Abstract: In this paper,the principle is studied of poor heat transfer effect in the three line horizontal central hot water suppliers which are popularized in south China region was studied.An idea of putting inserts like twisted belts and spiral wire into the third line pipe to augment the heat transfer effects is put forward.The experimental and calculating results shows that the heat transfer situation is improved.

Key words: horizontal-type； central hot water supplier； heat transfer augmentation； inserts；