Optimization and evaluation of topology fins and nanoparticles on performance of multi-tube latent heat thermal energy storage unit

Latent heat thermal energy storage (LHTES) is an important technique for heat recovery and utilization as well as the development and utilization of renewable energy, which can solve the existing problems in the heat supply-demand mismatches in terms of time, space or intensity effectively. However, the low thermal conductivity of phase change materials (PCMs) significantly reduces heat storage and release efficiency. To improve the thermal storage performance of LHTES units, the fin structures of heat storage systems are generated by the topology optimization method, and then a corresponding numerical model of the multi-tube heat source LHTES unit has been established, where topological fins and nanoparticles enhanced phase change material (NEPCM) are both used. The results show that the presence of topology fins and NEPCM improves remarkably the thermal storage performance of LHTES units, while the fin volume fraction has a greater effect on thermal storage performance than that of the nanoparticles. The LHTES unit with a fin volume fraction of 0.1 and nanoparticle volume fraction of 0.05 exhibits the smallest uniformity index and field synergy angles, while the corresponding complete heat storage time is reduced by 83.74% and complete heat release time is shortened by 87.50% as compared to those of the LHTES unit without topology fins and nanoparticles, respectively. Response surface method (RSM) constructs relationships between fin volume fraction, nanoparticle volume fraction, and performance parameters. Furthermore, the technique for Order Preference by Similarity to Ideal Solution (TOPSIS) provides guidance for designs based on different operational priorities.