Experimental study on start-up and steady-state heat transfer performance of heat pipe with liquid bypass line for accelerating working fluid

This study investigates the start-up and steady-state heat transfer performance of a heat pipe with a bypass line for accelerating a working fluid. The interface resistance by the counterflow of vapor and liquid under the operation of a heat pipe has a significant effect on the heat transfer performance. An experimental study was conducted on the thermal performance improvement of a heat pipe, which was induced by a reduction in the flow resistance above the phase interface with a counterflow. A heat pipe was connected to the evaporator start and condenser end with a liquid bypass line. The liquid bypass line was designed to improve the steady-state heat transfer performance of the heat pipe by bypassing a portion of the liquid inside the condenser to the evaporator without passing through the capillary structure. Acetone was used as the working fluid, and the effect of the bypass line on the heat transfer performance of the heat pipe was experimentally investigated. The input thermal load, coolant temperature, and inclination of the heat pipe were selected as the experimental variables. The heat transfer performance of the heat pipe was evaluated by the thermal resistance, and the normal operation mode and bypass operation mode were quantitatively compared. When the bypass line was used, the thermal resistance of the heat pipe decreased by up to a maximum of 61%.