Thermal Performance of Cylindrical Heat Pipes with Varying Evaporator Lengths

Abstract

The thermal characteristics of heat pipes with varying lengths of evaporator section was investigated keeping condenser and adiabatic section length constant. Three heat pipes with evaporator length of 0.05 m, 0.010 m and 0.015 m respectively were fabricated. Both adiabatic and condenser section length was kept constant at 0.01 m respectively. Studies were carried out separately using die-ionized (DI) water and methanol as working fluid.  The heat input at the evaporator was varied from 50 to 300W in heat pipes charged with DI water and from 25 to 200 W in the heat pipes charged with methanol. Total thermal resistances of the heat pipes as well as those of both evaporator and condenser resistances separately were measured and results were analyzed.  Methanol charged heat pipes showed the best performance when the evaporator length was longer than adiabatic and condenser section. But for heat pipes with deionized water, the heat pipes with equal length of evaporator and condenser showed the best performance. The length   of  evaporator section strongly affects the  heat transport limit and thermal resistance of the heat pipe.  Thermal resistance of the heat pipe varies with evaporator length and the working fluid used.