Experimental investigation on the performance improvement of tubular solar still using floating black sponge layer

The experimental study in this manuscript aims to enhance the performance of tubular solar distillers. The tubular distillers are characterized by having a large surface area for receiving and condensing compared to a single-slope distiller, and accordingly, the use of floating sponge layers is a good and very effective choice in increasing the rate of evaporation and thus improving the cumulative yield of the tubular distillers. In order to obtain the optimum specifications of the sponge layers that achieve the highest performance of the tubular distillers, four tubular distillers were designed and constructed; the first is a reference distiller without sponge and the other three tubular distillers contain the sponge layers with different specifications. The experimentations were conducted in two stages: in the first stage, three different thicknesses of the sponge layer (20, 30, and 40 mm) were studied. In the second stage, three different densities of the sponge layer (16, 20, and 30 kg/m3) were studied. All test cases were compared with reference distiller under the same climatic conditions of Egypt. The results show that the utilization of a floating sponge improves the tubular distiller performance. The peak improvement in the accumulative yield of tubular distillers was achieved in case of utilizing a sponge layer with a 30-mm thickness and 16-kg/m3 density. The reference distiller gives maximum accumulative yield of 3.72 L/m2 day while the floating sponge layer utilization improves the accumulative yield to 5.92 L/m2 day with 59.2% improvement. Also, the utilization of floating sponge layer reduced the cost of distillate yield by 36.3% compared to reference distiller.