Views:0 Author:Site Editor Publish Time: 2021-02-24 Origin:Site
The plate heat exchanger is a wall-to-wall heat exchanger. The hot and cold fluid transfers heat through the heat exchanger plates, and the fluid directly contacts the plates. The heat transfer method is heat conduction and convection heat transfer. The key to improving the heat transfer efficiency of the plate heat exchanger is to increase the heat transfer coefficient and the logarithmic average temperature difference.
To improve the heat transfer coefficient of the heat exchanger, only by simultaneously increasing the surface heat transfer coefficient of the hot and cold sides of the plate, reducing the thermal resistance of the dirt layer, selecting plates with high thermal conductivity and reducing the thickness of the plates, can the heat exchange be effectively improved. The heat transfer coefficient of the device.
a. Improve the surface heat transfer coefficient of the plate
Because the corrugation of the plate heat exchanger can cause the fluid to produce turbulence at a small flow rate (Reynolds number-150), it can obtain a higher surface heat transfer coefficient, the surface heat transfer coefficient and the geometric structure of the plate corrugation and the medium The flow status is related. The waveform of the plate includes herringbone, straight, spherical and so on. After years of research and experimentation, it has been found that the corrugated cross-section shape is triangular (sine-shaped surface heat transfer coefficient is large, pressure drop is small, stress distribution is uniform under pressure, but processing is difficult?) Herringbone plate has high surface transmission thermal coefficient, and the greater the angle of the corrugation, the higher the flow velocity of the medium in the flow channel between the plates, and the greater the surface heat transfer coefficient.
b. Reduce the thermal resistance of the dirt layer
The key to reducing the thermal resistance of the fouling layer of the heat exchanger is to prevent fouling of the plates. When the plate fouling thickness is 1 mm, the heat transfer coefficient is reduced by about 10%. Therefore, care must be taken to monitor the water quality on both sides of the heat exchanger to prevent fouling of the plates and prevent debris in the water from adhering to the plates. Some heating units add chemicals to the heating medium in order to prevent water theft and corrosion of steel parts. Therefore, attention must be paid to the water quality and viscosity caused by sundries to contaminate the heat exchanger plates. If there are viscous debris in the water, special filters should be used for treatment. When choosing medicaments, it is advisable to choose non-sticky medicaments.
c. Use plates with high thermal conductivity
The plate material can choose austenitic stainless steel, titanium alloy, copper alloy, etc. Stainless steel has good thermal conductivity, with a thermal conductivity of about 14.4 W/(m•K), high strength, good stamping performance, and is not easy to be oxidized. The price is lower than that of titanium alloy and copper alloy. It is used more in heating engineering, but it is resistant to chlorine. The ability of ion corrosion is poor.