Enhanced entropy generation and heat transfer characteristics of magnetic nano-encapsulated phase change materials in latent heat thermal energy storage systems

The objective of the current study is to investigate the importance of entropy generation and thermal radiation on the patterns of velocity, isentropic lines, and temperature contours within a thermal energy storage device filled with magnetic nano-encapsulated phase change materials (NEPCMs). The versatile finite element method (FEM) is implemented to numerically solve the governing equations. The effects of various parameters, including the viscosity parameter, ranging from 1 to 3, the thermal conductivity parameter, ranging from 1 to 3, the Rayleigh parameter, ranging from 102 to 3 x 102, the radiation number, ranging from 0.1 to 0.5, the fusion temperature, ranging from 1.0 to 1.2, the volume fraction of NEPCMs, ranging from 2% to 6%, the Stefan number, ranging from 1 to 5, the magnetic number, ranging from 0.1 to 0.5, and the irreversibility parameter, ranging from 0.1 to 0.5, are examined in detail on the temperature contours, isentropic lines, heat capacity ratio, and velocity fields. Furthermore, the heat transfer rates at both the cold and hot walls are analyzed, and the findings are presented graphically. The results indicate that the time taken by the NEPCMs to transition from solid to liquid is prolonged inside the chamber region as the fusion temperature theta f increases. Additionally, the contours of the heat capacity ratio Cr decrease with the increase in the Stefan number Ste.