The Diffusion Coefficient or diffusivity expresses the rate or how fast a material can diffuse into another. In this article we will discuss about the topic “is diffusion coefficient constant?”.
At the beginning of this article we should properly know about the Diffusion and Diffusion Coefficient. So here first we will discuss about their definitions and then discuss the related factors to know whether a Diffusion Coefficient remains constant or not.
Diffusion is the process where atoms, molecules or particles combine together as a result of their random motion or kinetic energy associated with them.
Diffusion is the process by which one matter is transported from one part of a system to another due to the random molecular motion.In other words diffusion is the outcome of spreading up of atom or molecules in a system from higher concentration to lower concentration region.
Dissolving of salt in water, escaping of air from a balloon, spreading of ink in a glass of water all are the example of diffusion encountered in our daily life.
Diffusion of blue ink in water; Image Credit: flickr.com
In the above figure we can see an example of diffusion where blue ink is diffused in water giving a blue colour to the whole mixture.
If we spray a perfume in a room, a fragrance spreads throughout the entire room is also an example of diffusion.
Case hardening process is the example of Diffusion in solids where diffusion of carbon molecules take place through the surface of the steel to make the surface strong.
As diffusion phenomenon occurs between two regions of different concentration, it also occurs across two membranes, between outside and inside of cells
Including Fick’s first and second law Diffusion constant is an important parameter in lots of equations of Physics and Chemistry
Diffusion Coefficient depicts the diffusion mobility, the higher the Diffusivity or Diffusion coefficient of a substance in comparison to the other in a pair of species, the faster they mix into each other.
Diffusion coefficient is the parameter which measures how quickly one matter diffuses into the other. The S.I unit of Diffusivity is m2/s.
We can get the mathematical expression for Diffusion Coefficient from Fick’s laws.
Fick’s Laws
Diffusivity or Diffusion Constant(D) is the constant of Proportionality encountered in Fick’s Law. The easiest explanation of Diffusion is given by Fick’s laws.
According to Fick’s First law of diffusion, the molar flux due to diffusion is proportional to the concentration gradient where molar flux refers to the amount of substance flow through a unit area within a unit time interval and concentration gradient is the change in the value of quantity.
Fick’s first law can be used to derive his second law which in turn is identical to the diffusion equation.
A diffusion process that obeys Fick’s laws is called normal or Fickian diffusion; otherwise, it is called anomalous diffusion or non-Fickian diffusion.
According to Fick’s Second law of diffusion, The rate of change of concentration of the solution at a point in space is proportional to the second derivative of concentration with space.
From Fick’s first law, we know that molecules move from a region of higher concentration to lower concentration that means it relates directly the diffusive flux to the gradient of concentration.
Where J: diffusion flux
D: diffusivity
x: position
From Fick’s second law, we can predict the change in concentration along with time.
Diffusion process is influenced by various factors. The changes in these factors bring changes to the rate of Diffusion.
The factors affecting Diffusion Coefficient are listed below:
Molecular Size of diffusing matter: Heavier particles move slowly in comparison to the lighter particles. Since diffusion process is fully associated with the movement of molecules, so the molecular size affects the rate of diffusion. Therefore, heavier molecules diffuse more slowly than lighter molecules.
Temperature: A faster moving molecule posses higher kinetic energy, as soon as the temperature is added to a system the molecules inside the mixture moves faster due the higher kinetic energy experienced by each molecule. Molecules with higher kinetic energy can diffuse at a faster rate.
Pressure: Generally pressure is considered as a influencing parameter in case of diffusion in gases, an increase in pressure results a higher rate of diffusion. Because when pressure increases the gas molecules come closer to each other and they have to move a shorter distance to get diffuse.
But as liquids are incompressible in nature the affect of pressure in case of liquid is negligible
Surface Area: For a large surface area of interaction results faster rate of diffusion.
Viscosity of the solvent: If the viscosity of the medium through which the particles have to move or diffuse is too thick or very viscous, then the rate of diffusion automatically slows down. In case of a less viscous medium the particles move more easily.
Properties of the solution(concentration, pH etc.): Diffusion is the process by which one matter is transported from one part of a system to another due to the random molecular motion. For a greater difference in between the concentration of two regions, faster will be the movement of the molecules. As soon as the distribution of molecules reaches the equilibrium condition, the rate of diffusion becomes slower.
All the factors give a combined affect on diffusion coefficient.
The vane pump working in automobile sectors, air conditioning system and power steering for the vehicles. The vane pump working is not suitable for high viscous liquid substance, it is suitable for moderate viscous liquid.
Vane positive displacement pump is a part of positive displacement pump. These vane pumps in various situation of the pressure deliver a fixed amount of flow rate. This vane positive displacement pump is also known as self priming pump. Inside this pump the liquid is pressurized under the impact of the vane.
This vane pump is not applicable for the liquid which is in high viscous. By the help of this pressure of the liquid is changes from high to low. For moderate and low viscous liquid this type of pump is absolutely appropriate. The liquids are such as liquid petroleum gas, ammonia, water, solvents, petrol and many more.
It classified as the sections of suction or vacuum pump. It is very similar to scroll compressor. The vane pump is contained some equipment such as impeller, casing, runner, vane. The multiple vanes are rotate when the rotor takes its motion. In the vanes impellers are placed.
The updated versions of the vane positive placement pump have a contact surface in the contact line between the rotor and stator.
The vane pumps are uses in a large amount in the field of automobiles, air conditioning system, steering of vehicles, fuel transport, loading of fuel in terminals.
In the vane displacement pump the vane is present and by taking of the pump liquid substance is lifted to the desired area of the fields. Inside the rotor of the pump one or more than one vane are installed and it moves under the cavity. The pressure relief valve is also placed in the pump thus it could unwanted pressure is produce inside the rotor that it could not able to failure the pump.
Vane pump parts:
In the vane positive displacement pumps a fluid substance is flow from one place to another place in low pressure to high pressure. The length can be varied for keeping contact pump’s wall as well as vane rotors.
The parts of the vane positive displacement pump and their related facts are given below,
The shaft of the pump is placed in the rotor. When the rotor is moves under taking the power from the prime mover the shaft also starts to move in a rotation motion. The shaft is connected in the motor of the pump with the help of prime mover.
Casing:
Casing is equipment which is works as the protection of the system. In vane positive displacement pump the casing is use to protect the pump. All parts of the pump are protected under the casing.
Casing is classified in two sections and they are,
Inlet port
Outlet port
Inlet port:
Fluid is entering when pressure of the liquid is compressed and sucks the liquid by the inlet port.
Outlet port:
Fluid is discharge when pressure of the liquid is released and drains the liquid by the outlet port of the vane positive displacement pump.
Rotor:
Slots are carried by the rotor. The slots are placed in that manner where the distance of the each other should be same.
Cam ring:
Inside the casing cam ring is situated. Mainly the wall of the casing the cam ring is attached.
Sliding vanes:
In the rotor’s slot the sliding vanes are placed. The shape of this equipment is rectangular and spring is used to attach it with the slots. Spring is generally use for flexible movement of the sliding vanes. Sliding vanes are placed in this way that it could moves in the rotor without any problems.
