Thermal performance of an ammonia loop heat pipe using a rectangular evaporator with liquid-guiding channels

Abstract

In order to enhance the heat transfer capacity of a stainless steel-ammonia loop heat pipe using a rectangular evaporator, liquid-guiding channels were adopted to significantly reduce the liquid flow resistacne in the evaporator wick. An experimental system was established, and extensive experimental studies have been implemented to investigate its startup characteristics, heat transfer capability and thermal resistance. To be specific, the effects of heat load, evaporator attitude and antigravity on the startup performance were evaluated. According to the experimental results, the loop heat pipe showed excellent startup performance, which could realize the startup at small heat loads for different attitudes of the evaporator. Both adverse evaporator attitude and anti-gravity can cause an increase of the operating temperature of the loop heat pipe, due to poor cooling effect of return liquid and increased heat leak from the evaporator respectively. The loop heat pipe could achieve a heat transfer capability up to 300 W, corresponding to a heat flux of 20 W/cm2. The minimum system thermal resistance reached as low as 0.048 K/W at the head load of 140 W. The present study contributes greatly to the future loop heat pipe applications in high heat flux electronics cooling.