchanger efficiency:
Water to water heat exchanger efficiency can be explain as, the type of heat exchanger device which carry liquid cooling and which is appropriate process for reduce heat from many classifications of industrial methods.
Air to air heat exchanger efficiency:
In the unit of air to air heat exchanger air runs for long time is greater the device of heat exchanger. The amount of recovery heat is about 80 percentages. The units of air to air heat exchanger are long, rectangular and shallow.
What affects heat exchanger efficiency?
The effect of the heat exchanger efficiency is with the increasing of capacity ratio for the counter flow heat exchanger is also an increase and with the increasing of capacity ratio for the flow heat exchanger is also a decrease.
What is the maximum efficiency for parallel flow heat exchanger?
No matter how large the exchanger is or how high be the flow of overflow at transfer coefficient, the maximum efficiency for parallel flow heat exchanger is 5%.
The term “Total reflux” will be briefly discussed in this article. Reflux is a part of distillation process which is related to vapours condensation and also back to condensate to the source of the system.
Total flux can be explain as, the condition of a method where the two state of a matter liquid and vapor can pass through in the column although product will be not decreases. The law of mass conservation is state that the total reflux is not possible to happen.
Only for the continuous operation total reflux is accepted by the beginning up.
Total reflux ratio:
Reflux is used widely for apparatus setup in the laboratory distillation, continuous distillation columns in industries.
Total reflux ratio can be describe in this way,
Total flux ratio can be explain as, returning all the excess amount of product is again back to the column as the form of flux and the liquid of the system is again back to the reboiler for vaporisation and fed to the column.
So the total flux is,
F = 0, W = 0, D = 0
VN+1 = Ln
In the reflux ratio the total reflux ratio is represent as limiting value.
The method of total reflux is essential to determine the number of plates is needed in the minimum number.
Product withdrawal rate will be zero in the total reflux ratio.
Total flux formula:
Total flux can be derive as, the net amount of electric field lines which are passes through a certain area in a fixed time.
The total flux formula is derive below,
From where the electric field lines are passes the plane is normal then the total flux can be express as,
Now in the case if the plane is lifted with an angle of θ then the projected area will be A cos θ in that case the total flux foe the plane will be express as,
φ= EA cosθ
Where,
E = Magnitude for the electric field
A = Area by which the amount of electric flied will be determine
θ= The angle which is created by the surface of the plane and the direction of the electric field by which the electric field is flow parallel to the axis.
Image – Laboratory apparatus using reflux to supply energy to chemical reactions. An Erlenmeyer flask is used as a receiving flask. Here the distillation head and fractionating column are combined in one piece; Image Credit – Wikipedia
How to calculate total flux?
The relationship between the total flux and the net number of lines of electric field is directly proportional to each other by which the surface area the total flux is flow.
Total flux can be calculated in three ways, they are listed below,
If the field from where the total flux flow is uniform then total flux through a small surface area can be written as,
dφE = E.dS
Where, The Electric field which is express as E is multiplied by area component which is perpendicular to the given field.
Total flux through a surface:-
The total flux through a surface is S, for this reason surface integral can be express as,
Total flux through a closed surface:-
The dimensional formula for the total flux through a closed surface is L3MT-3I-1 and S.I unit of the through a closed surface is kg.m3.s-3.A-1
Total flux through a closed surface is discuss below,
Where,
E = Electric field
S = Any type of closed surface
Q = The total amount of electric charge inside the surface of S
ε0= Electric constant which is also known as Permittivity and value is
Total flux through a closed surface is also identified as, Gauss Law for the electric field in a surface area. The equation stays in integral form and the equation is form of the Maxwell’s equation.
Total reflux condition is possible?
No, total reflux condition is not possible.
The total reflux in general an operating situation in the column where the two states of a matter such as vapor and liquid are passes by each other and in this situation no product is reduced.
Where,
R = L/V = ∞ and D = 0
The slope value in the operating line is, L/V = 1.0
The slope value in the operating line is represent the mass balance for the each plate of y = x.
Total reflux in distillation:
Total reflux is used in a large of industrial fields such as distillation columns, fractionators like chemical plants, petroleum refiners, and natural gas and also in petrochemical processing industries.
Total reflux in distillation is the type of condensed vapor from which distillation method is done and after completing the process the vapor again back to the process. The liquid used in this that is recycled back to column’s top portion which is known as reflux.
Image – The reflux system in a typical industrial distillation column; Image Credit – Wikipedia
What is total luminous flux?
The term total luminous flux, luminous power or photometry derives as the measurement of the light of perceived power. The radiant flux and total luminous flux is not the same factors. The S.I. unit of the total luminous flux is Lumen.
Image – Photopic (black line) and scotopic (green line) luminosity functions. The photopic includes the CIE 1931 standard (solid), the Judd-Vos 1978 modified data (dashed),and the Sharpe, Stockman, Jagla & Jägle 2005 data (dotted).The horizontal axis is wavelength in nm; Image Credit – Wikipedia
What is total heat flux?
Total heat flux has both magnitude and direction for this reason total heat flux is a scale of vector. The S.I. unit of the total heat flux is watts per square metre.
The total heat flux or thermal flux can be derive as, the amount of heat flow density, rate of heat flow intensity or heat flux density is a expression of flow of energy of a particular space in a fixed time.
Image – Diagram depicting heat flux through a thermal insulation material with thermal conductivity, k, and thickness, x. Heat flux can be determined using two surface temperature measurements on either side of the material using temperature sensors if k and x of the material are also known; Image Credit – Wikipedia
Law of Fourier’s in one dimension:-
The total heat flux can be determined from Fourier’s law. Most of the matter which is stays in solid heat is transfer from one space to another space by convection method.
Mathematical form of law of Fourier’s in one dimension is given below,
Where,
k = Thermal conductivity
In the equation the negative sign represent that flow of the heat direction is from lower side to higher side.
What is total ion flux density?
Total ion flux density can be deriving as; the total amount of ion flux is passes by a particular fixed area to the perpendicular direction of the ion flux. The total ion flux density S.I. unit is Teslas or Webers per square meter.
Mathematically the total ion flux density can be written as,
B = μH
Where,
B = Flux density
μ = Ion flux density
H = Ion field
What is total radiation flux?
Total radiation flux can be any classification of radiation such as sound, particles radioactive, electromagnetic.
Total radiation flux is a measurement of physical parameter by which receiving of particle radiation can be determine through a matter from a particular given source.
The mathematical form of total radiation flux is given below,
Where,
L = Total radiation flux
r = The distance from the source of radiation
The units of the total radiation flux is watt per metre squared (W.m-2) and kilograms cubic metres (kg.s-3).
Total flux through a closed surface:
The dimensional formula for the total flux through a closed surface is L3MT-3I-1 and S.I unit of the through a closed surface is kg.m3.s-3.A-1
Total flux through a closed surface is discuss below,
Where,
E = Electric field
S = Any type of closed surface
Q = The total amount of electric charge inside the surface of S
ε0 = Electric constant which is also known as Permittivity and value is
Total flux through a closed surface is also identified as, Gauss Law for the electric field in a surface area. The equation stays in integral form and the equation is form of the Maxwell’s equation.
Frequent Asked Questions:-
Question: – Explain and classified distillation depends on the applications and techniques.
Solution: – Depend on the applications and techniques the distillation can be classified generally in four sections they are,
In the method of simple distillation the matter which is already evaporated is passes by the tube which is made with plastic. This condition is happened when liquid mixture contains higher temperature means stays in heated situation. The process of condensation is completed that time end portion of the plastic tube is by cool chill water to outer wall of the plastic tube. After that the gas in condensed in the wall of the plastic tube and passes the heat to the chill cool water. Taking the heat the chill cool water became hotter and chemical matter is condensed in the end portion of the plastic tube.
Steam distillation:-
Steam distillation is a processby which we can separate heat-sensitive components from a mixture. For this reason steam distillation is used as a purification method for mixture having impurities. The components in the mixture should be volatile in order to do this separation. The principle behind steam distillation process is to separate the components by vaporisation precess them at temperatures below their actual boiling point. Unless otherwise, some compounds may decompose at their boiling points and the separation cannot be done accurately.
Vacuum distillation:-
In the process of the vacuum distillation the heat is not essential. In the method of vacuum distillation pressure stays at the above of the mixture of liquids. The value is decreases than the normal value of vapor pressure and evaporation took place of the most volatile particles.
Fractional distillation:-
Fractional distillation is the process used to separate hydrocarbon components in crude oil. The fractional distillation method includes the separation of important components according to the difference between their boiling points. In other words, it uses distillation for the fractionation of crude oil.
Question: – Explain about magnetic flux.
Solution: –Magnetic flux can be deriving as, the net amount of magnetic field lines which are passes through a certain area in a fixed time.
Image – The magnetic flux through a surface—when the magnetic field is variable—relies on splitting the surface into small surface elements, over which the magnetic field can be considered to be locally constant. The total flux is then a formal summation of these surface elements; Image Credit – Wikipedia
Formula:-
The formula for the magnetic flux is,
φ B = B. A = BA cos θ
Where,
φB = Magnetic flux
B = Magnetic field
A = Area
Theta = The angle which is created by the surface of the plane and the direction of the magnetic field by which the magnetic field is flow parallel to the axis.
In this article we will discuss about fanning friction factor for laminar flow. Laminar flow is the simplest form of flow in which the layers of fluid do not intersect with each other.
The fluid layers flow very smoothly in a laminar flow, there two other types of flows too which we will discuss in detail in this article. We will first discuss about laminar flow, transient flow and turbulent flow. We will also discuss about their properties. Then we shall discuss about a dimensionless number called as Reynold’s number.
What is laminar flow?
A laminar flow is a type of flow in which the fluid moves in a very smooth manner and the layers of fluid do not intersect each other and rather flow in parallel lines.
To check whether a flow is laminar or not we take help of Reynold’s number. This is a dimensionless number which tells us about the type of flow, whether it is turbulent or transition or laminar flow. In later section of this article we shall study about Reynold’s number.
Reynold’s number is a dimensionless number which helps us find the type of flow of fluid The flow maybe laminar, turbulent or transitional. It is very important to know the type of flow while dealing with fluid machinery.
To find the value of Laminar flow, we need the fluid’s kinematic viscosity, density of the fluid and the velocity of the fluid with which it is flowing. The Reynold’s number can also be used to find the frictional losses in the pipe. We shall study more about Laminar flow in this article.
What is Fanning factor?
Like Reynold’s number, Fanning factor is also a dimensionless number that is used while performing calculations in continuum mechanics’ calculations.
It can be defined as the ratio between the local shear stress to the local flow kinetic energy of the fluid. Mathematically, Fanning factor can be given by the following formula-
Where,
f is the Fanning factor
Tau is the local shear stress
u is the bulk flow velocity
Rho is the density of the fluid.
What is Fanning factor for laminar flow?
We have discussed in the above sections about both Fanning factor and Laminar flow. Now let us see what is the formula for Fanning factor for a laminar flow.
For a laminar flow, Fanning factor is given using the formula given below–
f=16/Re
Where,
Re is the Reynold’s number
How do you calculate Fanning’s factor?
In simple terms, a quarter of Darcy’s friction factor gives us Fanning’s friction factor. The formula for Fanning’s friction factor is different for different types of flows.
We shall discuss about the formula used in laminar flow. For a fluid flowing in round tube with laminar flow, the Fanning factor will be given by the following-
f= 16/Re
Where,
Re is the Reynold’s number
Is Friction Factor higher with laminar flow?
Yes. The friction factor is higher with laminar flow. We can prove this by looking at the formula of friction factor. We have already discussed the formula for friction factor in the above section.
From the formula we can see that the friction factor is inversely proportional to Reynold’s number. Reynold’s number is least for a laminar flow hence resulting into higher value of friction factor.
Fanning friction factor use
The name itself suggests that the friction factor is related to friction. And we know how important it is to know the amount of frictional losses taking place in the flowing fluid.
It is also important to know a rough estimate of losses in kinetic energy taking place due to head loss and pressure loss. Fanning friction factor helps us to find the values of these quantities. By knowing these values we can design the pipes accordingly to avoid much loss due to friction.
Friction factor units
We have studied about the formula for finding the friction factor. If we work out the units of all the quantitites that have been used in the formula we will see that everything cancels out and the ratio comes out to be 1.
