Influence of encapsulate material thickness and its thermal conductivity on solidification time of phase change material in spherical capsule for cool thermal storage- A novel correlation

Buildings account for 39% of global GHG emissions. In any building, space cooling/heating consumes the maximum electricity. Recently, encapsulated phase change materials (PCMs)-based cool thermal energy storage (CTES) systems have gained huge attention due to its numerous advantages in meeting building space cooling demand. Energy is stored inside these capsules in the form of latent heat. Considering the relevance of PCM solidification in capsules, two novel correlations are proposed to determine the inward and outward solidifi-cation time of phase change material (PCM) inside/around a spherical capsule based on its thermal conductivity and thickness. Further, an experimental investigation is also performed to validate the correlation. The corre-lation agrees closely to the experiment with a maximum inaccuracy of around 6.6%. Thereafter, a parametric analysis is also carried out to analyse the impact of both the parameters on inward solidification time of PCM. The results showed a significant reduction in solidification time up to a capsule thermal conductivity value of 0.3 W/mK. Beyond 10 W/mK thermal conductivity, capsule thickness did not affect solidification. The incorporation of these correlations into software will benefit engineers working in the fields of CTES, refrigeration, food processing, and plastics industries.

Automated summary

Buildings contribute to 39% of global GHG emissions, with space cooling/heating being the largest electricity consumer. Encapsulated phase change materials (PCMs)-based cool thermal energy storage (CTES) systems have gained attention for their advantages in meeting building cooling demand by storing energy as latent heat. This study proposes novel correlations to determine PCM solidification time inside/around a spherical capsule, and validates them through experiments. These correlations, along with the parametric analysis, can benefit engineers in CTES, refrigeration, food processing, and plastics industries.