Influence of void ratio on thermal stress of PCM canister for heat pipe receiver

Influence of void ratio on thermal stress of PCM (phase change material) canister for heat pipe receiver under microgravity is numerically simulated. LiFCaF2 (80.5-19.5 mol%, melting point: 763 °C) PCM is used as a latent thermal energy storage medium for its high latent heats of fusion. Accordingly, mathematical model and numerical method are offered. A judgment for convergence is accomplished. Numerical results show that the thermal stress in PCM canister increases as void ratio increases. Void cavity prevents the heat transfer between canister wall and PCM zone during both sunlight and eclipse periods. The temperature gradient is very significant when void ratio reaches the maximum. So the lifetime of heat pipe receiver may decrease as void ratio increases. The corresponding maximum thermal stress of different void ratios during eclipse periods is lower than that during sunlight periods. If the designed material of PCM canister can satisfy the strength during sunlight periods, it must be safe and reliable during eclipse periods and the necessary overall performance can be maintained. The research results can be used to guide designing the PCM canister for heat pipe receiver.