Mechanical

In this article the topic of “Quasi static process example” will be discuss with quasi static process example related details. When the sliding friction force is work on that time it became irreversible.

5+ Quasi Static Process Example is listed below,

• In the daytime the expansion of railway tracks
• Charging of Smartphone
• Growing of a tree
• Growing of hair
• Growing of nail

In the daytime the expansion of railway tracks:-

In the thermodynamic the Quasi Static Process is defined as very slow process. Quasi Static Process appear infinitesimally slow.In the Quasi Static Process all the state stays in equilibrium. The expansion of railway tracks in the morning is one of the examples of Quasi Static Process. During the morning time the metal steel, cast iron  with which the railway track made of it absorb the heat and expansion is happened.

The expansion of railway tracks are happened in very slow process to avoid accident a certain amount of gap is present in between two railway tracks.

Charging of Smartphone:-

Another example of the Quasi Static Process is charging of a Smartphone. During the charging of the Smartphone it takes a long time.  The Smartphone need to charge when is needed. But we should not fall below twenty percent or more than the twenty percent and fully avoid discharging the battery of the Smartphone if not calibration is needed. Should to unplug the Smartphone when the charge stays between eighty percent to hundred percent.

Some process to make faster of the charging of Smartphone:-

1. Avoid wireless charging
2. A wall socket should be use
3. Turn the phone off
4. Should to carry a power bank
5. High quality cable should be use
6. Enable airplane mode
7. Case of the phone need to remove
8. Enable charge mode

Growing of a tree:-

Growing of a tree is another example of the Quasi Static Process. Growing a tree takes a very long time and go through some stages of the life cycle. The states of the a life cycle are,

• Sprout (Germination)
• Seedling
• Sapling
• Mature Tree

Sprout (Germination):-

When a seed could find appropriate condition the seed need to stable and secure its life itself. At the first of the state the roots are breaks from the seed. Anchoring it and takes water for grow of the tree. In the next step of the germination is takes place that it could emergence of the embryonic shoot.

After that the shoot grows up and pushes up by the soil.

Seedling:-

The shoot is became a seed when it come above of the ground. In this stage the tree faces most risk because in this particular state the tree can faces dieses and also facing damage such as deer grazing. The trees which have long life span for them sapling became longer such as oaks, yews and in other way the trees which have short life span for them sapling became shorter such as wild cherry, silver birch.

Sapling:-

A tree is called a sapling when it became near about 3 ft tall. The length of a sapling is totally depending on the family of the tree. Some characterises is carried by the sapling they are listed below,

• Flexible trunks
• Smoother bark comparative to the mature trees
• An inability to make flowers
• An inability to make fruits

Mature Tree:-

A tree is called mature when it begins to make flowers and fruits. In the stage of producing flowers and fruits the tree stays at most productive state. Depend on the species the tree make flowers and fruits.

Growing of hair:-

Growing of hair is another example of the Quasi Static Process. In this process hair takes time to grow and growing of hair is slow process. just like quasi static process.

Growing of nail:-

Growing of nails is another example of the Quasi Static Process. In this process hair takes time to grow.

Frequent Asked Question:-

Question: – Describe about the thermodynamic processes.

Solution: – A thermodynamic ring is a sequence of several processes. The thermodynamic process is start and ends at the very same thermodynamic state.

The thermodynamic processes are listed below,

• Isothermal process
• Isobaric process
• Isochoric process
• Adiabatic process

Isothermal process:-

When the system is undergoes to change from one state to the other state, but that time system does not change its temperature. The temperature of the system remains constant.

Thus, in our example of hot water in a thermos flask, if we remove a certain quantity of water from the flask but keep its temperature constant at 50 degree Celsius, the process is said to be an isothermal process.

Isobaric process:-

When the system is undergoes to change from one state to the other state, but that time system does not change its pressure. The pressure of the system remains constant. The process is said to be an isobaric process.

Isochoric process:-

When the system is undergoes to change from one state to the other state, but that time system does not change its volume. The volume of the system remains constant. The process is said to be an isochoric process.

The heating of gas in a closed cylinder is an example of an isochoric process.

Adiabatic process:-

The process during which the heat content of the system or a certain quantity of matter remains constant is called an adiabatic process.

Thus, in the adiabatic process, no heat transfer between the system and its surroundings occurs.

Question: – Describe about the workdone by thermodynamic processes.

Solution: – The workdone by thermodynamic processes is done by foue proceeses, they are listed below,

• Constant pressure or Isobaric process
• Constant volume or Isochoric process
• Constant temperature or Isothermal process
• Polytropic process

Constant pressure or Isobaric process:-

Constant volume or Isochoric process:-

Constant temperature or Isothermal process:-

Where, Pressure express as p differ with volume express as v.

PV = P₁P₂ = C

So, W_1-2 = P₁V₁ln(V₂/V₁)

Polytropic process:-

W_1-2 = (P₁V₁ – P₂V₂)/n-1

In this article the topic of “Crystal lattice examples” will be summarize. The term pattern of crystal lattice is created by the points. Crystal lattice is use to personate the place of repeating structural substance.

5+ Crystal Lattice Examples are listed below,

• Sodium chloride
• Snowflakes
• Sucrose
• Diamond
• Quartz

Sodium chloride:-

The sodium chloride is actually an ionic mixture. For make the compound of sodium chloride the chloride and sodium is mix together in 1:1 ratio. The common name of the sodium chloride is common salt or halite, table salt.

Chemical formula for the sodium chloride is NaCl.

Properties of the Sodium Chloride:-

1. Sodium Chloride can be easily soluble in the water. In some other liquids the sodium chloride can be insoluble or partially soluble.
2. Sodium Chloride is white crystal.
3. Sodium Chloride is very good quality conductor because of the movements of the free ions.
4. Molar mass of the Sodium Chloride is 58.443 gram per mol.
5. Density of the Sodium Chloride is 2.17 gram per cubic centimetre.
6. Boiling point of the Sodium Chloride is 1465 degree centigrade.
7. Melting point of the Sodium Chloride is 800.7 degree centigrade.
8. Heat capacity of the Sodium Chloride is 50.7 joule per Kelvin mol.
9. Solubility in water of the Sodium Chloride is 360 gram per 1000 gram pure water at the temperature of 25 degree centigrade.
10. Solubility in ammonia of the Sodium Chloride is 21.5 gram per litre.

Preparation of the Sodium Chloride:-

When chloride and sodium is comes together in the ratio of 1:1 at that time the solid matter is made which is known as Sodium Chloride.

2Na(s) + Cl₂(g) → 2NaCl(s)

Snowflakes:-

Snowflake is single ice crystal.  The snowflakes have sufficient size to amalgamate to each other.

