The total heat transfer coefficient is a parameter used to measure the heat transfer resistance of heat exchanger. Increasing the flow rate between plates can improve the heat transfer coefficient, but increasing the flow rate will increase the resistance of the heat exchanger, so the power consumption of the circulating pump will be increased, which is not economical. In order to better control the resistance requirements, some measures are needed to assist. Today we will introduce the method of changing the resistance of plate heat exchanger.
1、 Multi process combination can be used to change the resistance of plate heat exchanger. When the flow rate of cold and hot medium is large, multi process combination can be used. When the flow rate of cold and hot medium is small, more processes can be used to improve the flow rate between plates, so as to obtain higher heat transfer coefficient.
2. In the plate heat exchanger bypass pipe: when the cold and hot medium flow is relatively large, the bypass pipe can be set between the inlet and outlet of the large flow side to reduce the flow into the plate heat exchanger and reduce the resistance. 3. The two sides of the mixed plate have the same corrugated geometry. According to the angle of herringbone corrugated, the mixed plate can be divided into hard plate and soft plate. The angle is generally about 120 degrees for hard plate, less than 90 degrees, and about 70 degrees for soft plate. The heat transfer coefficient of the hard plate of the mixed plate is high, the resistance is large, and the soft plate is on the contrary. Therefore, the combination of soft plate and hard plate can form three different characteristics of high, medium and low flow channels, which can meet the needs of different working conditions. However, when the ratio of cold to hot medium is too large, the mixed plate is not suitable.
The average velocity of medium in the flow passage of heat exchanger should be 0.3 ~ 0.6m/s, and the resistance of plate heat exchanger should be no more than 100KPA. Different types of equipment should be selected according to different flow ratio of hot and cold medium.
