Transportation And Human Exposure To Particles With Different Diameter In Industrial Buildings

The completed area of industrial buildings in China exceeded 500 million square meters in 2017,which increases about 51% compared to 2007.As the scale of manufacturing is increasing,high pollution caused by industrial production leads to a peak incidence of occupational diseases in China.Solid particles,one of the most common pollutant in industrial buildings,which is still inevitably exist the pollutant escape phenomenon even if ventilation system adopted.The long-term exposure of workers to particles will cause great harm to human health.Based on the theory,numerical and experimental methods,this study aims at investigating the transportation and human exposure of particles with different diameter in industrial buildings.Conclusions intend to evaluate particles pollutant more accurately,then realize the better environmental control and individual protection.The complex coupling relationship between high-temperature particles and airflow field results in the transportation process changed,compared to those with room temperature.Therefore,the study starts from identifying dynamic characteristics of single high-temperature particle in airflow field,through numerical simulation based on dynamic mesh.A calculation model dynamic heat transfer of single-particle is established.By calculating the pressure resistance and viscous resistance on the micro-element of particle surface,the drag force during particle movement process was accurately calculated.Result prove that single hot particle has larger drag force and smaller falling speed during free-falling process,while a smaller drag force and slower velocity attenuation in rising process,compared to room temperature particle.The hot particle,therefore,has a longer movement time in airflow field.Through the analysis of dynamic characteristics for single hot particle in airflow field during rising process,high-temperature particles transiently produced from welding process is investigated.The calculation model of coupling heat transfer between particles and airflow is established.After obtaining the information of airflow distribution through welding test,the transportation and dynamic distribution of high-temperature particles with different diameters are illuminated by numerical simulation.Results prove that hightemperature particles with longer movement time and stronger dispersion in environment.Besides,high temperature particles with diameter of 1-30 ?m will separate from airflow during the movement.According to the transportation characteristics for particles with different initial temperature and diameter,three dynamic distribution modes are proposed.Furthermore,conclusions clarify that the particle's physical properties are very important for studying the air-solid two-phase flow.It also indicates that controlling airflow does not mean pollutants are controlled well.Based on the dynamic characteristics of free-falling single hot particle,the transportation of free-falling high-temperature particles in typical industrial process is studied.The high-speed imaging system is used to qualitatively study the difference of flow patterns between high-temperature particles and room-temperature particles.Then,three influencing factors,which are drop height,hipper outlet diameter,and particles' initial temperature,are induced to study the PM10 generation rate through experimental measurement.The PM10 generation rate during falling and colliding process influenced by single factor is quantified.Results show that the transportation of PM10 for roomtemperature particles is mainly attribute to the rebound dusting in the collision process.However,as particle's initial temperature increasing,PM10 escape during falling process is aggravated.Therefore,more PM10 particles will move to the surrounding environment results in escape dusting becomes dominate.Thereafter,the regression equation of PM10 particles in escape dusting zone is established based on the multi-factor analysis.Conclusions quantify PM10 dusting rate of free-falling particles influenced by multiple factors.For the sake of evaluating solid particle contaminants more accurately,on the one side,the transportation of high-temperature particles needs to be studied.However,the pollution sources could not be controlled completely for many practical reasons.The escaped particles will be inhaled directly human,or inhaled after mixing with the ambient airflow.Therefore,it is also necessary to study the transportation process of particles from the environment to human's respiratory system.Through using monodisperse particles generation device(VOAG),the facial mucosal deposition exposure and lower airway exposure for particles with different particle diameter are quantified.The quantitative relationship between them is analyzed.A three-dimensional vitro geometry model based on the CT scan of real human facerespiratory-lung is established.The experiment bench for face deposition and lower airway exposure to particle with different diameter is built.The technique of fluorescence particle transfer is adopted.The quantity of particle deposition on human facial mucosa area in the static/inhalation state are measured for monodisperse particles with diameter of 0.6 ?m,1 ?m,2 ?m,3 ?m and 5 ?m.Then,the influence of inhalation airflow on particle deposition is analyzed.Through measuring particles mass of lower airway exposure for bronchial below level 7,the difference between facial mucosal deposition exposure and lower airway exposure with different particle diameter is obtained.Then,the percentage of inhalation exposure of the respiratory zone into the lower airway for particles with different diameter is also determined based on the quantitative analysis of lower airway exposure measurement results.Results reveal that for particles with diameter of 0.6 ?m,1 ?m and 2 ?m,the mass of particles which deposit on facial mucosa area is smaller than lower airway exposure.Particles with diameter of have the largest lower airway inhalation exposure percentage,more than 34% particles will inhale from breathing zone to lower airway.The lower airway exposure is 5.7 times larger than facial deposition exposure.Particles with diameter of 3 ?m and 5 ?m are less affected by the inhalation flow,and the lower airway exposure of 3 ?m particles is slightly larger than facial mucosa deposition.Meanwhile,only 5% of 5 ?m particles could penetrate 7 levels bronchi from respiratory zone.Attributing to larger diameter,5 ?m particles are easily accumulate in the facial mucosa area within a short time.The facial deposition exposure is 1.8 times of the lower airway exposure,and the risk of mouth exposure is extremely high.The above research conclusions provide a basis for accurately evaluating human exposure to particles with different diameter.