Effect of Cover Inclination and Water Depth on Performance of a Solar Still for Indian Climatic Conditions

Abstract

Effects of condensing cover inclination and water depth on the convective heat transfer coefficient and yield have been studied for a passive solar still. Three solar stills with an effective basin area of 1m2 each have been studied for three inclinations of condensing cover, namely, 15deg, 30deg, and 45deg. An identical solar still, but with a fixed cover inclination of 30deg, has also been tested to evaluate the effects of varying water depth. Outdoor experiments have been conducted for New Delhi climatic conditions (28°37′N∕77°13′E). Hourly variations of temperatures (water, vapor, and cover) and of distillate yield have been recorded and analyzed to determine convective heat and mass transfer coefficients. The resulting calculative extrapolation of experimental data from clear-day operation shows that the combination of minimum water depth and 15deg inclination of the condensing cover leads to maximum annual distillate yield for the climatic conditions of New Delhi. However, a cover inclination of 45deg is almost equally effective on an annual basis, but with better winter performance.