Abstract
A parametric numerical investigation has been performed of three-dimensional combined thermal-solutal capillary and buoyancy convection performances of micropolar multi-walled carbon nanotubes-water nanofluid. The governing equations are given based on vorticity-vector potential formulation and numerically resolved with finite volume method. The effects of Rayleigh number (10(4) <= Ra <= 10(6)), micropolar parameter (0 <= K <= 5), buoyancy ratio (- 2 <= N <= 0), Marangoni number (0 <= Ma <= 1000), and nanofluid concentration (0.0055% <= phi <= 0.557%) on Sherwood/averaged Nusselt number are examined along with their impact on the streamlines, isotherms, and isoconcentrations. The results imply the significant impact of surface tension on the heat/mass transfer rate, in low Rayleigh number in particular Besides, the averaged Nusselt and Sherwood numbers are improved significantly due to arise in the Marangoni number originated from unidirectional effects of surface tension and buoyancy for the thermal-dominated regime. Within solutal-buoyancy governed zone, however, an opposite trend is evidenced. Heat/mass transfer rate is overestimated when the micropolar theory is not taken into consideration. Also, the performance of multi-walled carbon nanotubes/water nanofluid depends on the nanoparticles volume concentration. Hence, there is a critical nanofluid concentration beyond which the intensity of flow increases and then declines.