Influence of Void Ratio on Phase Change of Thermal Energy Storage for Heat Pipe Receiver

In this paper, influence of void ratio on phase change of thermal storage unit for heat pipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. Numerical method is offered. The liquid fraction distribution of thermal storage unit of heat pipe receiver is shown. Numerical results are compared with experimental ones in Japan. Numerical results show that void cavity prevents the process of phase change greatly. PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as the void ratio increases. The utility ratio of PCM during both sunlight periods and eclipse periods decreases obviously as the void ratio increases. The thermal resistance of void cavity is much higher than that of PCM canister wall. Void cavity prevents the heat transfer between PCM zone and canister wall.