Thermo-Fluid Analysis of a Single Slope Water Distillation Unit using Numerical Approach

Abstract

A numerical study has been performed using COMSOL Multiphysics to investigate the interactions between heat transfer (HT) and fluid (FL) during solar desalination via a single-slope solar still. The model consisted of a shallow saline basin, a black absorbing plate, insulated walls, and an inclined glass cover that was the condensation surface. A two-dimensional multi-physics modelling approach enabled the simulation of the combined temperature, velocity, pressure and thermophysical behaviour of the humid air cavity. Results obtained from simulations show that the areas of highest temperature within the still existed immediately adjacent to the black absorbing plate and saline water, while the lower temperature regions were adjacent to the inclined glass cover. This confirms the existence of a thermal gradient capable of providing the evaporative/condensate temperature drive. Longitudinal temperature profiles demonstrated a gradual temperature change along the length of the still, while both velocity and pressure demonstrated significant discontinuities near the end of the cavity. In addition, mass flowrate demonstrated very slight but perceptible differences in kinematic viscosity across the dimensions of the enclosure. In summary, results from the study suggest that the thermal field within the still is relatively smooth, while the flow field is highly dependent upon position within the cavity.