Plate heat exchanger is a new type of high-efficiency heat exchanger composed of a series of metal sheets with certain corrugated shapes stacked together. Thin rectangular channels are formed between various plates for heat exchange. Plate heat exchangers are ideal equipment for heat exchange between liquid and liquid, as well as between liquid and vapor. It has the characteristics of high heat transfer efficiency, low heat loss, compact and lightweight structure, small footprint, easy installation and cleaning, wide application, and long service life. Under the same pressure loss, its heat transfer coefficient is 3-5 times higher than that of a tube heat exchanger, occupying one-third of the area of a tube heat exchanger, and its heat recovery rate can reach over 90%.