Types of the snowflakes:-

Snowflakes can be divided in eight broader groups,

1. Plane crystal
2. Column crystal
3. Germs of ice crystal
4. Combination of plane and column crystal
5. Rimed crystal
6. Irregular crystal
7. Aggregation of snow crystal
8. Other solid precipitation crystal

Sucrose:-

Another term for the sucrose is table sugar or sugar. The sucrose molecules have 11 oxygen atoms, 22 hydrogen atoms and 12 carbon atoms. 

Properties of the Sucrose:-

1. Sucrose can be easily soluble in the water. In some other liquids the sucrose can be insoluble or partially soluble.
2. Sucrose is white crystal.
3. Sucrose is odour less.
4. The taste of the sucrose is sweet.
5. Molar mass of the sucrose is 342.30 gram per mol.
6. Density of the sucrose is 1.587 gram per cubic centimetre.
7. Melting point of the sucrose is 186 degree centigrade.

Diamond:-

Diamond is a rare, naturally occurring mineral composed of carbon. Each carbon atom in a diamond is surrounded by four other carbon atoms and connected to them by strong covalent bonds – the strongest type of chemical bond. This simple, uniform, tightly-bonded arrangement yields one of the most durable and versatile substances known.

It is also chemically resistant and has the highest thermal conductivity of any natural material. Diamond is the hardest known natural substance.

Properties of the Diamond:-

1. Density of the diamond is 3.5 to 3.53 gram per cubic centimetre.
2. Melting point of the diamond is depending on the pressure.
3. Specific gravity of the diamond is 3.52±0.01.
4. An optical property of the diamond is isentropic.
5. Formula mass of the diamond is 12.01 gram per mol.
6. Colour of the diamond will be brown, gray, and yellow to colourless.

Quartz:-

In the Earth’s crust Quartz is one of the most common minerals. As a mineral name, quartz refers to a specific chemical compound having a specific crystalline form. t is found in all forms of rock: igneous, metamorphic and sedimentary. Quartz is physically and chemically resistant to weathering. When quartz-bearing rocks become weathered and eroded, the grains of resistant quartz are concentrated in the soil, in rivers, and on beaches. The white sands typically found in river beds and on beaches are usually composed mainly of quartz, with some white or pink feldspar as well.

Properties of the Quartz:-

1. Formula mass of the quartz is 60.083 gram per mol.
2. Melting point of the quartz is1670 degree centigrade to 1713 degree centigrade.
3. Quartz is brittle type.

Crystal lattice types:

The crystal lattice is classified in sever sections they are listed below,

• Triclinic system
• Tetragonal system
• Monoclinic system
• Hexagonal system
• Orthorhombic system
• Trigonal system
• Cubic system

The classification types of the crystal lattice is describe below,

Triclinic system:-

In the triclinic system the three axes are dangling at each other. In the system of the triclinic the length of the axes remains same. On the base of three dangling angles various types of crystal can make paired faces.

Examples:-

Examples of the triclinic system are listed below,

1. Amazonite
2. Labradorite
3. Kyanite
4. Rhodonote
5. Turquoise
6. Aventurine Feldspar

Tetragonal system:-

The tetragonal system is containing three axes. The main axis of the tetragonal system can be differing in length. The length of the axis can be longer or shorter. Other two axis of the tetragonal system stays in the same plane and the are will be at same length. Depend on the structure of the rectangular inner the shape of the tetragonal system crystal will be four sided prism, double and eight edgy pyramids, pyrite and trapezohedrons.

Monoclinic system:-

The monoclinic system is containing three axes. The two axes of the monoclinic system stay at right angle to each one and the third one axis is dangling. The three axes of the monoclinic system have different length.

The inner structure of the monoclinic system contain prism and basal pinacoids with the inclined end faces.

Examples:-

Examples of the monoclinic system are listed below,

1. Gypsum
2. Diopside
3. Howlite
4. Hiddenite
5. Vivianite
6. Petalite

Hexagonal system:-

The hexagonal system is containing three axes. Among the four axes the three axes are stays in the similar plane and the fourth one is stays in plane. The axes of the hexagonal system are intersecting to each other at the angle of sixty degree. In the hexagonal system the crystal shape will be based on the inner structure such as four sided pyramid, double sided pyramid, double pyramid,

Examples:-

Examples of the hexagonal system are listed below,

1. Apatite
2. Cancrinite
3. Beryl
4. Sugilite

Orthorhombic system:-

The systems of the orthorhombic have three axes. The axes of the orthorhombic system intersect at the right angles to every with other. The length of the axe will be different to each other. In the orthorhombic system the crystal shape will be based on the rhombic structure such as double pyramid, pyramid, pinacoids, and rhombic pyramid.

Examples:-

Examples of the orthorhombic system are listed below,

• Lolite
• Tanzanite
• Topaz
• Zoisite

Trigonal system:-

In the system of the trigonal the axis and angels are similar to hexagonal system. In the system of the trigonal have three sides and in the system of the hexagonal have six sides. In the trigonal system the crystal shape will be based on the inner structure such as rhombohedra, scalenohedral and three sided pyramid.

Examples:-

Examples of the trigonal system are listed below,

• Calcite
• Agate
• Ruby
• Tiger’s eyes
• Jasper
• Quartz

Cubic system:-

In the system of the cubic the three angles are intersect with the right angles. The are will be in same length. In the cubic system the crystal shape will be based on the inner structure such as cube, octahedron, hexaciscoherdron.

Examples:-

Examples of the cubic system are listed below,

1. Gold
2. Silver
3. Diamond
4. Garnet

In this article the term “Laminar flow in pipe” and laminar flow in pipe related several facts will be discussed. Streamline flow is another term for the laminar flow.

Laminar flow in pipe or stream line in pipe can be describe as in this way, when a fluid is flow inside a tube or pipe in a motion that time there is no breakdown is present between the layers. In the low velocity the fluid can flow very smoothly without any transverse mixing.

What is laminar flow in pipe?

Laminar flow in pipe can be characterized by highly ordered motion and smooth streamline. The laminar flow in pipe fluid is flow uniformly in both direction and velocity.

The laminar flow in a pipe can be deriving as,

1. If the range of the Reynolds number is 2000 and less than 2000 then this flow of fluid is known as laminar flow.
2. Mathematical analysis of the laminar flow is not complicated.
3. Velocity of the laminar flow is very low for this reason the flow of the fluid is fluid very smoothly without any transverse mixing.
4. Regular movement can be observe in the fluids which in laminar flow and flow in a motion.
5. Laminar flow in generally rare type of flow of fluid.
6. Average motion can observe in which side the fluid is flowing.
7. In the laminar flow the velocity profile is very less in the center section of the tube.
8. In the laminar flow the velocity profile is high in the wall of the tube.

Laminar flow in pipe formula:

With the help of Poiseuille’s equation we can understand the pressure drop of a flowing fluid is happened for the viscosity. The equation of Hegen Poiseuille’s is applicable for Newtonian fluid and incompressible fluid.

