The problem of free convection fluid flow and heat transfer in a square cavity with a flush mounted heat source on its bottom wall and two heat sinks on its vertical side walls has been investigated numerically. Via changing the location of the heat sinks, six different arrangements have been generated. The cavity was filled with Cu-water nanofluid. The governing equations were discretized using the finite volume method and SIMPLER algorithm. Using the developed code, a parametric study was undertaken, and effects of Rayleigh number, arrangements of the heat sinks and volume fraction of the nanoparticles on fluid flow and heat transfer inside the cavity were investigated. Also for the middle-middle heat sinks arrangement, capability of five different water based nanofluids on enhancement of the rate of heat transfer was examined and compared. From the obtained results it was found that the average Nusselt number, for all six different arrangements of the heat sinks, was an increasing function of the Rayleigh number and the volume fraction of the nanoparticles. Also it was found that at high Rayleigh numbers, maximum and minimum average Nusselt number occurred for middlemiddle and top-bottom arrangement, respectively. Moreover it was found that for the middle-middle arrangement, at high Rayleigh numbers, maximum and minimum rate of heat transfer was obtained by Cu-water and TiO 2 -water nanofluids, respectively.

The present study aims to evaluate the mixed convection flow and heat transfer of functionalized DWCNT/water nanofluids with variable properties in a cavity having hot baffles. The investigation is performed at different nanoparticles volume fraction including 0, 0.0002, 0.001, 0.002, and 0.004, Richardson numbers ranging from 0.01 to 100, inclination angles ranging from 0 to 60° and at constant Grashof number of 10 4 . The results presented as streamlines and isotherms plot and Nusselt number diagrams. According to the finding with increasing nanoparticles volume fraction and distance between the left hot baffles of nanoparticles average Nusselt number enhances for all considered Richardson numbers and cavity inclination angles. Also with increasing Richardson number, the rate of changes of average Nusselt number increase with increasing distance between the left hot baffles. For example, at Richardson number of 0.01, by increasing L 1 from 0.4 to 0.6, the average Nusselt number increases 7%; while for similar situation at Richardson number of 0.1, 1.0, and 10, the average Nusselt number increases, respectively, 17%, 24%, and 26%. At all Richardson numbers, the maximum value of average Nusselt number is achieved for a minimum length of left baffles.

Abstract. The present numerical study aims to investigate the e ects of uncertainties of di erent conductivity models on mixed convection uid ow and heat transfer in a square cavity lled with Al2O3-water nano uid. The left and right vertical sides of enclosure are maintained at high and low constant temperatures, respectively, while the bottom and top horizontal sides of the enclosure are kept insulated. Furthermore, the right wall moves from down to up with a constant velocity, Vp. To approximate the nano uid e ective thermal conductivity, ve most commonly used models, namely, Maxwell, Khanafer and Vafai, Corcione, Chon et al., and Patel et al., are employed. Finite volume method and SIMPLER algorithm are used in order to discretize the governing equations. Simulations are performed for nanoparticles volume fraction ranging from 0 to 0.05 and Richardson number ranging between 0.01 and 100. The results indicate that there are signi cant di erences between the average Nusselt numbers predicted by the ve employed conductivity models.