| The Under Floor Air-conditioning System owns a long but not prevalent history, with many distinctive features such as the superiority providing better indoor air quality, greater energy saving potential, economic value and flexible adjusting mechanism, it has drawn the increasing attention of air-conditioning technicians. The mechanism of the Underfloor air conditioning, the distribution of indoor temperature and velocity field, the determination of load, and the design of air distribution, as well as the development of relevant terminal equipments have already be studied thoroughly. Recent years, some domestic projects, especially the imported ones prefer to adopt Underfloor air supply system. Based on the above factors, this paper focus on experimental study on the indoor air distribution and sedimentation characteristics of inhalable Particles in Underfloor air distribution system.This paper firstly reviews the domestic and foreign research status of the indoor air distribution and sedimentation characteristics of inhalable Particles in Underfloor air distribution system, and summarizes the existing problems. The velocity field map and vector graph under certain wind speed are depicted respectively using the simulation software of FLUENT and PIV experimental model. It is pointed out that there exist two remarkable vortexes on the both sides of the center of the room, which are coincident with the actual floor air supply air distribution. With the air supply speed of 1m/s, the wind velocity at the entrance near the ground (except air outlet) drops to almost zero, which makes it difficult for the particles adhering to the ground to overcome the adhesion to form the secondary suspension.This paper probes into the movement mechanism of the inhalable particles'distribution, and lays a theoretical foundation for theoretical research. After analyzing the concentration variation of inhalable particles with Underfloor air distribution system shutdown, establish a suspension model for particle concentration and obtain the analytical solution, thus deduce the law of inhalable particles'concentration variation with time. Based on the model, calculate the deposition loss rate and deposition velocity with the experimental data. The results indicate that there exists linear relationship between the deposition loss rate and particle size when particles are greater than 1μm; the deposition loss rate and attenuation rate of the particles with diameter smaller than1μm are lower than that of particles with diameter greater than1μm, meanwhile, the concentration of the former is much larger than that of the latter under the stability condition. It is further confirmed that the coarse particles deposit for gravitational settling while smaller particles'sedimentation is determined by Brownian Diffusion.
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