The equation of Hegen Poiseuille’s is not applicable for close entrance of the pipe. The equation of laminar flow is,

Where,

Δp = The amount of difference of pressure which is occur in the two end points of the pipe

μ = The dynamic viscosity of the flowing fluid in the pipe

 L = Length of the pipe

Q = Volumetric flow rate

R = Radius of the pipe

A = Cross sectional area of the pipe

The above equation is not appropriate for very short or very long pipe and also for low viscosity fluid. In very short or very long pipe and also for low viscosity fluid turbulent flow is causes, for that that time the equation of Hegen Poiseuille’s is not applicable. In that case we applied more useful equation for calculation such as Darcy – Weisbach equation.

The ratio between from length to radius of a tube is more than the one forty eighth of Reynolds number which is valid for the law of Hegen Poiseuille’s. When the tube is very short that time the law of Hegen Poiseuille’s can be result as high flow rate unphysical.

The flow of the fluid is restricted by the principle of Bernoulli’s under excepting restrictive condition just because of pressure is not can be less than zero in an flow of incompressible.

Δ p = 1/2ρ v^-2

Δ p = 1/2ρ(Q_max/π R²}²)

Laminar flow in pipe derivation:

The equation of laminar flow is,

Where in,

• The Pressure Gradient 
• The radius of the narrow tube
• Viscosity 
• Length of the arrow tube
• Resistance

The Pressure Gradient (\Delta P):-

The pressure differential between the two ends of the tube, defined by the fact that every fluid will always flow from the high pressure to the low-pressure area.

The flow rate is calculated by the 

Δ P = P₁ – P₂

The radius of the narrow tube:-

The flow of liquid direct changes with the radius to the power four.

Viscosity (η):-

The flow rate of the fluid is inversely proportional to the viscosity of the fluid.

Length of the arrow tube (L):-

The flow rate of the fluid is inversely proportional to the length of the narrow tube.

Resistance(R):-

The resistance is calculated by 8Ln/πr⁴ and hence the Poiseuille’s law is

Q = (Δ P) R

Heat transfer in pipe flow:

The equation of thermal energy convection-diffusion is given below,

The left-hand side equation is consider convective heat transfer, which transferred by the fluid’s motion. The radial velocity is zero, so the first term equation of the left-hand side can be avoided.

The right-hand side of the equation is representing the thermal diffusion. Since the flow is laminar, we can assume that the dimensionless Eckert number, which represents the ratio between a flow’s kinetic energy and its heat transfer driving force, is small enough to disregard viscous dissipation.

Therefore, the thermal energy equation can be supplemented with the velocity profile defined in the previous section.

A constant heat flux value condition implies that the temperature difference between the wall and the fluid is equal. However we already know that the temperature of the fluid is of non-constant value within the pipe. Therefore, we shall introduce a bulk mean temperature denoted by:

Assuming that the local temperature gradient and the bulk mean temperature gradient in the streamwise direction are equal and of constant value, integration of the aforementioned thermal energy transport equation results in the following formula for radial temperature distribution:

Where, a = k/ρc is the thermal diffusivity coefficient . The mean temperature gradient can be obtained by applying the desired volumetric flow rate Q and heat flux q to the heat conservation equation:

Qρc dT_m/dz = πDq

To satisfy the constant wall flux condition, the value of the wall temperature has been coupled with the bulk mean temperature gradient.

Laminar flow in pipe boundary conditions:

Laminar boundary layers are appear when a moving viscous fluid is comes in the touch with a surface which is state in solid and the boundary layer, a layers of rotational fluid forms in response to the action of no slip boundary and viscosity condition of the surface.

Reynolds number for laminar flow in pipe:

The values for the laminar flow for the particular determination of Reynolds number is depend on the pattern of the flow of the fluid through a pipe and geometry of the system through which fluid is flow.

The expression for the Reynolds number for laminar flow in pipe is given below,

Re = ρuD_H/μ = u D_H/ν = QD_H/νA

Where,

Re = Reynolds number

ρ = Fluid density of the pipe and unit is kilogram per cubic meter

u = The mean speed of the flowing fluid in the pipe and unit is meter per second

μ = The dynamic viscosity of the flowing fluid in the pipe and unit is kilogram per meter second

A = Cross sectional area of the pipe and unit is meter square

Q = Volumetric flow rate and unit is cubic meter per second

D_H = Hydraulic diameter of the pipe through which fluid is flowing and unit is meter

ν = The kinematic viscosity of the flowing fluid in the pipe and unit is meter square per second

The expression of ν is,

ν = μ/ρ

Nusselt number for laminar flow in pipe:

When internal laminar flow is fully developed in that case, Nusselt number for laminar flow in pipe can be express as,

N_u = hD_h/k_f

Where,

N_u = Nusselt number

h = Convective heat transfer coefficient

D_h = Hydraulic diameter of the pipe through which fluid is flowing

k_f = Thermal conductivity for flowing fluid in the pipe

Friction factor for laminar flow in pipe:

Friction factor for the laminar flow can be express as,

f_D = 64/Re

Where,

f_D = Friction factor

Re = Reynolds number

Where,

ν = The kinematic viscosity of the flowing fluid in the pipe and unit is meter square per second

μ = The dynamic viscosity of the flowing fluid in the pipe and unit is kilogram per meter second

ρ= Fluid density of the pipe and unit is kilogram per cubic meter

v = Mean flow velocity and unit is meters per second

D = Diameter of the pipe through which fluid is flowing and unit is meter

ν = μ/ρ

Fully developed laminar flow in pipe:

Fully developed flow is appearing when the viscous effects are happened for the shear stress by the fluid particles and tube wall create a fully developed velocity profile. 

For this to appear the fluid must go through a length of a straight tube. The velocity of the fluid for a fully developed flow will be at its fastest at the centre line of the tube (equation 1 laminar flow).

The velocity of the fluid at the walls of the pipe will theoretically be zero.

The fluid velocity can be expressed as an average velocity.

v_c = 2Q/πR²……eqn (1)

The viscous effects are caused by the shear stress between the fluid and the pipe wall. In addition, shear stress will always be present regardless of how smooth the pipe wall is. Also, the shear stress between the fluid particles is a product of the wall shear stress and the distance the molecules is from the wall. To calculate shear stress use equation 2.

Due to the shear stress on the fluid particles, a pressure drop will occur.  To calculate the pressure drop use equation 3.

P₂ = P₁ – Δ P…… eqn (3)

Finally, the viscous effects, pressure drop, and pipe length will affect the flow rate. To calculate the average flow rate, we need to use equation 4. 

This equation can only applies to laminar flow.

Q = πD⁴ΔP/128μ L…… eqn (4)

Laminar flow in circular pipe:

In a circular pipe from where fluid is flow in laminar the diameter is express as D_c, for that case the friction factor of the flow is inversely proportional to the Reynolds number by which we can easily published or measured physical parameter.

