Effect of Y-shaped fins on the performance of shell-and-tube thermal energy storage unit

Abstract

Phase change materials (PCMs) are well known for their inherent poor thermal characteristics, which consequently results in limited thermal efficiency for thermal energy storage systems (TESS). The current work numerically attempts to improve the thermal efficiency of TESS by employing Y-shaped fins with nano-enhanced PCM (NePCM). The NePCM is contained inside the cylindrical TESS, while water, as heat transfer fluid (HTF), is pumped through inner pipes. Three different configurations of the TESS were studied and compared; case 1: the reference case (with no fins), case 2: with two Y-shaped fins attached to the tubes, and case 3: with four Y-shaped fins attached to the tubes. The finite element method is employed to discretize the system's governing equations. Besides the influence of the TESS configuration, the impact of HTF temperature (338 and 348 K) and the volume fraction of the nanoparticles (0–0.08) were also addressed. The evolution of temperature contours and liquid fraction of the three different configurations under the two different HTF temperatures are discussed and analyzed. The findings revealed that using nanoparticles with 8 vol% enhanced the thermal conductivity during melting by 19%. The melting process was accelerated by 87% when the HTF temperature was higher (348 K). Finally, TESS with four Y-shaped fins was found to be the most effective as it achieved a 48% melting time reduction compared to the base case (case 1).