Hence we can conclude that the Fanning’s friction factor has no units. Just like Reynold’s number it is a dimensionless number. The factor in itself is a ratio between two similar quantities hence the friction factor has to be dimensionless.
Fanning friction factor formula
Fanning friction factor is the ratio between the local shear stress and the kinetic energy density of flow. We have already discussed the formula in the above sections but we shall study about it one more, this time for turbulent flow also.
The section below gives us the Fanning’s friction formula for both laminar and turbulent flow of a fluid flowing in a round pipe-
Laminar
The Fanning friction formula for a fluid flowing in a laminar flow in a round pipe is given below-
f = 16/Re
Turbulent
The Fanning friction factor formula for a fluid flowing in a turbulent flow in a round pipe is given below-
Fanning friction factor pressure drop
Friction is the major reason for pressure drop to take place. The friction will decrease the velocity of the flow of the fluid and also decreases the pressure as the fluid flows in the pipe.
The pressure drop is directly proportional to the Fanning friction factor. Greater the value of Friction factor greater will be the pressure drop against the ends of pipe. Hence we can say that pressure reduces as the fluid flows through the pipe.
Factors affecting Reynold’s number
The formula of the Reynold’s number is given below-
From the above formula we can conclude that the value of the Reynold’s number depends on the density of the fluid flowing, its dynamic viscosity, velocity with which the fluid is flowing and the equivalent diameter of the cross section through which the fluid is flowing.
How are Darcy’s Friction Factor and Fanning’s friction factor related?
Both Darcy’s friction factor and Fanning’s friction factor represent the amount of friction taking place inside the fluid and tells us how much pressure drop is taking place inside the pipe.
Mathematically, Darcy’s friction factor is four times the Fanning’s friction factor. Both of these factors identical and represent the same quantity that is friction and are also used to find the same thing that is pressure drop. The only difference between them being the factor four that is multiplied by Fanning’s friction factor to find the value of Darcy’s factor.
Reasons for pressure drop inside a pipe
There can be many reasons for pressure drop to take place for a fluid flowing inside a pipe. Some of the reasons are given in the list below-
Friction from the walls of pipe will decrease the pressure of the fluid. The pressure of the fluid exiting the pipe will be lesser than the pressure of the fluid entering the pipe.
Bends in or narrowing of a pipe also contribute to the pressure drop inside the pipe.
Obstructions inside a pipe
Sensors attached inside the pipe that also acts as additional obstructions to the flowing stream of fluid.
This article discusses about heat exchanger examples. The name makes it easier for us to understand the meaning of heat exchanger.
The heat exchanger is nothing but an equipment that exchanges heat between two substances in order to bring down or elevate the temperature to desired levels. In this article we shall study about what a heat exchanger is, what are its different types and different examples where heat exchangers are used.
Heat exchanger is an equipment used to transfer heat between the working fluid and the fluid whose temperature is to be brought down or increased.
Heat exchangers uses hollow tubes through which the fluids are passed. The fluids have temperature difference between them due to which heat transfer takes place. The most important thing for heat transfer to take place is temperature difference between the two objects/fluids. In this article we shall discuss about the different types of heat exchangers and their examples.
Types of heat exchangers according to the direction of flow of fluids
According to the direction of flow of fluids relative to each other, we can classify heat exchangers in to three types. These types are given in the list below-
Parallel flow heat exchanger- When the fluids flow in the same direction relative to each other, the heat exchanger will be referred to as parallel flow heat exchanger. The temperature of the hot fluid decreases whereas the temperature of cold fluids increases.
Counter flow heat exchanger- When the fluids flow in opposite direction relative to each other, then the heat exchanger will be referred to as counter flow heat exchanger. We can find the effectiveness of the heat exchanger using the formula discussed in the later sections of this article.
Cross flow heat exchanger- As the name suggests, cross flow heat exchangers are those heat exchangers in which the fluids flow perpendicular to each other. The tubes make ninety degrees to each other.
Types of heat exchangers according to the transfer process
The classification of heat exchangers on the basis of transfer processes are given in the list below-
Indirect contact type- In this type of arrangement, the fluid streams separate and the heat transfer takes place continuously through a dividing wall in and out of the wall in a transient manner. Different types of indirect contact type heat exchangers include storage type heat exchanger, fluidized bed heat exchanger etc.
Direct contact type– In the direct contact type heat exchanger, two fluids exchange heat with each other by coming in direct contact with each other. They exchange heat and then get separated from each other.
Effectiveness of Heat exchanger
The effectiveness of heat exchanger is a ratio between the actual heat transfer taking place to the maximum heat transfer that can take place in the heat exchanger.
The significance of effectiveness is that it allows the designers to predict how a given heat exchanger will perform a new job. The trial and error procedure is eliminated if we know the effectiveness of the heat exchanger.
Heat exchanger examples
The places where heat exchangers are used are given in the list below-
Air pre heaters
The name suggests that the air is being heated prior to sending it to perform any other process. For examples, they can be used in boilers for increasing the thermal efficiency of the power plant. Pre heated air will improve the quality of fuel input into the power plant.
Economizers
It is an alternative to the air conditioning system. Economizers use outside air to cool the building instead of running compressors like those used in air conditioning system. This also saves a huge sum of money as it saves energy.
Evaporators
Evaporators are used to convert any liquid to its gaseous form. The temperature of the liquid remains the same. The phase change process is an isothermal process. The evaporators are used in boilers to change the liquid water to gaseous steam. In evaporators, the temperature of fuel is same as it undergoes phase transformation. On the other hand the temperature of the colder fluid increases that is used as working fluid inside the heat exchanger.
Superheaters
Superheaters are used inside boilers that convert the wet steam to dry steam. The dry steam is that steam in which there is no liquid water content. The dryness fraction of dry steam is 1 or 100%. The superheaters are used for superheating the steam. The quality and enthalpy of superheated steam is greater than the normally used wet steam or saturated steam.
Condensers
Condensers are opposite to what evaporators are. Condensers bring back the liquid from its gaseous state without changing its temperature. The condensers are simple heat exchangers that absorb heat from the steam and convert it back to liquid water. The amount of heat absorbed is equal to the latent heat of vapourisation of water. Similar to the evaporators, the fuel’s temperature remains the same and the temperature of hot fluid that is used as working fluid inside the heat exchanger decreases.
Cooling towers
A cooling tower is a tower used to reject heat from the system to the surroundings. The heat expelled out of the system is waste heat that holds no use in the further process. These towers appears as chimneys through which a cloud of gas is expelled out. This gas cloud is nothing but the gas of working fluid. Heat is being dissipated in the form of steam.
Swimming pool heat exchanger
A swimming pool heat exchanger transfers heat from a hot water stream to the cooler pool water stream without making them come in direct contact to each other.
Hydraulic oil cooler
A hydraulic oil cooler cools the hydraulic oil. These can be used in power packs, power washers and engines, almost anywhere the hydraulic oil is used. The hydraulic oil needs to be cooled because without cooling, the oil may catch fire due to higher temperatures and may be fatal for the operator as well as the machinery.
Boilers
The most common use of heat exchangers is in boilers. The boilers use heat exchangers to heat the liquid water such that it gets converted in to steam. In the entire phase change process, the temperature of the liquid/gas remains the same meaning it is an isothermal process. We have already discussed in the above sections how heat exchangers work inside a boiler.
Water jackets
In water jackets, water is used to cool or heat the exhaust running through the engine. We can see jacketing in rocket engines, the hot exhaust gases heat up the fuel and then the fuel is sent back for combustion. This increases the combustion efficiency of the rocket engine. In automobiles, water jacketing is used to cool the engine and prevent excessive heat loss. The water jacketing brings down the engine temperature.
Other types of heat exchangers
On a broader basis, there are many more types of heat exchangers. They are given in the list below-
Heat exchangers are a pivotal part of many devices and systems that we use daily. They are found in home heating systems, car engines, and industrial processes. But what exactly is a heat exchanger, and how does it work? Let’s delve into the fascinating world of heat exchangers.
Definition of Heat Exchanger
A heat exchanger is a device designed to efficiently transfer (or exchange) heat from one medium to another. These mediums are usually separated by a solid wall to prevent mixing or contamination. The mediums can be gas, liquid, or even solid, and can be the same (e.g., air to air) or different (e.g., air to water).
Main Purpose of Heat Exchanger
The primary purpose of a heat exchanger is to transfer heat between two or more fluids, achieving desired temperatures without letting the substances mix with each other. For instance, in a car engine, a heat exchanger uses air to cool down the hot engine coolant. Similarly, in a home heating system, a heat exchanger transfers heat from the furnace‘s hot air to the cooler air circulating in the building.
Importance of Heat Exchanger
Heat exchangers play a crucial role in many applications. They are vital for thermal efficiency, heat recovery, and temperature control in various systems. Here are some reasons why heat exchangers are so important:
Energy Efficiency: Heat exchangers can recover waste heat from industrial processes, improving overall energy efficiency. This heat recovery process can significantly reduce energy costs and environmental impact.
Temperature Regulation: In systems like car engines or industrial machinery, heat exchangers help maintain optimal operating temperatures, preventing overheating and potential damage.
Comfort and Safety: In buildings, heat exchangers ensure a comfortable indoor temperature and provide hot water. They also play a role in systems like refrigerators and air conditioners.
Industrial Processes: Many industrial processes require precise temperature control. Heat exchangers provide this control, ensuring product quality and safety.
Heat Exchanger Design and Operation
The design of a heat exchanger depends on its intended application. Key factors include the types of fluids involved, the desired temperature change, and the available space. Heat exchanger design also considers the heat transfer coefficient, heat capacity rate, and potential for fouling (build-up of unwanted material on the heat exchanger surfaces).
The operation of a heat exchanger involves fluid flow through tubes or channels. The heat transfer process occurs as one fluid heats up the exchanger’s walls(the “hot” fluid), and another fluid cools it down (the “cold” fluid). The efficiency of this process depends on the materials used, the flow rates, and the temperature difference between the fluids.
Regular inspection and cleaning are essential for maintaining heat exchanger performance. Over time, fouling can reduce the heat transfer efficiency and cause a pressure drop. In severe cases, it can lead to system failure or even a dangerous situation like a crack in the exchanger.
Maintenance tasks include cleaning the heat exchanger tubes and checking for signs of wear or damage. If necessary, repair or replacement of components may be required. Proper heat exchanger maintenance can extend the device’s lifespan, improve its efficiency, and prevent costly breakdowns.
Heat Exchanger Applications
Heat exchangers have a wide range of applications. They are used in heating, ventilation, and air conditioning(HVAC) systems, power generation, waste heat recovery, and many industrial processes. Some specific examples include:
Home Heating Systems: A heat exchanger transfers heat from the furnace to the air circulated throughout the home.
Car Engines: Heat exchangers (or radiators) cool the engine coolant, preventing the engine from overheating.
Power Plants: Heat exchangers transfer heat from the combustion process to produce steam, which drives the turbines.
Refrigeration Systems: Heat exchangers remove heat from the refrigerant, allowing it to cool the inside of the refrigerator or air conditioner.
Understanding the Function of Heat Exchangers
Heat exchangers are crucial components in a wide range of applications, from air conditioning systems in buildings to engines in vehicles. They function by transferring heat from one fluid to another, without the two fluids coming into direct contact. This heat transfer process is fundamental to the operation of many systems and is governed by the heat transfer coefficient.
Heat Transfer Coefficient
The heat transfer coefficient (h) is a measure of the heat transfer rate between the surface of the heat exchanger and the fluid flowing through it. It is influenced by several factors, including the type of fluid, its velocity, and the surface area of the heat exchanger. The higher the heat transfer coefficient, the more efficient the heat exchanger is at transferring heat.
For instance, in a heat exchanger where water is used to cool a system, a higher heat transfer coefficient would mean that the water can absorb more heat from the system, thus cooling it more effectively.
Heat Transfer Functions
Heat transfer in a heat exchanger can occur through three main mechanisms: conduction, convection, and radiation.
Conduction is the process of heat transfer through a solid material. In a heat exchanger, this occurs when heat is transferred from the hot fluid to the heat exchanger material (usually metal), and then to the cold fluid.
Convection is the process of heat transfer through a fluid (liquid or gas) caused by the fluid’s movement. In a heat exchanger, this occurs when the hot and cold fluids flow over the heat exchanger’s surfaces.
