Optimizing rotational velocity for melting performance of heat storage tank containing metal foam in building heating system

Abstract

Phase change thermal energy storage (TES) represents a crucial technology for enhancing the efficiency of solar energy utilization, and optimizing the heat transfer performance of TES units has attracted significant interest. In this investigation, a computational model of a horizontal tube-and-shell TES unit was used to analyze heat transfer performance under both active and passive enhancement methods involving the integration of metal foam and the application of rotational conditions, and a rotating TES experimental platform was constructed to verify the numerical model. Meanwhile, the charging performance of composite phase change material (CPCM) under various rotational speeds was investigated. Optimal rotational conditions were selected by comparing parameters such as complete melting time, heat storage rate, heat storage capacity, temperature response rate, and liquid phase, temperature, and velocity distributions. The results indicate that the inclusion of metal foam improves the heat storage efficiency of the phase change material (PCM), resulting in a reduction of the total melting time for CPCM device by a factor of 36 compared with pure PCM device under stationary condition. Additionally, the melting rate of the rotational setup is improved compared to the stationary setup, particularly for CPCM units. Subsequently, a detailed analysis of TES units under various rotational speeds revealed that as the rotational speed increases, the complete melting time decreases. Specifically, at a rotational speed of 0.6 rpm, the melting time decreases by 12 %. Moreover, the rotational mechanism also enhances the temperature uniformity within the TES unit. Notably, further increasing the rotational speed beyond 0.6 rpm does not alter the complete melting time.