Using water-filling and air-releasing to design a natural vacuum solar desalination system

Water-filling and air-releasing were used to design a natural vacuum solar desalination system. The system was tested in various weather conditions to determine the operational regularity and total performance evaluation indices at different flow rates and temperatures. Economic analysis was applied to calculate the cost of freshwater produced. Results showed that the system performed better under the constant flow rate input of 0.150 kg/s with a heat collection area of 18.0 m². The efficiency and recovery ratios could reach 87.821 and 3.858%, respectively and these were 1.568 and 1.631 times the values before heat recovery. Moreover, the average freshwater yield could reach up to 6.018 kg/h. When seawater was added at a constant temperature while considering utilisation of waste heat at night, efficiency could reach 84.256% when the heat collection area was 14.4 m² and this was 1.080 times that of 18.0 m². The recovery ratio could reach 4.133% when the area was 18.0 m² and this was 1.069 times that of 14.4 m². After calculation, the cost of freshwater was about 0.0113 $/kg and this had certain advantages over other systems.