[Characteristic of Ultrafine Particles Transferring Through Building Envelopes]

Penetration and transmission characteristics of outdoor particulate matter through building envelope structure into indoor and its influencing factors were studied by experimental and numerical simulation methods. With the aid of fast mobility particle spectrometer (fast mobility particle sizer, FMPS), particle number concentrations were measured and particle penetration rates were obtained. The effects of slit size and flow pressure on the infiltration process were studied. Compared with numerical simulation and experimental results, the trend was consistent. Experiment and simulation results showed that when the slit was 1 mm high, the penetration rate of particulates with small particle size was small. Its leading influence factor was Brownian diffusion movement, with the increase of particle size, the penetration rate increased. Particle penetration rate was enhanced with the increase of inlet pressure and particle size, but decreased with the increase of slit length. Simulation results showed that the particle penetration rate was enhanced with the increase of slit height. Among all the factors, slit height was the dominant one. When the particle size was more than 30 nm, the penetration rate was close to 1. When the slit height was reduced to 0.25 mm, the penetration rate of particles with size of near 300 nm reached the maximum of 0.93. With the increase of the particle size, particle penetration rate showed a trend of decrease, and gravity settling began to dominate. The experiment result showed that when the slit height changed, the dominant factors of particles subsidence to the wall were changed. At low concentration in a certain range, the particle number concentration had little effect on the penetration rate. The range of particle number concentration of inside and outside I/O ratio was 0.69- 0.73. The correlation coefficient R2 was 0.99. The linear correlation was obvious. The particle penetration rate in slit straight way was significantly greater than that at the corner of the channel.