Comparing trapezoidal and circular configurations to evaluate the impact of shell geometry on thermal energy storage performance

Abstract

This research investigates the influence of shell and inner tube geometry modifications on the thermal performance of latent heat thermal energy storage (LHTES) systems employing phase change materials (PCMs), aiming to overcome the low thermal conductivity and weak melting zones commonly observed in conventional configurations. Several shell-and-tube configurations with circular, rectangular, and trapezoidal geometries were investigated numerically. The novelty of the present study lies in the combined optimization of both shell and inner tube trapezoidal geometries to enhance natural convection and improve heat distribution inside the PCM domain. Numerical simulations evaluate melting time, enhancement ratio, energy storage density, and mean power for each case. Results indicate that the conventional Circle-Circle configuration has the longest complete melting time (CMT) of 5440 s. Fully trapezoidal shell-and-tube designs significantly enhance heat transfer, with Trapezoidal-Trapezoidal 03 achieving a remarkable reduction of 23.53%, lowering the CMT to 4160 s. The enhancement ratio analysis shows that Trapezoidal-Trapezoidal 03 achieves a maximum improvement of 18%, whereas other trapezoidal configurations attain enhancements between 4% and 13%. The superior performance of trapezoidal geometries is mainly attributed to improved heat distribution toward the lower PCM region, reduced thermal dead zones, and stronger natural convection circulation. Regarding energy performance, Trapezoidal-Trapezoidal 03 achieves a mean power of 735 W, while Circle-Trapezoidal 01 and 02 exhibit the highest energy storage densities of 206.24 and 207.88 kJ/kg, respectively. These findings demonstrate that the optimal configuration depends on the targeted application, whether prioritizing rapid melting or higher energy storage density. The present results may contribute to the design of more efficient thermal energy storage systems for solar thermal and industrial waste heat recovery applications.