A thermal energy storage system employing phase change material (PCM) for rapid heat discharge was studied numerically and experimentally. In the numerical studies, paraffin wax FNP-0090 (product of Nippon Seiro Co. Ltd.) was used as the PCM and was encapsulated in four different capsules (sphere, cylinder, plate and tube) for investigating the effects of geometrical configurations. The capsules filled with PCM were placed in a rectangular tank. Water was used as the working fluid in a rectangular tank. Water was used as the working fluid in the circulation system to discharge the storage tank. A one-dimensional model was used for solving the water temperature distribution along the flow direction in the tank and a conductive one-dimensional phase change model was used for simulating the solidification process of the PCM inside the capsules. The effects of the capsule diameter and shell thickness and the void fraction on the performance of the heat storage system were also investigated. Results shown include the variation of the outlet water temperature of the storage tank with time, the temperature and heat release distributions of the PCM along the flow direction in the tank at different times, etc. A plate heat exchanger was used as a heat storage tank for experimental study. FNP-0090 was filled into the channels (the space between two plates) of one side of the heat exchanger and water flowed in the channels of the other side of the heat exchanger. The effect of flow rate and initial temperature on the outlet fluid temperature and heat release was investigated. The numerical results and the experimental data agreed within 10%.

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