Impeller:
Impellers are used to convert the energy. The impellers are placed in the vanes of the pump. When the power is generating by the impellers it convert energy mechanical to output power.
In the industry of automobiles and steering of vehicles it is used in wide range. One of the most commonly used vane type pump is unbalanced vane positive displacement pump.
The liquid substance in the vane positive displacement pumps not facing any leakage in the vane tip and housing.
The lateral thrust which is appearing in the shaft of the rotor when the working purpose of the unbalanced vane pump is not too well. The lateral thrust can be explained as when the pressure is differentiating between the outlet valve and suction valve. This unwanted situation decreases the bearing lifetime of the shaft.
A cylindrical shaped rotor is placed in the counteracting in the housing which is also in shaped circular. The both centre for the housing and rotor not coincide to each other. The housing and rotor is placed as that manner where their distance should be same to each other.
The cylindrical rotor also contained radial grooved. The rotor is installed in the pump’s drive shaft. The grooves are carried vanes, and vanes are placed in same distance to each other and moved freely using centrifugal force in rotation method. The rotors are moved inside the cam ring. The surface contact is take place between the rotor and cam ring.
In the balanced vane positive displacement pump’s inside the pressure is always stays in balanced position. The two inlets are contained by the pump. This is the main reason behind the balanced pressure. The balanced vane positive displacement pump carried one outlet and two inlets.
The inlet valves of the unbalanced pump are installed in the opposite direction to each other and outlet valve is also placed opposite to inlets valve. The offset is not present inside the balance vane positive pump.
In the casing the whole system of the balanced pump equipments are placed. The shape casing of the balance vane pump is elliptical. The centres are same for the both rotor and casing.
The purpose of the inlet valve is to suck the fluid substance from the outer side and the purpose of the outlet valve is to drainage the fluid substance to the outside of the pump.
If we go through the two vanes’ cavity then can observe that the size of the inlet valve to outlet valve is decreases.
In the balance vane positive displacement pump there is no lateral thrust is appear. The inlets and outlet valve is balancing their thrust force to each other.
Pressure amount inside the rotor in the area of the exit is too higher than the normal pressure but the position of the outlet valves are opposite to each other for this reason the force became equal and net load is not present in the bearing shaft and the lifetime of the bearing shaft is increases.
In the variable displacement vane positive displacement pump the vanes of the rotor is not connecting directly to the housing.
The pockets sizes are different for the variable displacement vane positive displacement pump and also allow the different size. Size of the pockets can be change by the help of the adjusting screw.
Delivery rates are also different for the variable displacement vane positive displacement pump.
When the adjusting screw is moves in upward and downward direction as the same time reacting ring also moves in upward and downward in same time. Due to the he reaction ring movement changing the centre of the both rotor and ring is changes.
A ring is present in the variable displacement vane positive displacement pump’s middle portion of the casing and vane. This ring shaped equipment is known as reaction ring. This rings works as a connector between the spring and adjusting screw.
The flow rate is changes due to changes sizes of the pockets in the vane pump’s rotor.
Vane pumps working:
The vane positive displacement pump working process is briefly discuses in below,
At the beginning of the process starting the power is generated by the motor which is driven by electric and power is go through by the shaft of the rotors. The rotor and shafts are connected to each other and when the rotor is start to move by using centrifugal pump the shaft is also moved.
Multiple vanes are carried by the rotor.
The outside liquid substance is hit the vanes of the shaft that time kinematic energy is convert into speed and goes into the casing.
In the casing pressure is increases and liquid is sucks by the inlet valve.
Pressure is squeezing and drain by the discharge valve.
Working of vane pump
Vane pumps application:
The applications of the vane positive displacement pump is given below,
Filling up for the liquid petroleum gases’ cylinders.
Bulk transferring is done by the help of this vane positive displacement pump for ammonia and liquid petroleum gas.
Beverage processing done by thisvane positive displacement pump.
In gas application vane positive displacement pump is widely used.
In automobile sector vane positive displacement pump is used.
In oil applicationvane positive displacement pump is used.
Where high pressure is used as the application there vane positive displacement pump is used. In automobile sectors for steering of the vehicles this pump is used.
In air conditioning system vane positive displacement pump is used.
This article discusses about brake fluid types. The braking fluid is used as hydraulic fluid inside the braking system of vehicles.
Hydraulic force is applied with the help of hydraulic fluid. The fluid uses Pascal’s law for transferring the force from one end to other. We shall see more about types of braking fluid, mechanism of braking system and other related topics.
Generally the braking force applied to the braking pedal is very less than the actual force needed to stop the vehicle in motion. The braking fluid converts this force into pressure and amplifies it enough that the resulting amplified force can stop the vehicle.
Brake fluids are of four types. The designation of these brake fluids start with DOT that means Department of Transportation. The four types are-
DOT 3
DOT 3 is a glycol based braking fluid. The term is a standard term used in US. DOT 3 is equivalent to SAE J1703.
DOT 4
DOT 4 is also a glycol based braking fluid generally used as a temperature upgrade for DOT 3. Most cars after 2006 used DOT 4 brake fluid as their standard braking fluid.
DOT 5
A braking fluid that is silicone based and also it is completely different from the series of DOT (2,3,4,5.1) It does not mix with water and other brake fluids. It is recommended that this braking fluid should not be mixed with other braking fluids.The biggest advanatage of silicone over other materials is that silicone based fluid has more stable viscosity index with working conditions having a wide variety of temperature values.
DOT 5.1
Although, DOT 5 was a better version among other DOT versions. Lack of its acceptance led rise to DOT 5.1 which is again a glycol based braking fluid. It gives functioning similarities with silicone based braking fluid and can be termed as non silicone version of DOT 5. That is a version having similar properties of DOT 5 while using Glycol ether based raw materials.
Brake fluid properties
The braking fluid undergoes extreme conditions as the vehicle runs sometimes on smoother road and sometimes on rough and bumpy road. The weather may be hot sometimes, rainy sometimes and sometimes cold.
According to these conditions the braking fluid cannot be changed every now and then. So it has to have properties such that it can bear extreme situations. The ideal properties for a braking fluid are-
High breaking point- As the vehicle experiences immense heating during its operation, it is recommended to have a braking fluid which can operate at high temperatures.
Good low temperature properties– Sometimes the temperatures are below normal levels during cold, at this time the braking fluid may solidify if it does not have good low temperature properties.
Good viscous properties- The braking fluid should have an optimum amount of viscosity. It should not be loose and also not thick that it does not move easily.
Anti corrosive properties– The braking fluid should have anti corrosive properties otherwise it will corrode the material used in braking lines damaging the entire braking system.
Physical stability– A good braking fluid has good physical stability that means it should not get distorted or change its phase once it is subjected to huge amount of force and pressure.
Chemical stability- A good braking fluid does not mix with other liquids, it should have good chemical stability. It should maintain its chemical structure and should not be easily contaminated by outside impurities.
