Study On The Application Of Aerosol And Relevant Issues In In-Place Testing Of HEPA Filter

Nowadays both manufacturers and customers begin to pay more attention to the high efficiency particulate air (HEPA) filter performance, since requirement for the air cleanliness class in modern industry becomes higher and higher. It is clear that ripe theories and scientific methods about in-lab test of HEPA filter performance have been existing for long time. However, there is rare research on how to improve the testing quality and efficiency for installed HEPA filter. In order to solve the above problems, study on the distribution of aerosol in HVAC duct is needed. So aiming at aerosol and relevant issues in in-place test of HEPA filter, this thesis makes an all-around research by using academic analysis, experiments and CFD (Computational Fluid Dynamics) method.Based on the review and analysis of existing research and problems in performance testing of HEPA filter, referring to the European standard (EN1822) and other standards, ex. Japanese and American standards, a filter performance testing platform is designed and built.Before the experiments, simple aerosol distribution formula in air duct is obtained via necessary assumption and modification to the boundary conditions on the basis of typical diffusion model of point source. According to the formula, how the air velocity affects the aerosol diffusion is discussed.Supervised by academic calculation, this paper optimizes the aerosol sampling system including how to deal with the measurement error and choose the proper sampling probe. Then for the sake of satisfying the "Dimensional Consistency" rule required by overseas standards, the minimum stable length on aerosol diffusion in air duct is researched; additionally, factors such as air velocity, emanation concentration, emanation location and duct dimension which may influence the minimum stable length is analyzed. Finally, it launches a study on the concentration difference between general and branch duct.Research conclusions provide some useful proposals concerning how to select sampling equipment and probe, how to set the sampling location and adjust emanation concentration etc for in-place testing of HEPA filter, which are much practical.