The Research On Penetration Coefficient Of Atmospheric Fine Particles Between Indoor And Outdoor

In recent years,haze pollution of our country has become increasingly serious,so that fine particles become the primary pollutant in many cities.Compared with coarse particles,fine particles invade the human body more easily to stimulate the disease.Studies have shown that the penetration of outdoor particulates is the main source of particulate matter in the room.Compared with foreign countries,air tightness of our construction envelope is poor leading to more outdoor particles enter the room through the building crack.Therefore,it is of great significance to study the indoor and outdoor penetrating and transport characteristics of fine particles.The paper studied the penetrating coefficient from three parts: theoretical research,experimental cabin research and experimental study.First,based on the theory of penetration mechanism,the study introduced the calculation formula of the penetration coefficient,and it is concluded that the main influencing factors of penetration factor were pressure difference,crack length and crack height,particle size,temperature and humidity.Second,the study built experimental cabin to discuss penetration coefficient.The experimental chamber contained all the influencing factors of the penetration coefficient introduced by the theoretical formula,which can study the influence of the pressure difference,the crack condition,the particle size,the temperature and the humidity on the penetration coefficient.Compared with the previous study,the experimental platform increased the temperature and humidity links,having more comprehensive parameters.It can controlled the parameters more quickly and accurately through the design of the system,which improved the accuracy and operability of the experiment.During the experiment,the pressure gradient were set to 4Pa,6Pa,8Pa,10 Pa and 12 Pa,the crack height were 0.25 mm and 1mm,the crack length were 4.3cm and 9.4cm,the temperature was controlled at 5-25 ℃,relative humidity was in the 30-70%.Based on the experimental data,quantitative analysis of correlation between the factors and penetration coefficient was made.At H = 1mm,the pressure difference and the penetration coefficient can be unified with a non-linear function.At H = 0.25 mm,the pressure difference and the penetration coefficient can be unified with a linear function.There were gravity sedimentation displacement and the brownian diffusion displacement under the action of gravity and brownian diffusion.When the crack height close to or less than the maximum net displacement(the maximum between the two),the penetration coefficient was proportional to the crack height,inversely proportional to the crack length;when the crack height far greater than the maximum net displacement,within a certain range,penetration coefficient did not change with the crack height and the crack length.The penetration coefficient decreases with increasing particle size,and the smaller the H,the longer L,the smaller the pressure difference,the greater the decrease.There is a negative correlation between the particle size and the permeability coefficient,and the relationship between them can be expressed by the cubic equation.There is no significant correlation between temperature and humidity and penetration coefficient within the range of sample data.Based on the above correlation analysis and the theory of penetrating coefficient,a semi-empirical formula of penetration coefficient is established.With high accuracy,the form of the semi-empirical formula is simple and easy to be used in the measurement.Finally,the investigation of the particulate matter pollution of 8 office buildings in Dalian City was carried out,it was concluded that the penetration coefficient of the tested objects was changed between 0.75 and 0.90.At last,the measured value was compared with the calculated value of the semi-empirical formula.Considering the material roughness into the model,the accuracy of the model was improved.