Chuen-Shii Chou

Velocity profiles of granules in moving bed filters

The velocity fields in three symmetric and two asymmetric louver-walled moving bed systems were studied experimentally. The horizontal and vertical velocity distributions at five levels of the louver section were plotted. The results indicate that the velocity profiles of filter granules are influenced by the louver geometry. When the louver angle is steep, the velocity profile of filter granules is close to plug flow. When the louver section is shallow, the quasi-stagnant zones exist along the louver walls. The kinematic model for predicting the granule velocity distribution is used for analyzing the three symmetric louver configurations at different height levels.

Kinematic model for granular flow in a two-dimensional flat-bottomed hopper

Abstract Employing the kinematic model proposed by Nedderman and Tuzun and the boundary conditions for granular media in a two-dimensional flat-bottomed hopper with eccentric and centric discharge, two boundary-value problems were constructed. The heights of the stagnant zone for two kinds of granular materials after hopper eccentric and centric discharge were experimentally measured. We postulated that the kinematic constant would be proportional to the height of the stagnant zone. Employing experimental results and the Newton-Raphson method, the kinematic constants under eccentric discharge were obtained. The profiles of the horizontal and vertical velocity components for eccentric as well as centric discharge were then calculated. The theoretical predictions obtained using the kinematic model qualitatively agree with experimental results obtained using a simple image analysis.

Velocities in moving granular bed filters

Abstract This paper concerns the velocity fields of three symmetric louver-walled moving-bed systems. The louver angles were 10°, 20° and 50° in the three experimental tests. The particle-tracking method and image-processing technology were employed to measure the granule velocity fields in the louver sections. The horizontal and vertical velocity distributions extracted from the velocity fields at five levels of the louver section were plotted and discussed. The velocity profiles of filter granules are influenced by the louver geometry. In the steeper louver–angle system, the velocity profile of filter granules is similar to plug flow. The stagnant zones exist along the louver walls in the filter system with shallow louver sections.

Preparation of a Counter Electrode with P-Type NiO and Its Applications in Dye-Sensitized Solar Cell

This study investigates the applicability of a counter electrode with a P-type semiconductor oxide (such as NiO) on a dye-sensitized solar cell (DSSC). The counter electrode is fabricated by depositing an NiO film on top of a Pt film, which has been deposited on a Fluorine-doped tin oxide (FTO) glass using an ion-sputtering coater (or E-beam evaporator), using a simple spin coating method. This study also examines the effect of the average thickness of TiO2 film deposited on a working electrode upon the power conversion efficiency of a DSSC. This study shows that the power conversion efficiency of a DSSC with a Pt(E)/NiO counter electrode (4.28%) substantially exceeds that of a conventional DSSC with a Pt(E) counter electrode (3.16%) on which a Pt film was deposited using an E-beam evaporator. This result is attributed to the fact that the NiO film coated on the Pt(E) counter electrode improves the electrocatalytic activity of the counter electrode.

Flow patterns and stresses on the wall in a moving granular bed with eccentric discharge

The flow patterns and stresses on the wall in a moving granular bed with eccentric discharge were investigated experimentally. The flow pattern histories of granular solids in the moving bed were recorded using a digital camcorder. The image processing system included a frame grabber. A new pressure gauge for simultaneously measuring the normal and shear stresses of granular solids was used. During filling the granular material, the variations in stresses acting on the side walls with time in a granular bed were observed. Also, the dynamic wall stresses were obtained during the eccentric discharge. Employing the results obtained by stress measurements and image processing, the pressure pulsation phenomena in a moving granular bed may be understood further.

Numerical simulation of flow patterns of disks in the asymmetric louvered-wall moving granular filter bed

Abstract Using the Discrete Element Method (DEM) model [P.A. Cundall, O. Strack, Geotechnique, 29 (1979) 47.], the granular solid flow pattern histories, velocity field and quasi-stagnant zone development close to the louvered walls of six kinds of 2-D asymmetrical moving granular filter beds were studied numerically. The numerical results reported here and the experimental results [J.T. Kuo, J. Smid, S.S. Hsiau, C.Y. Wang, C.S. Chou, Filtr. Sep., 35(6) (1998) 529.] provide fundamental and important information for designing moving granular bed high-temperature flue gas cleanup filters.