Radiation is the process of heat transfer through electromagnetic waves. It plays a minor role in most heat exchangers, but can be significant in high-temperature applications, such as furnaces.
How Heat Exchangers Function
The operation of a heat exchanger is based on the principle of heat transfer. In a typical heat exchanger, two fluids of different temperatures flow through separate channels. The hot fluid loses heat to the heat exchanger material, which then transfers the heat to the cold fluid. This process continues until the temperatures of the two fluids equalize or until the heat exchanger is shut off.
For example, in a car engine, a heat exchanger (or radiator) uses air to cool the engine coolant. The hot coolant flows through tubes in the radiator, transferring heat to the radiator’s metal fins. Air flowing over the fins then absorbs the heat, cooling the coolant.
Heat Transfer Function of Time
The rate of heat transfer in a heat exchanger can change over time due to several factors, including changes in the temperatures and flow rates of the fluids, fouling of the heat exchanger surfaces, and degradation of the heat exchanger materials.
For instance, the buildup of scale or other deposits on the heat exchanger surfaces (a process known as fouling) can reduce the heat transfer coefficient, leading to a decrease in the heat exchanger’s performance over time. Regular cleaning and maintenance of the heat exchanger can help to mitigate this issue.
Heat exchangers are devices that facilitate the transfer of heat from one medium to another. They are widely used in various industries, including HVAC, automotive, and power generation. The heat transfer process in these devices is crucial for their thermal efficiency. Now, let’s delve into the different types of heat exchangers.
Double Pipe Heat Exchanger
The double pipe heat exchanger, also known as a pipe-in-pipe system, is the simplest type of heat exchanger. It consists of one pipe inside another larger pipe. One fluid flows through the inner tube while the other flows through the annular space between the two tubes. The heat transfer occurs through the wall of the inner tube.
The design of this type of heat exchanger is straightforward and easy to install. However, its heat transfer coefficient is relatively low, which means it’s not as efficient as other types. Despite this, it’s commonly used in industries due to its simplicity and low cost. Regular inspection and cleaning are essential for maintaining its performance and preventing fouling.
Baffle Heat Exchanger
The baffle heat exchanger is a type of shell and tube heat exchanger. It features a series of baffles or metal plates that direct the fluid flow across the tube bundle. This design increases the turbulence of the fluid, enhancing the heat transfer process and improving the exchanger’s thermal efficiency.
However, the increased turbulence also results in a higher pressure drop, which can affect the overall efficiency of the system. The baffle design also makes the exchanger more prone to fouling, requiring regular maintenance and cleaning. Despite these challenges, baffle heat exchangers are widely used due to their high heat transfer rates and robustness.
Plate Heat Exchanger
The plate heat exchanger consists of a series of thin, corrugated metal plates stacked together. The plates create channels for the fluids to flow between them. The corrugated design increases the turbulence of the fluids, enhancing the heat transfer process.
Plate heat exchangers are known for their high thermal efficiency, compact size, and low fouling tendency. However, they can be challenging to clean and maintain, and they may not be suitable for high-pressure applications. They are commonly used in HVAC systems, power plants, and food processing industries.
Tube Heat Exchanger
Tube heat exchangers, also known as shell and tube exchangers, are the most common type of heat exchanger. They consist of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid flows through the tubes, and the other flows outside the tubes but inside the shell.
Tube heat exchangers are known for their robust design, high heat transfer rates, and ability to handle high pressures and temperatures. However, they are relatively large and require more space compared to other types of exchangers. They also require regular inspection and cleaning to prevent fouling and maintain their performance.
Heat exchangers are integral components in a variety of systems and industries, from home heating to large-scale industrial processes. They function by transferring heat from one fluid to another, without the two fluids directly interacting. This heat transfer process is central to their operation and efficiency. Let’s delve into the specifics of how heat exchangers function in various applications.
Heat Exchanger Function in Furnace
In a furnace, the heat exchanger plays a crucial role. It separates the combustion process from the breathable air in your home, ensuring safety and efficiency. The furnace burns fuel (like gas or oil) to produce heat. This heat warms up the metal walls of the heat exchanger. As cool air from your home flows over the warm exchanger, it absorbs the heat and is then redistributed back into your home.
This process is a prime example of a heat exchanger’s ability to transfer heat from one medium (the hot furnace gases) to another (the cool air in your home) without the two ever coming into direct contact. This is crucial not only for thermal efficiency but also for safety, as it prevents harmful combustion gases from entering your home’s air supply.
Heat Exchanger Function in Chilled Water System
In a chilled water system, a heat exchanger is used to cool down water that will be circulated throughout a building for air conditioning purposes. The heat exchanger uses refrigerant to absorb heat from the water, thus cooling it down before it is sent through the building’s air handling units.
The heat absorbed by the refrigerant is then expelled outside the building, ensuring that the interior remains cool. This is a prime example of a heat exchanger’s application in heat recovery and its role in maintaining a building’s thermal comfort.
Heat Exchanger Function in Oil and Gas Industry
In the oil and gas industry, heat exchangers are used in a variety of ways. For instance, they are used in the process of refining crude oil. The crude oil is heated in a furnace, and then it flows into a heat exchanger where it is cooled by water or air.
Heat exchangers are also used in natural gas processing plants to cool and condense the gas. This is a critical step in the process, as it allows for the removal of impurities and the collection of valuable byproducts.
In these applications, heat exchangers must be made from materials that can withstand high temperatures and pressures, such as certain types of metal. Regular inspection and maintenance are also crucial to ensure their performance and longevity.
Heat Exchanger Function in Chiller
In a chiller system, a heat exchanger is used to transfer heat from the liquid being cooled (usually water) to the refrigerant. The refrigerant absorbs the heat from the water, causing it to evaporate. The now cool water is then circulated throughout the building for cooling purposes.
The refrigerant, now in a gaseous state and carrying the absorbed heat, is then compressed and sent to another heat exchanger. Here, it releases the heat it absorbed earlier, condenses back into a liquid, and the cycle begins anew.
Car Heat Exchanger Function
In a car, a heat exchanger, often referred to as a radiator, is used to cool the engine. As the engine runs, it generates a lot of heat. If this heat is not properly managed, it could lead to engine overheating and potential damage.
The car’s heat exchanger uses coolant to absorb heat from the engine. The hot coolant then flows through the radiator where it is cooled by air flow. The cooled coolant is then recirculated back into the engine, and the process repeats.
Components of Heat Exchangers
Heat exchangers are devices designed to transfer heat from one medium to another. They are critical in many industrial processes, including power generation, chemical processing, and HVAC systems. The main components of a heat exchanger include the shell, tubes, tube sheets, baffles, and tie rods. Now, let’s delve into the details of these components and their roles in the heat transfer process.
Shell
The shell is the outer casing of a heat exchanger. It is typically made from a durable material like metal to withstand the pressure and temperature of the heat transfer process. The shell houses the tubes and other internal components, and it also directs the flow of the shell-side fluid.
Tubes
The tubes are the primary heat transfer surface in a heat exchanger. They are usually made from materials with high thermal conductivity, such as copper or stainless steel, to facilitate efficient heat transfer. The fluid flowing inside the tubes is known as the tube-side fluid. The design of the tubes, including their diameter, length, and arrangement, significantly affects the heat exchanger’s performance.
Tube Sheets
Tube sheets are the plates that hold the tubes in place. They are typically made from the same material as the tubes to prevent differential thermal expansion, which could lead to cracking or other damage. The tube sheets also prevent the tube-side and shell-side fluids from mixing.
Baffles
Baffles are components installed inside the shell to direct the flow of the shell-side fluid across the tubes. This increases the fluid’s velocity, enhancing the heat transfer coefficient and improving the heat exchanger’s thermal efficiency. However, baffles also cause a pressure drop, which must be considered in the heat exchanger design.
Tie Rods
Tie rods are used to hold the baffles in place and maintain the structural integrity of the heat exchanger. They are usually made from strong, heat-resistant materials.
Heat Exchanger Types
There are several types of heat exchangers, including shell and tube, plate, and regenerative heat exchangers. Each type has its unique design features, advantages, and applications.
Shell and Tube Heat Exchangers
Shell and tube heat exchangers are the most common type. They consist of a shell housing a bundle of tubes. One fluid flows inside the tubes, while the other flows outside the tubes but inside the shell. This design is versatile and can handle a wide range of temperatures and pressures.
Plate Heat Exchangers
Plate heat exchangers consist of a series of thin, corrugated plates stacked together. The fluids flow in alternate channels between the plates, allowing for efficient heat transfer. Plate heat exchangers are compact and efficient, but they are not suitable for high pressure or temperature applications.
Regenerative Heat Exchangers
Regenerative heat exchangers, also known as heat recovery units, use the same fluid for heating and cooling. The fluid is alternately heated and cooled in a cyclic process, making these units highly efficient.
Heat Exchanger Applications
Heat exchangers are used in a wide range of applications, from heating homes to cooling industrial processes. Here are a few examples:
HVAC Systems: Heat exchangers are used in HVAC systems to transfer heat between the air inside a building and the outside air, or between the air and a coolant fluid.
Power Generation: In power plants, heat exchangers are used to convert the heat energy from burning fuel into electrical energy.
Chemical Processing: Heat exchangers are used in chemical plants to control the temperature of chemical reactions, which can affect the reaction rate and product yield.
Automotive: In cars, heat exchangers are used to cool the engine and the passenger compartment.
Heat Exchanger Maintenance and Operation
Proper maintenance and operation are crucial for the performance and longevity of a heat exchanger. This includes regular cleaning to prevent fouling, inspection for damage or wear, and repair or replacement of worn-out components. The fluid flow rates, temperatures, and pressures should also be monitored and controlled to ensure optimal heat transfer and prevent damage to the heat exchanger.
Heat Exchangers in Different Systems
Heat exchangers are integral components of many systems, facilitating the heat transfer process from one medium to another. They are designed to optimize thermal efficiency, and their applications are diverse, ranging from heating homes to cooling large industrial processes.
Refrigeration System
In a refrigeration system, heat exchangers are used to cool a substance or space. The refrigerant, often a fluid, absorbs heat from the substance or space that needs to be cooled and then flows through the heat exchanger. Here, the refrigerant releasesthe absorbed heat, thereby cooling down before it is recycled back into the system.
The heat exchanger design in a refrigeration system is crucial for its efficiency. The heat exchanger tubes must be made of a material with high thermal conductivity, such as copper or aluminum, to facilitate the heat transfer process. Moreover, the tubes should be kept clean to prevent heat exchanger fouling, which can reduce thermal efficiency and increase the heat exchanger pressure drop.
Chillers are another application of heat exchangers. They use a refrigeration cycle to cool water, which can then be used in air conditioning systems or industrial processes. The chiller’s evaporator acts as a heat exchanger, absorbing heat from the water and transferring it to the refrigerant.
The heat exchangerheat capacity rate, which is the product of the mass flow rate of the fluid and its specific heat capacity, is a key factor in the performance of the chiller. A higher heat capacity rate means that the heat exchanger can absorb more heat, leading to a cooler output water temperature.
Air Conditioning System
In an air conditioning system, heat exchangers are used to cool and dehumidify the air. The system’s evaporator coil acts as a heat exchanger, absorbing heat from the indoor air and transferring it to the refrigerant. This cools the air, which is then circulated back into the building.
The heat exchanger operation in an air conditioning system is influenced by several factors, including the heat exchanger heat transfer coefficient, the heat exchanger heat load, and the fluid flow rate. Regular heat exchanger maintenance, such as cleaning and inspection, is necessary to ensure optimal performance and prevent issues such as heat exchanger fouling or heat exchanger repair needs.
Crude Oil Cooling
Heat exchangers are also used in the petroleum industry for crude oil cooling. The hot crude oil flows through the heat exchanger tubes, transferring its heat to a cooling medium, usually water or air. This cools the crude oil, making it easier to transport and process.
The heat exchanger materials used in this application must be resistant to corrosion and able to withstand high temperatures and pressures. Moreover, the heat exchanger design must ensure a high heat transfer rate to cool the crude oil efficiently.
Frequently Asked Questions about Heat Exchangers
Heat exchangers are integral components in a variety of systems, from home heating systems to industrial processes. They facilitate the transfer of heat from one fluid to another, enhancing thermal efficiency. Let’s delve into some frequently asked questions about heat exchangers.
