Effect of Leakage Modification and Cooling Flow Rate Increase of Water-Cooled Condenser on NVD System Performance Equipped with Vacuum Tube Collectors

Lack of access to sufficient fresh water is a major threat to people around the world, and to prevent this, extensive research is being done to find new ways to purify different sources of brackish water at lower cost, energy and environmental impacts. The purpose of this study is to produce the freshwater through an NVD system using vacuum tube collectors and vacuum creation by a vacuum pump. Hence, this kind of system could be considered as an innovative combination one; in addition, the effect of different vacuum pressures on yield, then the effect of leakage modification and flow rate increase of cooling water on the system performance were experimentally investigated.

In this research, a vacuum pump was utilized to create an initial vacuum, and when it is switched off, a barometric water column maintains the vacuum naturally throughout the consecutive days. The vacuum collectors were used in order to enhance the saline water heat transfer; later the system performance was continually examined. After the improvements were carried to the system, the yield and efficiency were analyzed and compared with the first test. Furthermore, a pressure gauge, a pyranometer and some thermocouples were applied so as to measure the system pressure, solar radiation and temperatures respectively.

The current study found that the yield and efficiency of the system increased by raising the vacuum pressure; besides, after the leakage modification and cooling water flow rate enhancement, the efficiency has been insignificantly varied in the first consecutive days resulting in a superior capability to produce fresh water for more than three days without reusing the vacuum pump.

The results of this study indicated that raising the vacuum pressure increased the yield and efficiency so that they reached to 8.114 kg/m2d and more than 51% respectively. Moreover, the efficiency slightly varied and as a result, the system would be able to produce freshwater for more than three days without reutilizing vacuum pump.