Browsing by Author "BAI, HL"

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A MODEL FOR PREDICTING PERFORMANCE OF AN ANNULAR DENUDER SYSTEM
(1995-10-01)
LU, CY
;
BAI, HL
;
LIN, YM
;
環境工程研究所
;
Institute of Environmental Engineering
A mathematical model for simultaneous gas diffusion, aerosol diffusion and evaporation is presented to predict performance of the annular denuder system. Approximating the aerosol size distribution by a lognormal function and using the statistical method of moment, the evolution of the three aerosol moments and the mass balance equations for the two associated gases in the annular denuder system are obtained. The governing equations were cast into dimensionless form and the performance of the model was validated by the existing data available in the literature. The effects of governing dimensionless groups on the model performance were evaluated in the sensitivity analysis. The model was then applied for sampling nitric acid gas using a typical range of atmospheric aerosol and gas properties to derive the performance equation of the annular denuder system. The methodologies presented herein are helpful in providing design and operational criteria of the annular denuder system for a real sampling of atmospheric reactive gases that minimizes measurement artifacts.
A MODEL TO PREDICT THE SYSTEM PERFORMANCE OF AN ELECTROSTATIC PRECIPITATOR FOR COLLECTING POLYDISPERSE PARTICLES
(1995-11-01)
BAI, HL
;
LU, CS
;
CHANG, CL
;
環境工程研究所
;
Institute of Environmental Engineering
This paper presents a model for predicting the performance of an electrostatic precipitator (ESP) for collecting polydisperse particles. The particle charge was obtained by modifying Cochet's charge equation; the particle size distribution was approximated by a lognormal function; and then the statistic method of moments was employed to obtain a set of the first three moment equations. The continuous evolution of the particle size distribution in an ESP is easily taken into account by the first three moment equations. The performance of this model was validated by comparing its predictions with the existing data available in the literature. Effects of the particle size distribution on the ESP performance were examined, and the results indicated that both overall mass and number efficiencies are lower for inlet particles with a larger mass median diameter and a higher geometric standard deviation. The methodology introduced may be applied to develop design criteria and determine optimal operating conditions of an ESP for improving the collection efficiency of the submicron particles.
A THEORETICAL-STUDY ON THE EVAPORATION OF DRY AMMONIUM-CHLORIDE AND AMMONIUM-NITRATE AEROSOLS
(1995-02-01)
BAI, HL
;
LU, CS
;
LING, YM
;
環境工程研究所
;
Institute of Environmental Engineering
A theoretical model has been developed to investigate possible mechanisms and parameters which may influence the evaporation behavior of dry ammonium chloride and ammonium nitrate aerosols. The model results compared well with the experimental observations available in the literature. Effects of particle polydispersity, gas-particle interaction, flow pattern of the system, particle number concentration, and accommodation coefficient an the evaporation of dry ammonium chloride and ammonium nitrate were quantitatively determined. The particle size distribution has a significant effect on the overall evaporation rate. A negligence of the size distribution and inappropriate use of the evaporation theory would lead to departures from experimental observations.