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. A solidification-melting model
upon the enthalpy-porosity method is specially provided to deal with phase
changes. The liquid fraction distribution of thermal storage unit of heat
pipe receiver is shown. The fluctuation of melting ratio in PCM canister is
indicated. Numerical results are compared with experimental ones in Japan.
The 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 void ratio increases. The utility ratio of PCM during both
sunlight periods and eclipse periods decreases obviously with the improvement
of void ratio. 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.