基于竖管降膜的多效太阳能苦咸水蒸馏器设计及性能分析.

Freshwater and energy are indispensable resources for human survival and social developments. However, fresh water scarcity is expanding and intensifying around the world because of rapid population growth, industry development, abnormal climate and urbanization. Especially, the shortage of useful water has become more obviously for isolated or arid regions. Great amount of groundwater in these regions found in wells usually remains brackish water. To obtain safe and pure drinking water, various brackish water distillation technologies have been increasingly recommended as a viable alternative. However, conventional distillation processes have indicated highly energy consumption, and potential environmental impacts due to the utilization of fossil fuels. It is necessary to utilize solar energy for the brackish water distillation, in order to meet the high requirement of potable water and agriculture in the remote and arid regions blessed with ample amount of solar energy. This paper therefore designed a novel multi-effect solar brackish water distillation device based on vertical tube falling film, which allows testing of four operational modes, i.e., single-effect, double-effect, triple-effect and four-effect. Compared with conventional solar brackish water distillation device, some advantages can be achieved, such as falling film evaporation, multi-effect operation, smaller thermal resistance, and higher efficiency of thermal utilization. The working principle was introduced for the four-effect device and structure. A theoretical analysis of heat and mass transfer process of the device was carried out. The water yield, evaporation temperature and condensation temperature of the device for four operation modes were tested under the fixed heating power operation. The effects of the different operation effects on the water yield per energy and GOR (Gain Output Ratio) were investigated, together with the economic analysis of the multi-effect devices. The results demonstrated that when the heating power was 200W, the water yield per energy and the total water production of the four-effect device were 1.45 g/kJ and 1.039 kg/h, indicating an increase by 36.80% and 35.88% than that of the triple-effect device, respectively. The steady-state operation temperature was 83.76 ℃, while the total temperature difference of evaporation and condensation was 19.07 o C in the four-effect device. The GOR of four-effect device can reach 3.36. The payback period of four-effect device was 5.69 years. Performance and economic analyses of the devices indicated a wide applicability of the system, especially for remote and arid regions. [ABSTRACT FROM AUTHOR]