Study of the heat transport capacity of a novel gravitational loop heat pipe

Abstract

This article presented a theoretical analysis of the heat transfer limits associated with a gravitational loop heat pipe (LHP), which involves the utilization of an innovative liquid feeding/distributing and vapour/liquid-separating structure. The mathematical equations governing the heat transport capacity were applied to simulate several commonly known heat transfer limits of the pipe, namely, viscous, sonic, entrainment, capillary, boiling and liquid filling mass limits. This will allow the determination of the actual figure of the limitation and analyses of the factors effecting the limits, including the loop operational temperature, wick type, evaporator diameter/length, evaporator inclination angle, vapour column diameter in the three-way fitting, liquid filling mass and evaporator-to-condenser height difference. During the study, the heat-transfer limits associated with the three-way fitting for liquid feeding/distribution and vapour/liquid separation were given particular attention. The results derived from the analytical model indicated that the compound screen mesh wick can achieve better thermal performance over the sintered powder and open rectangular groove wicks. It was also found that the heat transport capacity of such LHP operation is positively proportional to the operational temperature, evaporator diameter, evaporator inclination angle, vapour column diameter within the three-way fitting, liquid filling mass and evaporator-to-condenser height difference, and in a reciprocal order to the evaporator length. With the specified loop configuration and operational conditions, the LHP can achieve a high heat transport capacity of around 900 W. Overall, the work presented in this article provided an approach to determine the heat transfer limitations for such a specific LHP operation that will be of practical use for the associated system design and performance evaluation.