Study On Particle Concentration Variation And Transport In Residences

As people in average spend half of time in their residence,air quality in residential buildings have become a focusing problem.Aerosol particles with diameter less than 2.5 micrometer(PM_2.5)can be inhaled inside the human body and pose threat to health,particles in residential environment have been paid more and more attention.As one of the regions that people often stay in,living room of residences have important effect on indoor air quality.However,air quality in living room can be influenced not only by cooking-generated particles from kitchen,but also from outdoor ambient particle concentration level.Research on particle concentration,distribution and influential factors in living room of urban residential buildings are scarce.Based on this,this study investigates particles mass concentration distribution and diffusion characteristics of living room in urban residential buildings.The research methods include literature search and investigation,real-time monitoring of particle mass concentration and numerical simulation.Prediction of indoor PM_2.5 mass concentration was studied under outdoor penetration and cooking period.First of all,PM_2.5 mass concentration in living room of urban residential buildings worldwide is collected in the past two decades.Concentration differences between regions and influential factors are analyzed.Chinese indoor PM_2.5concentrations are in high level.Concentrations in living room are affected by indoor activities,ventilation,building performance,outdoor ambient level and seasons.Then,six typical residences are selected to monitor PM_2.5 mass concentration in living room in heating season.Corresponding hourly outdoor ambient PM_2.5 concentrations are recorded.Indoor and outdoor concentration variations are analyzed.Influence of penetration and cooking fume on indoor concentration level are studied,respectively.Besides,particle mass concentrations with different diameters,PM_0.5,PM_1.0,PM_2.5,PM_5.0 and PM₁₀ are monitored.PM_2.5 mass concentration vararion are obtained to study the effect of outdoor penetration and cooking on indoor concentration level.Following,theoretical of particle transport mechanism from kitchen to adjacent room is analyzed.Model with residential kitchen and living room of small size is established.Oil temperature,PM_2.5 emission rate and air volume of range hood are determined.Standard k-εturbulent model with discrete particle model is applied for simulating indoor airflow and particle distribution.Four different grid numbers are tested and verified with experimental data based on the data in literature.Then,different kinds of make-up air cases in kitchen are put forward based on ventilation modes in normal residences.As previous studies are mostly conducted in well-organized test chambers,make-up air from kitchen window under open and closed conditions in residences make indoor airflow more complicated.Parameters of natural make-up air are determined.Air temperature,velocity magnitude and particle mass concentration are simulated under different vent cases.Influence of different make-up air,volume,temperature and exhaust on indoor environment are analyzed.Besides,oil temperature and PM_2.5 emission rate changing with cooking time are established.User define function is compiled for transient simulation.Air temperature,velocity and particle mass concentration in indoor environment are obtained during the whole cooking process.Influence of oil temperature and emission rate variations on indoor environment are studied for particle transmission and distribution characteristics.Finally,according to source emission and deposition characteristics,air exchange rate,indoor and outdoor concentration,influential factors are analyzed.A two-zonal model with kitchen and adjacent room is set up.Differential equation of particle transportation under infiltration and cooking period are performed level based on monitoring data and numerical study for household PM_2.5 mass concentration prediction.Range value of the key factors are analyzed.Fitness equations are performed compared with data for rationality of the model.Results show that by minimizing time step size and appropriate value,concentration can be predicted with good accuracy in this model.In conclusion,this study is on concentration level and particle distribution in living room of urban residential buildings combined with methods of field monitoring,numerical simulation.Key factors on concentration variations are studied,concentration levels are predicted.This work can provide theoretical support for improvement of indoor air quality in urban residences.