Estimation of convective heat transfer coefficient and water-productivity in a tubular solar still - CFD simulation and theoretical analysis

Typical solar stills suffer from their low productivity and it is very important to design an optimum device. CFD simulation can assist engineers to enhance the performance of a solar still for a given cost. In this study, we investigate the ability of a 2-D CFD simulation in computation of heat and mass transfer in a tubular solar still. The results show that there is acceptable agreement between the results of CFD simulation and experimental data reported in the literature. CFD simulation indicates a recirculating zone with a clockwise direction inside the enclosure. The results also imply that the most condensation takes place on the upper side of the glass cover. Moreover, we propose new relations to estimate water productivity, heat and mass transfer coefficients in the tubular solar still. Based on these relations, we suggest characteristic curves to estimate water-productivity in different operational conditions. The results of curves show inverse effect of glass temperature, and direct effect of water temperature on the performance of a tubular solar still.