Combined conjugate free convection and thermal radiation in a porous inclined enclosure occupied with Cu-Al2O3 hybrid nanofluid

Abstract

This study deals numerically with a steady laminar combined conjugate natural convection and thermal radiation heat transfer within an inclined porous enclosure occupied with Cu-Al2O3 /water hybrid nanofluid; the thermal conductivity and nanofluid viscosity are correlated experimentally. The centered heat sink and source are attached respectively to the upper and lower enclosure walls at a set distance of 0.5 from the sidewall and were parameterized with length values of 0.2, 0.4, 0.6, 0.8, and 1. This analysis is performed in wide ranges of enclosure inclination angles (0≤ α ≤ 180°), thermal radiation parameters (0≤ Rd ≤ 200), hybrid nanofluid volume fractions (0.1, 0.33, 0.75, 1, 2, 3, 4, and 5%), Rayleigh numbers (103≤ Ra ≤ 106), Darcy numbers (10−5≤ Da ≤ 10−2), medium porosities (0.1≤ ε ≤ 0.9), and thermal conductivity ratios (1≤ γ ≤ 10). The Nusselt number increases as the heat sink/source length decreases. This trend is even more pronounced when the length of the sink/source is reduced. Furthermore, the average Nusselt numbers for the fluid and solid matrix gradually increase as the inclination angle of the enclosure varies from 0° to 45°. However, beyond 45°, both Nusselt numbers exhibit a noticeable decrease with increasing inclination angle of the enclosure. The average Nusselt number of the fluid significantly increases with varying thermal radiation parameters. When the thermal radiation parameter ranges from 0 to 2 and 0 to 200, the average Nusselt number of the fluid increases by 192% and 7343%, respectively. The Nusselt numbers significantly improve when the porosity decreases and the thermal conductivity ratio increases. For a porosity of 0.1 and a porous thermal conductivity ratio ranging from 1 to 10, the average Nusselt number of the fluid increases by approximately 129% and 141% when the Darcy number increases from 10−5 to 10−2.