Ground-based investigations on phase-moving phenomenon with space sublimation cooling for lunar exploration missions

The lunar surface is a typical vacuum environment, and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission. In addition to the radiator, the sublimator is recommended as one of the promising options for heat rejection. The sublimator makes use of water to freeze and sublimate in a porous medium, rejecting heat to the vacuum environment. The complex heat and mass transfer process involves many physical phenomena such as the freezing and sublimation phase change of water in the porous medium and the movement of the phase-change interface. In this paper, the visualized ground-based experimental approaches of space sublimation cooling were presented to reveal the moving law of three-phase point and the growth phenomenon of ice-peak and icicle in microchannels under vacuum conditions. The visualized experiments and results prove that the freezing ice is divided into the porous ice-peak and the transparent icicle. As the sublimation progresses, the phase-change interface moves downward steadily, the length of the ice-peak increases, but the icicle decreases. The visualized experiments of space sublimation cooling in the capillary have guiding significance to reveal the sublimation cooling mechanism of water in the sublimator for lunar exploration missions.