Numerical investigation of latent heat storage unit with dual helical tube

Abstract

The application of latent heat storage systems in waste heat recovery has become a promising solution for energy storage. This study proposes a configuration using dual helical tube, specifically designed for industrial waste heat recovery applications. This study investigates the thermal performance of a horizontal dual helical energy storage unit under natural gravity. It considers various parameters, including helical diameter, the number of helical turns, and eccentricity. When an eccentricity of 5 mm is used, the overall energy storage time is reduced by 30.86 %, and the energy storage density is at its highest (3.11 × 10−4 kW/cm2). Adjusting the outer helical tube to 9 turns produces the highest energy storage efficiency (0.9252). Additionally, the heat transfer characteristics during simultaneous energy storage and release processes have been studied. The results indicate that as the temperature difference or velocity ratio between the heat transfer fluids increases, the liquid fraction at steady state decreases. This decrease in liquid fraction requires a longer time to reach the steady state. When the outer helical tube is filled with the hot fluid and counter flow configuration is adopted, it achieves higher levels of absorption and release power at steady state. The influence of velocity on absorption and release power is more significant than that of temperature difference.