Application of Taguchi method to determine the optimal water depth and glass cooling rate in solar stills

The current study investigates the optimization of solar stills (SSs) productivity under different levels of solar radiation intensity, film cooling flow rate and water depth. Taguchi method is applied to perform a minimum number of experiments and to find the optimal water depth and cooling rate that maximize the productivity of the SS. An orthogonal array, signal-to-noise ratio and analysis of variance (ANOVA) are used to investigate the influence of the operating parameters on the solar still productivity. Taguchi method and ANOVA result several that water depth is the most influencing parameter. Furthermore, the results show that increasing the solar radiation and water film cooling improve the productivity. However, increasing the flow rate more than 4 kg/hr has a slight effect on the productivity. On the other hand, decreasing the water depth leads to a great enhancement in the productivity due to the faster evaporation and condensation rates. The levels of the operating parameters under-investigation are selected as follows: solar radiation intensity (5587,5673 and 5741 W/m2/day), film cooling flow rate (2, 4 and 6 kg/hr) and water depth (0.5, 1 and 1.5 cm). The improvement in the productivity with film cooling was about 6.05% at the water depth (0.5 cm). A regression equation was formulated to determine the relation between the operating parameters as independent variables and the productivity as a dependent variable.