Numerical simulation of MHD double diffusive natural convection and entropy generation in a wavy enclosure filled with nanofluid with discrete heating

Rujda Parveen,T.R Mahapatra

doi:10.1016/j.heliyon.2019.e02496

Rujda Parveen, T.R Mahapatra

Open Access

https://doi.org/10.1016/j.heliyon.2019.e02496

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Journal: Heliyon	Publication Date: Sep 1, 2019
Citations: 61	License type: cc-by

Affiliation: Visva-Bharati University

Abstract

A numerical investigation of entropy generation, heat and mass transfer is performed on steady double diffusive natural convection of water-based Al2O3 nanofluid within a wavy-walled cavity with a center heater under the influence of an uniform vertical magnetic field. The top horizontal wavy wall, left and right vertical walls of the enclosure are kept at low temperature and concentration of Tc and cc whereas central part of the bottom horizontal wall is maintained at high temperature and concentration of Th and ch and the remaining part is kept adiabatic where temperature and concentration gradient are taken as zero. The Bi-CGStab method and Tri-diagonal algorithm are used to solve the governing equations. The study has been performed for several relevant parameters such as Rayleigh number (103≤Ra≤105), Hartmann number (0≤Ha≤60), buoyancy ratio number (−2≤N≤2), volume fraction of nanoparticles (0.0≤ϕ≤0.2) and different undulation number of the upper wavy wall (n). The Prandtl number and Lewis number are kept fixed at Pr=6.2 and Le=2. The effect of these parameters are revealed in terms of streamlines, isotherms, isoconcentrations, entropy generation, average Nusselt number and Sherwood number. Results indicate that heat and mass transfer rate augment as Rayleigh number and volume fraction of nanoparticles increase and are found to drop with the increase in Hartmann number and buoyancy ratio.

Highlights

Fluid dynamics induced by the combination of temperature and concentration gradients is called double-diffusive convection
We have considered Magnetohydrodynamic doublediffusive natural convection of Al2O3-water nanofluid in a wavy enclosure
The upper and the vertical walls are maintained cold while the remaining part of the lower wall are considered to be adiabatic

Summary

Introduction

Fluid dynamics induced by the combination of temperature and concentration gradients is called double-diffusive convection. Double diffusive natural convection heat transfer has fundamental aspects in modern life. As well as in scientific fields such as astrophysics, biology and chemical processes, geosciences etc In most of these applications, numerous enclosures of various shapes (including rectangular, triangular, trapezoidal, rhomboidal, sinusoidal or ellipsoidal) have been considered to analyze the heat and mass transfer effects. Lee and Hyun [1] investigated the double-diffusive convection in a rectangular enclosure. They reported that Nusselt number reduces monotonically as the buoyancy ratio rises from a small value. Mahapatra et al [3] analyzed the effect of buoyancy ratio on double-diffusive mixed convection with uniform and non-uniform heating of walls

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