Effects of pore structures on the capillary and thermal performance of porous silicon nitride as novel loop heat pipe wicks

Porous Si3N4 ceramics with monomodal and bimodal pore size distribution are selected as novel wick materials for loop heat pipe. The capillary and thermal performance of porous Si3N4 wicks is investigated by tailoring their pore structures. The wicks with larger permeability affected by their pore structures exhibit lower filling coefficient representing better capillary performance, due to lower frictional resistance of the fluid flowing through them during the liquid uptake process. It is essential for wicks with excellent capillary performance to establish the balance between the improved permeability derived from the increased pore size and the reduced capillary force caused by that. Moreover, the wicks using working fluid with lower viscosity, larger surface tension and higher density show better capillary performance according to the comparison of three different working fluids. The effective thermal conductivity of wicks is determined by their total porosity. The comparison of experimental values and calculated values of effective thermal conductivity indicates that the most suitable calculated curve is provided by Alexander model based on limited data in the test. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Porous Si3N4 ceramics with monomodal and bimodal pore size distribution are selected for loop heat pipe wick materials. Tailoring the pore structures influences capillary and thermal performance, with wicks showing larger permeability having lower filling coefficients and better capillary performance. Wicks using working fluids with specific properties exhibit better capillary performance, and effective thermal conductivity is determined by total porosity.