Study On Indoor PM_2.5Concentration Distribution And Control Strategy Of Office Buildings In Cold Regions

In recent years,environmental pollution has become a hot issue that people generally pay attention to in today’s society.With the development of technology and the improvement of people’s living standards,people gradually realize the importance of indoor air quality.People spend more than 90%of their time indoors in buildings.The quality of indoor air quality directly affects people’s health^[1].Therefore,it is necessary to clarify the relationship between indoor and outdoor particle mass concentration,indoor PM_2.5 concentration distribution and indoor PM_2.5 concentration control strategy.The main content of this article is:First,In this article,from 2018-3-20 to 2018-3-31 and from 2018-4-1 to 2018-4-12,two office buildings with different airtightness test points 1（located in airtightness）of a university in Shenyang City 8-level green building)and measuring point 2（located in the air-tight level 4 general building）were measured.According to the actual measurement results,the PM_2.5 concentration level is clarified,and the relationship between indoor and outdoor PM_2.5 concentration is analyzed and sorted out.Second,Numerical simulation and analysis of indoor PM_2.5:By simulating the indoor PM_2.5 mass concentration and velocity distribution under two operating conditions,the previous measurement results were further verified.And analyze the indoor PM_2.5 distribution under the two working conditions,and get the general law of indoor PM_2.5 distribution.Third,Research on the control strategy of indoor PM_2.5 concentration:According to the mass balance equation,by studying the efficiency and installation position of the filter under the primary return air system to the distribution of indoor PM_2.5,a mode conducive to controlling PM_2.5 is obtained,And give suggestions for this.The results show:Conclusion 1:The measured results show that:the daily average concentration of particulate matter in indoor measurement points 1 and 2 and outdoor measurement point 3 are generally consistent with time.The outdoor concentration decreases and the indoor concentration decreases;3.The percentage of days with good PM_2.5 at measuring point 1 and measuring point 2 is 17%,100%,92%and 92%,92%and 100%respectively.The PM10 compliance rate is 50%,100%,100%and 91%,91%and 100%,respectively.From the analysis results,it can be seen that the proportions of measuring point 3 and measuring point 2 have rebounded,which is mainly due to the reduction of fossil fuel combustion after the end of heating.The reason why the proportion of measuring point 1 slips is that the equipment room piping of measuring point 1 is modified and constructed,which strengthens the disturbance of the indoor airflow,causing the suspended particles to re-suspend and diffuse in the room,resulting in a larger concentration.Conclusion 2:The measured results show that:both the mass concentration I/O ratio of measuring point 2 and measuring point 1 are greater than 1.Mainly consider the reason.Unmeasured point 2.The air tightness of the outer window is poor.The larger wind speed makes the penetration through the gap of the outer window into the room larger and the speed of the permeated wind increases.The PM_2.5 that has settled on the window sill and indoors is suspended again,causing the indoor PM_2.5 concentration to become larger.When the outdoor wind speed is large,the outdoor PM_2.5 concentration is usually very low,so the I/O is relatively large.In addition,the outdoor PM_2.5 concentration changes,and the indoor PM_2.5 concentration has a certain time delay during the rise and fall,which is also the reason for the large fluctuation of the I/O ratio even greater than 1.In practice,the above-mentioned reasons often occur at the same time and work together;the mass concentration I/O ratio is greater than 1 during the test.This may be due to the good air tightness of the envelope structure of measurement point 1 and the ability to block more The outdoor particulate matter enters the indoor,and can also block the indoor discharge from the outdoor.When the concentration of outdoor particulate matter suddenly decreases,and the indoor concentration increases due to the renovation,the particles cannot be discharged out of the room through the gap between the doors and windows in time,and the indoor concentration value is still high.Conclusion 3:The simulation results show that the outdoor PM_2.5 pollution concentration reaches 72μg/m3 under the condition of heavy pollution,and the highest indoor PM_2.5 pollution reaches 6.75μg/m3 under the condition of excellent outdoor concentration.The difference ratio between the measured value and the simulated value obtained under the two working conditions is less than 3.71μg/m3 and 0.29μg/m3,less than 2%,and the accuracy is high and consistent.The simulated value is slightly lower than the measured value,which may be due to the movement of personnel during the test.The flow velocity from the front to the back of the office gradually decreases,the highest velocity is 0.13m/s,the lowest velocity is 0.011 m/s;the central velocity is 0.065 m/s,so PM_2.5 particles can be uniformly free on this plane diffusion.Conclusion 4:This paper simulates the distribution of PM_2.5 pollutants for six working conditions,and finds that the airflow organization has a great influence on the distribution of PM_2.5 pollutants.The average velocity of the indoor air flow obtained from the simulation is from the highest 2m/s to the lowest 0.02m/s.In areas where the airflow velocity is fast in the room,the airflow streamlines are dense,which promotes the diffusion movement of the airflow,and the PM_2.5 pollutant mass concentration is low;the area where the airflow velocity is slow is conducive to the PM_2.5 pollutant suspension and precipitation,and the mass concentration is highly Larger.Moreover,with the use of the primary return air system,the indoor PM_2.5 mass concentration can reach a good level and above.Outdoor concentration is 219.32μg/m3,indoor concentration can reach 30μg/m3.As the filtration efficiency increased from 0.1 to 0.2,the indoor PM_2.5 mass concentration also decreased.The filtration efficiency on the return air duct is increased by 10%,and the concentration is reduced by more than 30%.Conclusion 5:Through actual measurement and simulation analysis,a simple introduction is made from the estimation of indoor PM_2.5 concentration to discuss the two aspects of filter control and air purifier control.The control of the filter is mainly through the indoor and outdoor PM_2.5 concentration to control the switch of the new fan group,return fan group,fresh air electric valve,return air electric valve and other devices.The resistance of the air conditioner and unnecessary wear of the fan;ultimately improve the air quality and create a healthy and comfortable indoor air environment.Air purifier control mainly considers the noise,energy saving,purification PM_2.5 intelligent control purifier on,off and sleep mode to ensure indoor air quality and environment.