Experimental Study of a Reversible Loop Heat Pipe

Abstract

An experimental investigation of a reversible loop heat pipe was conducted to determine the operating limits and performance characteristics as a function of the thermophysical and geometric parameters, the heat input, and the cooling intensity. Variations in both the temperature and heat transport capacity were measured and analyzed to accurately evaluate the transient operating characteristics. In addition, the maximum heat transport as a function of the mean evaporator temperature, the ratio of heat transport to heater input power as a function of the mean evaporator temperature, and the overall thermal resistance as a function of the overall heat transport capacity were examined. The results indicated that the operating limits and performance characteristics of these devices were a strong function of the cooling intensity, with the maximum heat transport corresponding to a cooling intensity of 290 W/°C, more than twice that obtained for a cooling intensity of 72 W/°C. Observation of the transient startup characteristics indicated that the optimal mean evaporator temperature for reliable startup was in the range of 35 to 60°C. Using these operating parameters, overall thermal resistances as low as 0.02°C/W were measured.