Effect of Gap Between Absorber Plate and Condenser Cover on the Performance of a Solar Still

Abstract

In this study, a conventional single slope solar still is designed, fabricated and experimentally analysed for desalination of brackish water. Solar still was fabricated using locally available materials. The effect of depth of water was first investigated. It was verified that an increase in depth of water in the basin decreases the daytime productivity (or yield) of the solar still. However, an increase in depth of water improves the overnight productivity of the solar still. Also, the effect of varying the gap between absorber plate and condenser cover of the solar still is presently analysed. A separate absorber plate (in the form of water tray) was fabricated for this purpose, so that it can raised from the bottom using polystyrene sheets while the condensing cover remains fixed at top of the solar still cavity. For performance evaluation, experiments with different gaps were conducted on best possible clear days under similar conditions of environment. Temperatures within the solar still were analysed and distillate yield was recorded at regular intervals of time during the evaluation period. The yield was analysed in terms of productivity of fresh water per unit area of the absorber plate. It was found that reducing the gap between the absorber and condenser cover increases the yield of distilled water. This can be recognized as higher rate of convective heat transfer between the heated water surface and condensing cover.