Taking the help of Darcy – Weisbach equation laminar flow in circular pipe can be express as,

Δp/L = 128/π = μQ/D⁴_c

Where,

Δp = The amount of difference of pressure which is occur in the two end points of the pipe

L = Length of the pipe through which fluid is flow

μ = The dynamic viscosity of the flowing fluid in the pipe

Q = Volumetric flow rate of the flowing fluid in the pipe

Instead of mean velocity the flowing fluid in the pipe volumetric flow rate can be used and its expression is given below,

D_c = Diameter of the pipe through which fluid is flowing

Laminar flow in a cylindrical pipe:

The cylindrical pipe which one contain flowing full, uniform diameter express as D, the loss of pressure for the viscous effects express as \Delta p is directly proportional to the length.

Laminar flow in a cylindrical pipe can be taking the help of Darcy – Weisbach equation is given below,

Where,

Δp = The amount of difference of pressure which is occur in the two end points of the pipe

L = Length of the pipe through which fluid is flow

f_D = Darcy friction factor

ρ = Fluid density of the pipe

<v> = Mean flow velocity

D_H = Hydraulic diameter of the pipe through which fluid is flowing

Laminar flow in a pipe velocity profile:

Laminar flow is appearing at very low velocities, under a threshold at that point the flow of the fluid is became turbulent.

The pipe velocity profile for laminar flow can be determined using the Reynolds number. The pipe velocity profile for laminar flow is also depending on the density and viscosity of the flowing fluid and dimensions of the channel.

Where,

Re = Reynolds number

ρ = Fluid density of the pipe and unit is kilogram per cubic meter

u = The mean speed of the flowing fluid in the pipe and unit is meter per second

μ = The dynamic viscosity of the flowing fluid in the pipe and unit is kilogram per meter second

A = Cross sectional area of the pipe and unit is meter square

Q = Volumetric flow rate and unit is cubic meter per second

D_H = Hydraulic diameter of the pipe through which fluid is flowing and unit is meter

ν = The kinematic viscosity of the flowing fluid in the pipe and unit is meter square per second

The expression of ν is,

ν = μ/ρ

Laminar flow in vertical pipe:

Flowing of fluid in laminar in vertical pipe is given below,

Laminar flow in rough pipe:

The pressure drop in a fully developed laminar flow through pipe is proportional to mean velocity or average velocity in pipe. In laminar flow, the friction factor is independent of roughness because boundary layer covers the roughness.

The term “Boiling characteristics” and boiling characteristics related conditions will be prate in this article. Boiling is a very quick vaporization condition for any liquid substance when it reaches to boiling point.

10+ Boiling Characteristics in a mini channel is listed below,

• Specific heat
• Cross sectional area
• Temperature
• Volumetric flow rate
• Mass flow rate
• Thermal conductivity
• Heat transfer coefficient
• Heat flux
• Density
• Pressure drop

Specific heat:-

Specific heat can be deriving as; the amount of heat is needed to raise the temperature of one gram of a matter by one Celsius degree. The units of the specific heat are such as calories or joules per gram per Celsius degree.

Specific heat is also known as massic heat capacity. As an example, the specific heat of water is 1 calorie (or 4.186 joules) per gram per Celsius degree.

Formula:-

The formula for the specific heat is,

Where,

Q = Heat energy is absorbed by a substance

m = Mass of a substance

c = Specific heat capacity of a matter which is depend upon the material of the matter

ΔT= Change in temperature

Cross sectional area:-

The term cross sectional area in geometry is defined as; the shape is carry by the intersection of the surface of a solid substance. The cross sectional area is present in three dimensional shape is a two dimensional shape of the geometry. In other way cross sectional area is that, the shape is can get through cutting rigid parallel to the foundation.

Types of cross sectional area:-

The cross sectional area can be classified in two sections,

Vertical cross sectional area

Horizontal cross sectional area

Temperature:-

For a material temperature represent a physical quantity which helps to understand the state of the matter. Temperature can measure with the help of thermometer. In body temperature and heat both are not same physical parameter.

The physical parameters which are affect temperature such as, thermal conductivity, strength, corrosion, solubility, density vapour pressure and many more.

When the temperature is increases that time the boiling of a matter is also increases and if the temperature is decreases that time the boiling of a matter is also a decrease.

Volumetric flow rate:-

In the field of engineering and physics volumetric flow rate is widely used. Another form of the volumetric flow rate is fluid flow rate or volume flow rate.

Inside of a pipe or a channel, the volume of the liquid substance is moving through a cross sectional area of the pipe or channel in a particular fixed time period at some standard condition where the temperature and pressure is remains unchanged.

In another word we could express that, the volumetric flow rate is the ratio between the changes of volume with the change in time.

Formula:-

The formula of the volumetric flow rate in piping system is,

Volumetric flow rate = (Flow velocity of the liquid substance) *(Cross sectional area of a pipe or a channel)

The mathematically form of the volumetric flow rate of the piping system is,

Q = vA

Where,

Q = Volumetric flow rate of a liquid substance

V = Velocity of a liquid substance

A = Cross sectional area through which fluid is flow by a open system

Mass flow rate:-

Mass flow rate can be defined as the molecules present in the liquid substance are flow through in a given cross sectional area in a fixed time period at standard condition.

Formula:-

The formula of mass flow rate is,

Mass flow rate = (Density of the fluid)* (Velocity of the liquid)* (Cross sectional area)

The mathematical form of the mass flow rate is, ṁ = dm/dt

Where,

ṁ= Rate of the mass flow for the fluid substance

dm = Change in mass

dt = Change in time

Thermal conductivity:-

Thermal conductivity states that the rate at which heat is transferred through a given material is proportional to the negative value of the temperature gradient. And it is also proportional to the area through which the heat flows, but inversely proportional to the distance between the two isothermal planes.

The formula for the thermal conductivity is,

K = Qd/AΔT

Where,

K = Thermal conductivity of a matter and unit is Watt m^-1K^-1

Q = The net quantity of heat transfer by a material and unit is Watts or Joules/second

d = Distance by the two planes which are isothermal

A = Area of the surface and unit is square meters

ΔT= Temperature difference and unit is Kelvin

Heat transfer coefficient:-

Heat transfer coefficient can be deriving as, the amount of heat can be passes through in a system per unit area in a fixed time period. For this reason the space in added in the equation of heat transfer coefficient which is express the space over which the total amount of heat transfer of heat included.

