Technically and economically optimal water flow rate glass film cooling for hemispherical drinking water distillers

Solar desalination through hemispherical distillers gave large condensation surface area with small volume for low cost yield production. Cooling of the condensation glass surface gave homogenous water film cooling led to high productivity. The present study investigated the effect of the water flow rate for glass cover cooling toward the enhancement of hemispherical distiller performance. To obtain the optimal water flow rate for cooling of the glass cover, eight different water flow rates 0.5-4 L/h with 0.5 L/h flow step were experimentally tested to determine the best flow rate for high performance. To attain this goal, three hemispherical distillers were designed, constructed, tested under the same weather conditions. The first and second are the modified hemispherical distillers glass film cooling with X referring to the flow rate, and the third is a conventional hemispherical distiller which represented the reference case. The experimental results presented that; the water flow rate of 2.5 L/h gave the optimal flow rate for cooling of the glass cover to achieve the highest performance of hemispherical distillers. Cooling of the glass cover at a rate of 2.5 L/h for modified hemispherical distillers gives an accumulative yield of 5.17 L/m(2)/day with an improvement of 43.61% compared to conventional hemispherical distiller. Also, the daily efficiency of modified hemispherical distillers with water flow rate of 2.5 L/h was 50.7% with an improvement of 42.3% compared to conventional hemispherical distiller. The techno-economic analysis presented that the smallest payback period was achieved at a cooling flow rate of 2.5 L/h.