Experimental study of the thermal performance of a PCM in heat sinks

Abstract

Phase change materials (PCMs) can be great solutions as heat sink for energy storage in microgravity conditions. To guarantee the reliability of the systems, the thermal behavior of the PCMs and their degradation should be understood. Two different configurations of heat sink devices, a cylindrical and a finned hollow parallelepiped based on phase change material (PCM), were investigated. The hydrated salt sodium phosphate dibasic dodecahydrate (Na₂HPO₄·12H₂O) was used as the PCM material, in three different volumes. Were also investigated the effect of copper sponges in the effective thermal conductivity, and the thermal property degradation in the finned heat sink by the sequential heat cycles. The PCM was replaced in each experiment and two power supply heat flux levels were studied. In the second heat sink configuration, consisting of finned heat sink hollow block provided with internal fins, the PCM was not replaced, to observe its property degradation. Power supplied in finned devices varied from 75W to 100W. Experimental results showed a reduction of approximately 50% in the maximum temperature of the heat sink when the copper sponge is inserted. Gaps in hydrated salt decrease the thermal conductance of the heat sink. The PCM thermo-physical properties degradation is negligible for a few numbers of continuous heating cycles.  In the case of finned block device, it was observed a variation of 6% in latent heat storage at the first cycles when the same test was realized several times. Contact area loss increased up 15% at the end of the experiments.