Studies On Distribution And Deposition Of Indoor Particulate Matter

Particulate matter is one of the important factors that influence the indoor airquality, especially the particulate matter below PM10which is more harmful to human.This thesis makes a study on the migration and distribution of indoor particulatematter via the combination of numerical simulation and experimental test. Meanwhile,a qualitative evaluation of the influence of particulate matter on the indoor air qualityis conducted. The k-εtwo-equation model is applied to the turbulence model inthe numerical simulation, and Lagrangian random walk model is adopted to trace themotion of particulate matter. The influences of the factors including air supplyvelocity, the particle size and wall roughness, etc., on the distribution and depositionof the indoor particulate matter are analyzed with the hypothesis that the indoorparticulate matter only comes from the outdoor. Mass of the Particulate MatterConcentration Tester （TSI8530） and Particulate Matter Counter （Lighthouse5100）are used to test the concentration distribution of the indoor particulate matter underthe condition of natural ventilation, ventilation via air conditioning and no ventilation,and part of the simulation calculation are verified.The results are shown as follow:（1）The indoor particulate matter takes the axis of air supply window as centerand diffuses all around in the form of horn. When the wind velocity is low, theconcentration distribution of particulate matter is quite uniform with higher depositionrate, and when the wind velocity is high, it is concentrated with a lower depositionrate, because most of the particulate matter escapes outdoor with the flow. Particulatematter with the smaller particle size is easy to form the suspension particles and isdifficult to settle down. Particulate matter with the large particle size is mainlyaffected by gravity settling mechanism and is easy for settlement.（2）With the increase of wall roughness, the penetration rate of particulate matterwith the particle size of2.5μm decreases. When the wall roughness is above0.3mm, the penetration rate of particle becomes steady.（3）Through the test of the mass concentration （ρ_zm、 ρ_km、 ρ_m respectively）and number concentration （N z、N k、N respectively） of the indoor particulate matterunder the condition of natural ventilation, ventilation via air-condition and noventilation, the result shows that ρ_zm> ρ_m>ρ_km and N_z> N>N_k. Theconcentration of indoor particulate matter under the condition of natural ventilation ishigher than that under the condition of natural ventilation because the outdoorparticulate matter is relatively high. Under the condition of ventilation via air-condition, the concentration of particulate matter decreases due to the purification ofair from the filter of air conditioning. Therefore, the concentration of particulatematter under the condition of ventilation via air-condition is lower than that under thecondition of no ventilation. Particulate matter with the small particle size （below3μm）which is most harmful to human constitutes the main part of indoor particulatematters. To evaluate the indoor air quality from the angle of concentration ofparticulate matter and ignore the influence of the CO₂、VOC and so on, ventilation viaair-condition ranks the best air quality, and then it is no ventilation and naturalventilation.Influences on the concentration distribution and deposition of the indoorparticulate matter, and the influence of outdoor particulate matter on the indoor airquality under the condition of natural ventilation are analyzed in the thesis. It isexpected to provide suggestions and references for the influence of particulate matterin the evaluation of indoor air quality.