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The present study outlines a mathematical framework for evaluating the energy and exergy efficiency of charging operations involving two distinct phase change materials (PCMs) denoted as PCM1 and PCM2, as well as various heat transfer fluids (HTF) and thermal energy storage (TES) systems. Using a phase change material (paraffin wax RT55 and lauric acid) in a concentric thermal storage system is investigated experimentally herein using a triple pipe heat exchanger (TPHX). As part of a three-pipe (TPHX) system, the innermost pipe transports water (hot water). The inside pipe of the exchanger is coated with paraffin wax, while the outer pipe is constructed of lauric acid. To this end, experiments were conducted to examine how changes in flow rates, input temperatures, and Stefan numbers (selected in response to charge situations) affect PCM's energy and exergy calculations. Energy-exergy efficiency and entropy generation were both found to be enhanced by increasing the intake flow rate and temperature. As the intake flow rate is increased from 11 L/min to 52 L/min, the complete melting time is reduced by 12%, 15.7%, and 19.09% for PCM1, while reduce by 23.25%, 24.5%, and 25% for PCM2, while as the input temperature is increased from 316 K to 328 K, the melting time is reduced by 36.2%. Also, the results show that the energy stored, energy efficiency and exergy efficiency at PCM1 is bigger than PCM2 at same flow rate. Where energy storge increase by 15% at minimum flow rate and 12.85% at maximum flow rate, the energy efficiency of PCM1 increase by 47% then PCM2 at maximum flow rate, while increase by 43% at minimum flow rate, while exergy efficiency of PCM1 increase by 9.45% then PCM2 at maximum flow rate, while increase by 8.47% minimum flow rate. Evaluating the Nusselt number and the entropy generation number can also help boost the efficiency of a thermal storage system.

Three models of latent heat storage with circular fins were studied numerically and experimentally in this paper. The models were shell‐and‐tube, shell‐and‐nozzle, and shell‐and‐reducer. These models were investigated for two different inlets of heat transfer fluid (HTF), from the bottom and top of the models, so the number of studied cases was six. The results of the comparison between the cases showed that the different HTF inlet with a fixed mass flow rate greatly affects the completion time of the melting process; the bottom inlet of HTF accelerates the melting compared to the top inlet because it enhances the role of natural convection. Compared with shell‐and‐tube with bottom HTF inlet, the shell‐and‐nozzle with bottom inlet reduces the melting time by 11.2%, while the shell‐and‐reducer with bottom inlet delays the melting by 24%. The results of the top HTF inlet cases showed that shell‐and‐nozzle delays the melting by 16% compared with shell‐and‐tube, while the melting is not completed in shell‐and‐reducer. Shell‐and‐nozzle with a bottom HTF inlet shows the shortest melting time and the best thermal performance among all the other cases due to the geometric design of the model. On comparing the numerical and experimental results, good agreement was found between them.