Improving performance of tubular solar still by controlling the water depth and cover cooling

Recently, tubular solar still (TSS) is considered as one of the preferable options for pure acquisition water, particularly, for small applications located in coastal and arid regions. Such areas are usually doesn't have a sufficient power source for water desalination or infrastructure to transport pure water. This paper presents an improvement in the daily rate of water production by offering TSS integrated with cover cooling. The system consists of a transparent solar tube to increase the amount of solar irradiance, which is combined with a black basin to enhance the absorption and improve the water evaporation. TSS was manufactured using lightweight materials, gaining strong and durable weight, from locally available materials. In this study, different basin water depth (0.5, 1, 2, and 3 cm) were investigated to obtain the best water depth. Furthermore, trying various water cover cooling flow rate (1, 2, 3, and 4 L/h) to get the optimal water-cooling flow rate. The experimental results show that the TSS with lower water depth gives the best performance, where the productivity was reached to 4.5 L/m(2), while with the large water depth at 3 cm give a daily productively of 3 L/m(2). Also, the best cooling water flow rate was obtained at 2 L/h. Under the best conditions corresponding to 0.5 cm water depth and 2 L/h cooling water flow rate, the maximum efficiency was achieved, which was about 54.9%. In comparison with TSS without cooling, the proposed TSS successfully improved the yield and efficiency of the TSS by about 31.4% and 32.6%, respectively. Moreover, the daily thermal exergy efficiency increased by about 9%. From an economic point of view, the cost per liter of clean water output was found to be 0.023 $ and 0.019 $ for TSS without and with cover cooling, respectively. (C) 2019 Elsevier Ltd. All rights reserved.