Two methods for thermal conduction analysis of bi-porous sintered structures

Loop heat pipes (LHPs) have consistently garnered attention for effectively managing thermal conditions in critical electronic components of spacecraft and satellites. Particularly intriguing are LHPs equipped with bi-porous capillary wicks, demonstrating commendable flow and thermal dissipation capabilities. Despite its significance for evaluating the phase-transition heat transfer in porous structures, the effective thermal conductivity (ETC) has not been understood mechanistically. This study aims to establish an efficient procedure for predicting ETC in bi-porous wicks through a comparative analysis of analytical and numerical methods. The analytical ETC expression was formulated using thermal resistance network and neck formation theory. Mean-while, the numerical model utilized the Finite volume method (FVM) combined with a 3D porous structure created by Diffusion-Limited Aggregation (DLA) algorithm. The investigation revealed a congruence between two methods and the measured ETCs of interstitial-pore samples containing fine nickel powders. However, undesirable results were shown for coarse samples due to the irregular particle shapes. In samples with formation pores, the numerical model excels in characterizing the spatial distribution and scale of pores, albeit at the expense of time consumption and model complexity compared to the analytical one. Both methods prove valuable for ETC modeling of sintered bi-porous structures according to desired applications.