“Plate and frame heat exchangers” are used for various purposes in the industrial sector. The temperature and heat transfer inside the plate and frame heat exchanger always move from high to low.
Heat exchangers are widely used in the industrial sector, plate and frame heat exchangers are one of them. Plate and frame heat exchanger uses metal plate as the medium through which heat transfer between two liquids can be done. It takes a frame and is clamped between a follower and the head.
What is a plate and frame heat exchanger?
Plate and frame heat exchanger is a device most suitable heat exchanger for the exchange of pressure from low pressure to medium pressure by means of pressurized fluid. It is used in free cooling, boilers.
A plate and frame heat exchanger is a device used in a sequence of metal plates where heat freely moves from one fluid to another. The plate and frame heat exchanger of the plate are stacked on top of each other to form a sequence channel so that the pressurized fluid can pass through it.
How does a plate and frame heat exchanger work?
Plate and frame heat exchanger is a device that is widely used in small welded designs. The main feature of plate and frame heat exchangers is that the pressurized fluid can be easily distributed over the metal plates.
Gaskets of plate and frame heat exchanger The plates reduce heat through the surface of the exchanger and help to separate the hot medium from the cold medium. Because of this, low temperature liquids, gases and high temperature liquids, gases use the lowest level of energy.
The working principle of plate and frame heat exchanger is derived from deep down in the section,
Several plates are stacked together at the beginning of the process .
Gaskets are used inside the plate and frame heats exchanger, thus allowing to prevent liquids that are entering through the plates in turn . Gaskets can be easily moved to the left or right side to form a block. Two liquids will certainly flow in each channel of the plates. The holes in the gasket plates in a plate and frame heats exchanger are aligned in such a way as to channel a pipe through which fluid can flow.
If we go through the plate and frame gasket plates of the heats exchanger we can see that the alternate gasket plate is the side block.
If the cooler fluid can pass through the plate and frame the heat exchanger then the fluid is entering from the top left inlet.
After entering the cooler fluid, it can flow through plate 2, plate 4 and plate 6 . After that the cooler fluid left a higher temperature and discharged from the left side down out .
In the next step the high temperature fluid enters from the right side of the lower inlet so it can flow through plate 1, plate 3 and plate 5 . Then the hot fluid discharges from the top right side outlet .
The gasket of the plate and frame heats exchanger allows fluid to flow inside the special channel.
In this process plates that have channels through which fluids flow with different temperatures and always tend to move fluids from warmer temperatures to colder temperatures.
The higher temperature fluid transfers a smaller amount of thermal energy to the lower temperature fluid . Two liquids of different types never combine and they never meet , it is only because of their separation from each other that the wall of the metal plate is separated. Due to this the liquid of low temperature was heating up and the liquid of low temperature was cooling down. The amount of heat exchange in plate and frame heat exchanger is simple type.
We must always ensure that, the protective sleeve needs to be attached with the tightening bars on the thread. More thermal energy must be insulated .
Fluid flow is reverse current .
The counterflow working principle is most effective only because of the log mean difference of the temperature. The logarithmic average (LMTD) of the temperature difference is greatest.
Types of plate and frame heat exchanger:
Plate and frame heat exchangers can be classified into four categories. they are,
- brazed plate and frames heat exchanger
- gasket plate and frame heats exchanger
- welded plate and frames heat exchanger
- Semi Welded Plate And Frame Heats Exchanger
The types details of plate and frame heats exchanger classification are given below,
brazing plate and frame heat exchanger:
The structure of the brazed plate and frame heat exchanger consists of both the equipment name gasket and the frame. Brazed plate and frame heat exchangers mainly use for small applications but now a days brazed plate and frame heat exchangers widely for larger applications. It is mainly used in the refrigeration and automotive sectors.
Use in brazed plate and frame heat exchangers Stainless steel and copper brazing is used to make its plate for this reason it has high corrosion resistant characteristics. These brazed plates and frame heat exchangers are very lightweight and efficient hence this type of heat exchanger is economical.
The brazed plate and frame heat exchangers has thin metal plates to separate the pressurized fluid, but the metal blades together to seal completely. The seal of this heat exchanger is made with the help of positioning and brazing of metal plates allowing the flow of fluid to be determined. It has both high pressure and high temperature.
The benefits of using a brazed plates and frame heat exchangers are,
- Exchangers are used.
- low maintenance cost.
- The construction design is easy.
- The heat loss is very less.
Gasket plate and frame heat exchanger:
Several thin metal sheets are used to form the channel structure in a gasketed plates and frame heats exchanger. Heating or cooling capacity can be increased or decreased by adding or reducing internal thin metal sheets. The purpose of its repair or washing may also be different. The metals used to make thin plates are stainless steel, platinum and mild steel. The gasketed plate and the heat exchangers gasket in the frame are made of rubber.
In process engineering, automotive sector, heavy duty HVAC gasket plate and frame heats exchanger are widely used.
