The heat exchange system of heat exchanger usually carries out heat exchange by means of heat conduction convection. Heat transfer is a common process of heat transfer, in which there is no relative displacement between the parts of the fluid; convection of heat exchanger is a process of heat transfer caused by the relative displacement of the particles in each part of the fluid. Convection in heat exchanger is divided into forced convection natural convection. Forced convection uses mechanical energy (such as agitation) to make fluid convection heat transfer.