Heat Exchanger Transfer Function
What is the function of a heat exchanger?
A heat exchanger’s primary function is to transfer heat between two or more fluids without them mixing. This heat transfer process can involve gases or liquids and can be used for both heating and cooling purposes. The fluids can be the same or different; for example, air to air, water to water, or air to water.
How does a heat exchanger work?
A heat exchanger works by allowing a hot fluid to flow past a cold fluid, separated by a solid wall (usually metal) to prevent mixing. The heat from the hot fluid is transferred through the wall and into the cold fluid, which becomes warmer. This process is governed by the heat transfer coefficient, which depends on the materials used, the fluid flow rates, and the surface area available for heat transfer.
What is heat exchanger efficiency?
Heat exchanger efficiency is a measure of how effectively the exchanger transfers heat from the hot fluid to the cold fluid. It is calculated by comparing the actual heat transfer to the maximum possible heat transfer. Factors that can affect efficiency include the heat exchanger design, the materials used, and the presence of any fouling (deposits that can build up on the heat exchanger surfaces and impede heat transfer).
Location of Heat Exchanger in a Furnace
Where is the heat exchanger located in a furnace?
In a furnace, the heat exchanger is typically located between the combustion chamber and the blower. The combustion gases heat up the exchanger, and then the blower pushes air across its surface. The air absorbs the heat and is then distributed throughout the building.
What happens if the heat exchanger in a furnace cracks?
If a heat exchanger cracks, it can allow combustion gases, including carbon monoxide, to leak into the building’s air. This situation is potentially dangerous and requires immediate attention. Regular heat exchanger inspection and maintenance can help prevent such issues.
Heat exchangers are used in a wide range of applications. In homes, they are used in heating systems to transfer heat from a furnace or boiler to the air or water used for heating. In cars, they are used in the radiator to remove heat from the engine coolant. In industrial settings, they can be used for process cooling, heat recovery, and many other applications.
What is a regenerator in the context of heat exchangers?
A regenerator is a type of heat exchanger that temporarily stores heat from a hot fluid and then releases it to a cold fluid. This process is used in some industrial processes and power generation systems to improve thermal efficiency.
What materials are used in heat exchangers?
Heat exchangers can be made from a variety of materials, including metals like steel, copper, and aluminum, which have high thermal conductivity. The choice of material depends on the heat exchanger design, the fluids being used, and the operating conditions.
Frequently Asked Questions
1. What is the importance of a heat exchanger in thermal efficiency?
A heat exchanger plays a crucial role in enhancing thermal efficiency. It allows heat transfer from one medium to another without direct contact, minimizing energy loss and maximizing efficiency. It is used in various industries, including HVAC, oil and gas, and power generation, to improve energy conservation and process efficiency.
2. How does a heat exchanger function in the heat transfer process?
A heat exchanger functions by allowing heat to flow from a hot fluid to a cooler fluid without the two fluids coming into direct contact or mixing. This heat transfer process is facilitated by the exchanger’s material, which is typically metal due to its high thermal conductivity.
3. What is the main purpose of a heat exchanger in a chiller system?
In a chiller system, the heat exchanger’s main purpose is to transfer heat from the liquid being cooled to the refrigerant. This process cools the liquid, which can then be circulated through a system to absorb heat and cool equipment or conditioned spaces.
4. What types of materials are commonly used in a heat exchanger?
Heat exchanger materials must be thermally conductive to facilitate heat transfer. Common materials include various metals such as copper, aluminum, stainless steel, and titanium. The choice of material depends on factors like the type of fluids being used, the expected heat transfer rate, and the operating conditions.
5. How does a baffle heat exchanger function?
A baffle heat exchanger uses baffles, or obstructions, to direct the flow of fluid and increase the turbulence. This increased turbulence enhances the rate of heat transfer and improves the exchanger’s overall performance.
6. What are the key components of a heat exchanger?
The key components of a heat exchanger include the shell (outer casing), tubes (where one fluid flows), tube sheets, baffles, and headers. These components work together to facilitate efficient heat transfer.
7. How does a heat exchanger work in an oil and gas industry application?
In the oil and gas industry, heat exchangers are used to control process temperatures. They can heat crude oil to reduce its viscosity for easier transport, or cool down gases and liquids to safe temperatures before storage and transport.
8. Where is the heat exchanger located on a furnace?
In a furnace, the heat exchanger is typically located between the combustion chamber and the blower. It absorbs heat from the combustion gases and transfers it to the air that is blown through the HVAC system.
9. What is the role of a heat exchanger in a chilled water system?
In a chilled water system, the heat exchanger transfers heat from the chilled water to the refrigerant. This process cools the water, which can then be used to cool buildings or industrial processes.
10. How does the heat transfer function of a plate heat exchanger work?
A plate heat exchanger uses a series of thin, corrugated plates to transfer heat between two fluids. The plates are arranged to create a network of parallel flow channels. One fluid flows through the odd-numbered channels, and the other fluid flows through the even-numbered channels. The corrugations in the plates induce turbulence, which enhances heat transfer and efficiency.
In this article “Application of heat exchanger” and application of heat exchanger related facts that will be talk. Heat exchanger is a device which one exchanges the heat between two different temperature fluids.
13+ Application of Heat Exchanger is listed below,
Warm the muscles of the back with the heating pad:-
From the definition of heat exchanger we can understand that two matters when they are stays in different temperature start to exchanging temperature until they reach to the same temperature. The matters can be separated by a wall which will be stays in solid state to stave off amalgamation or the matters can be stay in direct contact to each other. For the case of warm the muscles of the back with the heating pad the matters are divided by solid state .
When warm heating pad is applied in the back of the patient that time heating pad contain high temperature and back of the patient stays at low temperature but when two different temperature is comes closer they start to heat exchanging between to each other and as a result the temperature starts to come in equilibrium condition. The patient easily can take the temperature from heating pad and gets comfort from his back muscle pain.
Mixing hot food item with a spoon:-
For the case of mixing hot food item with the help of spoon the matters are not divided by solid state they stay at direct contact to each other. When warm food item is comes to connect with cold spoon that time hot food item contain high temperature and spoon stays at low temperature but when two different temperature is comes closer they start to heat exchanging between to each other and as a result the temperature became starts to come in equilibrium condition. So, mixing hot food item with a spoon is another example of application of heat exchanger.
Mixing cold food item with a spoon:-
For the case of mixing cold food item with the help of spoon the matters are not divided by solid state they stay at direct contact to each other. When cold food item is comes to connect with comparative hot spoon that time hot food item contain low temperature and spoon stays at high temperature but when two different temperature is comes closer they start to heat exchanging between to each other and as a result the temperature became starts to come in equilibrium condition. So, mixing cold food item with a spoon is another example of application of heat exchanger.
Making of tea:-
For the case of making of tea the matters are not divided by solid state they stay at direct contact to each other. When warm water is mixing with the cold milk that time hot water contain high temperature and cold milk stays at low temperature but when two different temperature is comes closer they start to heat exchanging between to each other and as a result the temperature became starts to come in equilibrium condition. So, making of tea is another example of application of heat exchanger.
Shaking hands:-
Shaking hand between two different people is another example of application of heat exchanger. When two hands are shaking that time the body temperature of two people definitely stay at different temperature but when the hands get closer that time heat exchanging started and as a result the temperature comes in an equilibrium condition.
Touch into the overheated oven the matters are separated by a wall which will be stays in solid state. For the case when warm heated pan is touched by hand that time heated oven contain high temperature and hand stays at low temperature but when two different temperature is comes closer they start to heat exchanging between to each other and starts to come in equilibrium condition for this reason when overheated oven is touched injury can be appear.
Touch ice cube:-
Touching an ice cube is another example of application of heat exchanger. For the case when in a cool ice cube is touched by hand that time ice cube contain low temperature and hand stays at high temperature but when two different temperature is comes closer they start to heat exchanging between to each other and starts to come in equilibrium condition for this reason when cooled ice cube is touched we feel cold.
Refrigeration system:-
From the term of refrigeration we can get that cooling an area, system or matter to decreases or maintain the temperature below the surrounding one the rejection of heat at a higher temperature. Refrigeration a human made artificial cooling system. Energy that is present in state of heat is rejected from a reservoir which stays in low temperature to a reservoir which stays in high temperature. The application of refrigeration is in wide range such as cryogenics, household refrigerators, air conditioning and industrial freezers.
Image – Commercial refrigeration; Image Credit – Wikipedia
Humans:-
The nasal passage of the human being is works as a heat exchanger. By the help of nasal passage cold air is enter and hot air is exist. The effectiveness of the nasal passage easily can be examined putting the hand in front of exhaling and face, firstly by the nose and in next step by the mouth.
Air conditioning:-
With the air conditioning system in certain place or maintain the temperature, air purity and relative humidity below the surrounding one the rejection of heat at a higher temperature. The air conditioning system is applied for personal comfort. It industries air conditioning system widely used to ensure appropriate operation of parts or machinery.
Image – Air conditioning condenser units outside a building; Image Credit Wikipedia
Countercurrent heat exchangers naturally appear in the circulation system of birds, fish and marine mammals. Arteries into the skin bearing warm blood are intertwined along from the skin bearing cold blood, causing the warm blood of the arterial to transfer heat with cold blood venous.
Image – Counter-current exchange conservation circuit; Image Credit – Wikipedia
Petroleum refineries:-
Petroleum refineries or oil refineries is a engineering industrial field where the petroleum is transfer and after that the petroleum is refined into some useful products like kerosene, petroleum naphtha, heating oil, gasoline, fuel oils, diesel fuel and many more.
Sewage arrangement:-
Sewage arrangement is a waste treatment process by which contaminates are removed from sewage to created an effluent which is perfect for exit to the environment.
Image – Sewage arrangement plant; Image Credit – Wikipedia
Advantages of sewage arrangement:-
Time efficient
Eco friendly
Design is simple
Easy installation
Experts not needed
Maintenance cost low
Occupies meager space
Disadvantages of sewage arrangement:-
Power supply needed
Maintenance needed
Frequent Asked Questions:-
Question: – Describe the classifications of heat exchanger.
Solution: – The classifications of heat exchanger is listed below,
In this article “Crankshaft types” and how crankshaft types are related with others facts that will be discuss. In the system of power transmission crankshaft plays a very important role.
The crankshaft is a shaft which is rotate in a motion and transfer piston’s reciprocating motion to rotation motion. The types of crankshaft is listed below,
The parts of the welded crankshafts such are journals, crank web, crank pin, crank arms are separately manufactured and after that welded with each other. Among the all types of the crankshafts welded crankshaft is stronger and stable. For manufactured the welded crankshaft became very for costly and maintenance is also quite high for this reason in general application the welded crankshaft is not preferred.
Fully built crankshaft:-
In the fully built up crankshaft by its name it define that all components of the fully built crankshaft is manufactured and fabricated separately with taking helping of the pieces of the matter which are multiple separate. The parts which are machined separately they are crankpins, journals and crank webs. The parts are heated and finally artificially shrink fitted together.
When the parts are cooled loosing the excess amount heat the size of the parts are shrink and make a tight grip to each other. The end portion of the connecting rod of the fully built crankshaft is made with a single solid piece of the material.
The making of the fully built crankshaft is easy because small size parts are assembly to make bigger size equipment. The weight of the fully built crankshaft is heavier.
Semi built crankshaft:-
By the name of semi built crankshaft we easily can recognize that the every parts of the crankshaft is not arrange together some of the parts are only constructed and forged together to make a whole crankshaft design. The parts which are shaped, forged, built together in the semi built crankshaft are bearings, crank web. In diesel engine semi built crankshaft is used.
Billet crankshaft:-
With the help o the 4340 alloy steel the billet crankshaft is manufactured. The 4340 alloy made with chromium, nickel, molybdenum and aluminium. The billet crankshaft transfer maximum amount of power to the load. Minimal balancing is required to the billet crankshaft and also it have lowest amount of machining time for this reason in the system of power transmission this type of crankshaft widely used.
Forged crankshaft:-
By the name of forged crankshaft we easily can recognize that with the help of forging process the forged crankshaft is make. A block of metal or with a single piece of metal the forged and finally crankshaft shaped is given to it. For arranging the all parts of the forged process welding is not required. The engines where need medium speed like generator there only forged crankshaft can be used.
