Effect of Variable Adiabatic Length on a Heat Pipe Performance

The study was conducted to investigate the effects of length ratio [LR=Levap./Ladia., the relationship between two parts, the evaporator length (Levap.) and the adiabatic length (Ladia.)] on the thermal performance of heat pipe. In the current study, purified water was used as an operating fluid and charged in the evaporator through a power supply of 250Watt. A series of experiments were conducted using five length ratios (LR=250/150=1.7, 225/175=1.3, 200/200=1, 175/225=0.8, 150/250=0.6). This was designed to investigate the impact of the studied factors on steady state heat transfer characteristics in the heat pipe (HP). The results derived from the experiments showed that the positive performance of heat pipe was recorded near the length ratio LR=1, where the maximum coefficient of heat transfer (HTC) was 1695W/m2 .ºC. In addition, HTC gradually increased and decreased response to the fluctuated reactions of length ratio.