Numerical investigation on regulation and suppression of heat and mass transfer by varying thermal and solutal buoyancy force

Abstract

In this study, a three-dimensional numerical analysis is presented for regulation and suppression of heat and mass transfer by varying thermal and solutal buoyancy force with a rotating cylinder placed at the center of the cavity. The energy and concentration equations are coupled by Dufour and Soret parameters to have a mutual effect of concentration and temperature on heat and mass transfer. The thermal buoyancy in the flow is adjusted by varying Rayleigh number of Ra = 104, 105, 106 and the mixed convection in the flow is regulated by varying Richardson number of Ri = 0.5, 1, 1.5 at unity buoyancy ratio (N = 1), Soret number, Lewis number and Dufour number. The present heat and mass transfer solver is developed and validated using the open-source computational fluid dynamics (CFD) package OpenFOAM 5.0. The two vertical opposite sides of the cavity are maintained as isothermal and isosolutal (iso-concentration), and the remaining four surfaces with rotating cylinder are kept as adiabatic. The present analysis reveals the impact of the mutual coupling of heat and mass transfer with the presence of thermal buoyancy, solutal buoyancy including mixed convection flow. The increase in the forced circulation at fixed thermal and solutal buoyancy force increases the heat and mass transfer. The variation of Nu avg and Sh avg is observed to be steady even with increasing Ra, then changes to periodic and chaotic with the implementation of a rotating cylinder. The detailed analysis on the variation of thermal buoyancy at unity buoyancy ratio, forced convection is reported by plotting streamlines, temperature and concentration contours, average Nusselt and Sherwood number.