Simulation of evaporation and sublimation process in porous plate water sublimator based on a reduced CFD model

Abstract Water sublimator is an ideal high-efficiency heat rejection device working in the vacuum environment with a high thermal load. The ideal working condition for the water sublimator is the sublimation in a porous plate. In this study, the process of evaporation, freezing and sublimation in a porous plate are investigated numerically and experimentally. The mass transfer of the feedwater in the porous plate involves the theory of the rarefied gas flow in micro-channels. In order to establish a reduced CFD model in conjunction with the mathematical model, a dynamic heat transfer boundary is defined and a user-defined function (UDF) is prepared in the ANSYS Fluent software. Temperature and position of the evaporation/sublimation front, which significantly affects the heat dissipation of the sublimator is considered in the simulations. Furthermore, the thermal properties of the liquid water and ice are considered to simulate the different thermal conductive performance and freezing processes. In order to validate the simulation, a porous plate water sublimator is tested in a vacuum chamber. It is found that the simulation results are in an excellent agreement with the experiment. The present study focuses on the process before the cold surface reaches the low-temperature peak of 258 K from 283 K. Accordingly, it is found that the physical process before the cold surface reaches the low-temperature peak of 283 K. Based on the verified model, flows with different feedwater mass flow rates and heating fluxes in the porous plate are simulated. Obtained results show that an inappropriate matching of the water supply and the heating flux prevents the feedwater to enter the sublimation state in the porous plate. Moreover, it is concluded that the proposed CFD method simplifies the problem reasonably and significantly reduces the computational expenses.