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Abstract
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In this study, the effect of varying cross-section fins on energy storage performance has been studied. For this purpose, a vertical double-pipe heat exchanger has been numerically studied. During the melting and solidification processes, respectively, hot fluid and cold fluid pass through the inner tube. Six different fin geometries with curved and triangular cross-sections were examined and compared in the charging and discharging processes. Furthermore, for the fin geometry with the best performance, the effect of non-uniform spacing between the fins was also investigated. It is worth mentioning that the volume of phase change material as well as the total fins volume are considered constant in all cases. For a more detailed analysis, the results were presented in the form of temperature and liquid fraction contours, streamlines, changes in liquid fraction and average temperature over time, exergy, and energy efficiency diagrams. The results of this research showed that fin geometry has a significant effect on improving heat transfer rate and can reduce charging time by about 23 % and discharging time by about 31 %. Additionally, concentrating the fins at the bottom of the exchanger can reduce charging time by about 13 % compared to the uniform fin arrangement.
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