The engines which are bulky and heavy like two stroke engines there forged crankshaft is not suitable al all. Improving the strength of the forged engine induction hardening process is used. It is robust and moderate economical to use.
Image – Forged Crankshaft; Image Credit – Wikipedia
Solid single crankshaft:-
From the term of the solid single crankshaft we can recognize that this type of crankshaft is made with solid one single piece of material. The solid single crankshaft can work in bothlow speed and high speed for this particular reason in multi cylinder engine solid single crankshaft widely used. The end portion of the connecting rod with two pieces of material solid single crankshaft is made. This structure passes through cyclic tension and load during firing.
The solid single crankshaft is stressed for the reasons of axial vibration torsional vibration, misalignment of the main bearing.
Cast crankshaft:-
Cast crankshaft is made with casting malleable iron. In the engines of diesel and petrol cast crankshaft is used in a wide range. The manufacturing cost is very less comparative to the other types of crankshaft and its maintenance cost is also not too high. For improving tensile strength to the cast crankshaft heat preparation is done and for this reason rate of tear and wear is decreases. The lifetime of this crankshaft is also high.
The crankshaft of the diesel engine is made with alloy steel. For making the crankshaft of the engine at first alloy steel is heated at very high temperature and after that moulded in shape taking the help of forging die. The engine of the diesel have longer stroke comparative to bore diameter, for this particular reason the crankshaft use in the diesel engine larger than the other parts. Billet crankshaft is use in diesel engine for improving the performance than the other classifications of the crankshaft.
The types of crankshafts in marine engine are listed below,
Fully built crankshaft
Semi built crankshaft
Welded crankshaft
Forged crankshaft
Image – Continental engine marine crankshafts, Image Credit – Wikipedia
Frequent Asked Questions:-
Question: – Explain the causes behind the unbalancing of crankshafts.
Solution: – The causes behind the unbalancing of crankshafts is listed below,
Explosion or crankcase fire
For the reason of torsion and twist is evolved in the crankshaft.
For the reason of power stroke. After completing the power stroke inside the engine the piston of the engine exerted a jerk force inside the crankshaft thus the crankshaft can make rotation.
The motion of the reciprocating of the piston of the engine inside the chamber of the combustion.
Image – Flat-plane crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black); Image Credit – Wikipedia
Question: – Mention the symptoms by which we can recognize the bad conditions of the crankshaft.
Solution: – The symptom by which we can recognize the bad condition of the crankshaft are listed below,
Image – Schematic of operation of a crank mechanism; Image Credit – Wikipedia
Noise:-
When the excessive unwanted noise is produce inside the engine that time we can recognize the bad condition of the crankshaft.
Knocking:-
When inside the crankshaft main journal and connecting rod bearing extreme wear is produce that time knocking is appear in the engine of the machine. Knocking is the symptom by which we can recognize the bad condition of the crankshaft.
Difficulty in starting:-
When the system crate problem in starting that time we can recognize the bad condition of the crankshaft.
Excessive vibration of the engine:-
The CKP sensor easily can detect and bounds the generated vibration of the engine of the vehicle to produce stable power input. If unwanted excessive amount of vibration is produce in the engine that helps us to recognize bad condition of the crankshaft.
Stalling and Backfiring:-
When the default position sensor failure of crankshaft is happened that time backfiring and stalling is occur. The CKP sensor failure causes the engine of the system shut down abruptly and after that starting the engine of the system without any reason. The symptom by which we can recognize the bad condition of the crankshaft among them stalling and backing one of them.
Question: – Write the reasons failure behind the diesel engine.
Solution: – The reasons failure behind the diesel engine is listed below,
Misaligned crankshaft
Develop of the cracks on the fillets.
Excessive amount of vibration is appearing for the reason of torsion that can created cracks in the main journals and crankpin.
Excessive speeding of the engine on load.
Stray current or eddy current is passes from the faulty alternator.
Cylinder of the engine is over pressurized for the reason of hydraulic lock for the reason of water leakage in the system’s engine.
Question: – Write the advantages of crankshaft.
Solution: – The advantages of crankshaft is listed below,
Increases the power of the engine
Provides better torque
Greater efficiency
Smooth running
Question: – Write the disadvantages of crankshaft.
Solution: – The disadvantages of crankshaft is listed below,
In this article the topic named “Darcy friction factor” and Darcy friction factor related facts will be discuss. In fluid mechanics the Darcy friction factor equation is play a very important role.
The Darcy friction factor is a physical parameter which is related to head loss or loss of pressure for the reason of friction along the certain amount of length of a coil or pipe to the average velocity of the incompressible fluid. The Darcy friction factor is a dimensionless physical quantity.
What is Darcy friction factor?
The Darcy friction factor is a physical parameter which is use to describe the loss for a coil or pipe due to friction. The Darcy friction factor is applicable for both open channel flow and close channel flow.
The Darcy friction factor is a physical parameter which is describe as it is a physical quantity which is use for calculate the frictional energy loss. The Darcy friction factor is cased for resistance due to friction and velocity of the incompressible fluid inside a coil or pipe.
The Darcy friction factor widely used in turbulent flow for calculating the amount of head loss during the friction in the pipe.
Darcy friction factor formula:
The equation for Darcy friction factor is given below,
Hf = 4fLv2/2gD
Where,
Hf= Pressure loss or head loss
f = Coefficient of friction factor or Coefficient of friction factor
L = Length of the coil or pipe
v = Velocity of the incompressible fluid
g = Acceleration due to gravity (value of g is 9.8 meter per square second)
D = Diameter of the coil or pipe
Pressure loss equation:-
In a cylindrical coil or pipe where incompressible fluid is flow in a motion, the cylindrical coil or pipe which have a uniform diameter D, the pressure loss is appear during the viscous effect which is express as Δp is directly proportional to the length of the cylindrical coil or pipe can be express as with the help of Darcy – Weisbach equation,
Where,
Δp/L= The amount of pressure loss of per unit length is, which express as Pacals per meter
fD = Coefficient of friction factor or Coefficient of friction factor
ρ = The density of the fluid which is express as kg per cubic meter
Head loss form:-
The term of head loss which is express as Δh is the pressure loss appears for reason of friction in term of same length of a column of the incompressible fluid.
The mathematical form of the head loss is,
Δp =ρgΔh
Δh= The head loss appears for reason of friction in term of same length of a coil or pipe and unit is meter.
g = Acceleration due to gravity (value of g is 9.8 meter per square second)
It is beneficial the head loss appears for reason of friction in term of same length of a coil or pipe is,
Where,
L = Length of the coil or pipe and unit is meter
Darcy – Weisbach equation can be writing for head loss,
In form of volumetric flow:-
The relation between volumetric flow rate and mean flow velocity is,
Q = A * <v>
Where,
Q = Volumetric flow rate unit is cubic meter per second
A = Cross sectional area of the coil or pipe and unit is square meter
v = Velocity of the incompressible fluid which is express as meter per second
In a coil or pipe the fluid is flow with pipe diameter D_c,
Darcy – Weisbach equation can be written as,
Shear stress form:-
Darcy – Weisbach equation can be in form of shear stress,
When the value of Reynolds number is less than 2000 this type of flow called laminar flow.
Mathematical analysis of the turbulent flow is easy.
Velocity of the turbulent flow is too low.
Regular movement is appearing in fluids which are flow in a motion in laminar flow.
Laminar flow in general very rare type of flow.
The velocities profile of the flow laminar the wall of the pipe or rod maximum.
The velocity profile of the flow laminar in the center section of the rod or pipe is minimum.
Average motion is appearing in which side fluid is flowing.
Image – A closeup view of water pouring down; Image Credit – Wikipedia
Darcy friction factor for turbulent flow:
Maximum system of the fluid in the nuclear facilities is work with the flow type of turbulent flow. The resistance of this flow obey the equation of Darcy – Weisbach.
The friction of the turbulent flow is measurement of the shear stress which is applied in the wall of a rod or pipe during the flow of turbulent. The flow of turbulent is obeying the equation of Darcy – Weisbach which is directly proportional to square of mean velocity of the flowing fluid in a certain area.
Turbulent flow:-
Reynolds number is more than 3500 .
Velocity is too high.
Irregular movement is appearing
Average motion is appearing in which side fluid is flowing.
The velocity profile of the flow turbulent in a certain area is quickly drops when it comes to the wall of the pipe or rod.
The velocity profile of the flow turbulent in a certain area is clearly flat when it comes to the center section of the rod or pipe
Friction factor for turbulent flow formula:
The Colebrook–White equation is define as f for the Darcy friction factor, the function of for Reynolds number as Re, pipe relative roughness express as, ε / Dh for both smooth pipes and rough pipes.
The friction factor for turbulent flow formula is,
or,
Where,
Dh (m , ft) = Hydraulic diameter for filling the fluid in circular conduits
Dh = D= Inside diameter of the area from where flow of turbulent is flowing
Rh (m , ft) = Hydraulic radius for filling the fluid in circular conduits
Rh = D/4= Inside diameter of the area from where flow of turbulent is flowing/4
The equation of Colebrook is solved by numerically for its implicit nature. Now a day Lambert W function is also use to obtain outspoken reformulation the equation of Colebrook.
a = 2.51/Re
or,
10-1/2 = ax +b
p = 10-1/2
We will get,
px = ax + b
Expanded forms:-
Additional mathematical form of the equation of Colebrook is,
Where,
1.7384…. = 2 log (2 * 3.7) = 2 log (7.4)
18.574 = 2.51 * 3.7 * 2
And,
Or,
Where,
1.1364…. = 1.7384… = – 2 log (2) = 2 log
(7.4) – 2 log (2) = 2 log (3.7)
9.287 = 18.574/2 = 2.51 * 3.7
Darcy friction factor chart:
Darcy friction factor chart is combination of four physical parameters such as, pressure loss coefficient, Reynolds number, and relative roughness of the coil or pipe and diameter ratio of the coil or pipe.
Darcy friction factor chart is dimensionless physical factor with the help of Darcy – Weisbach equation can be written as,
Pressure drop can be calculate as,
Or,
Image – Darcy Friction Factor Chart; Image Credit – Wikipedia
The expression for Darcy friction factor for laminar flow is,
In the flow of turbulent the relation between Reynolds number represent as Re, friction factor represent as fD, and relative roughness represent as ∈/D is complicated.
The expression for Darcy friction factor for turbulent flow is,
Darcy friction factor for different materials:
The Darcy friction factor for different material is given below,
Pipe material
Absolute roughness
Feet
Microns
Copper or drawn brass
0.000005
1.5
Commercial steel
0.000150
45
Concrete
0.001 – .01
300 – 3000
Wood stave
0.0006 – 0.003
200 – 900
Wrought iron
0.000150
45
Riveted steel
0.003 – 0.03
900 – 9000
Darcy friction factor for pipe:
The moody chart or friction factor for pipe is plotted the relative roughness of a coil or pipe which is express as ∈/D and Reynolds number.
Darcy friction factor for water:
The moody chart or friction factor is for water derives as the pressure loss of water n a coil or pipe for the reason of friction between the pipe and the water flow inside of it.
Compressor isentropic efficiency is a crucial parameter that measures the performance of a compressor. It is a measure of how effectively a compressor can convert the input power into useful work by compressing the gas. In simple terms, it tells us how close the compressor’s actual performance is to the ideal, reversible process known as isentropic compression. The higher the isentropic efficiency, the better the compressor’s performance. This efficiency is influenced by various factors such as the design of the compressor, the type of gas being compressed, and the operating conditions. Understanding compressor isentropic efficiency is essential for engineers and technicians involved in the design, operation, and maintenance of compressors, as it helps in optimizing their performance and energy consumption. In this article, we will delve deeper into the concept of compressor isentropic efficiency, its significance, and the factors affecting it. So, let’s get started!
Key Takeaways
Compressor isentropic efficiency is a measure of how well a compressor can convert input power into useful work.
It is calculated by comparing the actual work done by the compressor to the ideal work that would be done in an isentropic process.
Higher isentropic efficiency indicates a more efficient compressor, as it can deliver more work output for the same input power.
Factors such as design, operating conditions, and maintenance affect the isentropic efficiency of a compressor.
Improving compressor isentropic efficiency can lead to energy savings and reduced operating costs.
Definition of Isentropic Efficiency
Isentropic efficiency is a crucial parameter used to evaluate the performance of compressors. It measures how effectively a compressor can compress a gas without any losses due to heat transfer or friction. In simple terms, it is a measure of how close a compressor’s actual performance is to the ideal, reversible, adiabatic compression process known as the isentropic process.