The benefits of using a gasketed plate and frame heat exchanger are,
- low maintenance cost.
- Leakage can be easily stopped.
- Replacing the expansion valve is not difficult.
- Do not face difficulty in cleaning thin metal plates.
Welded plate and frame heat exchanger:
If we look at the structure of welded plate and frame heats exchanger we can see that the inside structure is similar to that of gasket plate and frame heast exchanger.
The benefits of using a welded plate and frame heat exchanger are,
- Fluid loss is very less.
- This is a very strong type.
- Corrosive or hot liquids can easily move in it.
Semi welded plate and frame heat exchanger:
The inner metal plates are made and welded with the help of two plate pairings. Other Pairs of Gasket One pair is welded to form a fluid path and the other pair is gasketed to form a fluid path.
The benefits of using a semi welded plate and frame heat exchanger are,
- Fluid loss is very less.
- There is no difficulty in carrying heavy material.
Plate and frame heat exchanger diagram:
The diagram of plate and frame heats exchanger is given below,
Plate and frame heat exchanger applications:
Below are the applications of plate and frame heat exchanger,
- heat pump isolation
- water heater
- waste heat recovery
- free cooling
- cooling tower isolation
Heat Pump Isolation:
A graham plate chain exchanger is used to protect the heat pump from contaminants in the water supply. The high level of turbulence cab can be easily maintained by Graham plate series exchanger, which minimizes fouling and suitable for flowing high temperature fluids.
water heater:
Stainless steel is used to make water heaters. It has a high rate of heat transfer and resistivity to corrosion. Water heaters mainly use graham plate exchanger which is suitable for high temperature fluid flow.
Waste heat recovery:
Waste heat can be generated with the help of chillers, steam condensers, and many other processes are used to heat air or water. High efficiency and low temperature it helps to reduce energy cost.
free cooling:
The chillers of the refrigeration system are switched off to operate for free cooling and help reduce plant utility costs. Free cooling uses a graham plate exchanger. During the free cooling process, the air is pre-cooled with the help of cooling tower water.
Cooling Tower Isolation:
Cooling water is circulated in buildings with the help of cooling tower isolation. , In cooling tower isolation graham plate exchanger is used to reduce water turbulence.
plate and frame heat exchanger size:
There are certain steps to be followed for the measurement process of plate and frame heat exchanger. they are,
- get design data
- heat flow calculation
- Calculation of the required number of thin plates
- Confirmation of heat exchanger size
Get design data:
Calculating the size of the plate and frame heats exchanger requires the first step to be followed to obtain the design data at the beginning. The data that one must follow to run this process are listed below,
- properties of matter.
- Temperature for each fluid at the outlet and inlet.
- The pressure for the fluid at the inlet.
- acceptable pressure drop.
Calculation of heat flux:
If one knows the flow rate, specific heat, inlet temperature, exit temperature of the flowing fluid, or either the cold side or the hot side, the heat flow can be calculated easily.
With the help of the formula by which the heat flux can be calculated, is given below,
where,
= mass flow rate on the lower temperature side in kg per second
= specific heat towards lower temperature
= outlet temperature towards the lower temperature in Kelvin
= inlet temperature on the lower temperature side in Kelvin
= mass flow rate on the high temperature side in kg per second
= specific heat towards higher temperature
= outlet temperature towards higher temperature in Kelvin
= inlet temperature towards higher temperature in Kelvin
Heat flux can be determined with the help of heat transfer coefficient.
where,
H = Overall heat exchange coefficient
S = area of heat exchanger in square meters
Calculation of the required number of thin plates:
The required number of thin plates can be determined using this formula,
n = s / s
where,
n = required number of thin plates
S = total area of heat exchanger area in square meters
s = size of a particular single plate in square meters
Confirmation of the size of the heat exchanger:
The size of the heat exchanger can be determined using the Nusselt number.
where,
Nu = Nusselt Number
A = coefficient based on the corrugation of the plate
Re = Reynolds number
b = coefficient based on the corrugation of the plate
= Prandtl number
= number of panels on the wall of the plate
Plate and frame heat exchanger cleaning and maintenance:
Plate and frame heat exchanger cleaning and maintenance is carried out in three stages. They are listed below,
- scheduled repairs
- clean in place
- manual maintenance
scheduled maintenance:
The general procedure for cleaning and maintaining the plate and frame heat exchanger is scheduled maintenance. In this process the equipment of the heat exchanger is scheduled and regularly maintained and cleaned. This type of cleaning and maintenance process lasts at least six months.
clean in place:
In this process, the equipment of the heat exchanger is maintained and cleaned from time to time. This kind of cleaning and maintenance process does not require the plate to be opened, it helps to release excessive pressure inside the heat exchanger.
Manual Maintenance:
In this process the equipment of the heat exchanger is maintained and cleaned every year. This type of cleaning and maintenance process lasts at least more than a year.
