Numerical study of conjugate heat and mass transfer in a solar still device

Double-diffusive natural convection and surface thermal radiation in an inclined cavity that simulates a solar still device is studied numerically. The parameters considered were 103 ≤ RaT (RaM) ≤ 106, 8 ≤ A ≤ 16 and 15° ≤ θ ≤ 35°. The steady state 2-D governing equations have been solved by the finite volume method. Streamlines, isotherms, isolines of water vapor, mass flow rate of distillate and average Nusselt and Sherwood numbers as a function of Rayleigh number for different inclination angle are presented. The results show that surface thermal radiation modifies the fluid flow from one-cell to multi-cellular pattern due to the surface thermal radiation increases the velocity near the walls, as a consequence the average convective Nusselt number, the total Nusselt number and the Sherwood number were increased about 25%, 175% and 15%, respectively. The mass flow rate of distillate increases as A, Ra and θ increase. The most suitable case for a solar still device is that for RaT = 106, A = 16 and θ ≥ 25°.