The isentropic process is a theoretical concept in thermodynamics where a gas undergoes a reversible and adiabatic compression or expansion. During this process, there is no heat transfer between the gas and its surroundings, and there are no losses due to friction. The isentropic process is often used as a reference to compare the actual performance of compressors.
Isentropic efficiency is defined as the ratio of the actual work done by the compressor to the work that would be required in an ideal, isentropic compression process. It is denoted by the symbol ηs (eta-s). The higher the isentropic efficiency, the closer the compressor’s performance is to the ideal isentropic process.
Importance of Isentropic Efficiency in Compressors
Isentropic efficiency plays a vital role in determining the overall performance and energy efficiency of compressors. It directly affects the power consumption, heat transfer, and the amount of work required to compress a gas.
Energy Efficiency: Compressors are widely used in various industries, including refrigeration, air conditioning, gas turbines, and more. In these applications, energy efficiency is of utmost importance. By understanding and optimizing the isentropic efficiency of compressors, engineers can design more efficient systems that consume less energy and reduce operating costs.
Power Consumption: The isentropic efficiency of a compressor directly affects the power required to compress a gas. A higher isentropic efficiency means that the compressor can achieve the desired pressure with less work, resulting in lower power consumption. This is particularly important in large-scale applications where compressors operate continuously and consume a significant amount of energy.
Heat Transfer: In compressors, heat transfer occurs due to the compression process. The higher the isentropic efficiency, the lower the heat transfer losses. By minimizing heat transfer, the compressor can maintain a lower discharge temperature, which is crucial for the longevity and reliability of the system.
Typical Isentropic Efficiency of Compressors
The isentropic efficiency of compressors varies depending on their design, operating conditions, and the type of gas being compressed. Different types of compressors, such as centrifugal compressors and axial compressors, have different typical isentropic efficiencies.
Centrifugal Compressors: Centrifugal compressors are commonly used in applications that require high flow rates and moderate pressure ratios. They are known for their high isentropic efficiency, typically ranging from 75% to 85%. However, it is important to note that the efficiency of centrifugal compressors can vary significantly based on their specific design and operating conditions.
Axial Compressors: Axial compressors are widely used in aircraft engines, power plants, and other applications that require high-pressure ratios. They typically have isentropic efficiencies ranging from 85% to 90%. Axial compressors are known for their excellent efficiency and are often used in applications where energy efficiency is critical.
Enthalpy Entropy Diagram
Enthalpy Entropy Diagram
It is important to note that these values are general guidelines, and the actual isentropic efficiency of a compressor can vary based on factors such as design, maintenance, and operating conditions. Manufacturers often provide performance maps or curves that show the efficiency characteristics of their compressors at different operating points.
In conclusion, understanding compressor isentropic efficiency is crucial for evaluating compressor performance, optimizing energy efficiency, and reducing operating costs. By considering the isentropic efficiency, engineers can design and operate compressors more effectively, resulting in more efficient and reliable systems.
The Science Behind Compressor Isentropic Efficiency
A. Thermodynamics and Isentropic Efficiency
In the world of compressors, isentropic efficiency plays a crucial role in determining their performance. To understand compressor isentropic efficiency, we need to delve into the realm of thermodynamics. Thermodynamics is the branch of physics that deals with the relationships between heat, work, and energy. It provides us with the tools to analyze and optimize the performance of various energy conversion systems, including compressors.
One key concept in thermodynamics is the isentropic process. An isentropic process is an idealized process that occurs without any heat transfer to or from the system. In other words, it is a process that is both adiabatic (no heat transfer) and reversible (no irreversibilities or losses). Isentropic processes are often used as a reference for analyzing the performance of real-world processes, such as those occurring in compressors.
Isentropic efficiency, denoted by η_isen, is a measure of how well a compressor is able to achieve an isentropic process. It is defined as the ratio of the actual work done by the compressor to the work that would be required if the process were isentropic. In simple terms, isentropic efficiency tells us how close a compressor is to an ideal, lossless compressor.
B. Isentropic Compression Efficiency Formula
The isentropic compression efficiency of a compressor can be calculated using the following formula:
η_isen = (h1 – h2s) / (h1 – h2)
In this formula, h1 represents the enthalpy of the gas at the compressor inlet, h2s represents the enthalpy of the gas at the compressor outlet assuming an isentropic process, and h2 represents the actual enthalpy of the gas at the compressor outlet.
The isentropic compression efficiency is a dimensionless quantity that ranges from 0 to 1. A value of 1 indicates that the compressor is able to achieve an isentropic process perfectly, while a value of 0 indicates that the compressor is unable to achieve any compression at all.
Compressor isentropic efficiency formula
Isentropic Efficiency of Compressorformula is denoted by the ratio of ideal or isentropic work done to actual work done.
Here, T2’ denotes the exit temperature for ideal or isentropic case.
T1 denotes the temperature at inlet
T2 denotes the temperature at outlet for actual case
Cp is the specific heat, which is considered constant. In terms of compression pressure ratio, the above formula is denoted by:-
Where,
Where Pr is compression pressure ratio, γ is the ratio of specific heats Cp/Cv.
Form above, the Actual exit temperature T2 can be calculated by
Types of Compressors and Their Isentropic Efficiency
A. Reciprocating Compressor Isentropic Efficiency
A reciprocating compressor is a type of compressor that uses a piston to compress the gas. It is commonly used in applications where a high pressure ratio is required, such as in refrigeration and air conditioning systems. The isentropic efficiency of a reciprocating compressor refers to how efficiently it can compress the gas without any heat transfer or pressure losses.
The isentropic efficiency of a reciprocating compressor is influenced by several factors, including the design of the compressor, the type of gas being compressed, and the operating conditions. Generally, reciprocating compressors have high isentropic efficiencies, typically ranging from 70% to 90%.
One of the main advantages of reciprocating compressors is their ability to achieve high compression ratios, which allows for efficient gas compression. However, they also have some limitations, such as higher maintenance requirements and a higher level of noise compared to other types of compressors.
B. Centrifugal Compressor Isentropic Efficiency
Centrifugal compressors are widely used in various industries, including oil and gas, petrochemical, and power generation. They are known for their high flow rates and compact design. The isentropic efficiency of a centrifugal compressor is a measure of how well it can compress the gas without any heat transfer or pressure losses.
Compared to reciprocating compressors, centrifugal compressors typically have lower isentropic efficiencies, ranging from 70% to 85%. This is due to the inherent design characteristics of centrifugal compressors, such as the presence of impellers and diffusers, which introduce some level of inefficiency into the compression process.
Despite their lower isentropic efficiencies, centrifugal compressors offer advantages such as lower maintenance requirements, smoother operation, and the ability to handle a wide range of flow rates. They are often used in applications where a high flow rate is required, such as in large-scale industrial processes.
C. Axial Compressor Isentropic Efficiency
Axial compressors are commonly used in aircraft engines, gas turbines, and turbochargers. They are designed to handle large volumes of gas and achieve high compression ratios. The isentropic efficiency of an axial compressor measures how efficiently it can compress the gas without any heat transfer or pressure losses.
Axial compressors are known for their high isentropic efficiencies, typically ranging from 80% to 90%. This is due to their unique design, which consists of multiple stages of rotating and stationary blades that work together to compress the gas.
The high isentropic efficiency of axial compressors makes them ideal for applications where energy efficiency is crucial, such as in aircraft engines and gas turbines. However, they are also more complex and expensive to manufacture compared to other types of compressors.
D. Screw Compressor Isentropic Efficiency
Screw compressors are widely used in various industries, including refrigeration, air conditioning, and process gas compression. They are known for their compact design, high reliability, and low maintenance requirements. The isentropic efficiency of a screw compressor refers to how efficiently it can compress the gas without any heat transfer or pressure losses.
Screw compressors typically have high isentropic efficiencies, ranging from 80% to 90%. This is due to their unique design, which consists of two interlocking helical rotors that compress the gas as they rotate.
One of the main advantages of screw compressors is their ability to handle a wide range of flow rates and provide a continuous supply of compressed gas. They are also known for their quiet operation and low vibration levels. However, they may not be suitable for applications where a high compression ratio is required.
E. Scroll Compressor Isentropic Efficiency
Scroll compressors are commonly used in residential and commercial air conditioning systems, heat pumps, and refrigeration units. They are known for their compact size, quiet operation, and high reliability. The isentropic efficiency of a scroll compressor measures how efficiently it can compress the gas without any heat transfer or pressure losses.
Scroll compressors typically have high isentropic efficiencies, ranging from 70% to 80%. This is due to their unique design, which consists of two interleaving spiral-shaped scrolls that compress the gas as they orbit.
One of the main advantages of scroll compressors is their ability to provide a smooth and continuous flow of compressed gas, resulting in improved energy efficiency. They are also known for their low maintenance requirements and long service life. However, they may not be suitable for applications where a high compression ratio is required.
In conclusion, different types of compressors have varying isentropic efficiencies, which are influenced by factors such as design, gas type, and operating conditions. Understanding the isentropic efficiency of a compressor is crucial for selecting the most suitable compressor for a specific application, taking into account factors such as energy efficiency, flow rate requirements, and maintenance considerations.
Isentropic Efficiency in Different Systems
A. Gas Turbine Compressor Isentropic Efficiency
Gas turbine compressors play a crucial role in the operation of gas turbines, which are widely used in power generation and aircraft propulsion systems. The isentropic efficiency of a gas turbine compressor is a key parameter that determines its performance and energy efficiency.
The isentropic efficiency for a gas turbine is defined by following expression:
ηT=Real Turbine Work/ Isentropic Turbine Work
Isentropic efficiency is a measure of how well a compressor can compress the incoming air without any losses due to heat transfer or friction. It represents the ratio of the actual work done by the compressor to the ideal work that would be required in an isentropic (reversible adiabatic) process. In simple terms, it quantifies how close the compressor comes to an ideal, frictionless compression process.
Gas turbine compressors can be either centrifugal or axial flow compressors. Centrifugal compressors use centrifugal force to accelerate the air and then convert the kinetic energy into pressure energy. On the other hand, axial flow compressors use a series of rotating and stationary blades to compress the air in a continuous flow.
The isentropic efficiency of a gas turbine compressor depends on various factors, including the design of the compressor, the number of compressor stages, and the operating conditions. Higher isentropic efficiency indicates a more efficient compressor, as it requires less work to achieve the desired pressure ratio.
B. Refrigeration Compressor Isentropic Efficiency
Refrigeration systems are widely used in various applications, including air conditioning, food preservation, and industrial processes. The compressor is a vital component of a refrigeration system, responsible for compressing the refrigerant and increasing its pressure.
The isentropic efficiency of a refrigeration compressor is an important parameter that affects the overall performance and energy efficiency of the system. It measures the ability of the compressor to compress the refrigerant without any losses in the form of heat transfer or pressure drop.
Refrigeration compressors can be classified into different types, such as reciprocating, rotary, and scroll compressors. Each type has its own advantages and disadvantages in terms of efficiency, cost, and noise level.
To improve the isentropic efficiency of a refrigeration compressor, manufacturers focus on optimizing the compressor design, reducing internal losses, and minimizing leakage. Additionally, proper maintenance and regular cleaning of the compressor can help maintain its efficiency over time.
C. Heat Pump Compressor Isentropic Efficiency
Heat pumps are devices that transfer heat from a lower temperature source to a higher temperature sink, using mechanical work. The compressor in a heat pump plays a crucial role in raising the temperature of the working fluid and increasing its pressure.
Performance of a heat pump is defined by:
Where,
V= volume in cum/m
z= Compresibility facotor, 1 for air
ρ= density of air
R= universal gas constant, 286 J/(kg*К) for air
γ = ratio of specific heat, 1.4 for air
Calculating, by putting the above values we get
nw = 175.5 KW
Thus, the isentropic efficiency of compression is nw/na = 17.5./200 = 0.88 or 88%
Comparing the efficiencies of reciprocating compressors, centrifugal compressors and axial flow compressors, the later has the best efficiencies and ranges above 90%. This is mostly because of of minimum mechanical and aerodynamic losses it encounters as the gas traverses the path thoruch the compressing device.
A typical axial compressor is shown below. it has got alternate rotaing vanes and static airfoils, which converts the kinetic energy to pressure.
