Using internal sinusoidal fins and phase change material for performance enhancement of thermal energy storage systems: Heat transfer and entropy generation analyses

Abstract

In comparison to sensible energy storage, LHTES (Latent Heat Thermal Energy Storage) offers large storage energy densities per unit mass/volume at nearly constant temperatures. This study is carried out to assess thermo-hydraulic performance of the simultaneous utilization of sinusoidal internal fins and PCM (Phase Change Material) in LHTES systems. For this, a validated numerical framework is developed using Ansys-Fluent software. The RT82 is considered as working substance in a transient laminar flow. The geometrical parameters of fins, (including length, height, and thickness) are evaluated by defining 15 different geometries to look for the most optimal case in terms of faster PCM melting. Furthermore, the impact of fins’ material (copper and gold) is also involved in the investigations. A comprehensive sensitivity analysis is conducted to completely investigate different heat transfer and thermodynamic characteristics. The results illustrated that in case 4 (with H/L = 0.125 and thickness of 3 mm), the highest growth of normalized liquid fraction compared to normalized heat transfer coefficient is achieved which results in Dhl number of about 0.55. Also, the second-law analysis revealed that the lowest entropy is generated in this case. So that, 62% increment of liquid fraction and 59.5% reduction of entropy generation is observed in case 4 compared to a case with simple straight fins.