The overall rate of the heat transfer for mixed modes can be express as in the form of an overall heat transfer coefficient or overall conductance. In this case the rate heat transfer can be express as below expression,

Q̇ = hA(T₂-T₁)

Where,

Q̇ = Heat transfer rate

h = Heat transfer coefficient and unit is watt per square meter Kelvin

A = Area of the surface through which heat transfer is happened and unit is square meter

T₂= Surrounding fluid temperature and unit is Kelvin

T₁= Solid surface temperature and unit is Kelvin

Formula:-

The general equation for the heat transfer coefficient is given below,

h = q/ ΔT

Where,

h = Heat transfer coefficient and unit is watt per square meter Kelvin

q = Heat flux and unit is Watt per square meter

Thermal power through unit area express as, q = dQ̇/dA

ΔT= The temperature difference by the surrounding area of the fluid and surface of the solid and unit is Kelvin

Heat flux:-

The term heat flux has both magnitude and direction for this reason heat flux is a scale of vector. The S.I. unit of the heat flux is watts per square metre.

The 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.

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.

Formula:-

Mathematical form of law of Fourier’s in one dimension is given below,

φ_q = -K (dT(x)/dx)

Where,

k = Thermal conductivity

In the equation the negative sign represent that flow of the heat direction is from lower side to higher side.

Density:-

The density of a matter can be derive as, the mass contain of the matter per unit volume. The symbol is used to express the density for a matter is \\rho.

Formula:-

The formula of the density of the fluid is below,

ρ = m/v

Where,

ρ= Density of a fluid

m = Mass of a fluid

v = Volume of a fluid

From the law of conversion of mass we get a clear concept about the density of fluid. The conversion of mass flow rates states that, the amount of the mass of a particular object cannot not be created or destroyed. The mass of a body is measured by lever balance.

Pressure drop:-

The term pressure drop can be explain as, the dissimilation in net pressure between two points which are carried by a fluid as network. The pressure drop is appear when the frictional force is appear for the reason of resistance to flow, which is act as a fluid that it flow in a motion inside a pipe.

The pressure drop and flow rate of the fluid is dependent to each other. The pressure drop and flow rate of the fluid is directly proportional to each other means when the amount of flow rate of a fluid is increases that time the amount of pressure drop is also increases and the amount of flow rate of a fluid is decreases that time the amount of pressure drop is also decreases.

In this article “Forced convection heat transfer” term and forced convection heat transfer related facts will be prate in a brief manner. Forced convection heat transfer uses in pump, ceiling fan, suction device.

Forced convection heat transfer is a term that is a classification of transport or forced convection heat transfer is a mechanism which helps to produce motion of a flowing fluid by applying force from externally. Almost in everywhere forced convection heat transfer is used such as steam turbine, central heating and many more.

What is forced convection heat transfer?

Alongside thermal conduction, natural convection and thermal convection is are the classification of transferring the heat and also allow to sufficient quantity of heat energy should be transform without any hassle.

Forced convection heat transfer is actually a very special classification of heat transfer. By the help of forced convection heat transfer a fluid is impression to move from one are to another area by applying force from outer side. In this case the amount of heat transfer is an increase for this it’s another term is Heat Rises.

Forced convection heat transfer equation:

When potentially mixed convection is analyze in that case the physical parameter known as Archimedes Number.

In the Archimedes Number two conditions are involves forced convection and free of relative strength. Forced convection heat transfer equation is given below,

Ar = Gr/Re²

Where,

Ar = Archimedes Number

Gr = Grashof Number

Re = Reynolds Number

By the help of Grashof number buoyancy force is express and by the help of Reynolds number inertia force is express. So, from the forced convection heat transfer equation it is clear that Archimedes Number also means ration of Grashof number and square of Reynolds number.

When the value of Ar < < 1 then its represent forced convection heat transfer equation.

The another physical parameter to express forced convection heat transfer is Peclet number. Peclet number is ratio of movement by current means advection and movement from higher to lower concentration means diffusion.

Pe = UL/α

When the value of Pe > > 1 means advection dominates diffusion.

When the value of Pe < < 1 means diffusion dominates advection.

Forced convection heat transfer coefficient:

The equation of the forced convection heat transfer coefficient is discuss below,

Forced convection heat transfer coefficient in internal flow and laminar flow:-

Tate and Sieder give a concept of correlation to account for laminar flor in entrance effect.

A forced convection heat transfer coefficient in internal flow and laminar flow can be express as,

Nu_D = 1.86 (Re . Pr)^1/3 (D/L)^1/3 (μ_b/μ_w})^0.14

Where,

D = Internal diameter

μ_b = Fluid viscosity of bulk mean temperature

μ_w= Fluid viscosity at the wall temperature of the pipe

Nu_D= Nusselt number

Re =  Reynolds Number

Pr = Prandtl number

L = Length of the tube

When laminar flow is fully developed in that case Nusselt number stays at constant and value of the Nusselt number will be 3.66. In that case the forced convection heat transfer coefficient in internal flow and laminar flow can be express as,

Nu_D = 3.66 + (0.065 x Re x Pr x D/L)/(1 + 0.04 x (Re x Pr x D/L)^2/3

Forced convection heat transfer coefficient in internal flow and turbulent flow:-

When in a circular tube fluid is flowing in that case Reynolds number stays at the range between 10,000 to 12,000 and Prandtl number stays at the range between 0.7 to 120. Forced convection heat transfer coefficient in internal flow and turbulent flow can be written as,

hd/k = (0.023 jd/μ)^0.8 (μ c_p/k)ⁿ

Where,

d = Hydraulic diameter

μ = Fluid viscosity

k = Thermal conductivity for the bulk fluid

c_p = Isobaric heat capacity for the fluid substance

j = Mass flux

n = 0.4 for hotter wall than the bulk fluid and 0.33 for cooler wall than the bulk fluid

How forced convection does affect heat transfer?

The most advantage of the forced convection heat transfer than the free convection heat transfer is to able increasing more amount of heat transfer.

By the help of forced convection heat transfer the amount of heat transfer can be increases by the help of force exerted by outer side. The relations between the forced convection heat transfer and heat transfers is directly proportional. Increasing the forced convection the heat transfer of the system source also increases.

What affects Convective heat transfer coefficient?

The convective heat transfer coefficient is depending on some factors. They are listed below,

• Fluid velocity
• Density of the fluid
• Thermal conductivity
• Dynamic viscosity of the fluid
• Specific heat

Fluid velocity:-

Fluid velocity or flow velocity is a vector field. By the help of fluid velocity motion of a flowing fluid can be determine in the mathematical form. The total amount of length of the fluid velocity is determined as fluid speed. Flow velocity in fluids is the vector field that provides the velocity of fluids at a certain time and position.

The formula of the fluid velocity is given below,

Q = vA

Where,

Q = Volumetric flow rate of the liquid substance

V = Velocity of the liquid substance

A = Cross sectional area of the open system

Density of the fluid:-

From the law of conversion of mass we get a clear concept about the density of fluid. The conversion of mass flow rates states that, the amount of the mass of a particular object cannot not be created or destroyed. The mass of a body is measured by lever balance.

Density of fluid can be defined as the, an object which is containing mass is constant at standard temperature and pressure.

