An Experimental Study of Floating Wick Basin Type Vertical Multiple Effect Diffusion Solar Still with Waste Heat Recovery

Abstract

The present research work aims at reducing the unit cost of distillate produced in a solar still by incorporating suitable improvements in the existing basin type vertical multiple effect diffusion (VMED) solar still. Extensive literature survey was done to study the design innovations done by various researchers to enhance the distillate productivity of solar stills, particularly the basin stills. An improved and modified version of basin type VMED solar still, having multiple floating wicks in basin, and heat exchanger for waste heat recovery for feed water pre-heating (FW-BVMED-HR), has been developed. This floating wick basin type VMED solar still with waste heat recovery (FW-BVMED-HR) has double glass covers in its basin section. The partition plates had divided wick structure for uniform wetting, in which each of the wicks were fed by feed water from gravity flow, by individual feed tubes. Longitudinal rubber spacers were used to divide the cotton cloth wicks and maintain partition plate gaps, and also to effectively seal the partition cells on the border of partition plates. The basin section had internal stainless steel reflectors. The first partition plate was of copper and rest partition plates were of stainless steel. Another still identical in dimensions and features, to FW-BVMED-HR still, was fabricated. Without floating wick and heat exchanger, this still served as a reference still, for comparison experiments. The complete experiments were done in an order and hence the experimental set-up was also fabricated in stages. Initially, a basin still was fabricated, with copper plate as back wall, which was well insulated on the outer side. Few experiments were conducted on basin still to find out its productivity. The conventional basin still is then converted into basin type vertical single distillation cell (VSDC) solar still. In other words the conventional basin still is converted into basin type VMED still with two effects.