Experimental investigation of thermal energy storage using phase change material in a rectangular box containing aluminum foam

Abstract

Thermal Energy Storage plays a pivotal role in optimizing heat recovery systems and energy usage. In thermal energy storage applications, Phase Change Materials (PCM) are the primary components of the system. Paraffin waxes are commonly chosen as the phase change materials, particularly in low-temperature thermal energy storage systems. However, paraffin, being an organic material, exhibits low thermal conductivity, which significantly affects the efficiency of the thermal energy storage process. Indeed, there are various methods to enhance these materials' thermal conductivity, including adding nanoparticles, utilizing porous mediums, employing finned heaters, and more. In this study, a rectangular box was carried out by an experimental study to evaluate the effect of the number of aluminum foam pieces in a phase change material box on the melting and solidification processes. We aimed to enhance the thermal conductivity of the composite system comprising paraffin RT57 as the phase change material and aluminum foam. We compared the time-saving benefits of using porous materials in combination with the phase change material, both with and without porous media, within a rectangular box. The investigation involved twelve different cases, including cases with pure phase change material and phase change material coupled with one to three pieces of metal foam, each subjected to three different water inlet temperatures. Our findings indicate that the most significant time savings were achieved when three metal foam pieces were added. The enhancement in time savings for three metal foams was notable, with improvements of 10.6%, 13.3%, and 18.7% compared to the case using pure paraffin at water inlet temperatures of 75°C, 80°C, and 85°C, respectively, during the melting process. In addition, the presence of metal foams in cases with one to three layers of metal foam results in significantly more uniform temperature profiles compared to pure paraffin cases, without metal foam. This improvement has been attributed to the increased effective thermal conductivity achieved by incorporating metal foam. Furthermore, during the solidification process, the maximum time savings were observed in the case of three metal foams, with reductions of 37.7% and 32.6% compared to the pure paraffin case at inlet temperatures of 10°C and 20°C, respectively. These results highlight the substantial benefits of incorporating metal foams in the phase change material for efficient heat storage and release. Like the melting process, in the solidification process, the case with metal foam shows a more uniform temperature compared to pure paraffin.