Comprehensive Effects of Nano Enhanced PCM on the Thermal Performance of Elliptical Storage System

This study presents a numerical investigation into the thermal performance of TiO₂ nanomaterials dispersed in pure paraffin phase change material (PCM) within straight tubes of circular, triangular, and elliptical cross-sections, serving as thermal energy storage systems. A constant heat flux ranging from 1000 to 10,000 W/m² was applied as boundary conditions, with TiO₂ nanoparticles having an average diameter of 20 nm and a volume fraction of 1%. Numerical simulations were conducted using ANSYS FLUENT 18 to evaluate the thermal behavior of these geometries. The results reveal significant thermal enhancements when using the Nano-PCM blend compared to pure PCM. Specifically, the Nano-PCM exhibited temperature increases of 22.8%, 20.9%, and 15.9% for circular, triangular, and elliptical cross-sections, respectively. Furthermore, the elliptical system demonstrated superior thermal performance compared to the triangular and circular systems. The PCM temperature in the elliptical system surpassed the triangular and circular systems by 46% and 52.45%, respectively, while the Nano-PCM temperature was higher by 42.8% and 48.3%, respectively Entropy analysis showed similar trends, with the PCM entropy in the elliptical system exceeding that of the triangular and circular systems by 75.2% and 91.6%, respectively, and the Nano-PCM entropy increasing by 75.8% and 91.7%, respectively. The findings were compared with prior studies on cylindrical storage systems, where the maximum storage temperature was improved by 37% and 42.3% for PCM and Nano-PCM, respectively, highlighting the superior performance of the present approach. This work underscores the potential of elliptical systems and Nano-PCM blends to enhance thermal energy storage efficiency.