Browsing by Author "Chien, Chih-Liang"

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A New Cross-Flow Tube Bundle Heat Exchanger with Staggered Hot and Cold Tubes for Thermophoretic Deposition of Submicron Aerosol Particles
(2009)
Chien, Chih-Liang
;
Huang, Shih-Hsuan
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
A new tube cross-flow bundle heat exchanger has been designed and tested for thermophoretic deposition of submicron aerosol particles. The present design has five columns of hot and cold square tubes, respectively, arranged in a staggered manner to maintain a nearly constant temperature gradient in the direction of the aerosol flow. Each column has four tubes of 4 mm x 4 mm in cross section and the gap between the tube surfaces is 0.5 mm. The precipitator was tested experimentally using monodisperse NaCl test particles ranging from 38 to 397 nm in diameter at the aerosol flow rate of 0.6 and 1.2 L/min, respectively, at different temperature gradients. Results showed that the thermophoretic deposition efficiency increased with decreasing aerosol flow rate and increasing temperature gradient with the maximum thermophoretic deposition efficiency occurred at the aerosol flow rate of 0.6 L/min. The effect of inlet temperature of the aerosol flow on the efficiency was also tested and showed increasing inlet temperature increased the deposition efficiency. Numerical simulation was further conducted to validate the experimental data and good agreement was obtained. An empirical equation was also validated to facilitate the design and scale-up of the precipitator.
A real-time monitoring system for soluble gas pollutants and it's application for determining the control efficiency of packed towers
(2015-11-05)
Chien, Chih-Liang
;
Iswara, Aditya Prana
;
Liou, Yi-Ling
;
Wang, Bing-Tsai
;
Chang, Jui-Chiao
This study used a parallel-plate wet denuder coupled with an ion chromatograph (PPWD-IC) to monitor soluble gas pollutants in the exhaust stack and investigate the removal efficiency of packed towers. Gas pollutant concentrations measured by the PPWD-IC system were first validated with those obtained by a manual porous metal denuder sampler (PDS) as the reference sampler. The measured concentrations of the PPWD-IC system are in good agreement with those of the PDS with the coefficient of determination (R-2) greater than 0.93. The PPWD-IC system was then used to determine the removal efficiency of packed towers in high-tech factories. Results show that the PPWD-IC system is able to monitor multiple high-concentration gas pollutants semi-continuously, such as HF, HCl, HNO2, HNO3, CH3COOH, and NH3, in the exhaust stack with a temporal resolution of 20 min. The PPWD-IC system was employed to test the gas removal efficiency of a new honeycomb wet scrubber in an optoelectronic factory. The removal efficiency of the wet scrubber equipped with the honeycomb module at the liquid-to-gas ratio of 18.5 L/m(3) is shown to be close to 100% for HF (112.4-448.4 ppbv) and CH3COOH (696.3-6537.0 ppbv) and 99% for HCI (3394,9-10794.5 ppbv), respectively. (C) 2015 Elsevier B.V. All rights reserved.
Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions
(2015-01-01)
Chien, Chih-Liang
;
Tien, Chi-Yu
;
Liu, Chun-Nan
;
Ye, Huajun
;
Huang, Wei
The NCTU micro-orifice cascade impactor (NMCI) was redesigned and tested to enable the measurement and adjustment of the jet-to-plate distance (S) of the impactors by using a micrometer. Each stage of the NMCI contains an impaction plate and a nozzle plate which are separated. The bottom casing for impaction plate assembly and the nozzle plate holder of each stage are separated. Calibration results show that the cutoff aerodynamic diameter (d(pa50)) of the three lower stages (d(pa50) = 180, 100, and 56 nm) are close to the nominal values given in Marple et al. (1991). In addition, the S/W (W: nozzle diameter) effects on the d(pa50) for the three lower stages were investigated and an empirical equation was developed to facilitate the prediction of d(pa50) when the nozzle diameters may change slightly from one batch to another. The relationship between the nozzle diameter and pressure drop of the micro-orifice impactors at the fixed operational flow rate of 30 L/min was also established so that the nozzle diameters can be predicted from the pressure drop measurement. An empirical equation was proposed to express the correlation between the dimensionless cutoff size and the S/W ratio when considering isentropic flow to facilitate the design of microorifice impactors for S/W > 4. It is expected that the present NMCI could improve the accuracy of size classification of submicron particles below 180 nm, especially for nanoparticles.
