Experimental Study On The Purification Of PM_2.5 By Air Filter Based On Centralized Air Conditioning System

At present, the centralized air conditioning systems are mostly using the coarse and middle efficiency filter to purify the outdoor dust containing gas, but the effect is not obvious to the PM2.5. In order to improve the indoor air quality, must improve the filtration efficiency of the air filter to PM2.5. The traditional method is to increase the filter components, but this method will increase the resistance of the system. Therefore, it is necessary to study the filter with high efficiency and low resistance, large dust capacity based on the traditional filter, in order to achieve lower energy consumption and investment, guarantee a better indoor environment. Therefore, this topic starts with the filter material and the design of the device of the air filter, launches the research of the low resistance and high efficiency filtration device.First of all, investigate the ambient air quality status of Shanghai from 2013 to 2015, and monitor indoor and outdoor PM2.5 of library reading room and air conditioning room. Results show that the average concentration of PM2.5 and PM10.0 don’t reach the ambient air quality standards for secondary concentration limit requirements from 2013 to 2015. The efficiency for PM2.5 of air conditioning system is low, and it is necessary to improve the filtration efficiency of air filter for PM2.5.Through the method of theoretical calculation, establish air purification model that air filter is applied to indoor and deduce the change law of indoor particle concentration, finally obtain the transient expression and stable expression of indoor particulate matter concentration in air conditioning room. The effects of PM2.5 concentration outdoor, initial PM2.5 concentration indoor, filter efficiency, and fresh air ratio on PM2.5 concentration in indoor were analyzed. which provided some theoretical guidance for the practical engineering.The filtration efficiency, resistance, dust holding capacity of commonly used filter material and electret filter material were compared and analysed through experiment, then analysed the filter performance of the electret filter material working in the actual environment with time going. The results show that the electret filter material has high efficiency, low resistance, large dust holding capacity, and its air quality factor for PM2.5 is high under different wind speed. But after the electret filter material dealing with isopropanol, its quality factor of PM2.5 is worse than coarse material under the rated wind speed of coarse material; is better than medium efficiency filter media and sub-high filter material under the corresponding rated wind speed; is equivalent to highly efficient filter media under the rated wind speed of highly efficient filter media. With the operation of electret filter material in the actual environment, the efficiency of electret filter material under high wind speed is declining faster than under lower wind speed, and filtering efficiency of the fine particles is reducing faster than that of the coarse particles. The resistance of the electret filter material increased little, but the unit area dust holding capacity increased in the constant.According to the test results of resistance, filter efficiency, dust holding capacity of, bag electret filter,box electret filter and sub-high filter F7, can conclude that electret bag filter and electret box filter can meet the filter resistance and filtration efficiency of the sub- efficient filter that the standard required.Finally, a high efficiency and low resistance composite air filter with gradient filter is designed, which can solve the problems of low efficiency, high resistance, low dust content and equipment space caused by two stages of filter.