Experimental Study On Solar Air Gap Membrane Distillation

Solar thermal-photovoltaic air gap membrane distillation system is a new type of brackish water desalination technology which combine solar energy with membrane distillation system, it used the solar to heat fluid, so when the heated fluid flow through the membrane surface, the temperature differences across the membrane can promote membrane distillation process, to achieve the purpose of desalination of brackish water.Firstly, the dimensional analysis method is used for analysis of thermoelectric cooling semiconductor membrane distillation system, and established the forecast model for flux. In thermoelectric cooling semiconductor membrane distillation system, it relies on electricity to heat the working fluid, so the required heat in air gap membrane distillation system is heated from 20 ℃ to the set temperature as total solar irradiance parameter. In process of dimensional analysis, mainly from the membrane structure, the fluid characteristics of thermal mass and the experimental operating conditions to analyze the influencing factors of flux. The determination coefficient R2 of multivariate regression model was 0.960, indicated a high degree of fitting equation, standard deviation t was 0.0598523, indicated the accuracy of experimental data is high. Compared experimental data with model predictions, except for a few points, the prediction error is less than 20%.During the process of building solar thermal-photovoltaic air gap membrane distillation system, self-designed miniaturized box of placed membrane structure and the cold water circulation structure. The box of placed the membrane module includes housing cover, the fixing member of cavity membrane, tank separator, and four pipeline connected channel of box; cooling water tank comprises a top cover with rotating nozzle, outlet, cooling plate, and the fixed piece of cooling plate. System membrane area is 0.0416m2, adopted 1.89m2 heat pipe vacuum tube collectors, photovoltaic panel output power is 235 W, both direct current pump rated power is 18 W. In the photovoltaic power system, choose the charge controller and power converter to adjust the circuit, choose the two electric meter to observe power generation and power consumption.The experiment of solar thermal-photovoltaic air gap membrane distillation is mainly test the daily output of water of Hohhot in October within system, the optimal matching of membrane area and collector area, the matching of photovoltaic panels actual output power and power consumption of system, and the stability of entire apparatus 24 hours continuous operation and the initial investment budget of system. The water production is 1807.9g in October 3, hydrothermal volume flow is 250L/h, cooling circulating water volume flow is 300L/h, the maximum hydrothermal temperature in eight days is up to 66.2 ℃; the highest water yield achieved from October 30 to October 31, the water production up to 2993.12 g, and the highest temperature is 76.2 ℃. The experiment shows that the solar thermal-photovoltaic air gap membrane distillation system can be operated stably, to ensure high production water of the system, collector area should not be less than 2.85m2, photovoltaic panels actual output power should be greater than169.1W. Contrasted the value of production water at night and during the day, in the system, the production water in the evening is far below the production water during the day.