In order to improve the cable current carrying capacity, the heat-conducting material was pumped into ducts to improve the situation of duct heat output.

The related perforating coating tool for a heat-conducting fin comprises: a hollow tube filled with conductive medium, some discharge holes on one end of the tube, and a spring scraper under the hole.

The one key to resolve the heat-transfer effect lies in making the refrigerant circulating rapidly and completely, the other one lies in decreasing the thermoresistance of evaporating section.