The outer shape of the polaris plate heat exchanger is compact and small gap.Then the heat transfer area per unit volume is increased. The installation area is about 1/2 to 1/3 of the shell-and-shell type, which generally saves floor space and construction cost. Each case has a volume of 1m3, the heat transfer area is about 80m2. In addition, the plate heat exchanger is easy to increase or decrease the heat exchange area. For the shell-and-tube heat exchanger, when the liquid processing capacity needs to be increased, the original heat exchange heat transfer area is almost impossible to increase, but the heat transfer area of the plate heat exchanger is easily increased, thereby increasing the processing capacity.