Compressibility- The entire functionality of braking fluid depends on its compressibility. If the compressibility is not good then it won’t be able to provide required pressure and so the braking system will fail which in turn means that the vehicle won’t be stopped.
Bike brake fluid types
Bikes usually use two types of braking fluids. These fluids are discussed in detail below-
DOT fluid- Above section discusses about DOT fluids in detail. They are mostly made of Glycol Ether based materials and generally each higher version has a better working temperature range. Except for DOT 5 which is a silicone based braking fluid and that has better properties than DOT 2, DOT 3 and DOT 4.
Mineral oils– This is the normal mineral oil that we purchase from grocery stores. This is generally meant for lighter vehicles such as two wheeler.
DOT brake fluid types
As discussed in the sections above, DOT brake fluids are classified into many types. Typical basis of classification is the working properties and the raw materials used while making the braking fluid.
The types of DOT braking fluid are-
DOT 2– Has a low working range of temperature.
DOT 3– Has a greater working temperature range than DOT 2.
DOT 4- Has even greater working temperature range than DOT 2 and DOT 3.
DOT 5- This is made up of silicone based materials and has better properties.
DOT 5.1– Although made of Glycol Ether based materials, it has similar properties as that of DOT 5.
Car brake fluid types
In cars usually glycol ether based brake fluids and silicone based brake fluids are used. These fluids are discussed in above sections. Most commonly used braking fluids in cars are DOT brake fluids. More specifically, following DOT brake fluids are used-
DOT 3- As discussed above it is a Glycol Ether based braking fluid that is used in lighter vehicles. This braking fluid can be used in hatchback cars that are light in weight. It has a smaller range of working temperature.
DOT 4- As discussed above, it is also a Glycol Ether based braking fluid that is used for comparatively heavier vehicles such as SUVs. This braking fluid has a greater working temperature range.
Auto brake fluid types
In autos, usually DOT 3 type of braking fluid is used. As an auto is considered in lighter weight vehicle type, it does not need higher versions of braking fluid like DOT 4 and 5. DOT 3 is sufficient for autos.
This article discusses about the relation between boiling point and pressure. A misconception lies among us that the boiling point is related to temperature only. But primarily it is the pressure which is responsible for the boiling to take place.
The boiling of liquid starts when the vapour pressure of the liquid starts touching the value of ambient or surroundings pressure. The pressure at which boiling takes place is called as saturation pressure. Pressure of the liquid keeps on increasing with increasing temperature. We shall study more about this relationship in this article.
What is partial pressure?
In simple words partial pressure is defined as the pressure exerted by a certain type of liquid molecules in a mixture.
This pressure is the exact same pressure that the liquid molecules must have exerted if these were the only molecules occupying the whole volume. Partial pressure term comes into play when there are more than one type of liquid molecules present in the system.
What is vapour pressure?
Vapour pressure is the pressure exerted by the liquid molecules when they are about to change into gaseous molecules.
The vapour pressure increases with temperature. The surface of the liquid starts boiling when the surface vapour pressure is equal to the ambient pressure. The atmosphere exerts some pressure on the liquid, when this value of atmospheric pressure is reached by vapour pressure, boiling starts taking place.
How does pressure affect boiling point?
Pressure, as discussed above, is one of the most important factor that affects directly the boiling point of any liquid.
For the surroundings, if the surrounding pressure is very high, it will take more time and more heat for the liquid to reach the ambient pressure value and hence the boiling point of the liquid will be more. When the ambient pressure is low then the liquid will reach the ambient pressure value soon. In this case, the boiling point will be lower as compared to boiling point at surroundings with high pressure.
Boiling point and pressure relationship
Now we have a clear view of how pressure affects the value of boiling point. The main factor affecting the boiling point is atmospheric pressure. (Although temperature also plays an active role)
We shall focus our discussion on relation between pressure and boiling point only. Lets us assume that the heat transfer rate is constant. This way the liquid molecules will slowly get heated up resulting in increase in their vapour pressure. As the vapour touches the ambient pressure, the liquid will start boiling.
The equation which draws the relationship between boiling point and pressure numerically is called as Clausius-Clapeyron equation.
The Clausius-Clapeyron equation is given below-
Does boiling point increase with pressure?
As and when the pressure of the ambient increases, the boiling point also increases but only upto the critical point.
It is the point where the properties of both the phases, that is, liquid and gases, are exhibited by the substance. We shall more about critical point in later sections of this article. Also, we can note this fact that the boiling point of the liquid decreases when the pressure drops until the triple point is reached.
How does boiling point increase with pressure?
The boiling point can be defined as the value of temperature at which the vapour pressure of liquid becomes equal to the ambient pressure. This value of temperature depends on the ambient pressure.
If the ambient pressure is more, it takes more time for the liquid’s vapour pressure to reach the value ambient pressure. The heat source constantly supplies heat to the liquid to increase its pressure. When the pressure at the outside is more then the boiling time will also be more.
How does water boil at low pressure?
At low pressures, the water starts boiling in a very short time. This is because the time required for the vapour pressure to reach the value of ambient pressure is less.
A notable example is that the food is cooked very fast on mountains. This is because the ambient pressure is very less compared to the pressure at sea level. The liquid takes more time to boil when it is at sea level.
Does water boil faster at high or low pressure?
We have discussed rigorously about the effect of pressure on boiling point. It is made to us very clear that the water will start boiling faster at lower pressures.
The reason being the same as discussed above. That is, the time required for the vapour pressure to reach the value of ambient pressure is less. The water starts boiling when the vapour pressure reaches the value of ambient pressure.
Factors affecting boiling point
We have discussed a lot of things about what affects the boiling point. Let us get a more detailed view on these factors.
The factors affecting the boiling point are given below-
Temperature– Temperature is responsible for increasing or decreasing the vapour pressure of the liquid. When the temperature is high, the vapour pressure increases and likewise, when the pressure is low, the vapour pressure decreases.
Vapour pressure– When the vapour pressure reaches the value of ambient pressure, the liquid starts boiling. The pressure exeerted by the liquid when it is about to change its phase is called as vapour phase.
Atmospheric pressure– As the name suggests, the atmospheric pressure is the pressure exerted by atmosphere. Atmospheric pressure plays a very important role in determining the boiling point of the substance. If the pressureexerted by atmosphere is less then the boiling point will also be less and on the other hand the boiling point will be more if the pressure exerted by the atmosphere is more.
What is critical point?
Simply put, critical point of a substance is that point at which the properties of liquid such as density, temperature, pressure etc are equal to that of its own gaseous state.
This can be said as an equilibrium state where the substance exists in both the liquid and gaseous phase. The molecules exhibit properties of both liquids and gases at the same time.
What happens at critical point?
When the temperature of the liquid is raised, the density of the liquid falls down and simultaneously the density of gas starts increasing.
When the densities of both liquid and gas become equal, then the particular point is called as critical point. Here both gas and liquid phase properties are exhibited by the substance.
This article discusses about thermal conduction examples. It is a mode of heat transfer which takes place by the collision of molecules present in the medium.