Axial flow compressors are generally employed for high flow rates primarily in jet engines, as turbines and some process apllications. For a given flow however, compared to a centrifugal machine which has a raidal flow componet, the axial flow compressors have lower wetted area and loe sealing requriement contributing to its higher isentropic efficiency.
Compressor Polytropic Efficiency vs Isentropic Efficiency
A. Understanding Compressor Polytropic Efficiency
When it comes to understanding the efficiency of a compressor, two important terms often come up: polytropic efficiency and isentropic efficiency. In this section, we will focus on understanding compressor polytropic efficiency.
What is Polytropic Efficiency?
Polytropic efficiency is a measure of how effectively a compressor can compress a gas. It takes into account the energy losses that occur during the compression process, such as heat transfer and friction. Unlike isentropic efficiency, which assumes an ideal, reversible process with no energy losses, polytropic efficiency considers the real-world conditions and factors that affect the compression process.
How is Polytropic Efficiency Calculated?
The calculation of polytropic efficiency involves comparing the actual work done by the compressor to the work that would be done in an ideal, isentropic process. The formula for polytropic efficiency is as follows:
The actual work done by the compressor can be determined by measuring the power input to the compressor motor, while the isentropic work can be calculated using the ideal gas law and the pressure ratio across the compressor.
B. Comparison Between Polytropic and Isentropic Efficiency
Now that we have a basic understanding of polytropic efficiency, let’s compare it to isentropic efficiency.
Isentropic Efficiency: The Ideal Case
Isentropic efficiency is a measure of how close a compressor comes to achieving an ideal, reversible compression process. In an isentropic process, there are no energy losses, and the entropy of the gas remains constant. This idealized process assumes that the compression is adiabatic (no heat transfer) and reversible (no friction or other losses).
Polytropic Efficiency: Accounting for Real-World Factors
Unlike isentropic efficiency, polytropic efficiency takes into account the energy losses that occur during the compression process. These losses can be caused by factors such as heat transfer between the gas and the compressor walls, friction in the compressor components, and non-ideal gas behavior. Polytropic efficiency provides a more realistic measure of how efficiently a compressor is performing under real-world conditions.
Comparing the Two Efficiencies
In general, isentropic efficiency is higher than polytropic efficiency because it assumes an ideal, lossless process. However, in real-world applications, achieving isentropic efficiency is not always possible due to the presence of energy losses. Polytropic efficiency gives a more accurate representation of the actual performance of a compressor.
It’s important to note that both polytropic and isentropic efficiency are valuable metrics for evaluating compressor performance. While isentropic efficiency provides an ideal benchmark, polytropic efficiency accounts for the real-world factors that affect compressor operation.
In summary, polytropic efficiency and isentropic efficiency are two measures used to evaluate the performance of compressors. Polytropic efficiency considers the energy losses that occur during compression, providing a more realistic measure of compressor performance. Isentropic efficiency, on the other hand, assumes an ideal, lossless process. Both metrics have their merits and are useful in different contexts.
Calculating Compressor Isentropic Efficiency
A. How to Calculate Compressor Isentropic Efficiency
Compressor isentropic efficiency is a crucial parameter that determines the performance of a compressor. It measures how effectively a compressor can compress a gas without any heat transfer or pressure losses. To calculate the compressor isentropic efficiency, you need to know the inlet and outlet conditions of the compressor, such as the pressure and temperature.
The formula to calculate compressor isentropic efficiency is as follows:
Isentropic Efficiency = (h1 – h2s) / (h1 – h2)
Where: – h1 is the enthalpy at the compressor inlet – h2s is the isentropic enthalpy at the compressor outlet – h2 is the actual enthalpy at the compressor outlet
The enthalpy values can be obtained from thermodynamic tables or through calculations using the specific heat capacity of the gas being compressed.
B. Practical Examples of Compressor Isentropic Efficiency Calculation
Let’s consider a practical example to understand how to calculate compressor isentropic efficiency. Suppose we have a centrifugal compressor that compresses air from an inlet pressure of 1 bar to an outlet pressure of 5 bar. The inlet temperature is 25°C, and the outlet temperature is 100°C. We want to determine the isentropic efficiency of the compressor.
First, we need to find the enthalpy values at the compressor inlet and outlet. Using the specific heat capacity of air (Cp), we can calculate the enthalpy as follows:
h1 = Cp * (T1 – Tref) h2 = Cp * (T2 – Tref)
Where: – T1 is the temperature at the compressor inlet – T2 is the temperature at the compressor outlet – Tref is the reference temperature (usually taken as 0°C)
Let’s assume Cp for air is 1 kJ/kg·K. Plugging in the values, we get:
In this example, the isentropic efficiency of the centrifugal compressor is approximately 43.24%. This means that the compressor is able to achieve 43.24% of the ideal isentropic compression process, considering the given inlet and outlet conditions.
By calculating the compressor isentropic efficiency, engineers can evaluate the performance of a compressor and compare it with other compressors. This information is vital for selecting the right compressor for a specific application and optimizing energy efficiency in various industries, including refrigeration, air conditioning, and power generation.
Improving Compressor Isentropic Efficiency
A. Performance Optimization for Better Efficiency
To improve the isentropic efficiency of a compressor, various performance optimization techniques can be employed. These techniques aim to enhance the efficiency of the compression process, resulting in reduced energy consumption and improved overall performance. Here are some key strategies for optimizing compressor efficiency:
Proper Sizing and Selection: Ensuring that the compressor is properly sized and selected for the specific application is crucial. This involves considering factors such as the required flow rate, pressure ratio, and operating conditions. Choosing the right compressor type (centrifugal or axial) and the appropriate number of stages can significantly impact efficiency.
Optimal Pressure Ratio: The pressure ratio, defined as the ratio of the discharge pressure to the suction pressure, plays a vital role in compressor efficiency. By carefully selecting the pressure ratio, it is possible to achieve higher isentropic efficiency. However, it is important to strike a balance, as excessively high pressure ratios can lead to increased mechanical losses and reduced efficiency.
Enhanced Heat Transfer:Improving heat transfer within the compressor can help increase efficiency. This can be achieved through the use of advanced cooling techniques, such as intercooling and aftercooling. These techniques involve removing heat from the compressed air between stages, reducing the temperature and improving overall efficiency.
Reduced Internal Leakage: Minimizing internal leakage within the compressor is crucial for improving efficiency. This can be achieved through proper sealing and maintenance of the compressor components. Regular inspections and maintenance can help identify and address any leakage issues, ensuring optimal performance.
Optimized Operating Conditions: Operating the compressor at its optimal conditions can significantly improve efficiency. This includes maintaining the compressor within its recommended speed range, avoiding excessive pressure drops, and ensuring proper lubrication. Additionally, controlling the inlet air temperature and humidity can help optimize performance.
B. Advanced Design and Technology for Efficiency Improvement
Advancements in compressor design and technology have paved the way for significant improvements in isentropic efficiency. Here are some key areas where advanced design and technology have contributed to efficiency improvement:
Improved Aerodynamics:Modern compressors incorporate advanced aerodynamic designs that optimize airflow and reduce losses. This includes the use of advanced blade profiles, optimized impeller and diffuser geometries, and the incorporation of computational fluid dynamics (CFD) simulations. These advancements help minimize flow separation, reduce pressure losses, and enhance overall efficiency.
Efficient Mechanical Systems:The mechanical systems within a compressor, such as bearings and seals, play a crucial role in overall efficiency. Advanced bearing technologies, such as magnetic bearings and oil-free designs, minimize friction losses and improve efficiency. Similarly, advanced sealing techniques help reduce internal leakage and improve overall performance.
Variable Geometry: Compressors with variable geometry offer enhanced efficiency by adjusting the compressor’s internal geometry based on operating conditions. This allows for better matching of the compressor’s performance to the system requirements, resulting in improved efficiency across a wider range of operating conditions.
Advanced Materials:The use of advanced materials, such as lightweight alloys and composites, in compressor construction helps reduce weight and improve efficiency. These materials offer better strength-to-weight ratios, reducing the energy required to drive the compressor and improving overall efficiency.
Smart Control Systems:The integration of smart control systems and advanced algorithms allows for real-time monitoring and optimization of compressor performance. These systems can adjust operating parameters, such as speed and pressure, to maximize efficiency based on the current operating conditions. This results in improved overall efficiency and reduced energy consumption.
C. Maintenance and Its Impact on Isentropic Efficiency
Regular maintenance plays a crucial role in maintaining and improving the isentropic efficiency of a compressor. Neglecting maintenance can lead to decreased efficiency, increased energy consumption, and potential system failures. Here are some key maintenance practices and their impact on isentropic efficiency:
Regular Inspection and Cleaning: Regularly inspecting and cleaning the compressor components, such as the impeller, diffuser, and inlet filters, is essential for optimal performance. Accumulated dirt, debris, and fouling can restrict airflow, increase pressure losses, and reduce efficiency. Cleaning these components ensures smooth airflow and optimal performance.
Proper Lubrication:Adequate lubrication of the compressor’s moving parts is crucial for reducing friction losses and maintaining efficiency. Regularly checking and replenishing lubricants, as per the manufacturer’s recommendations, helps ensure smooth operation and optimal efficiency.
Seal Maintenance:Proper maintenance of seals, gaskets, and O-rings is essential for minimizing internal leakage and improving efficiency. Regularly inspecting and replacing worn-out seals helps maintain proper compression and prevents energy losses due to leakage.
Vibration Analysis: Monitoring and analyzing compressor vibrations can help identify potential issues and prevent failures. Excessive vibrations can indicate misalignment, worn-out bearings, or other mechanical problems that can negatively impact efficiency. Timely detection and correction of these issues can help maintain optimal efficiency.
Performance Monitoring: Implementing a comprehensive performance monitoring system allows for real-time tracking of key performance parameters, such as pressure, temperature, and power consumption. Any deviations from expected values can be quickly identified, allowing for timely corrective actions to maintain optimal efficiency.
By implementing performance optimization techniques, leveraging advanced design and technology, and prioritizing regular maintenance, it is possible to significantly improve the isentropic efficiency of compressors. These improvements not only reduce energy consumption but also contribute to cost savings and environmental sustainability.
The Role of Isentropic Efficiency in Renewable Energy Systems
A. Isentropic Efficiency in Turbine and Compressor Systems
In the realm of renewable energy systems, isentropic efficiency plays a crucial role in optimizing the performance of turbine and compressor systems. These systems are integral components of various renewable energy technologies such as wind turbines, hydroelectric power plants, and solar thermal power plants. Understanding the concept of isentropic efficiency is essential for maximizing energy conversion and minimizing energy losses in these systems.
Isentropic Efficiency in Compressor Systems
Compressor systems are responsible for increasing the pressure of a fluid, such as air or gas, in order to facilitate various processes in renewable energy systems. Isentropic efficiency in compressor systems refers to the ability of the compressor to achieve the highest possible pressure increase with the least amount of energy input.
When a compressor operates under ideal conditions, it undergoes an isentropic process, which is a thermodynamic process that occurs without any heat transfer or entropy change. In this ideal scenario, the compressor achieves maximum efficiency, known as the isentropic efficiency. However, in real-world scenarios, compressors experience various losses, such as mechanical friction, heat transfer, and fluid leakage, which reduce their efficiency.
Comparing Isentropic Efficiency in Different Compressor Types
Different types of compressors, such as centrifugal and axial compressors, exhibit varying levels of isentropic efficiency. Centrifugal compressors, for example, are known for their high isentropic efficiency, making them ideal for applications that require high-pressure ratios. On the other hand, axial compressors are more suitable for applications that require a large volume flow rate.
The isentropic efficiency of a compressor is typically influenced by factors such as the pressure ratio, the number of compressor stages, and the design and operation of the compressor. By carefully considering these factors, engineers can optimize the isentropic efficiency of compressor systems in renewable energy applications.
B. Multi objective Optimization in Renewable Energy Systems
In the pursuit of enhancing the efficiency and performance of renewable energy systems, multiobjective optimization techniques play a significant role. These techniques aim to simultaneously optimize multiple objectives, such as maximizing energy conversion efficiency, minimizing energy losses, and reducing environmental impact.
