Optimizing Double‐Pipe Heat Exchangers Orientation for Low‐Temperature PCM in TES Systems

ABSTRACT To effectively store thermal energy as latent heat and mitigate shortages of energy during power outages, phase change materials (PCMs) offer numerous possibilities. This study investigates the impact of the heat exchanger's (HEX's) spatial orientation relative to gravity on the heat transfer rate. The inlet fluid temperature is determined using the Stefan number, with values of 0.44 having an inlet temperature of 358 K (melting) and 284 K (solidification), respectively. We compare the phase change results of RT50 for both vertical and horizontal orientations of concentric heat exchanger and hairpin heat exchanger (HHEX). The findings indicate that both HEXs in a vertical orientation and in a horizontal orientation yield the most significant improvements in PCM melting. The findings indicate that RT50 experiences shorter melting times when placed vertically upward compared with horizontal placement in the case of HHEX, but for HHEX, the melting time is shorter for horizontal cases, showing reductions of 13.68% and 21.33%, respectively. On the other hand, solidification has not undergone a significant change due to changes in the direction of gravity.