The formula of the density of the fluid is given below,

ρ = m/v

Where,

ρ = Density of the fluid

m = Mass of the fluid

v = Volume of the fluid

The S.I. unit of the density of the fluid is kilogram per cubic meter

Thermal conductivity:-

Thermal conductivity states that the rate at which heat is transferred through a given material is proportional to the negative value of the temperature gradient. And it is also proportional to the area through which the heat flows, but inversely proportional to the distance between the two isothermal planes.

The formula of the thermal conductivity is given below,

K = Qd/AΔT

Where,

K = Thermal conductivity and unit is

Q = The quantity of heat transfer unit is Joules/second or Watts

d = Distance by the two planes of the isothermal unit is  

A = Area of the surface unit is square meters

ΔT = Temperature difference unit is Kelvin

Dynamic viscosity of the fluid:-

Dynamic viscosity of the fluid can be deriving as the ration between the shear stress to the shear strain. The unit of the dynamic viscosity of the fluid is Pascal. By the help of dynamic we can easily understand which product how much thick and how can the fluid can flow in a motion means by the help of viscosity we can recognize the behaviour of the fluid.

The formula of the dynamic viscosity of the fluid is given below,

η = T/γ

Where,

η = Dynamic viscosity of the fluid

T = Shearing stress

γ= Shear rate

Specific heat:-

Specific heat can be deriving as; the amount of heat is needed to raise the temperature of one gram of a matter by one Celsius degree. The units of the specific heat are such as calories or joules per gram per Celsius degree.

Specific heat is also known as massic heat capacity. As an example, the specific heat of water is 1 calorie (or 4.186 joules) per gram per Celsius degree.

The formula of the specific heat of the fluid is given below,

Q = mcΔ T

Where,

Q = Heat energy

m = Mass of the fluid

c = Specific heat capacity

ΔT= Change in temperature

How to find convective heat transfer coefficient for air?

Common units which are used to measure the Convective heat transfer coefficient for air is listed below,

1. 1 W/(m²K) = 0.85984 kcal/(h m²0 C) = 0.1761 Btu/(ft² h 0 F)
2. 1 kcal/(h m²0 C) = 1.163 W/(m²K) = 0.205 Btu/(ft² h 0 F)
3. Btu/hr – ft² -0 F = 5.678 W/(m²K) = 4.882 kcal/(h m²0 C)

Forced convection heat transfer through a pipe:

When in a circular tube fluid is flowing in that case Reynolds number stays at the range between 10,000 to 12,000 and Prandtl number stays at the range between 0.7 to 120.

Forced convection heat transfer coefficient in internal flow and turbulent flow can be written as,

hd/k = 0.023 (jd/μ)^0.8 (μ c_p/k)ⁿ

Where,

d = Hydraulic diameter

μ= Fluid viscosity

k = Thermal conductivity for the bulk fluid

c_p = Isobaric heat capacity for the fluid substance

j = Mass flux

n = 0.4 for hotter wall than the bulk fluid and 0.33 for cooler wall than the bulk fluid

The properties of the flowing fluid are need for the application in the method of the equation and can be calculated at bulk temperature for this reason iteration can be avoided.

Application of forced convection heat transfer:

The Application of forced convection heat transfer is listed below,

1. Heat removal
2. Heat sink simulation
3. Thermal optimization
4. Heat sensitivity studies
5. Electric fan simulation
6. Computer case cooling
7. Cooling system design
8. Heating system design
9. Fan cooled central possessing unit
10. Water cooled central possessing unit
11. Printed circuit board simulation

Forced convection heat transfer examples:

Examples of the forced convection heat transfer is listed below,

1. Air conditioning system
2. Convection oven
3. Pump
4. Suction device
5. Ceiling fan
6. Hot air balloon
7. Refrigerator
8. Car radiators

Difference between free and forced convection heat transfer:

The major difference points between free and forced convection heat transfer is given below,

Parameter	Free convection heat transfer	Forced convection heat transfer
Definition	Free convection heat transfer is appearing for density difference between the higher temperature fluid and lower temperature fluid.	By the help of forced convection heat transfer a fluid is impression to move from one are to another area by applying force from outer side
Application	1. Heat exchanger 2. Gas turbine blades 3. Solar water heater 4. Nuclear reactor design 5. Aircraft cabin insulation	1. Air conditioning system 2. Pump 3. Suction device 4. Ceiling fan
Heat transfer rate	Heat transfer rate for free convection heat transfer low	Heat transfer rate for forced convection heat transfer high
External equipment	Not needed	Needed
Motion of particles	Slow	Move faster
Equipment size	The size of equipment used in the free convection heat transfer is larger.	The size of equipment used in the forced convection heat transfer is smaller.
Flow of molecules	Not controlled	Controlled
Heat transfer coefficient	Less	High
Movement of the molecules	For the reason of temperature and density difference free convection heat transfer work.	For the reason of exerted force apply forced convection heat transfer work.

How does forced convection heat transfer work?

Forced convection heat transfer work when the area of the gaseous substance or liquid substance is facing higher temperature or lower temperature comparative to greater than their neighbouring temperature and causes a difference between the system temperature and neighbouring temperature.

The temperature gap causes the spaces to move as the higher temperature less dense space rise, and the lower temperature more dense space sink.

This article discusses about two phase flow in pipes. The phases represent the state of matter. In a two phase flow the flow contains two states of matter mainly gas and liquid.

In this article we shall study how a two phase flow occurs in pipes. Heat transfer related to a two phase flow. We will also discuss the design of pipes which undergo two phase flow. Let us start our discussion with the definition of two phase flow.

What is a two phase flow?

As the name suggests, a two phase flow is a type of flow in which the contents that are flowing include two states of matter mainly gas and liquid.

The two phase flow can occur in many forms such as transitioning flows from pure liquid to pure gaseous states, separated flows as well as dispersed two phase flows. In dispersed two phase flows on phase is present in the form of bubble, particles, or droplets in carrier form.

Image credits: Rudolf Hellmuth, Two-phase Flow, CC BY-SA 4.0

Examples of Two phase flow

In large scale power systems, two phase flows were studied rigorously. Below are the examples or applications where two phase flow plays a very vital role in design process.

• Boilers – Pressurized water is passed through heated pipes and this water changes to steam while passing through the boiler. The boiler changes the phase of liquid water. During the phase transformation, the pipe will have a two phase flow that means gas and liquid phases will co exist.
• Nuclear reactors – In nuclear reactors, two phase flow is used to remove heat from the reactor core. In reactor core, the fuel is burnt. The fuel used is generally U-235.
• Cavitation – In pumps, when the operating pressure is nearly equal to the vapour pressure of the liquid, any increase in pressure will result into local boiling. This phenomenon of local boiling is called as cavitation.
• Electrolysis– Electrolysis is a technique which uses Direct Current (DC) to carry out a non spontaneous reaction.
• Clouds – We all have seen clouds up in the sky. They are aerosol consisting of a visible mass of liquid, droplets and other frozen particles that are suspended in the atmosphere.
• Groundwater flow – Groundwater is the water that flows beneath the surface of Earth. Two phase flow is used to study the movement of air and water in the soil.

