Experimental Study On Optimization Of Solar Membrane Distillation Based On Response Surface Methodology

The traditional desalination technology needs to consume the conventional fossil energy. It has high energy consumption and can pollute the environment. The membrane distillation technology can run under low temperature conditions, therefore, the membrane distillation can couple with solar energy and other low-grade energy. The traditional study uses the single factor analysis, which can't effectively analyze the interaction relationship among the various operating parameters. Therefore, in this study, the solar thermal-photovoltaic system coupled with the hollow fiber membrane distillation unit,taking advantage of the response surface methodology to design and analysis the experimental conditions. Build the experimental platform of solar thermal-photovoltaic membrane distillation system to analyze the interaction relationship among the operating parameters. From the aspects of theory and experiment to study the optimal permeate flux and energy consumption under the optimal operation conditions.Firstly, build the experimental platform of solar thermal-photovoltaic hollow fiber membrane distillation system, adopting the whole glass vacuum tube collector to provide heat for the membrane unit, and the photovoltaic (PV) modules to provide electricity for the systems. In order to make full use of solar energy, the vacuum collector and PV modules were installed on a fully automatic dual - axis solar tracking platform, which coupled with the membrane distillation to study the effect of different operating parameters on membrane flux.Secondly, the operation parameters and membrane flux in the solar thermal-photovoltaic membrane distillation system were analyzed by using the response surface methodology, which combined with the central composite design method to design the experiment of two different working conditions. According to the design working conditions designed by the response surface methodology to carry out experiments, and the experimental data are collected and analyzed.Then, use the Design-Expert software to analyze the experimental data, and the quadratic model was established by regression fitting to obtain the response surface map and the contour map. Analyze the influence of the operating parameters on the membrane flux and the mutual influence among the parameters. Obtain the optimal membrane flux and the optimal conditions of operating parameters. The results showed that the quadratic regression model of taking consideration of the inlet temperature of membrane unit, the flow flux of the membrane unit and the vacuum pressure is significant. The significant value F=21.33 and the deterministic coefficient value R2 =0.9505 , indicated the predicted membrane flux are strongly correlated with the experimental value. The optimal conditions of the simulation are inlet temperature 63?, flow rate 237L/h, vacuum pressure.0.75x105Pa, the predicted membrane flux is 6.05kg/m2·h, the experimental membrane flux is 6.26kg/m2·h, the error is 3.35% under the optimal operation conditions. When considering the influence parameters of inlet temperature of the membrane unit, the inlet flow rate of the membrane unit and the solar radiation degree, the variance analysis F=9.2, R2 =0.8922 showed that the model is well fitted. The optimal conditions of the simulation analysis are the flow rate is 232L/h, the inlet temperature of membrane module is 63? and the radiation rate is 700w / m2. The predicted permeate flux is 6.44kg/m2 ·h and the experimental value 7.24 kg/m2 · h, the error is 11.05%.Finally, the experimental platform achieve completely rely on solar energy for the membrane distillation system to provide energy for the first time. Therefore, analyze the change trend of the experimental parameters of current, voltage, power and so on. And analyze the effects of power consumption, vacuum degree and inlet feed temperature on permeate flux. According to the experimental data, the thermodynamic analysis of the system's heat consumption, energy consumption and power generation efficiency is carried out briefly.