Magnetohydrodynamics hybrid nanofluid in H-wavy enclosure: natural convection and entropy generation

Abstract

The present work examines numerically the natural convection along with the entropy generation within H-shaped enclosure with wavy walls filled by (Ag-MgO/water) hybrid nanofluid considering inner bodies and under the influence of horizontal magnetic field and thermal radiation using finite element scheme. The inner bodies of the circular shapes are kept at a hot temperature, while the two-sided wavy walls are kept at a cold temperature. The rest of the enclosure’s walls are thermally insulated. The influence of many parameters had been examined such as Rayleigh number \(({10}^{3}\le \text{Ra}\le {10}^{5})\), Hartmann number \(\left(0\le \text{Ha}\le 60\right)\) vertical location of inners bodies \(\left(0.2\le \delta \le 0.8\right)\), distance between inner bodies \(\left(0.3\le E\le 0.9\right)\), height of the enclosure walls \(\left(0.2\le B\le 0.8\right)\) and width of the enclosure wall \(\left(0.1\le A\le 0.9\right)\) in addition to the radiation parameter \(\left(0\le \text{Rd}\le 3\right)\) on fluid flow, heat transfer and entropy generation. The results of this study had been presented in terms of streamlines, isotherms, entropy generation, Nusselt and Bejan number. The results showed that the Nusselt number will be at its lowest value when the vertical location of the inner bodies is \(\left(\delta =0.8\right)\) and the influence of Hartmann number will be negligible at this value. Also, at high Rayleigh number \(\left(\text{Ra}={10}^{5}\right)\) increasing the distance between the inner bodies from \(\left(E=0.3\right)\) into \(\left(E=0.9\right)\) leads to increasing Nu by \(76\%\). However, increasing the height of the enclosure’s walls from \(\left(B=0.2\right)\) into \(\left(B=0.8\right)\) leads to enhancing Nu by \(0.02\%.\) However, increasing width of the enclosure wall from \(\left(A=0.1\right)\) into \(\left(A=0.9\right)\) leads to an obvious reduction in Nusselt number by \(20\%\). Additionally, it had been obtained that increasing the vertical location of the inner bodies, the distance between them and the width of the enclosure and reduction of the height of the enclosure’s wall lead to increasing Bejan number. Stronger magnetic fields enhance conductive heat transfer; increasing the Bejan number which represents irreversibility as noted at increasing Hartmann number from \(\left(\text{Ha}=0\right)\) into \(\left(\text{Ha}=60\right)\) leads to increasing Bejan number by \(79\%\).