Browsing by Author "TSAI, CJ"

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A FIELD-STUDY OF 3 COLLOCATED AMBIENT PM10 SAMPLERS
(1995-02-01)
TSAI, CJ
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
;
Institute of Environmental Engineering
The performances of three ambient PM10 samplers were studied at three monitoring stations in Taiwan. It was found that differences in the daily measured PM10 concentrations of the SA 1200 and Wedding high-volume samplers are now within +/- 10% since the former now has a closer cut-point to the latter than in the earlier SA 321 A model. The Wedding beta gauge automatic sampler was found to be applicable in rainy and humid weather conditions in Taiwan. Its daily PM10 concentrations are typically within +/- 10% of those of the Wedding high-volume sampler. The particle loading effect of Wedding high-volume and beta gauge samplers was found to be important. To avoid sampling errors due to the loading effect with ambient PM10 samplers, they must be cleaned regularly at an interval depending on the ambient particulate level.
ATMOSPHERIC AEROSOL SAMPLING BY AN ANNULAR DENUDER SYSTEM AND A HIGH-VOLUME PM(10) SAMPLER
(1995)
TSAI, CJ
;
HUANG, HY
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交大名義發表
;
環境工程研究所
;
National Chiao Tung University
An Annular Denuder System (ADS) was used to study sampling errors of total PM(10) and soluble ionic species concentrations determined by the high volume PM(10) (HVPM(10)) sampler. Experimental results show that in the HVPM(10) sampler, more alkaline glass fiber filters collect more sulfate and nitrate but less ammonium ion than quartz filters. However, total PM(10) concentrations do not seem to depend on the types of filters. Artifact sulfate concentrations in glass fiber filters of the HVPM(10) sampler are found to exceed those predicted by the Coutant's model. It is suggested that artifact sulfate and nitrate not only occur within filters but also in particle deposits. Chloride ion concentrations in the filters of the HVPM(10) sampler are underestimated significantly due to evaporative loss of ammonium chloride.
DESIGN AND EVALUATION OF A PLATE-TO-PLATE THERMOPHORETIC PRECIPITATOR
(1995-02-01)
TSAI, CJ
;
LU, HC
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交大名義發表
;
環境工程研究所
;
National Chiao Tung University
A plate-to-plate thermophoretic precipitator with high particle collection efficiency has been designed and tested. The precipitator consists of two flat plates separated by a 0.38-mm thermal insulating shim. The top plate is heated by a constant high-temperature water flow while the bottom plate is cooled by a constant low-temperature water flow. Through this forced convective heat transfer arrangement, a high and uniform temperature gradient is achieved between the two plates, where submicron aerosol particles can be collected efficiently and uniformly in the direction of the air flow. The precipitator was tested in the laboratory using NaCl and sodium fluorescein monodisperse test particles. When the temperature gradient ranges from 502-degrees to 879-degrees-C/cm and the Knudsen number ranges from 0.27 to 3.5, the experimental data show that the present precipitator collects submicron particles efficiently. Among previous theories, the thermophoretic velocity equation proposed by Talbot et al. (1980) is found to fit very well with the present experimental data.
PARTICLE COLLECTION EFFICIENCY OF 2 PERSONAL RESPIRABLE DUST SAMPLERS
(1995-09-01)
TSAI, CJ
;
SHIH, TS
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環境工程研究所
;
Institute of Environmental Engineering
This study determines acceptable flow rates for both SKC and 10-mm nylon cyclone samplers to match the sampling efficiency curve specified by the new American Conference of Governmental Industrial Hygienists (ACGIH) criteria for respirable dust sampling. Monodisperse test particles were used to evaluate the relationship of particle collection efficiency versus particle aerodynamic diameter by fluorometric technique. Original pow rate at 1.7 L/min for the 10-mm nylon cyclone sampler has been confirmed to match the ACGIH (1984) criteria for solid particles. The original flow rate at 1.9 L/min for the SKC cyclone sampler has been found to result in a solid particle collection efficiency curve slightly lower than the British Medical Research Council criteria. When sampling solid particles, the new ACGIH criteria was matched at the pow rates of 1.3 and 2.2 L/min for 10-mm nylon and SKC cyclone samplers, respectively. While the 2.2 L/min pow rate for the SKC sampler is consistent with most previous studies, the 1.3 L/min flow rate for the 10-mm nylon cyclone is quite different. Furthermore, experimental results indicate that the collection efficiency of the 10-mm nylon cyclone sampler is lower for liquid particles than solid particles when particles are larger than the cut point. The difference in collection efficiency due to particle material has been found to be insignificant for the SKC sampler. Pump pulsation and the orientation of a sampler also influenced particle collection efficiency.
SOLID PARTICLE COLLECTION CHARACTERISTICS ON IMPACTION SURFACES OF DIFFERENT DESIGNS
(1995-07-01)
TSAI, CJ
;
CHENG, YH
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交大名義發表
;
環境工程研究所
;
National Chiao Tung University
The effect of solid particle loading on the collection efficiency of a single-stage impactor with different impaction surface designs has been investigated. Experimental results show that the time-varying collection efficiency depends on the surface coating rendition, thickness of particle deposit, and impaction surface design. Deposited particles change the surface condition such that the particle collection efficiency decreases with time for the coated impaction surface while it increases with time for the uncoated impaction surface. However, after heavy loading, the collection efficiency eventually approaches nearly the same asymptotic value whether the impaction surface is coated or not. The impaction surface with an inverted conical cavity and an orifice plate alleviates particle bounce and reentrainment problems during particle collection process, resulting in a much greater collection efficiency than the conventional design, which uses flat impaction surface.
TRANSPORT AND DEPOSITION OF WEAR PARTICLES IN COMPUTER DISK DRIVES
(1992-03-01)
TSAI, CJ
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PUI, DYH
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LIU, BYH
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環境工程研究所
;
Institute of Environmental Engineering
To understand the roles that wear particles play in disk crashes, analytical and numerical approaches have been used to study three dimensional fluid flow and wear particle transport and deposition in computer disk drives. The study shows that wear particles are flying very close to the disk surface. They can deposit on the disk surface and cause damage to disk drives. Cooling air flow through the disk hub of corotating disks has been found to play important roles in removing wear particles from disk drives. Parametric study has shown that the optimum cooling air flow rate is 12 slpm for 8" disk with the Reynolds number of 150,000.