Purpose The purpose of this study is to investigate the onset of convection in microelectronics cooling in a trapezoidal thermal system saturated with a H2O based Ag-MgO (50-50%) binary hybrid nanofluid via stream function-vorticity (ψ-ζ) analysis and numerical simulation. Design/methodology/approach A uniformly heated block is positioned in the middle of the trapezoidal system. The block is considered in three different sizes, measured by aspect ratios of 25%, 50% and 75% of the trapezium height. The flow transport in the domain is magnetically controlled. The governing formulas are solved by using a fourth-order accurate compact finite difference scheme, which captures flow physics on low computational grids with high spatial resolution. Findings Quantitatively, the maximum heat transfer enhancement is achieved at AR = 0.75 and γ=75°, with corresponding increases in average Nusselt number (Nuav) ranging from 9.5% to 34.12% at Ra = 104, 8.43% to 29.78% at Ra = 105 and 7.27% to 35.21% at Ra = 106. The results reveal that the heated block significantly alters the thermal and flow structure, especially under higher Rayleigh numbers and inclined boundary configurations. These outcomes offer promising implications for real-world applications requiring efficient thermal management within confined enclosures. Originality/value This work’s originality is found in five key areas: the role of hybrid nanofluids with experimental correlations, the geometrical effects of the trapezoidal cavity, the influence of heated block aspect ratios (0.25 ≤ AR ≤ 0.75), the interaction with applied magnetic fields, and the implementation of higher-order compact computational techniques over a wide range of parameters.
Malo et al. (2026) studied this question.