Performance enhancement of double-wall-heated rectangular latent thermal energy storage unit through effective design of fins

Abstract

This study aims to numerically investigate the influence of different designs of fins on the performance enhancement of a double-wall-heated rectangular thermal energy storage unit (TESU). Stearic acid is used as the phase change material (PCM) which is enclosed in a rectangular enclosure with two vertical heated isothermal walls and two adiabatic horizontal walls. The rectangular horizontal fins assist the heated walls during the melting process of the PCM. The design parameter variations of fins include angles (A), shapes (S), lengths (L) while maintaining constant PCM volume. The base case is modeled by embedding heated six horizontal fins, three on each of the heated walls. configuration-A, which incorporates three variations of fin angles, significantly increases the melting time of PCM by 16% and reduces the averaged energy storage rate by 14.2%. Whereas, the combination of straight and angled type hybrid fins of configuration-S show appreciable improvement in thermal performance of TESU by enhancing the melting rate by 18% and average energy storage rate by 19.8%. The configuration-L, encompassing combinations of straight fins with different lengths and thicknesses is found to be most effective of all. The optimum case of configuration-L augments the melting performance of the TESU by 39.5% and the average energy storage rate by 65.07%. Moreover, for optimum configuration, two new correlations of melting Fourier number and average Nusselt number as a function of Stefan number and Rayleigh number, respectively, are proposed for a wide range of wall temperatures.