Numerical investigation into natural convection of nanofluids in an inclined square enclosure with non-uniform heated walls

Studying natural convection of nanofluids in enclosures with non-uniform heated walls is of importance in many engineering applications such as solar energy collection. In this study, we developed a Fully Higher-Order Compact (FHOC) finite difference method to investigate the natural convection and heat transfer of nanofluids in an inclined square enclosure with sinusoidal temperature distributions. Numerical simulations were performed over a range of amplitude ratios, inclination angles, phase deviations, nanoparticles volume fractions, and Rayleigh numbers. Results showed that heat transfer could increase significantly by increasing the amplitude ratio and inclination angles in nanofluids. Moreover, elevating the nanoparticles volume fraction did not always enhance the heat transfer of nanofluids. When the Rayleigh number Ra was low (Ra = 10(3)), the average Nusselt number decreased as the solid volume fraction parameter, phi, increased. On the other hand, elevating phi had favorable effects on the heat transfer of nanofluids when Ra was high (e.g., Ra = 10(4), 10(5)). With Ra = 10(4), the total heat transfer rate decreased with nanoparticles in the order of Cu, CuO, Al2O3, and TiO2. Finally, a correlated expression of the total average Nusselt number, the Rayleigh number, and the solid volume fraction of nanoparticles was empirically obtained. (C) 2019 Sharif University of Technology. All rights reserved.