Study Of The Filter Efficiency For Controlling Indoor Particulate Matter In Air-conditioning Buildings

Nowadays the haze had broke out frequently in many cities of our country, sopeople pay more and more attention to the problem of indoor particulate matterpollution. PM10and PM2.5are the evaluation index for the particulate matter pollution atpresent. The central air-conditioning system undertakes the task of controlling indoorair quality, it removes particulate matters from supply air through the filters installed inthe duct. Therefore, it has great significance to study how to control the indoorparticulate matter through the air-conditioning filters under the condition of so highoutdoor particle concentration, especially for the PM10and PM2.5.The existing air filters are mostly calibrated according to the counting efficiency,however, the indoor and outdoor air quality standards relate to PM10and PM2.5are givenby weight concentration, thus leading to the contradiction between the design andcalculation of the filtration efficiency and the filter selection. In addition, the existingstandards in our country have not made any provision for indoor fine particulate matterof PM2.5for the mass concentrations. Therefore, it’s unable to select the air filters forcontrolling indoor PM10and PM2.5.In view of the above problems, this subject is divided into two main parts, whichare theory research and experiment research. Specific research methods and mainconclusions are as follows:Firstly:(1) Indoor particle concentration model was set up, and if the limit of PM10concentration for the supply air can be able to meet the one for the indoor environmentby a instance was checked.(2) Indoor limit of PM2.5concentration was discussed, and the suggested standard value was given, the limit of PM2.5concentration in supply airwas calculated through the established model of the particle concentration.(3)According to the limit of PM10and PM2.5concentration for supply air and indoorenvironment, the theoretical matching relationship of filters for central air-conditioningis obtained.(4) The diagrams for matching filtration efficiency, and the diagram of howfresh and return air filter influence the main filter were draw. According to differentoutdoor conditions and fresh air ratio, the suggestions for how to adjustment theefficiency of fresh air and return air filters were presented.Secondly:(1) The experiment bench for testing filter material performance wasbuilt, and the existing filter materials were tested to obtain weight efficiency of PM10,PM2.5and corresponding resistance value under different filtration velocity.(2) Therelationship curve of filtration velocity between efficiency, and the resistance were gotthrough applying least square method for fitting the experimental data. The efficiencyand resistance value of filter materials at different levels were calculated under thefiltration velocity for engineering.(3) The relationship of filtration velocity betweenfiltration efficiency and the resistance were analyzed, and some suggestions were givenfor the application of filtration velocity of the filter materials at different levels. Theefficiency and resistance of filters under its filtration velocity for engineering weresummarized, and figures were drawn based on the filtration effic iency for PM10andPM2.5.Finally, the theory research and experiment research were combined, and therelationship for matching level of filters were obtained for different forms ofair-conditioning system, and different working conditions, under the requirements ofindoor concentrations of PM10and PM2.5.Conclusions：(1) The recommended indoor standard concentration of PM2.5was given out by35μg/m3, under this indoor standard, the concentration of PM2.5in supply air flow of theair-conditioning should be less than26.3μg/m3.(2) The burden of the main filter would be alleviated with the increasing efficiencyof fresh and return air filter. With the increase of outdoor particle concentration andfresh air ratio S, the influence degree of the fresh air filtration efficiency on the main filtration efficiency will increase gradually.(3) When the fresh air ratio is less than15%and the outdoor PM10concentration isless than0.85mg/m3, the efficiency of return air filter has more influence on alleviatingthe burden of main filter. When the fresh air ratio is less than15%and the outdoorPM2.5concentration is less than0.20mg/m3, return air filtration efficiency has moreinfluence on alleviating the burden of main filter.(4) When the level G1to G4air filter is applied, the filtration velocity about1.9m/s is recommended, and when the level F5air filter is applied, the filtration velocityabout0.77m/s is recommended, the purpose is to improve the efficiency.(5) The filter speed should be controlled in a small range as far as possible whenchoosing higher-level air filters. The resistance characteristic curve of the filtermaterials is mainly a rising curve.(6) The graphs of filtration efficiency for PM10and PM2.5, and the range ofresistance were obtained under the filtration velocity of engineering application. Thetables for matching models of filters for different forms of air-conditioning system weregot too.