Loop Heat Pipe Operating Temperature Dependence on Liquid Line Return Temperature

A Loop Heat Pipe (LHP) is a passive two-phase heat transfer device developed and successfully employed to cool spacecraft (satellite) electronics. The intrinsic benefits of this technology (lightweight, small volume, high thermal conductance) make it an attractive potential solution to many problems in ground vehicle thermal management. As most published LHP research has focused on cooling orbiting spacecraft components, there is little knowledge of how LHPs perform under the temperature extremes (−40°C to 40°C) and diurnal/seasonal fluctuations anticipated with terrestrial applications. Ambient temperature extremes mandate consideration of transport line heat exchange with the surroundings (parasitic losses/gains).

This paper presents results from an experimental investigation of liquid line return temperature impact on system performance for sink temperatures from −30°C to 40°C and evaporator loads up to 700 Watts. A heat exchanger is placed on the liquid line to control the temperature of the fluid returning to the compensation chamber and evaporator, and to compensate for heat exchange between the subcooled liquid and the environment. Control of the returning liquid temperature enables simulation of any subcooling condition desired, and evaluation of the impact on system performance from heating or cooling the liquid line.