The plate heat exchanger is a new type of high-efficiency heat exchanger made of a series of metal sheets with a certain corrugated shape. Thin rectangular channels are formed between various plates, and heat is exchanged through the plates. Plate heat exchanger is an ideal equipment for heat exchange of liquid-liquid, liquid-vapor. It has the characteristics of high heat exchange efficiency, small heat loss, compact and lightweight structure, small footprint, convenient installation and cleaning, wide application and long service life. Under the same pressure loss, the heat transfer coefficient is 3-5 times higher than that of the tubular heat exchanger, the floor area is one third of that of the tubular heat exchanger, and the heat recovery rate can be as high as 90% or more. There are three main types of plates: herringbone corrugated plate, horizontal straight corrugated plate and tumor-shaped plate.