This kind of heat exchanger is to bend the metal tube into various shapes suitable for the container and immerse it in the liquid in the container. The advantage of the coil heat exchanger is that it has a simple structure, can withstand high pressure, and can be made of corrosion-resistant materials; The disadvantage is that the liquid turbulence in the container is low, and the heat transfer coefficient outside the tube is small, in order to improve the heat transfer coefficient.