Influence of condenser bypass port area on maximum thermal load of heat pipe

Experimental works have been conducted to enhance the performance of heat pipes by focusing on the maximum thermal load, which is a very important performance indicator. Ordinal operation on the heat pipe occurs when the capillary force is sufficient to overcome the flow resistance of the working fluid. Therefore, one method of increasing the maximum thermal load is to reduce the flow resistance of the liquid and vapor with counter flow in the system. Moreover, the flow resistance of the working fluid is immediately dependent on the mass flow rate, and reducing the flow rate can effectively increase the maximum thermal load. The liquid bypass technique is one method of alleviating the flow resistance of the working fluid inner side a heat pipe container. In this work, a modified heat pipe system with one liquid bypass tube was manufactured and investigated, with the bypass tube being constructed so that some of the working fluid inside the condenser could be bypassed to an evaporator not going through a heat pipe interspace with vapor and liquid counterflow. Three bypass ports were located in the condenser; hence, the influence of bypass port area on thermal of heat pipe performance was investigated experimentally. Mass flow rate control valves were attached to these three bypass ports, and the maximum thermal loads according to the activation of each port were experimentally measured. The maximum thermal load in a horizontal position increased by up to 45.8% with an increase in the area of the bypass port. With the increase of the activated bypass port area, the condenser wall temperature increased by up to 15.9 °C. •The dry-out prevention performance of the heat pipe was able to be enhanced by the bypass line.•The maximum heat transfer rate was significantly increased by the bypass line.•Bypass line is a passive means for dry-out control without sacrificing operation temperature.•The maximum thermal load increased with an increase in the liquid bypass mass flow rate.