Browsing by Author "Xie, Guo"
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Item Open Access Experimental study on three-effect tubular solar still under vacuum and immersion cooling(Elsevier, 2021-06-28) Yan, Tiantong; Xie, Guo; Chen, Wenlong; Wu, Zhanglin; Xu, Jialing; Liu, YingzhangSolar still is widely used for supplying fresh water to small communities in remote areas. One drawback of this technique lies in the low freshwater yield. Recent studies on stills of multi-effect and vacuum design proved their potential for high yield. However, such systems suffer from high electricity consumption and insufficient cooling. In this study, a novel system with a periodic pressure control scheme and water immersion cooling has been proposed to mitigate these defects. A prototype was constructed and associated with a 0.19-m2 solar panel. A 5-day outdoor experiment was conducted to evaluate the overall performance. Results indicated that the highest yield during the test was 9.8 kg/m2 at operating pressure of 40 kPa. A significant performance ratio of 1.87 was achieved with immersion cooling, i.e., 0.42 higher than that with air cooling. Thermal analysis showed that the heat transfer coefficient of water immersion cooling was 15–50 times higher than that of air cooling. Compared with previous vacuum-operated systems, the specific electricity consumption of maintaining vacuum was greatly reduced, i.e., from 21.6 kJ/kg to 1.7 kJ/kg for the case at 60 kPa. The forecast cost of the distilled water is $0.012/kg, representing an affordable desalination technique for off-grid communities.Item Open Access Performance of multi-stage tubular solar still operating under vacuum(Elsevier, 2022-11-21) Chen, Wenlong; Xie, GuoMulti-stage solar desalination running under vacuum is a low-cost, effective and sustainable way to mitigate fresh water shortage. However, questions remain on the operation pressure (Pop) and stage number of the multi-stage solar still. To address these questions, a predictive model was developed for the yield of multi-stage tubular solar still under vacuum (MSSV) and validated against field experiments. A 3-stage tubular still under typical weather (i.e. 19.75 MJ/m2 cumulative solar radiation) produced maximum water yield (7.15 kg/m2) with optimal Pop (48 kPa), much higher than under normal (5.81 kg/m2) and lower pressure (1.58 kg/m2 with Pop=20kPa). At optimal Pop, a delicate balance exists between the energy adsorbed and dissipated. Stronger solar intensity leads to more water yield and higher optimal Pop, while increasing the stage number improved the fresh water yield with diminishing marginal effect and slightly shifted the optimal Pop to a lower value. Using water immersion cooling other than air cooling significantly increased the water yield from 7.15 kg/m2 to 10.51 kg/m2. The MSSV model enriched the fundamental understanding of energy utilization for solar desalination and could serve as a design tool to maximize the performance of multi-stage solar still by optimizing still parameters and geometry.