Thermal optimization of a PCM-based heat exchanger: A modeling approach

This study concerns the thermal performance of a thermal energy storage heat exchanger based on phase change materials (PCMs). The device consists of a series of vertical cavities filled with a PCM, which are subjected to heating and cooling along their vertical walls. A simplified theoretical model was developed using a lumped parameter approach and validated through experimental tests on a scaled-down cavity representative of the heat exchanger geometry. The primary objective of this study was to employ the modeling framework in formulating an optimization strategy aimed at improving system performance during the charging phase. Results indicate that enhancing the natural convection of the molten PCM, by integrating horizontal partitions within the cavity, substantially decreases the charging time, defined as the duration required for complete phase transition from solid to liquid. The reduction in charging time of a PCM-based heat exchanger prototype was found to be substantial (up to 50 %) when the effect of multiple partitions was investigated under constant wall temperature conditions, whereas the reduction was smaller (25–35 %) when heat exchange with an external fluid, at fixed mass flow rate and inlet temperature, was considered.