Balancing Efficiency and Environmental Impact
One of the primary objectives of multi objective optimization in renewable energy systems is to strike a balance between energy efficiency and environmental impact. While it is crucial to maximize the isentropic efficiency of compressor systems to achieve optimal energy conversion, it is equally important to minimize the environmental footprint associated with these systems.
By employing advanced computational algorithms and simulation tools, engineers can explore various design and operational parameters to identify the optimal configuration that achieves the desired balance between efficiency and environmental impact. This approach ensures that renewable energy systems not only perform optimally but also contribute to sustainable development.
Considering Exergy Analysis in Multi objective Optimization
Exergy analysis is another valuable tool in multi objective optimization for renewable energy systems. Exergy is a measure of the quality of energy and represents the maximum useful work that can be obtained from a system. By incorporating exergy analysis into the optimization process, engineers can identify areas of energy loss and inefficiency within compressor systems.
Through exergy analysis, engineers can pinpoint specific components or processes that contribute to energy losses and devise strategies to mitigate them. This approach enables the identification of opportunities for improving the isentropic efficiency of compressor systems, ultimately leading to enhanced overall system performance.
In conclusion, isentropic efficiency plays a vital role in optimizing the performance of turbine and compressor systems in renewable energy applications. By understanding and improving the isentropic efficiency of compressor systems, engineers can enhance energy conversion efficiency and minimize energy losses. Additionally, multi objective optimization techniques, coupled with exergy analysis, enable engineers to strike a balance between efficiency and environmental impact, ensuring the sustainable operation of renewable energy systems. Conclusion
In conclusion, the compressor isentropic efficiency is a crucial parameter that determines the performance of a compressor. It measures how effectively a compressor can convert the input power into useful work, without any losses. A higher isentropic efficiency indicates a more efficient compressor, as it can compress the gas with less energy consumption and minimal heat generation. On the other hand, a lower isentropic efficiency implies that the compressor is less efficient and may require more power to achieve the desired compression. It is important to consider the isentropic efficiency when selecting a compressor for various applications, as it directly impacts the energy consumption and overall performance. By understanding and optimizing the isentropic efficiency, engineers and designers can improve the efficiency and reliability of compressors, leading to cost savings and reduced environmental impact.
Frequently Asked Questions
1. What is the isentropic efficiency of a compressor?
Isentropic efficiency of a compressor is a measure of how much the actual performance of the compressor deviates from the ideal or isentropic process. It is calculated as the ratio of the isentropic work to the actual work done by the compressor.
2. How to calculate compressor isentropic efficiency?
The isentropic efficiency of a compressor can be calculated using the formula: η_isentropic = (h2s – h1) / (h2 – h1), where h2s is the isentropic enthalpy at the exit, h1 is the enthalpy at the inlet, and h2 is the actual enthalpy at the exit.
3. What is the difference between compressor polytropic efficiency and isentropic efficiency?
Polytropic efficiency is a measure of the work done during a polytropic process, which is a process that involves heat transfer. On the other hand, isentropic efficiency is a measure of the work done during an isentropic process, which is an idealized process that assumes no heat transfer.
4. What is the typical isentropic efficiency of a compressor?
The typical isentropic efficiency of a compressor varies depending on the type of compressor. For example, reciprocating compressors typically have isentropic efficiencies around 70-75%, while centrifugal compressors can have isentropic efficiencies as high as 85-90%.
5. How does the isentropic efficiency of a compressor affect its performance?
The isentropic efficiency of a compressor directly affects its performance. A higher isentropic efficiency means that the compressor requires less work to compress a given amount of gas, which makes it more energy efficient.
6. What factors can affect the isentropic efficiency of a compressor?
Several factors can affect the isentropic efficiency of a compressor, including the design of the compressor, the operating conditions, the type of gas being compressed, and the maintenance of the compressor.
7. How can the isentropic efficiency of a compressor be improved?
The isentropic efficiency of a compressor can be improved through various methods, such as optimizing the compressor design, maintaining the compressor properly, and operating the compressor at optimal conditions.
8. How does the isentropic efficiency of a compressor relate to the thermodynamic efficiency?
The isentropic efficiency of a compressor is a measure of how closely the compressor’s performance matches the ideal isentropic process. The thermodynamic efficiency, on the other hand, is a measure of how much of the input energy is converted into useful work. Therefore, a higher isentropic efficiency generally leads to a higher thermodynamic efficiency.
9. How does the isentropic efficiency of a compressor affect the refrigeration cycle?
The isentropic efficiency of the compressor affects the performance of the refrigeration cycle. A higher isentropic efficiency means that the compressor can compress the refrigerant with less work, which improves the efficiency of the refrigeration cycle.
10. What is the role of entropy in the isentropic efficiency of a compressor?
Entropy is a measure of the disorder or randomness in a system. In an isentropic process, the entropy remains constant. Therefore, if the compressor’s process is not isentropic and entropy increases, this indicates energy losses, which reduces the isentropic efficiency of the compressor.
In this article “Friction factor for turbulent flow” and friction factor for turbulent flow related several information will be discuss. The common method is to determine friction factor for turbulent flow is Moody diagram.
The friction factor is a physical parameter which is a dimensionless. The turbulent flow for a particular given type field is constant. The friction factor for turbulent flow only depends on the geometry of the channel and Reynolds number. The flow is called turbulent when Reynolds number is more than 3500.
What is the friction factor for turbulent flow?
Maximum system of the fluid in the nuclear facilities is work with the flow type of turbulent flow. The resistance of this flow obey the equation of Darcy – Weisbach.
The friction of the turbulent flow is measurement of the shear stress which is applied in the wall of a rod or pipe during the flow of turbulent. The flow of turbulent is obeying the equation of Darcy – Weisbach which is directly proportional to square of mean velocity of the flowing fluid in a certain area.
Turbulent flow:-
When the value of Reynolds number is more than 3500 this type of flow called turbulent flow.
Mathematical analysis of the turbulent flow is not too easy.
Velocity of the turbulent flow is too high.
Irregular movement is appearing in fluids which are flow in a motion in turbulent flow.
Average motion is appearing in which side fluid is flowing.
Turbulent flow in general very common type of flow.
The velocity profile of the flow turbulent in a certain area is quickly drops when it comes to the wall of the pipe or rod.
The velocity profile of the flow turbulent in a certain area is clearly flat when it comes to the center section of the rod or pipe.
Image – Turbulent flow in flowing of a river; Image Credit – Wikimedia Commons
Friction factor for turbulent flow formula:
The Colebrook–White equation is define as f for the Darcy friction factor, the function of for Reynolds number as Re, pipe relative roughness express as, ε / Dh for both smooth pipes and rough pipes.
The friction factor for turbulent flow formula is,
or,
Where,
Dh (m , ft) = Hydraulic diameter for filling the fluid in circular conduits
Dh = D= Inside diameter of the area from where flow of turbulent is flowing
Rh (m , ft) = Hydraulic radius for filling the fluid in circular conduits
Rh = D/4 = Inside diameter of the area from where flow of turbulent is flowing/4
The equation of Colebrook is solved by numerically for its implicit nature. Now a day Lambert W function is also use to obtain outspoken reformulation the equation of Colebrook.
or,
We will get,
px = ax + b
Expanded forms:-
Additional mathematical form of the equation of Colebrook is,
Where,
1.7384…. = 2 log (2 * 3.7) = 2 log (7.4)
18.574 = 2.51 * 3.7 * 2
And,
Or,
Where,
1.1364…. = 1.7384… = – 2 log (2) = 2 log
(7.4) – 2 log (2) = 2 log (3.7)
9.287 = 18.574/2 = 2.51 * 3.7
How to calculate friction factor for turbulent flow?
The process of calculating friction factor for turbulent flow is given below,
At first we need to determine the value of Reynolds number for the turbulent flow using this formula,
ρ x V x D x μ
In the next step relative roughness should be calculated using k/D formula which value to under 0.01
In the final step use the Moody formula for the roughness with the help of Reynolds number,
Friction factor for turbulent flow in pipe:
The range friction factor for turbulent flow in pipe is
For smooth pipe,
0.04 At Re 4000 to 1.01 at Re 3 x 106
For rough pipe,
0.045 At Re 4000 to 0.03 at Re 3 x 106
Friction factor for turbulent flow in smooth pipe:
Friction factor for turbulent flow in smooth pipe can be explained by the help of Blasius correlation. Blasius correlation is the simplest form of determine the Darcy friction factor.
Blasius correlation is only applicable for turbulent flow in smooth pipes it is not applicable for turbulent flow in uneven pipes. The value of 100000 of Reynolds number Blasius correlation is valid. In some cases of turbulent flow in uneven pipes is applied only because of its simplicity.
Mathematical equation of Blasius correlation turbulent flow in uneven pipes is given below,
After that the equation is corrected and express as,
With,
Where,
f is a function for the,
D = Pipe diameter express as meter, feet
R = Curve radius express as meter, feet
H = Helicoidal pitch express as meter, feet
Re = Reynolds number which is dimensionless
Reynolds number valid for,
0 < H/D < 25.4
Friction factor for turbulent flow in rough pipe:
The Darcy friction factor for turbulent flow in rough pipe means value of Reynolds number is more than 4000 is expressed by Colebrook – White equation.
or,
Where,
Dh (m , ft) = Hydraulic diameter for filling the fluid in circular conduits
Dh = D = Inside diameter of the area from where flow of turbulent is flowing
Rh (m , ft)= Hydraulic radius for filling the fluid in circular conduits
Rh = D/4 = Inside diameter of the area from where flow of turbulent is flowing/4
The equation of Colebrook is solved by numerically for its implicit nature. Now a day Lambert W function is also use to obtain outspoken reformulation the equation of Colebrook.
or,
We will get,
px = ax + b
Expanded forms:-
Additional mathematical form of the equation of Colebrook is,
Where,
1.7384…. = 2 log (2 * 3.7) = 2 log (7.4)
18.574 = 2.51 * 3.7 * 2
And,
Or,
Where,
1.1364…. = 1.7384… = – 2 log (2) = 2 log
(7.4) – 2 log (2) = 2 log (3.7)
9.287 = 18.574/2 = 2.51 * 3.7
Friction factors for turbulent flow in curved pipes:
In order to calculate the pressure drop with in a coil or pipe the friction factor should be calculated at first.
Friction factors for turbulent flow in curved pipes is discuss below,
D = Internal diameter of the coil or pipe
R = Darius of the coil or pipe helix
De = Dean Number
Rec = Transitional Reynolds number
fc = Friction factor of the coil or pipe which smooth
frough = Friction factor for a rough coil or pipe
fsmooth = Friction factor for a smooth coil or pipe
When a single phase flow is appear in a pipe or coil which shaped is curved a secondary flow pattern is introduce in the coil or pipe, in this time friction factor and fluid behaviour start to changes.
As the effect of stabilization of fluid flow the output is comes increases the Reynolds number at that point when flow is enter to the coil or pipe the transition flow form laminar flow to the flow of turbulent.
This condition mathematical form is given below,
To calculate the friction factor in a pipe or coil the Dean number is needed,
After this we easily can determine the friction factor for a smooth coil or pipe.
For,
De < 11.6
fc = 64/Re
For,
11.6 < De < 200
For, De > 2000
For calculation of totally turbulent flows determine the friction factor for a smooth coil or pipe using this equation,
The range is,
Moody diagram friction factor for turbulent flow:
In the flow of turbulent the relation between Reynolds number represent as Re, friction factor represent as fD, and relative roughness represent as ∈/D is complicated.
The expression for Moody diagram friction factor for turbulent flow is,
Image – Darcy Friction factor for Re between 10 and 10E8 for values of relative roughness; Image Credit – Wikimedia Commons
Frequent Asked Questions:-
Question:-Write about theDarcy friction factor chart.
Solution:-Darcy friction factor chart is combination of four physical parameters such as, pressure loss coefficient, Reynolds number, and relative roughness of the coil or pipe and diameter ratio of the coil or pipe.
Darcy friction factor chart is dimensionless physical factor with the help of Darcy – Weisbach equation can be written as,
Pressure drop can be calculate as,
Or,
Image – Equal-friction chart for air in metal duct (ε = 0.05 mm); Image Credit – Wikimedia Commons
The expression for Darcy friction factor for laminar flow is,
fD = 64/Re
In the flow of turbulent the relation between Reynolds number represent as Re, friction factor represent as fD, and relative roughness represent as ∈/D is complicated.
The expression for Darcy friction factor for turbulent flow is,
