CFD analysis of mixed convection and entropy generation in vented curved cavity under the radiation effects

A computational analysis was conducted to examine the heat transfer properties and entropy generation of MgO-Ag hybrid nanofluids undergoing combined forced and free convection in a two-dimensional curved enclosure with ventilation and an undulating heated surface. The governing equations in dimensionless form were solved numerically using the finite element method with a Galerkin approach. The impacts of Reynolds number from 10 to 200, Richardson number (0.1, 1, and 10), nanoparticle concentration ratio of MgO to Ag, number of waves along the heated wall from 0 to 8, radiation number from 1 to 6, and heat source from 0 to 2 are analyzed. The results demonstrate that increasing Re from 10 to 200 augments the average Nusselt number (Nu) by 182%, 184%, and 179% for Ri = 0.1, 1, and 10, respectively. However, this also leads to a growth in total entropy generation (S) by 175%, 177%, and 186% for the corresponding Ri values, primarily due to greater velocity gradients and viscous dissipation. Varying phi r from 0.25 to 1 enhances Nu by 6.8%, 6.7%, and 6.7% at Re = 10, 100, and 200, respectively. Increasing WN from 0 to 8 reduces Nu by 28%, 30%, and 30% at Re = 10, 100, and 200, respectively, while the maximum stream function (psi max) decreases by 2.7%, 3.3%, and 2.0% for the same Re values. The Bejan number (Be) analysis reveals that thermal irreversibilities dominate over viscous irreversibilities, with Be ranging from 0.56 to 0.78 depending on Ri and Re. The study provides valuable insights into the complex interplay between heat transfer enhancement and entropy generation in hybrid nanofluid-filled curved enclosures with wavy walls.