Heat is the energy existing between two difference which are thermally different from each other that is they both are having different temperatures. The heat energy flows just like the wind. It flows from the higher to lower temperature system. Out of which thermal conduction is one such type.
We can see thermal conduction taking place almost every day in our daily lives. It is responsible for us getting burnt when we touch a hot object. Let us see different examples of thermal conduction. They are given below-
Spoon getting hot when in contact with hot vessel
The molecules of vessel are continuously vibrating at high energies. This energy is transferred to the molecules of spoon which in turn gets hot. This way the transfer of heat takes place between the spoon and vessel through thermal conduction.
We feel hot after touching a hot object
Similar to the spoon and vessel example, the molecules of hot object transfers the energy to our skin, this gives us sensation of heat. This is also an example of thermal conduction as the sensation of heat occurs after contact.
Warming of muscles using heating pad
The heating pad has high energy molecules, this energy is transferred to the skin and then to the muscles. This way we feel relaxed once the heat reaches our muscles. This is also an example of thermal conduction.
Heat from liquid makes the cup hot
The molecules of heat are flowing with high energy, this energy is transferred to the surface of the cup which is contact with the liquid.
Holding warm hands make your hands warm too
A warm hand has more energy than the colder hand. The colder hand becomes warm once the energy is transferred to it. The energy transfer takes place until both the hands come at same temperature.
Ironing clothes
The hot iron transfers heat to the clothes. This is an example of thermal conduction between clothes and iron.
Walking on hot sand
Hot sand transfers heat to our feet when we walk on it. This is why our feet are burnt when we walk on sand with very high temperature. The thermal conduction takes place between feet and sand.
Touching a light bulb
The surface of the light bulb is very hot. Upon touching it, the heat is transferred from the surface of the light bulb to our hands which is why we feel warm after touching it.
Touching a hot stove
The stove is at higher energy state, after touching which, our hands are burnt due to heat transfer between stove and our hand.
Image: Stove surrounded with bricks prevents our hands from gettign burnt
Hot pan transfers heat to the block of ice. Ice starts melting once the temperature starts increasing beyond 0 degrees. As the heat is transferred from the pan, the temperature of the ice block increases and starts melting.
Melting chocolate in hand
Similar to the ice block example, the chocolate starts melting once it absorbs heat from one’s hand. This is due to thermal conduction.
Shallow frying of food such as cutlet
Shallow frying includes heat transfer from pan to the cutlet. Thermal conduction takes place between cutlet and the pan.
Touching a silencer of vehicle
Silencer becomes hot once the vehicle is started and used it for a while, the heat from the silencer is transferred immediately to our leg/hand when we touch it. This is due to a large temperature difference between both. It is recommended that we stand away from silencers as they get very hot sometimes specially right after using the vehicle.
Putting hands in hot water
The energy from hot water is transferred to the hands. This way thermal conduction takes place between hot water and hand.
Touching ice
Ice is colder than our hands, so the heat is being transferred from our hands to the ice block. This happens with the help of thermal conduction between ice block and our hands.
What is heat?
The energy flowing between the two systems solely because their temperatures are different is called as heat.
We shall see about different types of heat transfer in this article.
Modes of heat transfer
The transfer of heat from system to system can take place through various methods. Sometimes it needs a medium and sometimes it travels in vacuum.
We shall see different ways by which heat can be transferred from one system to another. They are discussed below-
Heat transfer by conduction- Heat conduction is a mode of heat transfer in which it is transferred with the help of collision of molecules present in the medium. The molecules keep vibrating and transfer the energy from on object to other. This type of heat transfer requires both the objects to be in contact.
Convection– Convection is a mode of heat transfer in which the heat is transferred as a result of movement of fluid particles between the two mediums. The fluid can be water or even air This is why we feel hot when we stand near boiling water.
Radiation– This form of heat transfer can take place in vacuum and is defined as the heat transfer which takes place in the form of waves or particles through space.
What is thermal conduction?
Thermal conduction is a type of heat transfer that takes place between two systems which are in contact.
The molecules inside these systems collide with each other for transferring the heat form one place to other. This type of heat conduction needs contact between two systems compulsorily for heat transfer to take place.
What is thermal conductivity?
Similar to electrical conductivity that is the ability of a material to conduct electricity, thermal conductivity also means the ability of a material to conduct transfer of heat.
Even the shape of cross section can affect the value of thermal conductivity. We shall study more about thermal conductivity in the sections below.
Heat transfer through different cross sections
Heat transfer also depends on the shape of the cross section. For a cylinder its different, for sphere its different and for a cuboid is different.
The formula for heat transfer for different shapes are given below-
Rectangular slab-
The heat transfer through a rectangular slab takes place normal to the cross section. The formula for heat transfer for a rectangular slab is given below-
where,
k is the thermal conductivity of the material
A is the cross section area
Delta T is the temperature difference between the two ends of slab
Delta x is the length of heat transfer
Sphere-
The formula for heat transfer through spherical shell is given below-
where,
a and b are the radii of outer and inner sphere respectively
Ta is the temperature at the surface of sphere with radius a
Tb is the temperature at the surface of sphere with radius b
Cylindrical shell-
The cylindrical shell, comprising two cylinders with an inner radius ( b ) and an outer radius ( a ), follows a specific formula for heat transfer. The formula is expressed as , where ( Q ) represents the heat transfer rate.
where,
a is the radius of outer cylinder
b is the radius of inner cylinder
Ta is the temperature of surface of outer cylinder
Tb is the temperature of surface of inner cylinder
This article discusses about steam table of water. Before studying about steam table of water, we will first understand the meaning of steam table, steam and its properties.
As water has liquid form, its gaseous form is called as steam. When we heat water enough to a temperature of 100 degrees celsius, then the liquid temperature starts converting to gas or steam. Let us discuss about steam and steam tables further in this article.
What is steam?
When water is heated to a certain temperature, it starts getting converted to a different phase. The liquid form of water gets converted to gaseous phase called as steam.
The conversion starts taking place at saturation temperature where both the phases of water co-exist with each other. Slight increase in temperature results in steam formation and slight decrease in temperature results in formation of liquid water.
Types of steam
Usually steam contains particles of liquid particles, but at certain temperatures the liquid particles also evaporate to become steam. This gives rise to a new type of steam.
Let us discuss abut different types of steam in the section given below. The types of steam are-
Wet steam– As discussed above, steam contains particles of liquid water. The resulting steam and water mixture is called as wet steam.
Saturated steam– The steam existing at saturation temperature is called as saturated steam. At this temperature the phases of water/steam co exist with each other. Any increase or decrease in temperature results in superheated steam or wet steam respectively. In this state, the vapour-liquid equilibrium is established.
Superheated steam– After heating the steam beyond the saturation temperature, the resulting steam we get is called as superheated steam .This steam is pure steam and no liquid particles are present in superheated steam.
Uses of steam
The steam can be used in many industrial applications. These applications are mentioned below.
Uses of steam are-
Agricultural uses– In agriculture, a soil sterilizing method is used to sterilize the soil. This is done with the help of steam in open fields or green houses.
