Gravity-Invariant Condition of Water Sublimator Characteristic Parameter Design: Analysis and Experiment

Abstract

Water sublimator is a kind of thermal control device, which takes advantage of the high latent heat of water and can reject spacecraft waste heat by evaporating/sublimating water to vacuum environment. Thus, sublimator could be exclusively be used for spacecraft which couldn't reject heat effectively through radiation. Sublimators has been successfully used in the spacecraft thermal management systems and the portable life support system (PLSS) of space suit. For the sublimator which will be used in micro-gravity or 1/6g environments, it's very important to evaluating their work performance's measurability and ground test results' creditability, through analysis of the gravity effect on their work performance. Detailed work mechanisms of liquid-gas/liquid-solid-gas phase change processes in sublimator porous structures were depicted, gravity effects on the fluidic flow in the work process of sublimator were analyzed, and restrain conditions for sublimator gravity-invariant characteristic parameter design were obtained. Analysis results indicate that the sublimator characteristic parameter which agrees with (Gr/Re^2)<0.1 has a very large value space. While Bond number and Rayleigh number provides more strict restriction of the gravity-invariant characteristic parameter. The gravity-invariant characteristic parameter of 1g environment meets the 1/6g gravity-invariant condition of lunar. For a sublimator with gravity-invariant parameter, its work performance in 1/6g or micro-gravity environment can be evaluated in earth's 1g environment. The reasonability of sublimator gravity-invariant parameter presented in this context is validated by the ground experimental results.