Design and test of a flat capillary pump with ceramic wick

Abstract

<p indent=0mm>A novel flat capillary pump was designed to solve the problem of heat leakage from the evaporator to the accumulator in flat capillary pumps. The materials used to obtain the porous wick and main shell were silicon nitride and low-thermal conductivity titanium alloy, respectively. The size of the resulting capillary pump was <sc>82.0 mm</sc> × <sc>53.0 mm</sc> × <sc>16.0 mm,</sc> and eight cylindrical silicon nitride porous wicks were arranged inside the pump. The pore size, porosity, and heat conductivity of the porous wick were <sc>0.5 µm,</sc> 70%, and 2.7 W/(m K), respectively. Experimental results showed that the flat evaporator loop heat pipe can be started quickly and that no obvious overheating occurs in the evaporator under a heat load in the range of <sc>5.0–20.0 W</sc> when the angle of the capillary pump is 0°. The time required to start the flat evaporator loop heat pipe remarkably increased and the temperature increment evidently increased under a <sc>5 W</sc> start load when the angle of the capillary pump was increased. However, when the start load was increased to <sc>20 W,</sc> the starting characteristics of the pipe improved. The heat-transfer ability of the flat evaporator loop heat pipe, equilibrium temperature of the accumulator, and thermal resistance of the pipe were subsequently tested, and results revealed that the heat transfer and heat flux limits are <sc>400.0 W</sc> and <sc>26.3 W/cm²,</sc> respectively. The equilibrium temperature of the accumulator changed with the heat sink and load, and this is consistent with the typical running characteristic of the loop heat pipe. The minimum thermal resistance tested was 0.018°C/W. Finally, the back heat leakage from the evaporator to the compensation chamber was estimated from the energy balance of the compensation chamber.