Numerical analysis of MHD combined convection for enhanced CPU cooling in NEPCM-filled a trapezoidal cavity

This study investigates the cooling of a central processing unit (CPU) using a nano-encapsulated phase change material (NEPCM)-water mixture in a trapezoidal cavity with rotating cylinders and baffles. A numerical model based on the finite element method (FEM) is employed to solve the governing equations. The system is subjected to a sinusoidal temperature profile from the CPU and a constant magnetic field. Key parameters examined include Reynolds number ( Re : 10–100), Richardson number ( Ri : 0.1–10), Hartmann number ( Ha : 5–80), NEPCM volume fraction ( ϕ : 0.015–0.035), Lewis number ( Le : 0.1–10), buoyancy ratio ( Nz : 1–5), NEPCM fusion temperature ( θ f : 0.1–0.9), and Stefan number ( Ste : 0.1–0.9). Results show that increasing Re and Ri significantly enhances heat and mass transfer, with the average Nusselt number ( Nu av ) increasing by up to 80.5 % and average Sherwood number ( Sh av ) by up to 147.9 %. The magnetic field suppresses convection, reducing Nu av by 12.7 % and Sh av by 39.5 % as Ha increases. Increasing ϕ improves heat transfer ( Nu av up by 32.5 %) with minimal effect on mass transfer. Le strongly influences mass transfer, with Sh av increasing by 284.6 % as Le increases. The NEPCM fusion temperature exhibits a non-monotonic effect on Nu av , with an optimal value at θ f = 0.5. In conclusion, the study reveals complex interactions between parameters, with Re , Ri , and Le having the most significant impacts on system performance. These findings provide valuable insights for optimizing CPU cooling systems using NEPCM-water mixtures and magnetohydrodynamic (MHD) effects.