Firstly, a high flow rate (14l/min) mixing type CNC (condensation nucleus counter) has been developed and its performance was evaluated. The counting efficiency of the CNC by use of the condensing vapor of ethylene-glycol and propyrene-glycol was found to be about 60 % and 100 % with 5 nm and 10 nm particles, respectively. Secondly, a new cumulative type electrical mobility analyzer has been developed, where the CNC above developed is combined as a detector of classified aerosol particles and a radio-active source is used as a charger of feed aerosols, and it was found that the analyzer was applicable to size analysis of low concentration (>1.5×107 particles/m3) and small (5 ∼ 100 nm) aerosol particles which followed log-normal size distribution.
A sampling line used for collecting aerosol particles for dust monitoring generally consists of vertical, horizontal and bent pipes. To estimate the aerosol deposition onto the sampling line as accurately as possible is required for proper evaluation of aerosol concentration. This paper describes the derivation of the reasonable equation of particle deposition velocities onto the vertical pipe wall, where a free flight model by Friedlander et al. and a turbulent particle diffusivity by Lin et al. were used. In particular, a problem concerned with the starting point of free flight of particles is eliminated, and the introduction of Brownian diffusivity for smaller particles and a correction factor to the assumed lag between fluid and particle motions, in the turbulent core of the flowing fluid, for larger particles makes the deposition velocity equation applicable for the whole range of particle size and fluid Reynolds number.
Measurements of particle number concentration were made in pulse count mode of a condensation nucleus counter (CNC) in order to evaluate particle coincidence error at high concentrations. A screen-type diffusion battery was used to change particle concentration by a constant factor. Existing correction theory was tested against the experimental data. The results showed that two parameters related to the viewing volume of the CNC was very important for the correction. One of them is sampling flow rate, and the other is effective time particles spend m the viewing volume. When the coincidence is appropriately corrected, concentration measurable in pulse count mode of the CNC (TSI model 3760) can be extended to 105 particles/cm3.
A new method of charging and collecting unit for submicron particles in closed room has been developed. The photoelectron emitted from an electrode by UV irradiation were used for the charging of particles. The developed unit resulted in several advantages as follows : 1) High clean for closed space was obtained with no artificial circulation. 2) Ozone-less unit. 3) High safety one with no use of high-voltage electric field.
Design concepts and methods of a quadrupole cell were described from the viewpoint of aerosol measurement by a light scattering method. The present quadrupole cell, which was manufactured based on the design concepts, showed an excellent performance as an electrodynamic balance for particle trap.
Errors of anisokinetic sampling in dust concentration measurements were investigated for flue gases from utility boilers in two thermal power plants. The fuels burned in the two power plants are heavy oil and coal respectively. The measurements were carried out in the range of 0.25 < Vo/Vs < 2.0, where Vo is the gas velocity in duct, and Vs is its suction velocity during anisokinetic sampling. Although the errors at the oil combustion plant were negligible since dust particles were very small, the results were seemed to be in agreement with the evaluation equation based on Dp50. However, the errors at the coal combustion plant were significant and in good agreement with the evaluation based on Dp50 and size distribution of particles, Davies Eq. and Belyaev Eq..