Drag Coefficient of a Spherical Particle Attached on the Flat Surface
(2011-10-01)
Liu, Chun-Nan
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Chien, Chih-Liang
;
Lo, Chu-Chun
;
Lin, Guan-Yu
;
Chen, Sheng-Chieh
The previous analytical solution for the drag coefficient (C(d)) for a spherical particle attached on the flat surface, which was derived by O'Neill (1968), is only valid in the creeping flow conditions. It is important to extend O'Neill's formula to cover a wide range of particle Reynolds number (Re(p)). In this study, the drag coefficient was calculated numerically to cover Re(p) from 0.1 to 250. For a particle suspended in the air, an empirical drag coefficient exists, which is defined as C(d) = f x 24/Re(p), where f is a correction factor depending on Re(p). The applicability of the correction factor f for O'Neill's analytical equation for the spherical particle attached on the flat surface for Re(p) = 0.1 to 250 was examined in this study.
High-efficiency parallel-plate wet scrubber (PPWS) for soluble gas removal
(2015-03-04)
Chien, Chih-Liang
;
Tsai, Chuen-Jinn
;
Sheu, Shiang-Ru
;
Cheng, Yu-Hsiang
;
Stank, Alexander Mihailovich
A parallel-plate wet scrubber (PPWS) was designed and tested to control low-concentration soluble acid gases using a multi-parallel-plate module (MPPM) to replace typical tower packings. The parallel plates in the MPPM were made of polypropylene coated with nano-TiO2 particles to enhance hydrophilicity for scrubbing liquid to form uniform liquid film. The gap between the plates was maintained at 3 mm, providing channels through which soluble gas pollutants in the upward gas stream were absorbed by the downward scrubbing liquid film on the surfaces. The removal efficiency was tested using HCl, HNO3, and CH3COOH of 0.02-2 ppmv at different retention times and liquid-to-gas ratios. Results show that when the retention time was 0.1, 0.3 and 0.5 s, the removal efficiency of the present scrubber for HCI, HNO3, and CH3COOH in low concentration was greater than 91%, 95%, and 98%, respectively. The MPPM significantly enhances the removal efficiency of the present scrubber, especially in low inlet concentration range (0.02-1 ppmv), which was greater than 99% for HCl and HNO3 and 98% for CH3COOH at the liquid-to-gas ratio of 18.5 L/m(3), the retention time of 0.5 s, and the pressure drop of 0.2 cm H2O. The experimental removal efficiencies of the MPPM are in good agreement with theoretical predictions. It is expected that the present PPWS can be scaled up as an efficient control device with low pressure drop for low-concentration soluble acid and basic gases. (C) 2015 Elsevier B.V. All rights reserved.
