Experimental Study On The Filtration Performance Of Intense Field Dielectric Outdoor Air Unit And Its Duct Structure Optimization

With the occurrence of frequent fog and haze weather in recent years,China has paid more and more attention to indoor and outdoor air quality.Outdoor air filter exhibits great performance to introduce outdoor air and filtrate it quickly The outdoor air units equipped with different filter media and duct structure have definitely various performance.At the same time,some special rooms,such as classrooms and office,have higher unit performance including air volume,filtration efficiency,noise,etc.In order to provide references for the application of air filter with low resistance and high efficiency,this paper studies the filtration performance and the duct structure of the intense field dielectric outdoor air filter device.Taking Shanghai as a typical city,the daily mean value of particulate matter was collected from January 2014 to October 2016,and the concentration of particulate matter and CO₂ were measured in an elementary school in Shanghai.The results showed that,in 3 consecutive years,the annually outdoor PM_2.5 concentration was higher than that of GB 3095-2012 standard.And it cannot be under effective control.In winter it exceeded the most serious.For the room with50-60 occupants,insufficient ventilation could lead to excessive CO₂ concentration,and the value can reach 2000 ppm within 45 minutes.In the case of severe haze,closing doors and windows can prevent indoor air from being polluted by outside air.Unfortunately,the concentration of indoor CO₂ and particulate pollutants can not be reduced to a comfort range.Therefore,the outdoor which will be introduced into the classroom,must be filtrated as clean air.The common filtration units in the new market cleaning device are investigated and some filter media are selected for performance test.A two-way fresh air purification test device is designed to replace a variety of different filter media and multiple filter media.The filtration characteristics of G4 primary filter,F7 filter,IFD device and HEPA filter are compared and analyzed.The study tests air flow,energy consumption,particle filtration efficiency.The results show that the IFD device has small flow resistance and low energy consumption,but its filtration efficiency on the particulate matter is not as high as that of the fiber.At the same time,the filter unit equipped with IFD and HEPA exceed more than 95% of filtration efficiency in both low and high air volumeAlso,this study investigates the performance of fresh air purification device with different duct structure.Taking the G4 primary filter + IFD filter + HEPA filter?H13?as the device filter unit,this study designs eight outdoor air filtration devices with different structure,and measures the air volume,noise,energy consumption,particulate filtration efficiency,CO₂ concentration.The results show that:?1?When regulating the motor frequency or replacing the outlet structure in a same fresh air filter device,the device noise has little variation and its value is only within 1.2dB?A?.It seems that changing the duct structure decreases a little device noise.For example,when the motor frequency is 50 Hz,the noise difference between maximum and minimum can reach 3d B?A?after replacing a new duct.?2?For the outdoor air unit with spherical diffuser but without baffle,the return air diffuser with larger exhibits smaller noise.?3?The diffuser structure has a little influence on the wind speed and the air volume.The air volume of the adjustable square shutter vent is relatively large,and the maximum air flow rate is 655.81m3 / h.The air volume obviously impacts the removal ability,and greater air volume brings higher removal ability and filtration efficiency.