Natural convection heat transfer of nanofluid in an enclosure saturated with square and circular blocks

In this paper natural convection heat transfer of nanofluid simulated in a box with square and circular blocks. Governing equations is solved using finite volume method by Fluent software and Nusselt number near the hot wall at different Darcy numbers, is obtained for box with square or circular blocks. Results show that when there is a few blocks, temperature contour and streamlines depend on blocks geometry while increasing the number of blocks decrease this dependency. For box containing heater element in square arrangement, conduction heat transfer is dominant while in horizontal arrangement convection is dominant. By growth of Rayleigh number and consequently increasing of rotational flow convection portion in heat transfer increases. Although most portion of heat transfer is by conduction and convection has little effect. In the next part of research effect of nanoparticle concentration in heat transfer is studied. Results show an increase in average Nusselt number and heat transfer coefficient for higher volumetric concentrations of nanoparticles. Time taken to reach steady state for water based nanofluid is less than time for water/ Copper oxide, ethylene glycol, and water/ Copper oxide, propylene glycol. Variation of heat transfer coefficient in term of Nusselt number for Copper oxide, ethylene glycol, and Copper oxide, propylene glycol nanofluids with increase of nanoparticle concentration is independent of Rayligh number