A study on thermal performance of a pump-assisted loop heat pipe with ammonia as working fluid

Abstract

Abstact This paper presents a loop heat pipe (LHP) with a pump to overcome the drawbacks of traditional loop heat pipes, such as limited heat transfer distance and temperature oscillation. The mechanical pump used in the loop is a centrifugal micropump which is light-weighted, small-sized and high-speed. In order to avoid the occurrence of cavitation and get a better character of the loop, ammonia is chosen as the working fluid. In consideration of the compatibility between working fluid and material, stainless steel is used to fabricate the whole loop. Meanwhile a biporous nickel wick is sintered to provide the capillary force. The effective heat transfer distance of the loop is 2320 mm. The experiment is conducted under different power of the pump and various temperature of the heat sink. Test results figure out that the system quickly responds to varible heat load and no temperature oscillation occurs. If the heated surface temperature is limited below 80 °C, the loop could handle a maximum heat dissipation of 370 W (heat flux = 36.35 W/cm2) when the power consumption of the pump is 4 W and the temperature of heat sink is −10 °C. Under this circumstance the thermal resistance of the evaporator is 0.176 K/W.