The coaxial heat exchanger is designed as a “tube in tube” structure. The outer tube is made of steel/copper, and the inner tube can be titanium, copper, copper-nickel depending on the requirements of working condition. For the inner tube is has many spiral grooves on the surface, which will enlarge the connection surface and get more heat transferred.
Since the temperatures of refrigeration and water are different, the heat will transfer from one with the high temperature to the other one. This is the counter-flow heat transfer principle, which allows the extensive exploitation of the super-heating of the refrigerant vapor and a super-cooling of the liquid refrigerant.