The Influence Of Humidity On The Distribution Of Indoor Particle

As one of the main pollutants, particles have a great influence onindoor air quality. Although a lot of researches about the indoor particledistribution have been made at home and abroad, there is no conclusionabout the effects of humidity on indoor particle distribution. The articlehas researched the influence by completing the following work.First, After briefly introducing the source of the indoor particulate,particle size range, factors that influence concentration and the harm tohuman health, this article states the research at home and abroad fromthree ways, which are theoretical research, numerical modeling andexperiment research. Then came to the conclusion that the researchesabout the indoor particle matter at present stage all haven’t consider theinfluence of humidity.Second, The article analyzes the force of a single particle in the flowfield, then use the particle transport equation and particle transport flux toanalyze the gas dynamics of the collision among particles and the force ofcoagulation after the dynamics, and then find out that when the relativehumidity is large, the effect of liquid bridge is the dominant force of thecoagulation of particles.Third, in experimental studies, in order to exclude the impact oftemperature changes on the experimental results and make a comparativeanalysis of the different distribution of indoor particulate matter underdifferent humidity conditions, a control system with constant temperatureand humidity has been established in the experiment room, and severaldifferent relative humidity conditions has been set by the humidity device.Using the scanning electron microscopy to observe the particle sourcerelease particles, the indoor particulate matter under the backgroundconcentrations and different humidity conditions, the article finds out thatonly when the relative humidity is65%or above, the coagulationbetween particulate matter is significant. The small particles of thedifferent forms and sizes condensate large particles with different formsand sizes, and the larger the relative humidity is, the more significant thecoagulation phenomenon is. Using the dust detector, the optical Particle Size spectrometer test to analyze the mass concentration, the numberdensity and size distribution of indoor particulate matter under differentconditions, the fact that when the relative humidity is80%comparedwith the other conditions, the attenuation speed of the indoor ofparticulate matter’s mass concentration is the minimum has been found.When the particle size range is0.3to2μm, the attenuation speed isminimum. When the particle size range is0.3~1.5μm, the percentagechange in the amplitude of the total particulate matter is also the smallest.Finally, the article reseaches that when the relative humidity is80%, thecritical relative humidity values about mass concentration of particulatematter, the number density and size distribution which changes over time.Every experiments have been carried out twice in each conditions and theexperimental results show good reproducibility.Forth, through CFD method, the article uses Fluent to simulate themovement of the indoor particle distribution in condition1(RH=35%),and uses experimental date to verify the correctness of numericalsimulation.The flow field indoor and the distribution of the particledensity and their changes over time are analyzed.Generally speaking, increasing the relative humidity may change themain force of coagulation and strengthen the coagulation phenomenonthrough which more small particles become large particles. The changesof mass density, number density and particle size distribution can makean influence on the distribution of indoor particles.