Application of partial wire mesh and particle image velocimetry for rectangular phase change material containers as efficient thermal energy storage systems

Abstract

An experimental setup is built to improve the charging process of a bio‐based phase change material inside a rectangular latent heat thermal energy storage (LHTES) system. In addition to experimenting with different porosities of full‐coverage wire mesh, a novel method of partial wire mesh placement at a proper location is used for improving conduction and maintaining natural convection, proven by the particle image velocimetry (PIV) method. Although acquiring PIV images from coconut oil is challenging because of the laser reflection, the image capturing and processing have been completed successfully. Temperatures inside the enclosure were measured using four K‐type thermocouples, and the melt fraction was calculated using captured images. The full‐size mesh results in a more uniform temperature distribution, and its charging time for porosities of 88% and 82% is decreased by 41% and 52%, respectively. The results of partial wire mesh placements indicate that a top‐only approach leads to a time reduction of only 7%. However, the bottom‐only approach yields a time reduction of 34% and the value of 3.8 for the charging time reduction over the porosity reduction parameter, which is the highest among all experiments. Additionally, this placement eliminates sudden temperature spikes, which improves the performance of the LHTES system and results in an economical and practical configuration. Moreover, the PIV test shows sustained convective velocities at the top half of the enclosure with a partial mesh at the bottom, demonstrating improved natural convection compared to that of a full‐size mesh implementation which weakens convection. Therefore, contrary to full‐size meshes used in previous works, a bottom‐only mesh placement can enhance conduction and convection simultaneously, which can be utilized in practical applications.