Two-phase mixture modeling of mixed convection of nanofluids in a square cavity with internal and external heating

• Mixed convection of nanofluids in a cavity is studied using Two-phase mixture model.
• The results show that, at low Ri, the distribution of the solid particles remains almost uniform.
• There is an optimum volume fraction of nanoparticles for maximum Nusselt number.

Steady state mixed convection heat transfer of nanofluid in a two-sided lid driven cavity with several pairs of heaters and coolers (HACs) inside is investigated numerically using two-phase mixture model. The governing equations have been discretized using the finite volume method while the SIMPLE algorithm has been introduced to couple the velocity–pressure. The influences of volume fraction, diameter and type of the nanoparticles, Richardson number, number of the Heaters and Coolers (HACs), external and internal heating and moving direction of the cavity walls on flow structure, the heat transfer rate and distribution of nanoparticles are investigated. The results of this investigation illustrate that, at low Richardson number by increasing number of the HACs, the heat transfer rate increases. On the other hand, at high Ri, a saturated number of HACs exists which beyond that the value of mean Nusselt number does not changes significantly. In addition, the results reveal that by reducing the diameter of the nanoparticles and Ri, the heat transfer rate increases. It is also observed that at high Richardson numbers, distribution of nanoparticles with dp ≥ 145 nm is fairly non-uniform while at low Richardson numbers particle distribution remains almost uniform. Moreover, it is found that by changing direction of the moving walls the heat transfer rate changes significantly.

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