Abstract:
In this research, a numerical analysis has been carried out on combined convection in a lid driven trapezoidal enclosure with sinusoidal wavy bottom surface filled with hybrid nanofluid composed of equal quantities of Cu and Al2O3, Cu and CNT, Cu and CuO, and Cu and TiO2 nanoparticles dispersed in water-based fluid. The left and right inclined walls of the trapezium have been considered as insulated while the top side of the cavity as cooled isothermally and the bottom sinusoidal wavy wall as hot. The two-dimensional governing partial differential equations of heat transfer and fluid flow with appropriate boundary conditions have been solved using finite element method of Galerkin's weighted residual approach built in COMSOL Multyphysics. The code validation has been shown. The implications of Richardson number, Prandtl number, number of waves, and solid volume fraction of nanoparticles of four types of hybrid nanofluids on the flow structure and heat transfer characteristics have been investigated in details. The comparison of heat transfer rate using hybrid nanofluids namely water-Cu-TiO2, water-Cu-CuO and water-Cu-Al2O3, water-Cu-CNT and clear water has been also shown. Results have been presented in terms of streamlines, isothermal lines and average Nusselt number of the above-mentioned hybrid nanofluids for different values of governing parameters. The numerical results indicate that the Richardson number has significant effect on heat transfer performance from Ri = 0.1 (forced convection) to Ri = 10 (natural convection) about 15%. Moreover, it is noticed that combination of two different nanoparticles suspension has a better performance of heat transfer than single nanoparticle. Also, higher rate of heat transfer is found by 14.7% for wavy surface than flat surface of the enclosure. Higher heat transfer rate is found about 4.1, 3.1, and 2% using water-Cu-CNT hybrid nanofluid with compare to water-Cu-TiO2, water-Cu-CuO and water-Cu-Al2O3, respectively. It is concluded that using hybrid nanofluid as heat transfer medium is more convenient than single nanofluid or base fluid.
