Performance improvement of tubular solar still via tilting glass cylinder, nano-coating, and nano-PCM: experimental approach

Although the solar distillers are one of the economic solutions for addressing the freshwater shortage problem around the world, these devices suffer from low productivity. In this paper, a simple and inexpensive modification was made in the tubular solar still (TSS) to improve its productivity. The adjustment is to tilt the glass cylinder, something to help the droplets move down and collect them as a distillate. The modified inclined TSS was abbreviated by ITSS. Then, three different inclination angles were investigated (2°, 4°, and 6°), and the performance of ITSS with these inclination angles was compared with that of TSS without inclination angle (0°). Moreover, to obtain additional productivity for ITSS, the basin was painted with a mixture of matte black paint with nanomaterials. Three types of nanomaterials were studied (copper oxide nanoparticles, titanium oxide nanoparticles, and silver nanoparticles). For further improvement in ITSS productivity, Ag nanoparticles mixed with phase change material (PCM) were employed beneath the ITSS base to work as thermal energy storage material. Experimental results revealed that the highest average daily productivity rise for ITSS over TSS was observed when tilting ITSS by 6°, where the daily productivity rise and thermal efficiency reached 24% and 37.6%, respectively. Besides, the average increase in daily distillate of ITSS was 34%, 30%, and 28.5% when using Ag, CuO, and TiO₂, respectively, compared to that of TSS. Moreover, ITSS with Ag provided the best thermal efficiency compared to the other operating cases, where it was 39.1%. In addition, ITSS-PCM-Ag showed a daily productivity of 62.5% more than that of TSS and a thermal efficiency of 43.5%.