Energy and exergy investigation of a eutectic phase change material for a triplex tube thermal energy storage with various configurations

Abstract

This study investigates the energy and exergy analysis of eutectic PCM melting (80% melting) within a numerically simulated triplex tube latent heat storage unit. The unit features inner pipes arranged in triangle, pentagon, square, and circular configurations. The parameters examined include mean melting temperature, melting fraction, exergetic efficiency, exergy destruction, heat transfer rate, entropy generation number, and system efficiency, all of which influence melting time. Previous research predominantly focused on cylindrical forms for all three tubes in triple-tube heat exchangers, neglecting diverse inner tube configurations. The study innovates by exploring various innermost tube shapes (triangular, square, pentagonal, circular) in a triple tube heat exchanger. The practical benefits include superior thermal performance for industries like oil and gas, chemical, food and beverage, and power generation. The pentagonal inner triplex tube thermal energy storage (TTTES) system outperforms triangular topologies with higher Stefan and Rayleigh numbers by 11.54% and 11.53%, respectively, at Fo=0.000254. In the pentagonal configuration, the eutectic phase change material (EPCM) experiences a melting rate of 75%, 200%, and 225% faster than triangular, square, and circular configurations within the TTTES. Additionally, the pentagonal inner tube stores 2.28%, 6.90%, and 5.60% more energy than its triangular, square, and circular counterparts after 200 seconds of melting. Thus, TES systems based on pentagonal configurations are more efficient in melting, surpassing triangular, square, and circular counterparts with eutectic PCM.