This study focuses on dynamic mechanism behind the formation of the freshwater zone around the Meimao Sandbank by use of 3D numerical simulation.The Meimao Sandbank is located along the southern bank of the South Pass...This study focuses on dynamic mechanism behind the formation of the freshwater zone around the Meimao Sandbank by use of 3D numerical simulation.The Meimao Sandbank is located along the southern bank of the South Passage in the Changjiang(Yangtze River) estuary,which is considered as a freshwater resource for Shanghai City.Interaction between runoff and tide is the main mechanism of the freshwater zone formation.However,the freshwater zone often suffers from saltwater intrusion in dry season.Tidal oscillation is stronger during spring tides,able to carry freshwater farther seaward.Therefore,it is more likely to occur during the ebb of a spring tide in dry seasons.In addition,the water zone is sensitive to runoff:when runoff decreases,it disappears,and vice versa.The northerly winds favor the formation of the freshwater zone.展开更多
Greenhouse solar-energy driven desalination technology is potentially well suited for supplying water and small scale irrigation in remote and/or rural areas, and for avoiding over-exploitation of available water reso...Greenhouse solar-energy driven desalination technology is potentially well suited for supplying water and small scale irrigation in remote and/or rural areas, and for avoiding over-exploitation of available water resources. The efficiency and productivity of these systems are however low, in part because the heat of evaporation has to be transferred as waste heat to ambient air during condensation. In order to maximize energy regeneration during condensation we propose an educator based system that lowers the evaporation process temperature by reducing pressure. The feasibility of the educator assisted passive solar desalination system is investigated using a detailed computational fluid dynamics analysis complemented by experiments. The study focuses in particular on the ability of the new design to lower the required evaporation temperature and thereby reduce the energy intensity of the process. Two configurations, with open and closed educator, are investigated and a detailed analysis of the thermofluid processes is presented. The configuration with a closed educator installed outside the evaporation chamber shows very promising performance. The proposed system can maintain the maximum temperature and pressure in theevaporation chamber below the desirable temperature and pressure thresholds （30 ℃ and 5 kPa）. The analysis and experimental data also show it is possible to further reduce energy requirements by reducing the motive water flow rates.展开更多
基金Supported by the Funds for Creative Research Groups of China (No. 40721004)the National Natural Science Foundation of China (No. 40976056)National Major Science and Technology Project of Water Pollution Control and Countermeasures (No. 2008ZX07421-001)
文摘This study focuses on dynamic mechanism behind the formation of the freshwater zone around the Meimao Sandbank by use of 3D numerical simulation.The Meimao Sandbank is located along the southern bank of the South Passage in the Changjiang(Yangtze River) estuary,which is considered as a freshwater resource for Shanghai City.Interaction between runoff and tide is the main mechanism of the freshwater zone formation.However,the freshwater zone often suffers from saltwater intrusion in dry season.Tidal oscillation is stronger during spring tides,able to carry freshwater farther seaward.Therefore,it is more likely to occur during the ebb of a spring tide in dry seasons.In addition,the water zone is sensitive to runoff:when runoff decreases,it disappears,and vice versa.The northerly winds favor the formation of the freshwater zone.
基金provided in part by the Deanship of Scientific Research, King Abdulaziz University, Jeddah, under Grant No. (1-135-36-Hi Ci)
文摘Greenhouse solar-energy driven desalination technology is potentially well suited for supplying water and small scale irrigation in remote and/or rural areas, and for avoiding over-exploitation of available water resources. The efficiency and productivity of these systems are however low, in part because the heat of evaporation has to be transferred as waste heat to ambient air during condensation. In order to maximize energy regeneration during condensation we propose an educator based system that lowers the evaporation process temperature by reducing pressure. The feasibility of the educator assisted passive solar desalination system is investigated using a detailed computational fluid dynamics analysis complemented by experiments. The study focuses in particular on the ability of the new design to lower the required evaporation temperature and thereby reduce the energy intensity of the process. Two configurations, with open and closed educator, are investigated and a detailed analysis of the thermofluid processes is presented. The configuration with a closed educator installed outside the evaporation chamber shows very promising performance. The proposed system can maintain the maximum temperature and pressure in theevaporation chamber below the desirable temperature and pressure thresholds （30 ℃ and 5 kPa）. The analysis and experimental data also show it is possible to further reduce energy requirements by reducing the motive water flow rates.
