| High efficiency particulate air filter (HEPA) is the core equipment of clean technology industry, how to promote its efficiency and optimize the performances is of great significance to the related industries. In recent years, the development of HEPA has caused attention of many countries, low resistance and high efficiency has become the common theme. In view of high price of the new filter material and the request of low carbon emissions, it’s necessary to make full use of the filter material and improve it’s whole service life.At present, HEPA usually have the following two aspects defect:the flow rectifier’s not reasonable designed causes the face air velocity’s uneven distribution, leading to the non-optimization use of the filter material; the unreasonable sampling way in filter leak detection makes a lot of aerosol residual causing great challenges to the filter’s service life and meanwhile exists aerosol time inconsistency and potential environmental pollution.This topic will be based on the numerical simulation technology, which has been widely used, to carry out analysis of the above two issues. The basic idea is:based on the corresponding assumptions and simplified, with the aid of CAD to construct the three dimensional filter model, mesh the model by GAMBIT software, and at last to carry out the numerical calculation with the FLUENT software. In order to validate the reasonability of the numerical simulation model and the accuracy of the boundary conditions, we also carry out the corresponding control test in this paper, by the contrast of the test and numerical simulation, we finally confirm it is reasonable that we use standard k-ε model as the turbulence model, substitute porous medium model for the filter material and define the speed entrance, pressure outlet boundary during the process of numerical simulation.For minipleat-style high efficiency particulate air filter, the distribution consistency of the filter’s inlet velocity is mainly affected by the flow rectifier, while different factors such as flow rectifier’s geometric structure, geometry, installation height, hole size, hole spacing, etc. has different influences on the performance of the flow rectifier. In this paper, to the main influence factors of the flow rectifier’ performance:the size, aperture ratio and the installation height, we will use the orthogonal test method to design the simulation test, establish different filter physical model and boundary conditions and at last carry out test research of the common2000m3/h,1500m3/h,1000m3/h and500m3/h HEPA mode. To the method of aerosol sampling, we first carry out the experiment research of aerosol sampling from different point source, proving that it is more conducive to shorten the mixed distance for more aerosol point. Then we carry out many sets of simulation test research under the certain circumstance of different numbers of point source, and the aerosol flow direction of downstream, upstream and vertical flow relative to the air flow. The establishment and processing of the model used the same method of velocity distribution uniformity phase.In this subject, we adopt relative error and not uniformity of the speed (concentration) distribution as evaluation index. The results show that:to different filter model, we should design different flow rectifier rather than only according to empirical. To the filter model of2000m3/h, the size of the flow rectifier is the main factor that affects the consistency of the windward air flow, and the optimal installation height is50mm. And to the other three kinds of air filter model, the consistency of the windward is mainly depending on the air flow percentage of opening of the flow rectifier. For aerosol compound, if the point source of aerosol is sufficient, it can be mixed evenly in the limited space of plenum. Of course it’s much easy to speed up the aerosol mix if the turbulent flow is strong enough. |
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