Working principle

In the process of heat transfer, it is an important problem to reduce the thermal resistance in the wall heat exchanger in order to improve the heat transfer coefficient. The thermal resistance mainly comes from the thin layer of fluid (called boundary layer) adhered to the heat transfer surface on both sides of the intermediate wall and the dirt layer formed on both sides of the wall during the use of the heat exchanger. The thermal resistance of the metal wall is relatively small. Increasing the flow velocity and disturbance of the fluid can reduce the boundary layer, reduce the thermal resistance and improve the heat transfer coefficient. However, increasing fluid flow rate will increase energy consumption, so reasonable coordination should be made between reducing thermal resistance and reducing energy consumption in design. In order to reduce the thermal resistance of dirt, try to delay the formation of dirt, and regularly clean the heat transfer surface.

Generally, heat exchangers are made of metal materials, among which carbon steel and low-alloy steel are mostly used to manufacture medium and low-pressure heat exchangers; In addition to being mainly used for different corrosion-resistant conditions, austenitic stainless steel can also be used as high and low temperature resistant materials; Copper, aluminum and their alloys are mostly used in the manufacture of low-temperature heat exchangers; Nickel alloy is used at high temperature; In addition to making gasket parts, some non-metallic materials have been used to make corrosion-resistant heat exchangers of non-metallic materials, such as graphite heat exchangers, fluoroplastic heat exchangers and glass heat exchangers.