A plate heat exchanger is a kind of heat exchanger which uses metallic plates for heat transfer between a hot and a cold fluid. The plates form channels between them and the end ports are arranged in such a way that the hot and cold fluid flow through alternate channels. The heat is transferred through the plates. The fluids are exposed to a very large surface area, creating a counter flow as they spread over the plates. This results in high heat transfer efficiency, and hence large temperature differences can be achieved from a relatively smaller unit. The size of the unit generally depends on the flow rates, temperature differences, desired pressure drops and nature of the two fluids.
Larger Plate heat exchangers usually use gaskets between the plates and the smaller ones are usually brazed. Plates can be corrugated to increase the effective surface area and impart turbulence to increase the heat transfer even more.