Enhancement of the maximum heat transfer rate of the heat pipe through the bypass line

초록

Dryout prevention is an important index of heat pipe performance. The balance between the capillary pressure supplied by the wick structure of a heat pipe and the flow resistance of the liquid returning to the evaporator determines the maximum heat transfer rate under which a steady state can be maintained. The maximum heat transfer rate is referred to as the capillary limit. If the heat pipe operates at a certain thermal load exceeding the capillary limit, then the onset of dryout in the wick structure occurs at the starting point of the evaporator and expands throughout the entire heat pipe over time. In this study, a bypass line for accelerating working fluid was first devised in order to improve the dryout prevention performance during heat pipe operation. The bypass line is designed so that a part of the working fluid can be bypassed without passing through the capillary structure by connecting the evaporator and the condenser. The liquid bypass line has the effect of increasing the maximum heat transfer rate of the heat pipe because it can increase the thermal load that can cause dryout by reducing the flow resistance of the working fluid on the phase change interface. Acetone was used as the working fluid. The effect of the bypass line on the heat transfer performance of the heat pipe was experimentally investigated. The maximum heat transfer rates of the heat pipe with and without the liquid bypass line were analyzed and compared at tilt angles of 0 degrees to 20 degrees. The results show that the maximum heat transfer rate was increased by approximately 35.5% using a horizontal arrangement.

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