Impact of chemical reaction on the convective heat transport in nanofluid occupying in porous enclosures: A realistic approach

Abstract

This work demonstrates the impact of chemical reaction on the convective instability and heat transport in nanofluid saturated porous enclosures utilizing linear and nonlinear stability analyses. The enclosures are considered to be rectangular, square and slender. A two-stage model is utilized for nanofluid with thermophysical assets observed from phenomenological and mixture rules; whereas the Darcy model is taken for porous medium under the assumption that nanoparticle flux is vanish on the boundaries. The numerical results are shown for four types of nanofluids. Base fluid considered is water, and with them four distinctive nanoparticles used are silver, copper, alumina and titanium oxide. Within the circumstance of linear stability regulation, the critical nanofluid Rayleigh-Darcy number, the critical wave number, and the frequency for stationary and oscillatory convections are obtained as a function of chemical reaction parameter, aspect ratio, nanoparticle Rayleigh-Darcy number, modified Lewis number, modified diffusivity ratio and heat capacity ratio. In the context of nonlinear theory, the convective heat transfer in the system is determined in term of Nusselt number for both steady and unsteady cases. It is found that the oscillatory convection is not possible for nanofluids with the boundaries conditions considered here. The result of rising the chemical reaction parameter, the nanoparticle Rayleigh-Darcy number, the modified Lewis number and the modified diffusivity ratio is to quick the beginning of convection and furthermore increment the rate of heat transfer across the porous enclosures, whereas the heat capacity ratio has no impact on the onset of convection. The amount of the heat transfer improves with raising the heat capacity ratio and the thermal conductivity ratio. The heat transfer drops with the aspect ratio for rectangular enclosure, while this result is revered for the slender and square enclosures. Also, the heat transfer increased respectively as much as 22.7%, 20.8%, 19.8% and 18.9% for W-Al2O2, W-TiO2, W-Cu and W-Ag nanofluids as compared to the base fluid of water.