EFFECT OF NON-CONDENSABLE GAS ON OPERATING TEMPERATURE FOR A MINIATURE LOOP HEAT PIPE

摘要

The generation of non-condensable gas (NCG) in the closed two-phase heat transfer devices is an unavoidable phenomenon, which can adversely affect the thermal performance of such devices.In this work, experimental investigation of the effect of NCG on the steady-state operating temperature of a ammonia-stainless steel miniature loop heat pipe (LHP) was conducted.In the experiment, nitrogen was injected into the LHP as the NCG, and the operating temperature of the LHP was tested at different NCG inventories, heat loads applied to the evaporator and power cycle conditions.Experimental results reveal that NCG elevates the steady-state operating temperature of the evaporator;meanwhile, the more NCG exists in the LHP, the higher the operating temperature.The effect on the operating temperature is very salient under a low heat load because the utilization of the condenser may be shortened by the working fluid redistribution from the reservoir to condenser.But in the high heat load region, the effect is insignificant and can be generally neglected.Besides, temperature hysteresis was observed at a small NCG inventory, but such phenomenon disappeared when the NCG inventory increased.