Atomization– Atomization of certain fuels used in burners is done with help of steam. Here the steam is used to separate the fuel mechanically.
Chemical uses– The chemical industry uses steam for humidifying, atomization, cleaning, sterilization etc purposes.
Mechanical uses– The steam engines use steam for running locomotives such as steam train. The mechanical energy is produced using the thermal energy produced while making the steam.
Concrete treatment– The curing of concrete is done with the help of steam. It improves the mechanical properties of concrete. It accelerates the compressive strength of concrete.
Cleaning– With the help of soot blowers, the team can be used for cleaning purposes. In boilers, steam is used to clean the boiler surface.
Sterilization– In various industries, the steam is used to sterilize the bottles so that any contaminants present can be cleaned and removed from the surface.
Electricity generation– The use of turbines in electricity generation is known to us. The freshly prepared steam is injected to the blades of turbine. These blades start rotating with the help of which the electricity is generated.
What is sub cooled water?
The term sub cool means that the liquid substance is existing below its normal boiling temperature. For water it is generally below 373 K or 100 degree celsius.
Below section provides a clear insight on steam table of sub cooled water. Subcooled water is used in expansion valve and compression safety.
Steam table for sub cooled water
Below given is the steam table for sub cooled water. The temperature and pressure discussed in this article are under certain range only. In actual the steam tables exist for a wide variety of values of pressure and temperatures.
Image: Table for Sub cooled water
What is saturated water?
The term saturation means that water is in a equilibrium state. The equilibrium occurs between the gaseous phase, that is, steam and the liquid state, that is, water.
Any increase in temperature will convert the vapour-liquid mixture to pure vapour and any decrease in temperature will convert the vapour-liquid mixture into liquid. It can be said that saturated state is a transition state of any liquid to gas or gas to liquid. The region under the saturation line comes under saturated region where liquid phase and vapour phase co exist and are in equilibrium with each other.
Steam table for saturated water
The steam table for saturated water is given in the table below. The steam table exists for a wider range of pressure and temperature values, here only a limited range is discussed.
Image: Steam table for Saturated water
What is compressed water?
Compressed water and sub cooled water are same in nature. Compressed fluid means it is under a mechanical or thermodynamic condition that forces it to be below saturation conditions. The region situated at left hand side of the saturation line is called as the sub cooled region. The dryness fraction in this region is 0.
What is superheated water?
Superheated means that the substance is heated above its saturation temperature. A liquid in such a state will start vaporising completely leaving behind no liquid particles.
The enthalpy of superheated water is much higher than that of sub cooled water. In a Mollier diagram, the region situated at right hand side of the saturation line is called as the superheated region. The dryness fraction of the substance is 1 in this region.
Steam table for superheated water
Superheated water is also called as superheated steam. This steam has no liquid water particles in it. The steam table for compressed water also exists for a wide range of temperature and pressure values, here only a limited range is being discussed.
Image: Steam table for compressed water
Mollier diagram
A Mollier diagram is a graphical representation of various thermodynamic properties of steam/air such as temperature, pressure, enthalpy and moisture content.
The Mollier diagram is used by design engineers while designing a power plant, the data is used for checking properties of the air at different temperature and pressure values. Mollier diagram is a very convenient design tool for thermal engineers.
This article discusses about master cylinder types, places where it is used and its working mechanism. The braking force applied by the driver is very less as compared to the actual force needed to stop the vehicle.
A master cylinder amplifies this braking force and is used to convert a mechanical force into hydraulic force. The hydraulic force is then again used for performing mechanical activities such as lifting weights or braking a car.
A master cylinder is a device used to convert a mechanical force to hydraulic force. This cylinder then controls the slave cylinders attached to the other end of the braking system.
A master cylinder is usually used in automotive industry mainly used to apply hydraulic pressure. These cylinders are commonly used in braking systems in automobiles. It is a very important machine component.
A master cylinder is used in hydraulic braking systems of automobiles. The need of using a hydraulic brake over a mechanical brake arises due to many reasons. They are-
Due to very high speed of vehicles, the braking force needed to stop the automobiles within a specified distance is much higher. Here the mechanical brakes fail, only hydraulic brakes can provide such a high braking force with utmost safety.
The front wheels require more braking force as the mass shift towards the front side of the vehicle during braking. This distribution of force can be done with the use of a master cylinder.
A driver typically applies a braking force in the range of 50-70 N. This is not enough for stopping the vehicle. A master cylinder multiplies this force which helps in stopping the vehicle.
Master cylinder acts as a converter that is it converts mechanical force applied on the brake pedal to hydraulic force which then is used for stopping the vehicle.
The use of master cylinder decreases the risk of failure as it creates independent braking system of front and rear wheels. This way the design is safer in comparison to conventional braking system.
Master cylinder types
Master cylinder can be classified into two types. The classification of master cylinder is done on the basis of number of cylinders used in the braking circuit of the braking system.
The following are the types of master cylinder-
Single circuit master cylinder– As the name suggests it consists of only one cylinder. For example a medical syringe. It uses only one cylinder for braking system. Such type of master cylinder circuit is used in light weighted vehicles such as two wheeler and small four wheeler cars. This type of circuit master cylinder distributes equal amount of braking force to all the wheels as it contains only one cylinder.
Tandem or dual circuit master cylinder– In the name it suggests that there are more than one circuits of master cylinders which are used for braking systems. Tandem circuit can be used where independent braking system is required for front and rear wheels. It is used in almost all cars because of its higher efficiency. This is also a safer design for vehicle braking system.
Master cylinder parts
A single circuit master cylinder consists of many parts. We will study about them in the description given below-
Reservoir
The reservoir stores the braking fluid. It is the hydraulic fluid used in braking system. Reservoir is generally made up of plastic.
Cylinder
This acts as a housing for piston. Inside the cylinder, movement of piston takes place. The material used for making cylinder is cast iron and aluminium. The cylinder is connected to reservoir through its inlet valve and to braking lines with the help of outlet valves.
Piston
The piston is the main part which exerts force on the braking fluid. As the brake pedal moves, the piston performs reciprocating motion due to which the hydraulic force is generated. This force is then converted to mechanical force.
Returning spring
It is commonly known fact that potential energy is stored inside a spring when it is deformed from its original shape. This potential energy helps the spring to come back to its original shape. In master cylinder also, returning spring is used for the braking pedal and piston to come to its original position.
Valve
Valve is the outlet portion through which the braking line is attached. The braking fluid is compressed and passes further to caliper through this valve.
Working of a single circuit master cylinder
We shall study the working of single circuit master cylinder in brief. When the brakes are not applied, the the braking fluid does not enter the braking lines.
The braking fluid enters the compression chamber as soon as the brakes are applied. This fluid is compressed due to movement of piston. The braking fluid after attaining a certain compressed pressure, is released to the braking lines due to which the brakes are applied to stop the vehicle.
Working of a tandem circuit master cylinder
The working of both tandem circuit master cylinder and single circuit master cylinder is majorly similar. The only difference between both of them is that in tandem circuit, more than one cylinder is used for braking circuit.