Improvement of the Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger by Using Radial Sheath Airflow: Numerical Study
(2013-04-01)
Chien, Chih-Liang
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
A single-wire corona unipolar charger with radial sheath air was proposed to enhance the nanoparticle charging efficiency. The charger consists of an insulated Teflon tube (inner diameter = 6.35mm) with a 6mm-long grounded porous metal tube placed at its center from which radial sheath air is introduced, and a discharge gold wire of 50m in the outer diameter and 6mm in the effective length. The performance of the charger was evaluated and optimized numerically. The effect of the position of the sheath air opening on reducing charged particle loss was found to be important and two designs were studied. In design 1, both ends of the 6mm wide sheath air opening are aligned with the ends of the 6mm-long discharge wire, while in design 2 the sheath air opening is shifted 2mm toward the left of the leading edge of the wire. At the same operating condition, design 2 was found to have less electrostatic loss than design 1 because of its smaller deposition region for charged particles. Compared to two unipolar chargers with the highest extrinsic charging efficiency for particles smaller than 10nm in diameter, design 2 operated at the applied voltage of +3.5kV, aerosol flow rate of 0.5 L/min, and sheath airflow rate of 0.7 L/min has a comparable extrinsic charging efficiency of 17.2%-70.5% based on particle number for particles ranging from 2.5 to 10nm in diameter. Copyright 2013 American Association for Aerosol Research
Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger
(2011)
Chien, Chih-Liang
;
Tsai, Chuen-Jinn
;
Chen, Hui-Lin
;
Lin, Guan-Yu
;
Wu, Jong-Shinn
A single-wire corona unipolar aerosol charger with a sheath air to avoid particle loss was designed and experimental charging efficiencies were obtained at a fixed aerosol flow rate of 1 L/min using monodisperse silver nanoparticles of 2.5 to 20 nm in diameter. The charger has a cylindrical casing of 30 mm in inner diameter in which a gold wire of 50 mu m in diameter and 2 mm in length is used as the discharge electrode. A two-dimensional (2-D) numerical model was developed to predict nanoparticle charging efficiency in the unipolar charger. Laminar flow field was solved by using the Semi-Implicit Method for Pressure Linked Equations (SIMPLER method), while electric potential and ion concentration fields were solved on the basis of Poisson and convection-diffusion equations, respectively. The charged particle concentration fields and charging efficiencies were then calculated on the basis of the convection-diffusion equation in which ion-particle combination coefficient was calculated by Fuchs diffusion charging theory (Fuchs, N. A. (1963). On the Stationary Charge Distribution on Aerosol Particles in a Bipolar Ionic Atmosphere. Geophys. Pura. Appl., 56:185-193). Good agreement between predicted and experimental extrinsic charging efficiencies was obtained. Numerical results showed the advantage of using sheath air to minimize charged particle loss and indicated the location where major charged particle loss occurred. It is expected that the present model can be used to facilitate the design of more efficient corona-wire unipolar charger in the future.
Response to Comment on "Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger"
(2014-01-01)
Chien, Chih-Liang
;
Tsai, Chuen-Jinn
;
Tran Thi Minh Phuong
;
環境工程研究所
;
Institute of Environmental Engineering
Fernandez-Diaz and Domat\'s preceeding Letter to the Editor argued that the geometry of the discharge electrode of the charger of our previous article entitled "Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger" was a needle but not a wire. Therefore, the boundary condition for the ionic charge density at the discharge wire surface used in the simulation was suspected to be not completely correct. In the present work, the exact shape of the tip of the discharge electrode was examined and found as a hyperbolic point. The experimental onset voltage was further compared with the theoretical onset values calculated by either wire-in-tube or point-to-plane assumption. Results show that the theory of needle-type discharge electrode is also not appropriate either for the boundary condition at the tip because of higher calculated onset voltages than the experimental data.
TUBE BUNDLE HEAT EXCHANGER OF CONSTANT TEMPERATURE GRADIENT FOR THERMOPHORETIC DEPOSITION OF AEROSOL PARTICLES
(2010-05-13)
TSAI, Chuen-Jinn
;
Huang, Shih-Hsuan
;
Chien, Chih-Liang
This invention is a tube bundle heat exchanger for thermophoretic deposition of aerosol particles. It has a housing with an internal chamber, and several cold and hot tubes. The cold and hot tubes are arranged in a staggered manner in the internal chamber of the housing. Low and high temperature fluids flow inside the cold and hot tubes, respectively. When the exhaust gas passes through the chamber, temperature gradient between the cold and hot tubes causes aerosol particles suspended in the exhaust gas to deposit on the surface of cold tubes to achieve the treatment of exhaust gas. Staggered arrangement of cold and hot tubes can maintain nearly constant temperature gradient in the direction of the gas flow thereby enhances the overall removal efficiency of particles.