1. Adopt multi process combination
When the flow rate of hot and cold medium is large, multi flow combination arrangement can be used, and more flow can be used on the side with small flow rate to improve the flow rate and obtain higher heat transfer coefficient. In order to reduce the resistance of the heat exchanger, a smaller flow is used on the side with large flow rate. The results show that the mixed flow pattern appears in the multi flow combination, and the average heat transfer temperature difference is slightly lower. The fixed end plate and movable end plate of plate heat exchanger with multi process combination have connecting pipes, so the maintenance work is heavy.
2. Asymmetric plate heat exchanger is adopted
The symmetrical plate heat exchanger is composed of plates with the same corrugated geometry on both sides of the plate, forming a plate heat exchanger with equal cross-sectional area of cold and hot flow channels. According to the heat transfer characteristics and pressure drop requirements of cold and hot fluids, the asymmetric plate heat exchanger changes several wave structures on both sides of the plate to form a plate heat exchanger with different cross-sectional areas of cold and hot flow channels. The angle diameter on one side of the wide flow channel is larger. The heat transfer coefficient of asymmetric plate heat exchanger decreases slightly, and the pressure drop decreases greatly. When the flow rate of hot and cold medium is large, the plate area of the heat exchanger with asymmetric single flow can be reduced by 15% – 30% compared with that with symmetric single flow.
3. Heat exchanger bypass pipe is set
When the flow rate of hot and cold medium is relatively large, a bypass pipe can be set between the outlet of heat exchanger on the side with large flow rate to reduce the flow into the heat exchanger and reduce the resistance. In order to facilitate adjustment, a regulating valve should be installed on the bypass pipe. In this way, counter current arrangement should be adopted to make the temperature of cold medium out of the heat exchanger higher, so as to ensure that the temperature of cold medium after combined flow at the outlet of the heat exchanger can meet the design requirements. The bypass tube of heat exchanger can ensure high heat transfer coefficient of heat exchanger and reduce resistance of heat exchanger, but the adjustment is a little complicated.
4. Selection of plate heat exchanger