Numerical study of heat and mass transfer in a solar still device: effect of the glass cover.

Abstract The numerical study of double-diffusive natural convection in an inclined rectangular cavity, that simulates a solar still, is carried out. Surface thermal radiation and heat conduction in a glass cover are considered. The study analyzes the effect of the glass cover, the aspect ratio (5 ≤  A  ≤ 20) and the tilt angle (15° ≤  θ  ≤ 35°). The value of A is related to the Rayleigh number. The values analyzed were 9.29 × 10 4  ≤  Ra  ≤ 6.56 × 10 6 , where the minimum value of Ra corresponds to A  = 20 and the maximum value of Ra corresponds to A  = 5. Streamlines, isotherms, iso-concentration of H 2 O, condensate of H 2 O and Nusselt and Sherwood numbers are presented. Results show that the energy transmitted through the glass cover causes asymmetry, increases the velocity near the walls, and modifies the flow pattern, and the heat and mass transfer. When A decreases, the multi-cell pattern decreases, and the convective heat and mass transfer increase up to 41%. As the tilt angle increases, the Sherwood and Nusselt numbers increase up to 3.8% and the condensate of water increases about 3% when the one-cell pattern prevails; when the multi-cell pattern decreases from θ  = 15° to θ  = 20° the Sherwood and Nusselt numbers decrease up to 22% and the condensate of water decreases up to 43%.