Characteristics of a two phase flow

The list below tells us about the characteristics of a two phase flow:

• All the dynamical problems are made non linear due to surface tension.
• At standard temperature and pressure, the difference between the densities differ by 1000 for air and water.
• The speed of sound changes while passing through a phase change. Compressible effects come into play.
• The phase changes are not in equilibrium and they do not happen necessarily.
• The flow – induced pressure drops can cause further phase change in the system.
• Two phase flows can give rise to counter intutive negative resistance type instabilities.

Types of two phase flow

The types of two phase flows depends on the state of matter of the contents participating in the flow. The types of two phase flow are given in the list below-

• Liquid- liquid flow – In liquid liquid flow, the contents of the flow include two different types of liquid that are immiscible. The solution is such that one liquid floats on other liquid because of difference in densities and inability to make or break bonds.
• Gas-liquid flow – In gas liquid flows, the gas droplets are present on the surface of the liquid. These droplets move faster than the liquid resulting in a slug flow.
• Gas-solid flow– Gas solid flow as the name suggests has solid particles suspended in a gas. These solid particles create abrasive action. For examples large sized impurities present in air is an example of gas solid flow.
• Solid liquid flow– Solid liquid flow has solid particles suspended in liquid stream. The solid particles do not mix with the liquid. They are immiscible.

Two phase flow in vertical pipes

Two phase flows in vertical pipes refers to interactive flow of two distinct phases in common interfaces. Each of them having their own individual mass and volume.

To calculate the flow rate in vertical pipe, the formula given below shall be used-

Where,

H is the discharge height

Q is the flow rate

K is the coefficient ranging from 0.87-0.97

D is the diameter of pipe

Two phase flow regimes in horizontal pipes

The flow regimes in horizontal pipes can vary dependin upon the temperature and pressure drop inside the pipe. In the next section we shall discuss about the flow regimes and patterns found in the horziontal pipe for a two phase flow.

In two phase flows inside a horizontal pipe, the patterns observed are- bubbly flow, stratified wavy flow, slug flow, intermittent flow, stratified flow, plug flow, annular flow and mist flow. Other types of patterns maybe observed depending on special temperature ranges and pressure ranges.

Two phase flow and heat transfer

Heat transfer does not necessarily take place between two same phase substances. But the heat can be transferred between two different states of matter too.

Generally in heat exchangers, liquid-liquid flow is used to transfer heat. In two phase flows, the temperature of both the constituents are different and we consider the average temperature and pressure of the flow.

Heat transfer in heat exchangers

In heat exchangers, the heat is transferred between two fluids such that the working fluid heats up or absorbs heat from the fluid flowing in the system.

Heat exchangers are used in many applications such as rocket engines, cooling towers, water jackets, geysers etc. The main purpose of heat exchangers is to heat or absorb heat from the fluid flowing in the system. Sometimes it may be required to heat up the fluid and sometimes it may be needed to cool the fluid. Sometimes only latent heat is absorbed meaning the temperature of the fluid in system remains same but only the phase transformation takes place.

This article discusses about slug flow in pipe. Slug flow is a pattern of two phase flow, more specifically a liquid-gas flow. In this pattern, the lighter fluid moves faster continuously which also contains gas bubbles.

A slug flow can cause pressure oscillations inside a pipe flow. Usually the heavier fluid is termed as slug that moves slower. But we can refer the bubbles of lighter fast moving fluid also as slug. In this article we shall study about the slug flow in detail.

What is a slug flow?

A slug flow is a pattern made in a two phase flow where the lighter fluid moves faster pushing along disperse gas bubble.

The term slug refers to heavier fluid that moves slowly. But we can be using this term for lighter fluid also that moves quickly. Slug flow happens inside a two phase flow, specifically a liquid-gas flow. The pressure oscillations in the pipe are caused by this slug flow. Let us study more about this flow in further sections of this article.

Image credits: MichaelFYP, Slug flow, CC BY-SA 4.0

What is slug load in piping?

Slug load in piping refers to the load applied by slug flow inside the pipe. The slug flow is characterized by intermittent sequence of liquid slugs which are then followed by longer gas bubbles flowing through the pipe.

As discussed in the above section, slug usually refers to heavy liquid that flows very slowly. But here we can refer to lighter fluid that has a swift movement. We can experience pressure oscillations inside pipe due to slug flow taking place.

Slug flow in horizontal pipeline

When the fluid dlow is taking place in a horizontal pipeline, then the resulting slug flow can be referred to as slug flow in horizontal pipeline.

To calculate the load applied by the slug flow in a horizontal pipeline we need to understand that it depends on few factors. These factors are Diameter of the pipe, cross section area of the pipe, resultant force, angle of bend (in case of horizontal pipe the angle is zero) and the length of the pipe. We shall study about the formula for calculating slug loads in next section.

Slug load formula in horizontal pipeline

We have discussed about the slug flow in horizontal pipeline and the factors on which the load depend. In the section below we shall discuss about the formula required to find slug load in horizontal direction.

The formula for slug load in horizontal pipeline is given below-

Where,

D is the diameter of the pipe

A is the cross section area of the pipe

L is the length of the pipe

Theta is the angle of bend

F is the resultant force

Slug flow in vertical pipes

When the pipe in which the slug flow is taking place is vertical, then the resulting flow is called as slug flow in vertical pipes.

The slug load in vertical pipes depends on various factors. These factors are diameter of the pipe, cross section area of the pipe, length of pipe, angle of bend (in case of vertical pipe the angle is ninety degrees), resultant force. In the next section we shall discuss about the formula for calculating slug loads in vertical pipe.

Slug load formula for vertical pipe

The factors on which the slug load depends is discussed in the above section. Now we shall discuss the formula used to calculate the slug load.

The formula for slug load in vertical pipe is discussed in the section given below-

Where,

D is the diameter of the pipe

A is the cross section of the pipe

L is the length of pipe

Theta is the angle of bend

Slug flow in inclined pipes

When the pipe through which the slug flow is taking place then the resulting flow is reffered as slug flow in inclined pipes. We shall see the factors on which the slug load in inclined pipe depends.

The slug load depends on the same factors as that of vertical and horizontal pipes. These factors are diameter of the pipe, cross section area of the pipe, length of the pipe and angle of inclination or bend. In the next section we shall discuss about the formula used for calculating slug load in inclined pipe.

Slug load formula for inclined pipe

The slug load formula depends on some factors and these factors are discussed in the above section already. In this section we shall use these factors and come up with a formula to calculate the slug load in inclined pipe.

The slug load formula is given in the section given below-

Where,

D is the diameter of the pipe

A is the cross section of the pipe

L is the length of pipe

Theta is the angle of bend

How to avoid slug flow in pipes?

