Experimental investigation on acceleration of working fluid of heat pipe under bypass line operation

Abstract

In a conventional heat pipe, the flow resistance is generated by the opposing flow of liquid and vapor across the phase-change interface. The flow resistance can impose a limitation on the heat transfer rate within the heat pipe, which can have an adverse effect on its overall efficiency. Therefore, reducing the flow resistance is essential for improving the heat transfer of heat pipe. The method of inducing a decrease in flow resistance is classified as an essential technology for improving the heat transfer performance of a heat pipe. In this study, experiments were conducted to induce operating fluid acceleration by decreasing the hydrodynamic resistance inside a heat pipe to improve thermal performance. A liquid bypass line connecting the three points of the condenser to the beginning of the evaporator was designed and installed, with four flow rate control valves attached to control the bypass flow rate at each bypass port. In this study, the working fluid acceleration was observed experimentally in bypass mode (all bypass valves opened) and normal mode (all bypass valves closed). According to the experimental results, the heat transfer efficiency of the heat pipe system improved by up to 106.5% in relation to the thermal resistance. The maximum thermal load in a horizontal position increased by up to 45.8% in the bypass mode.