Laboratory-scale moving granular bed filter was built in order to study the collection mechanisms of the moving bed. The distributions of granule moving velocity and packing density in the bed were measured with and without dust loading, and the distributions of collected dust in the bed were determined by sampling the granules directly from the bed. It was found that the use of louver facilitates the replacement of granules at the entrance region of the bed so as to achieve stable operation and that an increase in filtration velocity leads to a decrease in packing density because of the larger cavities formed in the bed. Further, the measurements of collected dust distributions in the bed revealed that the collection of dust particles occurs in a narrow entrance region of the bed and that the maximum dust retention on the granules depend on the granule moving velocity and the filtration velocity. Below the maximum dust retention, the amount of dust particles retained by the granules is found to be a function of total incoming particle load during the time period for which the granules are exposed to the aerosol stream.
A numerical S/N estimate, which is based on the S/N theory of a PMT(Photo-multiplier tube), in measuring aerosol particles by an ICCD camera was proposed for designing an optimal optical system. In this estimate, two coefficients were newly introduced to take account of both the light accumulation and the exposure time of the ICCD camera. The accuracy of this estimate was investigated experimentally for several particle sizes from 0.1 μm to 0.5 μm. We could easily measure the particles in an area about 46 mm× 15 mm, and the S/N estimations agreed with the experimental results about 5 %. Therefore, it was made clear that the estimate is very useful to design the 2-bimensional particle measuring system with the ICCD camera.