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With the increase in population and economic development, lack of fresh water for sustainable development has become increasingly serious social problems, desalination is one way to alleviate this problem. Among the many desalination methods, low-temperature multi-effect evaporation Because of high heat transfer efficiency, pretreatment is simple, low-grade waste heat from power plants to take advantage of greatly reducing the cost of water and equipment efficiently mitigate the occurrence of fouling and corrosion, etc., so has become the future mainstream of the second generation of the desalination plant technology. In this paper, low-temperature multi-effect evaporation desalination systems for the study, describes the physical model of the device, including the establishment of an evaporator, preheater, condenser, flash tank and injector thermodynamic process mathematical model, considering the boiling brine elevated steam demister, and the evaporator tube bundle in the flow path due to friction loss caused by the temperature difference, a variety of thermodynamic losses. And conservation of mass and energy conservation equations, based on the system of the thermodynamic process calculation methodology. Solving the above mathematical model and calculation of thermodynamic processes were completed under the program in VB6.0. Based on the effect of different feed water flow rate, the device is divided into streams and streams and string combinations of three kinds of processes. In this paper, these three processes, thermodynamic properties were calculated by comparing the analysis of mass concentration, the effect of feed water, minor steam production, fresh water and the evaporator heat transfer area than the three other methods of water can be seen out string and made with the highest combination of flow and less water than the evaporator heat transfer area, in addition, in this way the water flow spray density to meet the needs of, and has good thermal efficiency. For string and combination processes, in the same design parameters, the effect desalination unit with 6 different combinations, for example, the first effect of the heating steam temperature and the final effect evaporator evaporating temperature of the system thermal performance. For low-temperature steam ejector with multi-effect evaporation desalination systems (TVC-MED), this paper it works and thermal performance computing, including TVC and TVC operating parameters extraction position on the MED device performance . Using the calculation results, the TVC working steam temperature, working steam pressure, steam temperature and the evaporator suction efficiency than the fresh water to the device number, the evaporator heat transfer area, the injector and the injector outlet temperature coefficient analyzed. TVC MED desalination unit in the mounting position can be calculated, if properly used, thermal desalination performance and economics of fresh water can be greatly improved.
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