Performance assessment of a phase change charging mode in a vertical thermal energy storage system

Abstract

Summary In this work, the performance of a charging mode of a thermal energy storage system is investigated numerically, and results are assessed considering the first law and second law perspectives. The storage unit comprises parallel plates positioned vertically, and the heat transfer fluid flows within the spacing between the plates. The melting process of phase change material inside a rectangular enclosure is simulated considering the natural convection using an in‐house model codded in C++. The proposed model is validated with the numerical and experimental research from the literature. A parametric analysis is carried out to explore the influence of heat transfer inlet temperature and aspect ratio on the unit's first law and second law performance indicators. Analyses are also conducted by disregarding the natural convection to assess the convective mode of heat transfer on the time‐wise variation of the storage effectiveness and stored exergy. The results revealed that for the highest inlet temperature of the heat transfer fluid, the stored energy value increases from 133.85 to 250 kJ then drops to 240 kJ by varying the aspect ratio from 0.25 to 0.50 and from 0.50 to 1.00, respectively, for the natural convection dominated melting. On the other hand, regarding effectiveness, both with and without natural convection modes show the same aspect ratio variations trend. The effectiveness reduces from 0.9 to 0.40 by increasing the aspect ratio from 0.25 to 1.00 for the natural convection‐dominated melting mode. The effectiveness drops from 0.62 to 0.16 for the same variation in the aspect ratio for the conduction‐dominated melting mode. Besides, it is found that the highest stored exergy is observed in Case 9 w/NC situation with a stored exergy value of 13.3 kJ. The exergy efficiency changes approximately between 65% and 81% for all cases.

Numerical simulation of thermal energy storage system inside a spherical capsule under periodic boundary conditions

“…2 Moreover, it can contribute to noticeable energy savings as well as provide a significant decrease in greenhouse emissions. 3 The usage of phase change material (PCM) is essential in TES systems. In addition, phase change behaviors in PCM play a crucial role in the construction of the TES systems.…”