Manufacturing and testing of the double-layer wick structure in a loop heat pipe

The work develops a double-layer wick to improve the structural strength and transfer of the working fluid of a biporous wick under higher heat flux. The properties of double-layer wick different structures are utilized to enhance heat transfer performance in a loop heat pipe (LHP). The outer layer of the double-layer wick is the biporous wick, which utilizes large and small pores as channels through which to transport vapor and working fluid, respectively. The inner layer of the double-layer wick is the monoporous wick, which provides a high capillary force and increases the strength of the outer layer. A process for manufacturing the double-layer wick is developed. Experimental results demonstrate that at 85 °C, the limiting temperature of the evaporator wall, the maximum heat load of the double-layer wick reached 700 W, and the heat transfer coefficient of the evaporator was 116 kW/m2 °C. The minimum thermal resistance of the system was 0.08 °C/W. A comparison with the heat transfer performance of a monoporous wick demonstrates that the double-layer wick has a 67% higher maximum heat load (vs. 420 W for the monoporous wick) and an almost half lower total thermal resistance (vs. 0.17 °C/W for the monoporous wick).