In tandem circuit, after the actuation of primary circuit the secondary circuit is actuated. The braking pressure from first circuit is transferred to the second circuit. This way tandem circuit master cylinder applies braking force from more than one cylinder. It is a safer design for braking systems in vehicles.
Applications of single circuit master cylinder
As the name suggests only one single cylinder is used for braking application in single circuit master cylinder. It is used for light weight vehicles.
The applications of a single circuit master cylinder are-
It is used in braking systems of two wheelers like Bajaj, TVS and Apache etc.
It is also used in braking systems of various e-rickshaws which are light in weight.
Applications of tandem circuit master cylinder
Tandem circuit master cylinder uses more than one cylinder for braking system.
The applications of a tandem circuit master cylinder are-
It is commonly used in all kinds of four wheeler automobiles which are equipped with hydraulic braking systems.
Used in heavy duty vehicles because it provides a safer braking application than single circuit master cylinder.
The positive displacement pump types are can in very little amount of suction forces and in high pressure the positive displacement pump types can expand. Other name constant volume pumps for positive displacement pump types.
Positive displacement pump can be divided in three sections. They are,
In the reciprocating displacement pump a part named reciprocating is present and with the help of pump water is lifted. In reciprocating pump the components are attached in it name are valves, exit valve and inlet valve. When the liquid is suction into the pump that time the inlet valve stays open but the exit valve remain close in the other way when the liquid is discharge that time the exit valve is open but the inlet valve remain close.
The reciprocating positive displacement pumps contain one simple or more than one (Quad) cylinder. Most of reciprocating positive displacement pumps number of contains cylinder is double or triple.
The power can be generated manually which is driven by air or steam or by engine that can be driven by belt.
With this reciprocating pump displacement pump heavy viscous liquid such as oil, concrete can lifted to desired place. Where low rate of flow is needed for the high resistance fluid there also this reciprocating pumps are used.
In reciprocating pump the increasing vacuum is present in the end portion of the suction and decreasing vacuum is present in the end portion of the delivery. When the vacuum present in the pump start to expand, fluid start to moves inside of the vacuum in the same way when the vacuum present in the pump start to reduce, fluid start to discharge.
The working principle of the reciprocating pump then we can noticed that when plunger is move toward the direction of right then amount of pump vacuum is increases inside and in this condition fluid is suck . Now when plunger is move toward the direction of left then present fluid inside the pump is pressurized and delivery valve is open at that time and inside fluid is flow out from the vacuum.
Reciprocating valve classified in purpose of working of piston in two categorized. They are,
Single acting of the reciprocating pump:
In this type of pump only one direction motion is act. Means if suction is happening inside the pump then discharge and piston act in other motion of direction for this reason it is called single acting reciprocating pump.
Double acting of the reciprocating pump:
In this type of pump both direction motion is act at a time. Means if suction is happening inside the pump then discharge and piston can act in same motion of direction for this reason it is called double acting reciprocating pump.
Rotary pump:
One of the most used positive displacement pump type is rotary positive displacement pump. Inside the rotary positive displacement pump a rotary is present to lifted liquid by the help of the pump. Inside the rotary the liquid is moves in rotation motion and the liquid can go through from storage tank to delivery pipe.
The linear pump is one of the most used positive displacement pump. By the help of the tubing the waves are moved of the contraction into liquid. Individual reciprocating parts are continuously compressed in the flexible tubing’s straight parts for moves liquid.The liquid is moves in a direction of linear or straight. In any stationary location the linear pump can be situated. This pump cannot be used in crowded area. The main problem with this linear positive displacement pump is volume and noisy.
The most used linear pumps are chain pump and rope pump. The application of this pump is in medical, environment, decentralized wastewater treatment, pond aeration and many others.
The non positive displacement pump can be defined as the discharge flow rate for a liquid substance in the pump cab be changed depend upon the amount of pressure is applied in the outlet of the pump.
Non positive displacement types are categorized in some sections their names are given below,
In the gear positive displacement pump gear is present to moves the liquid substance and liquid is lifted by pump. By the gears of the gear positive displacement pump fluid pressure can be increases.
In this pump two gears are used to generate the process. One gear is driver which is also known as driver and another one is driven which is known as idler gear.
The liquid substance is goes between the gears the fluid is trapped. The gears when start to move the liquid substance is moves in a motion inside the gear from suction to end section of discharge suction. The pressure is increases and liquid substance is transform to the particular specified location.
The power gear connects to the shaft with the help of electric motor. The motor is started to rotate and power in generated and by the shaft power is supplied. After that when shaft starts to rotate the motion helps to rotating the idler gear. The power gear and idler gear rotate in the opposite direction to each other.
Vacuum is generating when the both gear start to rotate at the end section of the section side and by the suction valve fluid is suck.
Peristaltic hose pumps:
The peristaltic hose pump cannot use in the domestic purpose. It is so much noisy. The equipment inside the peristaltic hose positive displacement pump is rollers, rotor and flexible tube. This is also used in agriculture, water treatment and medicals.
In this type of positive displacement pump the helical rotor is placed and pump is used to lift the water.
The components are carried by the helical pumps are rotor, rubber stator. The helical rotor is rotate inside the helical stator and water is pumped by the cavities.
Piston pumps:
In the piston pump the piston which is placed inside the piston is moves and sucks the liquid which is present in pressurized situation. The piston in the piston positive displacement pumpproduce vacuum inside the cylinder and liquid is suck into the cylinder by the piston in the stroke of the 1st. After the 1st stroke while the 2nd stroke is acted outlet valve open and pressurized liquid is present in the cylinder that time suction valve remain close while piston is moves inside.
Hand pump and bicycle pump are the common examples of the piston positive displacement pump. Another type of the pump is double acting pump.
Diaphragm pumps:
The diaphragm is used inside the diaphragm positive displacement pump and pump is used to lifting the liquid.Expanding of the membrane of the diaphragm increases the volume of the cylinder and liquid is sucks in another process decreasing of the membrane of the diaphragm decreases the volume of the cylinder and liquid is drain.
It can be explained as the pump which converts the energy mechanical to hydraulic. In a day’s variable positive displacement pumps are used in a wide range in the industrial areas.
The variable positive displacement pumps are classified in two sections. They are,
From the Hook’s Law we get a clear concept about the topic of “How to find the stress strain curve”. In this article we will briefly summarize in below the topic of how to find stress strain curve.
If in a testing object the load is applying from the external side and deformation of the testing object is measuring then we find stress strain graph very easily. From the tensile testing we were getting how to find stress stain curve.By the help of this the material’s property can estimate such as,
By the help of the yield strength we can recognize whether a testing object is malleable or stubborn. In the yield strength point a testing object is cease into the elastic and after that it transforms into plastic.
With the help of yield we can decide which material is suitable for the particular testing object.
Modulus of Elasticity:
If we go through the Hook’s law get the clear concept of the Modulus of Elasticity. The other name for the Modulus of the elasticity is Young’s Modulus.
