Investigation on the thermal performance of shell and tube thermal energy storage system using paraffin wax as phase change material
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Date
2022-09
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G. B. Pant University of Agriculture and Technology, Pantnagar
Abstract
Energy conversion is an essential aspect of technology advancement, and hence its efficient generation and use are important in today's scenario. In present scenario, there is a large gap between demand and supply, and it is difficult to meet the current energy requirement. Thermal energy storage devices enable us to attain energy demand while simultaneously minimizing pollution. The semi-circular outer shell geometry of the LHTES unit with and without fins on the inner tube using paraffin wax as phase change material has not been investigated yet. Hence it has been decided to investigate the melting performance of paraffin wax numerically and experimentally for circular shell, semi-circular shell without fins and semi-circular shell with finned tube latent heat thermal energy storage (LHTES) systems. Numerical analysis of two-dimensional model of different configurations of the LHTES system has been performed in Ansys fluid fluent to investigate the thermal performance of paraffin wax. Since natural convection plays important role in the melting process so the outer shell geometry is modified to semi-circular so that whole PCM is present in the upper portion and the heat transfer between the solid PCM and liquid PCM improves. In order to further improve the thermal performance fins are added to inner tube of the LHTES unit. Therefore, five different configurations including three different semi-circular with finned tube for different fin angles ( = 60º, 90º, 120º), semi-circular without fin, circular configuration have been investigated for the melting performance of the PCM. The results for a semi-circular shell with a fin angle of 90º for the LHTES system are found better as the thermal energy storage rate of finned tube LHTES system is 0.11 kW, which is 110% higher as compared to circular and 88% higher as compared to the semi-circular LHTES system. The semi-circular shell with finned tube LHTES melts the PCM completely in 66 minutes which is 54.98% less than the circular LHTES system and 32.65 % less in comparison to semi-circular without fin configuration. Thermal energy stored in the circular and semi-circular without fins arrangement of LHTES unit is 275.7 KJ and 290.37 KJ respectively. The thermal energy stored in the semi-circular LHTES unit with fins on the inner tube is 297 KJ which is 7.72% more as compared to the circular configuration and 2.3% more than the semi-circular without fins arrangement for same time period of 7200 sec. The thermal energy storage efficiency of semi-circular with finned tube LHTES unit has been found 6.72% higher than that of the circular LHTES system and 2% higher than the semi-circular without finned tube LHTES.