Slug flow can create pressure oscillations inside the pipe. Although slug flow can be avoided by taking certain measures. These measures are discussed in the next section.

The following methods can be used to avoid slug flow in pipings-

• Usage of low point effluent drain or bypass
• Reducing line sizes to the minimum point permitted by the pressure drop
• Keeping the arrangement of pipe flow in such a way that it protects against the pipe flow.

Plug flow vs slug flow

The difference between the two is not too big that we equire a table of differentiation for it. Both the flows are actually very similar and hold similar meanings.

The only difference between a plug flow and a slug flow is that in plug flow the bubbles move at a slower rate than the bubbles in slug flow. Also, the size of bubbles are smaller in plug flow as compared to the size of bubbles in slug flow.

Examples of Slug flow

The list below shows the different places where slug flow is used.

• To produce hydrocarbons in wells and their transportation through pipelines.
• In geothermal power plants, to produce steam and water.
• Boiling and condensing of liquid vapour systems of thermal power plants.
• To cool core of nuclear reactors in emergency situations.
• In chemical reactors, to transfer heat and mass between gas and liquid.

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This article answers the question- why does boiler pressure drop? A boiler is a device used to procude steam or heat the working fluid that is used to generate power in further steps.

The fluid used inside the boiler does not necessarily boil. The heated fluid is further used in many applications like generating electricity, cooling and sanitation. In this article we shall study more about boilers and related questions.

What is a boiler?

As stated above, a boiler is a device used for heating the working fluid so that it can be used for further applications.

Even though the name suggests that the working fluid will boil but is not necessarily true. The working fluid can be used for further applications without reaching its boiling point. In next section we shall see the heat sources from which the boiler gets heat.

Sources of heat

There are many heat sources from which the boiler takes heat. These heat sources provide the necessary heat energy to the working fluid. This absorbed heat energy is then utilised or is converted to another usable form of energy.

The commonly used heat sources are burning of coal, oil, natural gas. Some boilers which are also called as steam generators produce heat with the help of nuclear fission. A nuclear fission is a process in which the atom splits to emit a huge amount of energy. In some applications Carbon Monoxide is also used as a heat source.

Image credits: Old Moonraker at en.wikipedia, Steam Boiler 2 English version, CC BY-SA 3.0

Materials used for making boilers

The boilers come in variety of materials. They mainly depend on the applications and the working temperature of the boiler. The next section discusses about the materials used for making boilers.

Pressure vessels of a boiler are generally made of steel and wrought iron. Stainless steel is not used in wetter parts of the boiler due to the risk of corrosion. In some steam models, Copper and Brass are used because these materials facilitate easy fabrication in small sized boilers.

Why does boiler pressure drop when heating is on?

When the heating is on the expansion of the steam takes place, due to this the pressure of the steam keeps on increasing.

Due to the increased pressure, the steam starts exerting pressure on the walls of boiler, if there is a leak in the boiler the boiler pressure will keep on decreasing. Another reason for the drop in boiler pressure is due to releasing of air or water to the radiator when bleeding it.

Why does boiler pressure drop overnight?

The main reason for pressure drop inside a boiler is leak. The leaks can take place in many forms. Sometimes it is done on purpose and sometimes it happens unknowingly.

The reasons of pressure drop may include leak in the pressure relief valve, a problem in the expansion vessel, air inside the system or a leak in the pipework itself.

Can a boiler lose pressure without a leak?

In most of the cases, almost 99%, the boiler loses pressure due to leaks only. There may be leaks in pressure relief valve, pipe work or in expansion vessel.

If there is no leak then there can be a fault inside the boiler or the pressure gauge must be faulty. Other than this, when the air or water is bled in the radiator, the pressure inside the boiler will decrease.

Does boiler pressure drop in summer?

The boiler pressure depends on the water content flowing through the pipelines. Generally in summers, the boiler pressure is low.

This happens due to the fact that the water content inside the pipelines is lesser because the boiler is kept idle for a longer time. A lower boiler pressure indicates that the amount of water being circulating in the system is dropped.

Why does boiler pressure drop in winter?

Boilers are subjected to additional pressure after they are kept idle for a long time in summers. When these boilers are put on to use during winters, the pressure on the boilers increase drastically.

Otherwise the boiler will lose pressure when the boiler has leak inside the relief valve or pressure tanks. When the cold water is heated the molecules of water expand in a random manner, if there is a leak the pressure will keep on decreasing from the boiler.

Types of boilers

Many types of boilers can be used to provide the heat to the system. The type of boiler that is to be used depends on the type of application, quantity of heat to be produced and the working fluid.

The different types of boilers are given in the list below-

• Gas boilers
• Oil boilers
• Husk fired boilers
• Water tube boilers
• Electric boilers
• Biomass boilers
• Waste heat boilers
• High efficiency boilers

Accessories used in boilers

Boilers come with many accessories and fittings. The list below shows the different accessories used in boilers-

• Pressuretrols – It is used to control the pressure inside the boiler. Usually the boilers have three types of pressuretrols- A manual-reset pressuretrol, operating pressuretrol and a modulating pressuretrol.
• Safety valves – It is used to relieve excessive pressure. Excessive pressure can lead to explosion. Using of safety valves ensure safety from explosions. As the safety valves release the excess pressure, hence no excess pressure no explosion.
• Water level indicators – The name itself suggests us about its functions. The water level indicators tells us about the level of fluid. Other names used are sight glass, water gauge or water column.
• Bottom blowdown valves – The blowdown valves provide a means for removing solid particles or sediments that settle at the bottom of boiler. These valves are installed at the bottom of boiler and occasionally used to remove the particulates by using the pressure from the boiler.
• Continuous blowdown valve – This valve allows the water to flow out continuously. The main purpose of this valve is to prevent water in the boiler to become saturated salts with dissolved salts.
• Trycock – This is used to find the water level inside the water boiler. This is generally used in water boilers.
• Flash Tank – The blowdown comes to this vessel with very high pressure. Here the steam can be flashed safely and be used in a low pressure system and can also be vented out to atmosphere.
• Hand holes: These are steel plates which allow for inspections of tubes and installation of pipes.
• Top feed: This is used to feed water from the top of boiler. This prevents the boiler from fatigue as the thermal stresses acting on the boiler are reduced.
• Low water cutoff: It is a safety switch that or an electrode with a safety switch that is used to turn off the burner or switch off the fuel supply to prevent it from running once the water level reduces below a certain limit. If a boiler is “Dry fired” means there is no water content in it then it can lead to catastrophic consequences.
• Automatic heat recovery system: This recovery system allows the blowdown only when the makeup water is flowing to the boiler. This results in maximum heat transfer taking place from the blowdown to the makeup water. In this case no flash tank is needed as the temperature of the blowdown discharge is similar to the temperature of makeup water.

Read more about Does Boiler Pressure Increase, Boiler Steam Temperature and Boiler Steam Drum.