Influence of partial discharging in a latent heat thermal energy storage unit: 3D numerical study

A deep understanding of the various operating modes is crucial to ensure an optimum exploitation of latent thermal storage systems. Incomplete discharge constitutes one of these operating modes, which can be of great interest, for example, in fluctuating demand situations. In the present paper, a 3D numerical study is carried out to investigate the effect of partial discharge on the performance of a finned multitube latent heat thermal energy storage unit. The analysis is performed on both the discharge and the subsequent charging processes. Partial discharge with 80% total solidification and full discharge with 100% solidification are compared in terms of process duration and energy released/stored. Erythritol and hytherm 600 were utilized as phase change material and heat transfer fluid, respectively. The results show that during the discharge process, partial discharge saves 47.7% of the process time, with only 20.7% of unused energy. As for the following charge, an equivalent time saving and unused energy of 20.4% and 21.5%, respectively, are obtained after a partial discharge as compared to full discharge. Furthermore, the local analysis shows that the melting front evolution is influenced by the partial discharge.