The Modulus of Elasticity states that if load is applied in a testing object within the limit of elastic then the stress and strain relation is directly proportional to each other.
Mathematically it can be written as,
σ = ∈
σ = E x ∈
Where,
E = Constant of the proportionality and it is the Modulus of the elasticity.
In the field of both engineering and the manufacturing the ductility is uses to define the suitability of the material for the operations in the field of manufacturing and also to understand the capacity for the materials absorb.
One of the most important mechanical term is uses in the engineering field is ductility. With this criterion we can draw amenability of a material. Ductility can be defined as the when a testing object is sustain deformation of plastic before the failure goes under the tensile stress.
Ductility is good charectertics for the metal but all metals are not ductile some are brittle in character. Polymer is also ductile material. The metals which are consider as a good ductility property is present such as copper, gold, tungsten.
Elongation:
Elongation of a material can be defines as the increases the length of the gauge is measured after the testing object’s fracture within the length of the gauge which is expressed its original length of the gauge in percentage.
Mathematically it can be written as,
(final length of the material – original length of the material) / original length of the material x 100
Stress strain curve ductility:
If a ductile metal testing object is situated in the compression testing machine and the external axial load is applied then the total amount of the elongation over the length of the gauge is measured in each and every increment of the axial load and process is continued until the failure of the metal testing object is takes place.
In the ductile metal testing object the area of cross sectional is known as stress and the length is known as strain. When the graph is plotted the stress is placed along the y axis and the strain is plotted along the x axis. The diagram is known as stress strain curve ductility.
In the stress strain graph various points are appear during the process. They are,
Proportional limit can be defined as the region of the stress strain curve which obeys the law of the Hook’s. In this limit the strain and stress is directly proportional to each other.In the picture AB represent proportional limit.
Elastic limit:
The elastic limit for the ductile material can be defined as if the axial load is removed from the testing object then it is the point limit from where the object cannot be back to its original form or in another word it also can be explain as if the ultimate maximum stress is developed in that way into the ductile testing object where residual deformation is no longer if axial load is permanently removed from it.In the picture BC represent elastic limit.
Yield point:
Yield point can be explained as the point of the region where the ductile metals start to deform into plastic.In the picture CD represent yield point.
The yield point in categorized in two sections,
Upper yield point
Lower yield point
Ultimate strength:
Ultimate strength can be defined as the ductile metal’s faces the maximum stress beyond the failure. The failure is appear beyond this region point.In the picture DE represent ultimate strength.
Breaking point:
At which point the failure is facing is called the breaking point. In the picture E represent breaking point.
How to find ductility from stress strain curve?
Ductile can be explain as a material is absorb the total amount of the tensile stress before taking the enduring deformation. This damage is mainly often in the decreasing the amount of area of cross sectional without any fracturing.
The ductility is measure from the stress strain curve in two methods,
The length of the gauge is increases of a particular material when tensile force acted on it is divided by the length of original. Percentage of the material’s original length is elongation.
Amount of the area of the cross sectional is decreasing:
It can be expressed in mathematically is,
Amount of the area of the cross sectional is decreasing (%) = 100 * (A_0 – A_f)/A_o
Where,
A_o = Original area of the cross section
A_f = Final area of the cross section
In this testing method temperature plays a vital role.
Both the formula is expressed in percentage and denoted that the material’s ductility is performed in correct way.
Stress strain curve yield strength:
By the help of the yield strength curve we easily can understand which application is more suitable for the testing of the material. Each and every material is facing the transition in another stage of the point elasticity to plasticity and ultimate facing the breakage.
At which point the metal is start itself changing it elastic to plastic is known as Yield point.
In ductile material the value of yield strength is more than the plastic.
How to find yield strength from stress strain curve?
If we go through the stress strain graph then we can observe there are lots point which are used to indicate from where the material start to transform itself from elastic to plastic. From them yield strength is one of them. When the graph is plotted the yield strength is denoted in the stress axis means to the y axis of the graph.
In the graph along the y axis the elongation is plotted and in the stress axis means in the x axis the stress is plotted. A line which should be straight is drawn slope of the starting point to the stress strain graph.
In this time the new line is intersected by the stress strain curve which is plotted along the y axis. The value of the stress expressed in pounds per square inch. The plotting method is done by the for the purpose of subtracting the amount of elastic strain from the total amount of the strain where permanent offset is present to indicate the remainder.
Stress strain curve elongation can be defined as in a tensile testing machine a testing object is placed and axial load is applied gradually at that time where the load is maximum.
How to find elongation from stress strain curve?
In the tensile stress testing method the testing object is facing the elongation that time the width and thickness is decreases in the area of the cross section.
When we observe the elongation on the stress strain graph applied axial load is drunken in the peak point as a result the balancing is became difficult for work hardening and deformation is appear in the testing object.
When the axial load is in peak point the cross sectional area is reduced and curve of the stress strain graph is compressed. Diffuse neck is form in the middle part of the testing object.
Elongation from stress strain graph Image Credit – Wikipedia Commons
Stress strain curve modulus of elasticity:
In the mechanical field the modulus of elasticity is very important factor to understand the property of material is suitable for the testing application. This not depends of the size, weight of the testing object.
In tensile testing machine the axial load is applied into the specimen the deformation is happened due to heavy load. The initial stage of the stress strain curve deformation is known as the modulus of elasticity.
How to find modulus of elasticity from stress strain curve?
In low strain the deformation of elastic is takes place. When we see the graph of stress strain the behaviour is very clear visible that strain is about less than 1 percent in a region of straight line. Its mean the elastic limit for the graph is 1 percent.
We know the formula of the Modulus of elasticity is,
E = \frac{\sigma}{\varepsilon}
So, at the beginning we need to identify the region in the strain stress curve where the deformation of elastic is happened. We already know that strain is about less than 1 means in other we can write the value of strain is 0.01. The stress for the stress strain curve is 250 Newton per square mm. Now putting the values in the formula easily can determine the value of modulus of elasticity.
Stress strain curve yield point:
In the stress strain curve the yield point particularly indicate the point where elasticity ended and plasticity is begins.
When the applied axial load the deformation is took place into the testing object but if load is removed from the yield point of testing object then the testing object can go back to its original shape.
How to find tangent modulus from stress strain curve?
At the starting of the process a straight line is drawn from the strain stress graph’s origin and need to find the slope present in the origin.
From the portion of the liner select two points and find the difference between their stress and strain point in the graph.
How to find yield point in stress strain curve?
At first we need to find the point 0.2 % in the horizontally means in the strain axis when we mark the point then a line is draw parallels to the region of the elastic in the stress strain graph and finally 0.2 % need to point which denoted yield stress and draw a line where it is intersect in the stress strain curve.
How to find ultimate tensile strength from stress strain curve?
Where the axial load is failure that should by divided by the initial cross sectional area.
Below of the yield point the testing objects tends to change elasticity to plasticity for the deformation.
Broken testing object measured by the percentage elongation.
Calculate the reduction of the area in percentage.
Stress strain curve area under stress:
Another term for the area under stress in the stress strain graph is toughness.
