Melting process of Carreau non-Newtonian nano-phase change material inside cylindrical energy storage system: Effect of thermal fins

Abstract

Melting of a non-Newtonian phase-change material in a finned porous vertical cylinder was numerically studied. The governing equations and corresponding boundary conditions were derived by the enthalpy–porosity technique in cylindrical coordinates. The equations were then non-dimensionalized and solved by the finite element method. The grid independence of the solution was evaluated, and the fluid dynamics code was validated by comparison with accredited numerical and experimental studies. The results were discussed regarding the number and size of thermal fins and the aspect ratio parameter regarding to the melting volume fraction, the total energy stored, the average Nusselt number, the average velocity, the contour of isotherms, and streamlines. The results showed that increasing the number of the fins from 1 to 5 and using larger fins instead of shorter ones positively affected the time required for completing the melting process by 16% and 20%, respectively. It is worth noting that a storage system with a higher aspect ratio (AR = 2) than a lower one (AR = 0.5) shortens the melting process by about 80%. The maximum value of the total energy stored remains constant with any change in the number and size of the fins; however, it is diminished by reducing the aspect ratio.