Evaluation of capillary performance of sintered porous wicks for loop heat pipe

Abstract

Thermal management for various applications has promoted the development and in-depth investigations of loop heat pipes (LHP) with sintered porous wicks. The capillary performance of sintered porous wicks, which integrates both capillary pressure and permeability, determines the operation and heat transfer performance of LHP. In this study, the capillary performance was accessed using the capillary rate-of-rise experiments. An infrared (IR) thermal imaging method was employed to monitor the capillary rise processes. Four kinds of sintered porous wicks, i.e., two Inco type 255 and 123 nickel wicks with powder size of 2.2–2.8μm and 3–7μm respectively, and two spherical and irregular copper wicks of 75–110μm, were characterized for the purpose of wick design of LHP. Two working liquids tests, ethanol and acetone, were conduced. Tests results show that the capillary performance determined by both liquids tests showed good agreement. It suggests that the capillary rate-of-rise experiments coupled with the IR thermal imaging method can provide an easy and accurate way to characterize the hydraulic properties of porous wicks of LHP. The copper porous wicks presented both larger permeability and capillary performance than the nickel wicks. The type 255 nickel porous wick outperformed the type 123 in both permeability and capillary performance.