Classification of heat exchangers

Heat exchangers suitable for various media, different working conditions, different temperatures and pressures have different structural types. The specific classification of heat exchangers is as follows: 

I. Classification according to heat transfer principles 

1. Wall-type heat exchanger: In a wall-type heat exchanger, two fluids with different temperatures flow in a space separated by the wall surface. Through the heat conduction of the wall and the convection of the fluids on the wall surface, heat exchange occurs between the two fluids. Wall-type heat exchangers include shell-and-tube type, tubular type, and other types of heat exchangers. Wall-type heat exchangers are currently the most widely used type of heat exchanger. 

2. Regenerative Heat Exchanger: The regenerative heat exchanger utilizes a heat storage body composed of solid materials to transfer heat from a high-temperature fluid to a low-temperature fluid. The hot medium first reaches a certain temperature by heating the solid material, and then the cold medium is heated through the solid material to achieve the purpose of heat transfer. There are various types of regenerative heat exchangers, such as rotary type and valve switching type. 

3. Fluid Connection Indirect Heat Exchanger: An indirect heat exchanger is a type of heat exchanger that connects two surface-type heat exchangers through the circulating heat medium. The heat medium circulates between the high-temperature fluid heat exchanger and the low-temperature fluid. The high-temperature fluid absorbs heat, and the heat is then released to the low-temperature fluid in the low-temperature fluid heat exchanger. 

4. Direct-contact heat exchangers are also known as mixed heat exchangers. This type of heat exchanger is a device where two fluids come into direct contact and mix with each other to conduct heat exchange. Examples include cooling towers and gas condensers. 

5. The double-effect heat exchanger is a device that combines both the indirect heat exchange between steam and water and the direct mixed heat exchange between water. Compared with the indirect heat exchange between steam and water, it has a higher heat exchange efficiency; compared with the direct mixed heat exchange between steam and water, it has higher stability and lower unit noise. 

II. Classification by Function 

1. The heater heats the fluid to the required temperature, but no phase change occurs during the heating process. 

2. Preheater The preheater preheats the fluid, providing standard process parameters for the operation. 

3. Superheater The superheater is used to heat the fluid (process gas or steam) to a superheated state. 

4. Evaporator The evaporator is used to heat the fluid, raising its temperature above the boiling point, causing the fluid to evaporate. Generally, there is a phase change involved. 

III. Classification by Structure 

It can be classified into: floating head type heat exchanger, fixed tube sheet type heat exchanger, U-shaped tube sheet heat exchanger, plate type heat exchanger, etc.