Effects of fin length distribution functions and enclosure aspect ratio on latent thermal energy storage performance of dual-wall-heated unit

Abstract

This study focuses on numerical investigation of performance enhancement of rectangular dual-wall-heated Latent Thermal Energy Storage Unit (LTESU) embedded with 12 horizontal fins, 6 on each of the isothermally heated walls. Stearic acid is used as the Phase Change Material (PCM). The fin designs are optimized by employing linear, quadratic, cubic, and exponential fin length distribution functions with decreasing slopes. The enhanced fin design is further improved for different aspect ratios of enclosure. Enthalpy-porosity model is employed for simulations after validating against experimental results. As compared to the reference case (equal-sized fins), linear and quadratic fin configurations intensify the PCM melting times by 31.7% and 24.3% while the averaged energy storage rates are enhanced by 46% and 31.4%. A marginal performance enhancement of LTESU is observed for cubic fin arrangement. The exponential fin configuration produces strong convection effects in PCM and increases the melting and energy storage rates by 35.2% and 52.69%, respectively, thus making it the best fin configuration. Additionally, aspect ratio and fin thickness of 0.5 and 1.5mm further intensify the melting and energy storage performance of PCM by 56.6% and 129%, respectively. Lastly, for optimum LTESU design, correlations for melting and heat transfer rates are proposed for different wall temperatures.