Buoyancy-driven flow and thermal activity of nano-enhanced phase change material in inversed U-shaped chamber

This work aims to contribute to the positive evolution towards a green world and green energy by studying the natural convection of Nano-Enhanced Phase Change Material NEPCM in an inverted U-shaped cavity. The side walls of the cavity are kept at a cold temperature, while the upper corrugated wall and the lower wall are insulated with the expectation of the hot square body. The governing equations were solved numerically using the Galerkin finite element method (GFEM). The effects of the following factors on the heat transfer rate are presented and discussed: Rayleigh number (Ra = 10³–10⁶), number of ripples of the upper wall (N = 1–4), position of the square body (left, centre, and right), volume fraction of nanoparticles (ϕ = 0–0.08), and magnetic field strength (Ha = 0–100). It was found that the effect of N on the heat transfer rate was insignificant, while increasing ϕ reduced the heat transfer rate. In addition, placing the square body near the cold sidewalls (left or right position) improved the averaged Nusselt number (Nu_avg), especially at low values of Ra. At the highest Ra studied, increasing Ha reduced the Nu_avg by 15 %.