Design And Research Of UV-LED Water Purification System Based On Fluid Dynamics And Radiometry

Ultraviolet light is widely used in the field of water purification,there are already various UV water purification devices on the market,most of them use mercury lamps to emit UV light.However,with the entry into force of the Minamata Convention,the pollution of mercury has become an urgent problem to be solved.UV-LED will gradually replace mercury lamp,which has the advantages of good monochromaticity,small size and no pollution.In addition,the sudden emergence of the COVID-19 also puts higher requirements on the UV sterilization system.In this paper,we established the CFD model and radiation intensity distribution model of water purification equipment based on computational fluid dynamics(CFD)technology and radiology principle.We built a geometric model of water purification equipment and UV-LED,and made a fast and flexible mesh division.Then we determined the operation model according to the calculation and the actual working environment,carried out the step-by-step simulation of convection field and radiation field model.And finally we coupled the output results of the two,then carried out the discrete processing.From geometric shape to hydraulic state and irradiation intensity distribution,we fully simulated the real scene of UV-LED water purification system,providing reliable simulation data for the application of UV-LED in water purification field.We used the discrete phase model(DPM)to implement particle tracer to simulate the movement of microbial particles in the water purification model.Then we found that the different velocity and residence time of microbial particles in different parts of the model,and the layout of UV-LED would affect the distribution of irradiation intensity.Therefore,we optimized the UV-LED layout to increase the irradiation intensity of the part where the particles reside for a longer time.The results show that,compare with the uniform in-line arrangement imitating the lamp,the optimized non-uniform UV-LED layout improves the UV dose obtained by microorganism.After that,we have evaluated the hydraulic status of the water purification model based on particle outflow rates and trajectories,as well as analyzing the time utilization of the equipment and the uniformity of microbial radiation exposure.Considering that the biological verification method needs to calculate the microbial concentration through the counting method,the efficiency is low when the cycle test is performed.Based on the Dissolved Oxygen(DO)fluorescence quenching method,we designed and developed a rapid verification method for effective UV dose,described the operation process of response curve determination with the help of related equipment,and deduced the correlation between the dissolved oxygen consumption rate and the concentration of microorganisms.Finally,we studied the response relationship between dissolved oxygen and effective UV dose.This solution is more efficient and stable than traditional biological verification methods.To sum up,we have studied the influence of hydraulic status,UV-LED layout and other factors on the effectiveness of UV-LED water purification system;developed and designed a more efficient effective dose verification method.The results of the thesis have important scientific and practical significance for the related design and research of UV-LED water purification equipment.