Assessing sustainable latent heat energy storage of RT 35 phase change material in double pipe heat exchangers: A study on concentric and hairpin designs

To reduce the reliance on conventional fuels and mitigate environmental degradation, phase change materials (PCMs) offer a promising alternative. This study compares the performance of melting and solidification processes in hairpin and concentric heat exchangers (HEXs), with the goal of designing effective latent heat energy storage systems for both domestic and industrial applications. The research highlights that the time required for melting and solidification depends on several factors, including the thermal diffusivity and viscosity of the PCM. Although the energy contained in both concentric and hairpin heat exchangers is equal due to the same quantity of PCM used, the time required for energy storage is shorter in the hairpin heat exchanger (HHEX) (146 min) compared to the concentric heat exchanger (CHEX) (207 min). Additionally, the study underscores the significance of selecting the appropriate PCM, noting that PCMs with higher latent heat values has more energy storage capacity. However, the efficiency of energy storage also based on the variation in temperature between the high-temperature fluid (HTF) and the starting temperature of the PCM. The study finds that the energy storage capacity of the hairpin heat exchanger (HHEX) is 1.8 times greater than that of the concentric heat exchanger (CHEX) when using RT 35 as the PCM.