Research On Filtration Performance Of Microfluidic Inertial Impactor In FCVS

When a serious accident of core melting occurs in a nuclear power plant,the pressure inside the containment will continue to rise.If the cooling system of the containment vessel fails at the same time,it will eventually cause the risk of overpressure failure of the containment,resulting in uncontrollable leakage of radioactive substances.Therefore,it is necessary to set up a Filtered Containment Venting System(FCVS)to maintain the integrity of the containment structure by actively releasing pressure during late-stage overpressure condition of the containment,and to effectively remove radioactive materials from the discharged gas through the filtering equipment in the system.In this paper,a novel microfluidic inertial impactor with a dust-holding structure is designed,and the combined filter system works in series as the first-stage filter device of FCVS.The equipment can separate radioactive aerosols from the flowing medium passively,with low flow resistance and no clogging.It can remove aerosol particles larger than the cut-off size while rapidly venting pressure,thereby reducing the total amount of aerosol filtration in subsequent equipment and improving the safety and stability of FCVS operation.This paper first conducts a numerical simulation study of the collection process of aerosol particles in the inertial impactor based on the severe accident conditions of nuclear power plants,using the discrete phase model in Fluent.The RosinRammler distribution is used to substitute for the polydisperse aerosols after a severe accident,and the relationship curve between the particle collection efficiency and the dimensionless particle size in the inertial impactor is obtained.Based on the collection efficiency curve,the cut-off particle size and the optimal flow rate of the impactor for capturing particles can be calculated.This study discusses the influence of different structural and operational parameters on the filtering performance of the novel microfluidic inertial impactor model.The study evaluates the overall performance of the filter through the quality factor to ensure low pressure drop while maintaining high filtration efficiency.The results show that to ensure sufficient collision between particles and the impact surface,the ratio of the microchannel cross-sectional width to the length of a single side pipe should not be higher than 1/2.The sensitivity of the collection efficiency to the ratio of the upper and lower side pipe lengths varies with different turning angles.Increasing the opening rate of the filtering unit and the height of the inertial outlet can optimize the filtering performance of the impactor.Through visualization experiments and filtration performance experiments,the particle deposition distribution,filtering performance,and dust holding capacity within an impactor were studied and analyzed.The main deposition location of aerosols within the impactor and the variation curve of dust holding capacity with the upstream powder output were obtained.The experimental data of efficiency agreed well with the results of numerical simulation,but there exists a critical velocity for a given structure of the impactor.When the airflow velocity exceeds the critical value,the collection efficiency decreases due to particle re-suspension.At this critical velocity,the collection efficiency of particles reaches a maximum value of 77.8%,and the inlet and outlet pressure drop of the impactor is only 2.4 kPa,which can meet the demand for rapid decompression.Based on the above numerical simulation and experimental research methods,the main structural parameters of the particle deposition and collection process in the inertial impactor and the optimization of the filtration performance have been mastered.This study can provide theoretical basis and data support for the development of new microfluidic inertial impactors.