The heat transfer characteristics of gravity heat pipes with different length and position of evaporator section and condenser section were investigated experimentally. The tested gravity heat pipes were all fabricated with copper tube and charged with distilled water. The heat pipe had the outer diameter of 9.52 mm with the thickness of 1.2 mm and total length of 250 mm. The experimental input power range was from 40 W to 160 W. The results showed that the length and the position of evaporator section and condenser section affected the heat transfer characteristics of gravity heat pipe. When moving up the evaporator section

the evaporator temperature was 1-6℃ lower. The thermal resistance and the evaporator temperature were decreased when moving down the condenser section. And the temperature difference between the condenser section and the adiabatic section was decreased by about 25%. Reducing the length of the condenser section or evaporator section had the negative influence on the heat transfer performance of a heat pipe

which should be restricted in the application of GHPs.