| The air quality in residential environment is closely related to human health. Particulate matters are the primary pollutant, carrying various bacteria. Setting up indoor air purifier is now imperative. Using filter materials in locations with a wide range of particulate matter diameters would suffer from filter net clogging problem, resulting in frequent filter material replacement and higher maintenance cost. Filter material with high efficiency and low resistance is of great significance in both human health and energy saving. This paper, taking filter materials used in particulate matter purification as the research object, seeks the design rules and principles for filter materials that give high filter efficiency, low resistance, large dust capacity and long lifespan.First, instruments such as GRIMM Aerosol Speotrometer were used to test the indoor and outdoor actual PMX density and diameter distribution at a college dormitory in Shanghai before and after human activities (cleaning bedding). It was found that the instantaneous value of PM10 density was higher than standard limit and human activities caused an sharp increase in the concentration of TSP. Diameters were in double-peak distribution peaking at 0.20-0.40μm and around 10μm. Therefore, self-purification of residential environment is necessary; meanwhile, taking care of both coarse and fine particulate matters is highly important to human health, energy saving and environment protection.The filtration efficiency for PM10 removal of commonly used pre-filter materials and electrets filter materials were tested, and the influence of particulate matter size, filter velocity, porosity and fiber diameter on the filtration efficiency were determined. The test result indicates that electret filter material has a better performance under various diameter ranges. Considering its use case and repeated usage problem, soaking procedure of electrets filter material in various solutions will largely decrease its efficiency, indicating that electrostatic effects is the reason of its high efficiency and low resistance and it does not apply in situations with rich polar molecules.In order to explore the influence of the structural parameters of air filter media on its resistance, a test rig was built to measure the resistance of selected filter materials. The comparison between experimental and theoretical results demonstrates that an amendment is required for the non-uniform distribution of fiber. In the meantime, based on the experimental results, resistance affection level of filter velocity, porosity, fiber fineness and thickness was analyzed. Relationship formulas between structural parameters and resistance were concluded and the value range weight of each parameter can be used to guide resistance reduction of cleaning materials.Based on the layout of pre-filter material and main filter material and the folding layout of two-layered composite material in air filters, resistance distribution and flow velocity field of filter layer cross-section under different porosities were compared by a value simulation method. The calculation of velocity field unevenness shows that it is related to resistance; compound materials have the characteristics of low resistance and even dust disposition that solve the material clogging problem.By adjusting the fabric layered structure and the filter layer structure of the filter material and replacing current dust in the surface layer with inner layered and scaled dust, excessive resistance increase caused by dust cake in material surface and device space problem due to series connection of pre-filter and main-filter are solved. From the performance study of material compounded from the outer-layer material with large capacity and low resistance and inner-layer electret material with high efficiency, it can be seen that the compound material provides high efficiency against fine particulate matters and keeps the resistance increase within 10%. |
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