Discrete ordinates simulation of radiative participating nanofluid natural convection in an enclosure

Natural convection was studied by discrete ordinates approach within a radiation enclosure in which nanoparticles absorption and scattering were taken into consideration. Nanofluid was prepared in deionized water as the base fluid and Al2O3 nanoparticles. In order to reach a semitransparent medium suspension, nanofluid was prepared by adding small amount of Al2O3 nanoparticles volume concentration. In addition, the Navier-Stokes equations were solved based on SIMPLE algorithm of finite volume method to simulate the natural convection and then coupling to radiation by discrete ordinates approach. Two-dimensional inclined rectangular enclosure was assumed, while the inner emissive walls were found to be diffuse-gray. The various values of Ra number and volume concentration of nanoparticles at different wavelengths were studied. The results declared that the wavelength had positive impact on the radiation heat flux. More accurate results were obtained in comparison with the previous researches used Roseland approximation, due to using the discrete ordinates method to consider the adsorption and scattering coefficients. With increasing nanoparticles volume concentration, the scattering coefficient increased; hence, the heat transfer of radiation declined. On the other hand, it enhanced the natural convective heat transfer. By coupling these two conclusions, it was observed that more volume concentration corresponded to less total heat transfer which implied the main outcome of present work and made it different from the present works used nanofluid.