Optimization Of Solar Membrane Distillation System Based On Multi-Objective Genetic Algorithm

Brackish water quality is common in remote areas of central and western China.Due to the remote location,large-scale desalination transportation cannot be carried out,which seriously affects the health and living standards of local residents.Membrane distillation,as an efficient desalination technology,is combined with solar energy technology to solve this problem.However,due to the high energy consumption of the system and the small membrane flux,it has not been widely used.Therefore,this paper takes the solar membrane distillation system as the prototype,builds the natural cooling membrane distillation system and the thermoelectric refrigeration membrane distillation system,analyzes them by response surface method,optimizes the operating conditions by multi-objective optimization algorithm,and analyzes the photothermal-photoelectric matching.Finally,the performances of the two cooling systems are compared.In the experiment of natural cooling cold end membrane distillation module,the hot end feeding temperature,hot end feeding flow rate,cold end cooling water flow rate and membrane area are taken as variables,and the membrane flux,thermal efficiency and energy consumption value are taken as target values for investigation.In the experiment of thermoelectric refrigeration membrane distillation,the feeding temperature at the hot end,the flow of cooling water at the cold end,and the input current of the thermoelectric refrigerator are taken as variables,and the membrane flux,the coupling and matching degree of the cold and hot ends,and the energy consumption value are taken as the target values.According to the experimental design scheme,According to the experimental design scheme,we substitute the experimental data into the support vector machine(SVR)for fitting,and substitute this fitting prediction model into the response surface method to perform the collaborative analysis between the variable and the target value.The model is substituted into the multi-objective optimization algorithm,and the optimal operation condition is obtained after the operation such as optimization operation.After optimization,the optimal conditions of the natural cooling membrane distillation system are obtained:the hot end feed temperature is 65.76?,the hot end feed flow is171.56 L/h,the cold end cooling water flow is 194.14 L/h,and the membrane area is 0.03m~2.The membrane flux is 20.20 kg/(m~2·h).The optimal operating conditions of the thermoelectric refrigeration membrane distillation system are:hot end feed temperature is75?,cooling water flow is 698.10 L/h,and the refrigerator input current is 8.44 A.In this optimal condition,the corresponding membrane flux is 13.98 kg/(m~2·h).It is verified that the difference between the target value and the actual value under the optimal conditions obtained by the two systems is within a reasonable range,which verifies the credibility of the results of the optimization process.Under the optimal operating conditions,the photoelectric area of the solar natural cooling film distillation system is 1.54 m~2,and the photovoltaic area of the solar thermoelectric cooling film distillation system is 4.31 m~2.After photothermal matching calculation,the collector area of the solar natural cooling film distillation system is 4.22 m~2,and the heat collecting area of the solar thermoelectric cooling film distillation system is4.00 m~2.From the perspective of economy,environmental protection and energy saving,solar natural cooling film distillation system has more advantages.Considering the stability of the cold end of the system,the solar thermoelectric refrigeration membrane distillation system should be adopted to better maintain the balance of cold end temperature.