关键词: 低温热管, 混合工质, 热阻, 传热极限

Abstract: The heat transfer performance of a cryogenic heat pipe using N2-Ar binary mixture as working fluid is experimentally studied and discussed in this paper.Heat pipe is a high efficiency heat transfer device by utilizing the liquid-vapor latent heat of working fluid，but the disadvantage is that the operational temperature range of heat pipe is limited by the triple point and critical point of working fluid.While，wide operational temperature range is required in some cases，especially in the cryogenic field referring to the cooling down process from room temperature to ultra-low temperature.In order to study the heat transfer performance of the cryogenic heat pipe using mixture as working fluid，an experimental setup is established，in which the liquid nitrogen at atmospheric pressure and resistive heating wire wound around the evaporator act as the heat sink and heat source，respectively.The working fluid is charged into the cryogenic heat pipe by a safe and effective method，without high charging pressure and complex equipment.The filling ratio in the experiments is 1.0.The temperature distribution along the entire cryogenic heat pipe and the inner pressure are measured during the experiments.These parameters are recorded after the entire cryogenic heat pipe reaches a steady state under a certain heating power，and the heating power applied on the evaporator is increased step-wisely until the heat transfer limit of the cryogenic heat pipe，which is signified by the abrupt rise of the evaporator temperature.The heat transfer performances of the cryogenic heat pipe with pure-N₂，pure-Ar and N₂-Ar binary mixture working fluid are tested in the experiments，and the results of different working fluids are compared with each other.It is found that the cryogenic heat pipe with mixture working fluid has wider operational temperature range than that of the two pure working fluid cases，and the thermal resistance of the cryogenic heat pipe with mixture working fluid is lower than that of the pure-Ar case and higher than that of the pure-N₂ case.The heat transfer limit of the cryogenic heat pipe with the mixture working fluid is the same as that of the pure-Ar case，e.g.160 W，higher than that of the pure-N2 case，e.g.110 W.

Key words: cryogenic heat pipe, mixture working fluid, thermal resistance, heat transfer limit