Numerical study of thermal storage tank lagged with phase change materials for domestic hot water application

Abstract

Phase change materials (PCMs) are gaining increasing attention and becoming popular in thermal energy storage because they can store thermal energy as latent heat through phase transitions. There are large numbers of PCMs that melts and solidifies at a wide range of temperatures, making them attractive in several applications including application for domestic use. The latent heat storage capability of PCMs when deployed in thermal energy storage technology improves the thermal storage efficiency. This study investigates the numerical modelling (using TRNSYS software) and thermal performance of a Phase Change Material (PCM)-lagged thermal storage tank (TST) for domestic hot water systems. A computational model was developed to simulate heat retention in PCM-lagged tanks using paraffin, PEG 4000, and sodium thiosulphate as storage media. Results indicate that PCM-lagged tanks significantly outperform conventional insulated tanks, maintaining water temperatures above 52.31°C after 24 hours compared to 24.65°C in non-PCM tanks. Sodium thiosulphate emerged as the most cost-effective PCM, offering optimal thermal stability at lower costs, while PEG 4000 demonstrated superior heat retention in larger volumes. Smaller tanks (0.01 m³) heated rapidly but cooled faster, whereas larger tanks (0.10–0.13 m³) exhibited prolonged heat retention, making them ideal for sustained demand.