Abstract Solar stills are convenient, cheap and ambient friendly but has the drawback of low production of potable fresh water. To explore better the concept and make more attractive for use some more research is necessary to improve the productivity and thermal performance of these units. In this paper a numerical study on an inclined type solar still is performed to investigate the influence of the water film thickness on the heat transfer and fluid flow inside the device cavity. The solar still system temperatures are calculated for four film thicknesses, 0.14, 0.5, 1.0 and 3.0 mm, through the Runge-Kutta method for the ambient conditions of Campinas, southeast of Brazil. The temperatures of the film and the glass are input to the computational fluid dynamics investigation. The radiative transfer and double-diffusive convection of air and vapor mixture are simulated considering the nongray Spectral Line Based Weighted-Sum-of-Gray-Gases method. The results indicate that the use of film thickness δw = 3.0 mm increased the temperature difference between the water film and the glass from 2.14 °C to 9.15 °C when compared to the film flowing over the bare plate, δw = 0.14 mm, and increased the rate of fresh water yield more than 2.0 times, for summer conditions and peak insolation hours. The use of transparent gas approach slightly overpredicted radiative and convective heat transfer inside the solar still cavity.

中文翻译：

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水膜厚度对倾斜式太阳能蒸馏器传热传质影响的综合研究

摘要 太阳能蒸馏器方便、便宜且环境友好，但具有饮用水淡水产量低的缺点。为了更好地探索概念并使使用更具吸引力，需要进行更多研究以提高这些装置的生产率和热性能。在本文中，对倾斜式太阳能蒸馏器进行了数值研究，以研究水膜厚度对装置腔内传热和流体流动的影响。针对巴西东南部坎皮纳斯的环境条件，通过 Runge-Kutta 方法计算了四种薄膜厚度（0.14、0.5、1.0 和 3.0 毫米）的太阳能蒸馏器系统温度。薄膜和玻璃的温度被输入到计算流体动力学研究中。考虑到基于非灰色谱线的灰色气体加权和方法，模拟了空气和蒸汽混合物的辐射传递和双扩散对流。结果表明，与流过裸板的薄膜相比，使用薄膜厚度 δw = 3.0 mm 使水膜和玻璃之间的温差从 2.14 °C 增加到 9.15 °C，δw = 0.14 mm，并增加了淡水产量的2.0倍以上，适用于夏季条件和日照高峰时间。使用透明气体方法略微高估了太阳能蒸馏器腔内的辐射和对流热传递。与流过裸板的薄膜相比，0 mm 使水膜与玻璃之间的温差从 2.14 °C 增加到 9.15 °C，δw = 0.14 mm，并使淡水产率提高 2.0 倍以上，适用于夏季条件和高峰日照时间。使用透明气体方法略微高估了太阳能蒸馏器腔内的辐射和对流热传递。与流过裸板的薄膜相比，0 mm 使水膜与玻璃之间的温差从 2.14 °C 增加到 9.15 °C，δw = 0.14 mm，并使淡水产率提高 2.0 倍以上，适用于夏季条件和高峰日照时间。使用透明气体方法略微高估了太阳能蒸馏器腔内的辐射和对流热传递。