Radiator is widely used to radiate heat into the air and is widely used in refrigeration and air conditioning, food processing, heating plants, power stations, etc.The thermal contact resistance between the copper tube and the aluminum fin of the heat exchanger is reduced after the tube expanding process, the pressure of the contact surface between the aluminum sheet and the copper tube is increased, so that some deformation occurs on the protruding part of the contact surface, so as to reduce the gap, increase the contact area, reduce the thermal contact resistance between the two, and strengthen the heat transfer. since the air cooler is going through water or medium, it must be a light tube, which can reduce the resistance of the liquid in the pipe.