| Inhalable particulates is one of the important factors that have adverse effects on human health. The distribution of indoor particulates is a very important aspect of scientifically evaluating indoor air quality (IAQ). Compared to the traditional upper air supply, Underfloor Air Distribution (UFAD) has been proved to have a promising future, which has many advantages on the flexible air vents arrangement, remarkable energy saving effect, etc. But there is no systematic study on whether the secondary suspension of inhalable particulates appeared in ground and the other wall by the way of blowing from the bottom, and how the particulates distribution is influenced, etc. The distribution of indoor inhalable particulates r and the characteristics of secondary suspension are studied experimentally and theoretically in this dissertation. The main research content and innovation are as follows:On the basis of investigations and studies of numerous documents, the necessity of studying movement and distribution of indoor inhalable particulates is expounded. The necessity of distribution rules of particles with different diameters is discussed through the analysis of a link between fine particles toxicity and grain diameter. By the look of research results already made, it still lacks systematicness and rigorous on study of movement, distribution and characteristics of secondary suspension of indoor inhalable particulates, especially in the systematical research on the characteristics of secondary suspension.On the basis of the relative research and the theory analysis of influencing factors of the concentration of indoor particulates from the floor in under-floor air distribution system(UFAD), the mass balance model (Eq. 5.21 ) of the concentration prediction of the indoor particulates is studied, and this method considers the suspending rate reduction with time. By the suspension percentage experiments, it was obtained that the influence factors of particles suspension are (in the turn of influencing degree): human's activities, the shape of air inlet and outlet,the initial concentration of ground fine particles,the supply air velocity under experimental conditions.In order to study the behavior and organization of suspended particles in a special fluid field of, the flow model of Underfloor air distribution system (UFAD) by conducting a little research on the flow field in advance is selected as research model in this dissertation basing on researching achievements and experience. The k-εturbulence model of gaseous phase conditions is performed for improving the parameter of turbulence near the inner wall. Being tested on circular and whirling air vents, the numerical solutions are determined, especially the wall shear stress and friction velocity field affecting the particles' distribution. Through the comparing results, the experimental value of many survey points is basically agree with the computational value of the corresponding points. The complex air distribution of whirling air vents obtained via the equation was in close compliance with relevant experiment results by correctly dealing with boundary conditions in this dissertation. The computational fluid model is established with the water as the working fluid of atomization, and its geometrical ratio is 1:10. Under the situation of circular air vents, the experimental cell flow field was further confirmed with the indoor flow field experiments of Particle Image Velocimetry (PIV) based on the similar principles(4) Based on the detachment mechanism of particulate matter from the wall, this dissertation presents detailed analysis to the force of the particulate matter in boundary layer of turbulence. Description of fluid force of solid phase (particulate matter) close to the wall was perfected. The models of drag force and shearing force that should be considered under the aerodynamic diameter of 0.1-10μm in this dissertation were confirmed. The detachment condition was obtained through analysis the detachment process of the particulate matter. Considering the theoretical model of adhesive force and empirical equation, the detachment model of particulate matter on the wall under the condition of flowing in the room was conducted.(5) The time scale of suspension was discussed and the motion of the particulate matter after detachment was studied abstractly. Based on full consideration of drag force, gravity, Brownian motion force, saffman lift force of the particulate matter, equation of motion of indoor particulate matter was obtained through the reasonable simplification. The indoor inhalable particulate matter distributed model using Lagrangian method and boundary conditions of the wall and method of calculation were perfected. The ending of the indoor particulate matter motion were divided three classes as suspension, trap and escape. Working on the breathing exposures of people is the suspending particulate matter, so the concept of particulate matter suspending lifetime is provided: the particulate matter suspending lifetime means the time of the particulate matter staying in the room after exhaust or before capture. The suspending lifetime can be obtained through calculating the track of particulate matter using Lagrangian method. When enough tracks are calculated, it will reflect the average suspending lifetime of the particulate matter. As the indicator evaluating the purification performance of indoor particulate matter pollution, it will be convenient used in engineering simulation.(6) Based on the indoor particulate matter distributed simplified model of this dissertation, the simulated calculation method of indoor particulate matter distribution was studied. Firstly, the measuring results of the flow distribution and concentration distribution of the particulate matter in the references were used to check the correctness of the model. Secondly, the concentration distribution was calculated when there were particulate matter pollution point sources in the room. Influence of different supply air parameters and pollution sources was simulated and analyzed through the combine of the dispersed phase model in the business software Fluent and user defined functions. It provides convenient method for forecast and control of the particulate matter exposures. Underfloor air distribution system was also simulated. If people walk slightly in the room, it will lead to air dust and dynamic variation of indoor particulate matter concentration. This model can predict this kind of ventilation and air purification. It also can provide theoretical direction to control the pollution through reasonable air distribution. This dissertation presents that Lagrangian method is an effective measure to simulate and calculate the steady and dynamic distributions of indoor particulate matter. The simulating and calculating method has sufficient theoretical basis. It is validated through the experiments and easy to carry out. Compare to similar methods, it is superior in the academic and engineering application.
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