The Study Of The Operating Characteristics Of The Solar Desalination System

Water is a precious natural resources,an indispensable substance on which human beings are relied,and also the driving force makes human society persistently.However,China and many countyies around the world are facing the problem of water shortage,which has been a serious threat to people’s lives and the development of the economic and society.Desalination technology has become one of the most important means to solve the problem of water scarcity.Especially the low temperature muti-effect distillation desalination technology which combine the solar which is a clean and renewble energy with desalination technology and take the use of small temperature falling film evaporator and multi-stage heatrecovery has become the promising development direction of the desalination technology.Different from the conventional energy, solar changes with respect to the time and this caused the operating parameters of the solar desalination system change with respect to the time.Thses operating parameters affect the operating characteristics of the solar desalination system.Therefore,there are two aspects of this article.First, according to the variation regulation of the solar radiation intensity with time, the dynamic mathematic models of the down-flow five effect distillation/flash desalination system powered by solar energy were developed. Under the design conditions, the static design calculation for the system had be done and the heat loads and the structure parameters of each distillatory in the system were determined. The results lay the foundations of the design and simulation for the system.Second, based on the above contect, the system operation characteristics were analyzed by numerical simulation under the conditions of solar intensity and ambient temperatures at Spring equinox, June solstice and Winter solstice in Shenzhen. The system has five effect distillations. By changing the system starting temperature, strong brine circulation ratio, cooling seawater temperature and atmosphere transparency, the operation parameters of the system like the hot water temperature in the hot water reservoir, transient water produced rate and performance coefficient of the system were obtained by simulation, in which the solar collector area and structure parameters of the distillatory are invariant.Simulation results show that when other conditions are the same, the hot water temperature in the hot water reservoir and transient water produced rate are higher with the starting temperature rise,so it is reasonable to start the system according to the design temperature(65℃).On the condition that the horizontal heat transfer tubes are moisted by the sea water, strong brine circulation ratio should be loower.If permitted, cooling seawater temperature also should be lower.The better the weather conditions are,the more favorable to the performance of solar desalination system and water production.Therefore,the solar desalination system should be set in the island or brackish water areas that solar energy is abundant and the water resources is scarcity.The results are helpful for the system operation and will have certain reference value at design of the system and analysis of performance.