Computational thermal analysis of a latent heat storage unit augmented with porous fins

Abstract

Phase change material (PCM)-based thermal energy storage systems provide a large capacity to store energy; however, PCMs are impaired by relatively low thermal conductivity. Presently, the use of copper foam annular fins was numerically investigated in a PCM-based thermal storage unit. Six copper annular fin cases were studied: three cases with 10 fins and three cases with 20 fins. The 10 and 20 fin cases included configurations with solid fins and two porous fin cases including 40 PPI with porosities of 90.91% and 97.20%. Simulations were completed in ANSYS-Fluent to examine the effects of porous annular fins on the charging and discharging cycles of a vertical shell-tube unit with Rubitherm RT-55 PCM. The cases were compared based on required time to completely melt and solidify the PCM, along with the energy response of the system. Charging times for the solid, 90.91% porous, and 97.20% porous 10 fin cases were 11.89, 19.92, and 23.33 h. The same cases discharged the system in 11.39, 19.50, and 27.28 h. Equal cases with 20 annular fins charged the system in 10.00, 22.78, and 28.08 h, and discharged in 9.08, 18.14, and 26.22 h. Increased convection from porosity cannot overcome reduction of effective thermal conductivity.