In the strain stress curve the amount of energy absorb in per unit volume ability of the material before failure is known as stress strain curve area under stress.
In the tensile testing machine the testing object is situated on it and axial load is gradually applied to the object that time stress strain graph is produce and underneath the curve stress – strain the area is easily can be measure.
Quick Points:
How to find area under stress strain curve?
In the tensile testing machine the testing object is situated on it and axial load is gradually applied to the object that time stress strain graph is produce and underneath the curve stress – strain the area is easily can be measure.
What is a Stress-Strain Curve?
A stress-strain curve is a graphical representation that shows the relationship between stress and strain for a material. It provides valuable information about the mechanical properties of a material and how it behaves under applied loads.
What is Stress and Strain?
Stress refers to the internal resistance or force within a material that arises when an external load is applied. Strain, on the other hand, is the deformation or change in shape experienced by a material in response to stress.
What is the significance of the Stress-Strain Curve?
The stress-strain curve helps engineers and scientists understand the behavior of materials under different loading conditions. It provides information about various mechanical properties such as elasticity, plastic deformation, yield strength, and ultimate tensile strength.
What is Elastic Deformation?
Elastic deformation is the temporary distortion of a material when stress is applied. In this stage, the material is able to return to its original shape once the stress is removed. It follows Hooke’s Law, which states that stress is directly proportional to strain within the elastic limit.
What is Plastic Deformation?
Plastic deformation occurs when a material is subjected to stress beyond its elastic limit. The material undergoes permanent changes in its shape and doesn’t return to its original form after the stress is removed. This is often observed in ductile materials.
What are the key points on a Stress-Strain Curve?
A stress-strain curve typically shows a linear proportionality between stress and strain in the elastic region, followed by a yield point where plastic deformation begins. There is a subsequent strain hardening region, leading to the ultimate tensile strength, and finally, fracture or failure occurs.
What is the Yield Point?
The yield point is the stress value at which a material begins to exhibit plastic deformation. It marks the transition from elastic to plastic behavior, where a significant change in strain occurs with little change in stress.
What is the Ultimate Tensile Strength?
The ultimate tensile strength is the maximum stress a material can withstand before failure. It represents the peak point on the stress-strain curve and indicates the material’s ability to withstand tensile forces.
What is the Modulus of Elasticity?
The modulus of elasticity, also known as Young’s modulus, is a measure of a material’s stiffness. It quantifies the relationship between stress and strain within the elastic limit and can be used to determine the material’s ability to resist deformation.
What is high head pressure? This question is answered in simple words as below,
Head pressure is the output pressure from the compressor in any system. Extreme high head pressure can cause some problems in the system.
The compressor is necessary equipment in the heat pump, refrigeration and air conditioning system. The high head pressure in this system can cause the failure of the compressor and its components in a period of time.
It ultimately affects the system’s performance, which reduces the cooling capacity or heating capacity.
For proper functioning of the system, all pressures like head pressure and the suction pressure should be designed well as per load calculation.
In earlier days, The problem of the high head pressure was checked by inspecting the condenser fan and condenser coil.
Nowadays, The problem is observed by checking restrictions in the refrigerant lines and the refrigerant charge condition.
High head suction pressure
High suction pressure is a common problem in the cooling systems
It can cause due to improper functioning of the compressor. If the compressor is not delivering sufficient refrigerant to the system, the suction pressure will increase accordingly.
One can understand the high head suction pressure with a better study of the refrigeration cycle. There are two types of pressures significant in the HVAC systems.
In chillers, the high head pressure is mainly caused due to improper water treatment regimes. The clogging of the coils can cause high head pressure in the chiller.
The condenser water loop is open to the atmosphere in the chiller. The dirty particles are concentrated with the working fluid and periodically clog the system. The clogging of the system affect the heat transfer between the surface and the working fluid. Ultimately, it facilitates heat transfer through the system.
The high head pressure is deteriorating the performance of the chiller. The condenser outside surface is exposed to an open environment in an air-cooled chiller. The dust particles from the atmosphere will stick on the compressor’s effective surface. It will insulate the surface partially and reduce heat transfer.
To avoid such abnormal conditions, one should clean the condenser coil periodically in a proper manner. The cleaning of the condenser can be done with light brushes.
What causes high head pressure in a refrigeration system?
High head pressure is generated because of the following reasons
It can cause rusting on the system’s components and the clogging of the elements like condenser coil, check valve, thermal expansion valve etc.
There are many others reasons like improper charging of the refrigerant, unsuitable operating condition, Improper cooling of the condenser.
Causes of high head pressure low suction pressure
For any HVAC system, The two pressures are to be maintained.
Excessive refrigerant, higher outdoor temperature, improper cleaning of coils are the main reason for both pressures.
Suppose the evaporator is not getting sufficient refrigerant from the compressor. It will not be able to provide proper cooling in the system. This problem can cause low suction pressure in the system. The defective metering device is also the probable reason for low suction pressure.
The outside temperature can also affect the system’s performance. The higher outside temperature can reduce the heat rejection from the system. Ultimately, it raises head pressure in the system. It is desirable to maintain the condensing temperature of the system. The difference of Temp. between the condensing pressure and the outside temperature should be high.
High head pressure in heat mode
The high head pressure in any device deteriorates the performance.
It is difficult to find the high head pressure in the heat pump during heat mode.
If we take a reading in the heating mode, we make sure that the larger diameter pipe is the delivery pressure and the smaller diameter pipe is the liquid pressure.
Any heat pump needs to charge it as a specified limit. It is difficult for any technician to charge heat pump during heating mode. The calculation for charging refrigerant is critical in heating mode. The overcharging of the refrigerant leads to many unwanted problems in the system.
One of the primary cause of head pressure to be high is the overcharging of the refrigerant.
High head pressure on heat pump
The high head pressure in any device deteriorates the performance.
It is difficult to find the fault of high head pressure in the heat pump during heat mode. The system should be adequately designed with specified coil sizes.
If the coil size is not as per design criteria, it is the main reason for the high head pressure in the system.
The airflow through the system should be enough as per requirement. It should be monitored periodically. It can be measured by finding static pressure in the system.
Insufficient airflow or restricted air can cause the problem of inefficient working. Cleaning of the coils is necessary for any systems discussed above. The filters should be cleaned well and replaced if they malfunction.
There are three service ports to measure the pressure. Take the reading of the pressure from all three ports in the system.
If we take a reading in the heating mode, we make sure that the larger diameter pipe is the delivery pressure and the smaller diameter pipe is the liquid pressure.
The pressure will fall below the limit if the flow is restricted from the inside coils. It Will reflect us by measuring pressure between the delivery line and the liquid portion line.
Any heat pump needs to charge it as a specified limit. It is difficult for any technician to assess the heat pump during heating mode. The calculation for charging refrigerant is critical in heating mode. The overcharging of the refrigerant leads to many unwanted problems in the system.
One of the primary cause of head pressure to be high is the overcharging of the refrigerant.
, where ( Q ) represents the heat transfer rate.
denotes the strain at which failure occurs.
represents the stress in the material.
