EFFECT OF PHOTOSTABILITY OF DYES ON ENHANCING THE PRODUCTIVITY OF SOLAR STILLS

Document Type : Original Article

Authors

1 Professor in faculty of Engineering, Minia University

2 Faculty of Engineering, Minia University

Abstract

The basin-type solar still is the most common and easiest to design. However, its thermal efficiency is low and so some way should be followed to enhance its productivity. In the present article dyes are added to water basin of the solar stills to increase the absorptivity of water for the solar irradiation thus raising its productivity. Three dyes of different photo-stability are used and are compared with respect to its hourly productivity, total productivity, efficiency and its production behavior along the day. The dyes used are: Black Naphthylamine 10 BR , Dark Green Dye and Red Carmoisine BA Ex. Results showed that the highest daily productivity of 2740 ml/m2 is given by the Black dye solution of 200 ppm concentration. For all stills, daily still productivity decreases with increasing water depth in the basin. The percentage increase in total still productivity due to the use of dyes was 37.55, 29.02 and 20.48%, for the Black, Green and Red dyes solutions, respectively; compared to the reference still. Percentage reduction of still productivity due to increasing water depth was 12.77, 8.95 and 9.17% for the Black, Green and Red dye solutions; when increasing water depth from 2 to 3 cm. The enhancing effect of the Black dye was mostly pronounced in the morning period since its photo-stability (expressed by the degradation half-life period) is much less than the other two dyes. However, for being darker in color, the enhancing effect of the Black dye was better than the other two dyes.

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