Study of the Applicability of TiO2/Dye Composite Particles for a Dye-Sensitized Solar Cell

This investigation designed and fabricated a working electrode with a layer of TiO2/dye composite particles on an indium–tin oxide (ITO) substrate for a dye-sensitized solar cell (DSSC). The dry particle coating technique was performed to coat the powder of the CuPc dye (copper phthalocyanine C32H16CuN8) on the surface of TiO2 powder by the Mechanofusion method. A layer of TiO2/dye composite particles was fabricated on the ITO substrate using the doctor blade technique and the working electrode was then sintered in a furnace at 165°C for 1 h. The performance of the DSSC with a layer of TiO2/dye composite particles on an ITO substrate was not inferior to that of the conventional DSSC by dipping the working electrode in the solution of dye. Furthermore, the effects of the mass ratio of TiO2 to CuPc dye and the rate of rotation of the rotating chamber in the Mechanofusion system on the short-circuit photocurrent were investigated. Most importantly, this study not only sustains the applicability of TiO2/dye composite particles to improve the performance of the DSSC, but also provides an alternate process, which can avoid the time that is needed to dip the working electrode into the solution of the dye in fabricating a conventional DSSC.

Flow patterns and stresses on the wall in a two‐dimensional flat‐bottomed bin

Abstract The flow patterns and stresses on the wall in a two‐dimensional flat‐bottomed bin with centric and eccentric discharges were investigated. The flow pattern histories of granular solids in the bin were recorded using a digital camcorder. A pressure gauge for simultaneously measuring the normal and shear stresses of granular solids was used. During filling with the granular material, the variations in stresses acting on the side walls with time were observed. The dynamic wall stresses were obtained during the centric and eccentric discharges. In addition, using Mohrs stress circle, an analysis of the stress state at the bin side‐wall was determined. The normal and shear stress fluctuation ranges predicted by Mohrs stress circle were close to the experimental results. The effect of the discharge slot position upon the wall stress was also demonstrated. Employing the results obtained using stress measurements and image processing, the pressure pulsation phenomena in a bin may be understood further.

The static and dynamic wall stresses in a circulatory two-dimensional wedge hopper

Abstract The stresses on the wall in a circulatory two-dimensional (2D) wedge hopper were theoretically and experimentally investigated. By extending the differential slice method of Walters, an ordinary differential equation for the vertical stress in the wedge hopper was derived. Employing the Runge-Kutta (order 4) method, the static wall stress distributions in the wedge hopper were numerically calculated. A pressure gauge for simultaneously measuring the normal and shear stresses of the granular solids was used. The static wall stress distributions produced by the granular solids were measured and compared with the theoretical prediction using the differential slice and Runge-Kutta (order 4) methods. The variations in the dynamic wall stresses with time in a circulatory 2D wedge hopper were obtained during granular material circulation. In addition, the variations in measured dynamic normal and shear stress results on the left-side wall with bed height were observed and compared with the theoretical results using the Silo Stress Tool. The research work reported here provides additional theoretical and experimental knowledge about granular flows in a wedge hopper to workers in this field, and also enhances the differential slice method application to granular flows.

Preparation of Graphite/Nano-Powder Composite Particles and Applicability as Carbon Anode Material in a Lithium Ion Battery

Graphite/nano-powder composite particles, which were prepared by coating nano-sized powder onto the surface of artificial mesophase graphite powder (MGP) in a mechanofusion system, were employed to modify the conventional carbon anode material in a lithium ion battery. The nano-size powder included nickel oxide (NiO) and ferric oxide (Fe2O3). The MGP/nano-powder composite particles were characterized using a scanning electron microscope, a laser particle size analyzer, a BET surface area analyzer and an X-ray powder diffractometer. The charge/discharge capacity of semi-batteries of lithium ion was measured using a battery charge and management system. The percentage of irreversible capacity decreased substantially from 7.98 (semi-battery with MGP carbon anode material) to 0.38% (semi-battery with MGP/nano-Fe2O3 composite particles carbon anode material) in the first round of charge/discharge tests. The maximum charge capacity increased from 288.07 (semi-battery with MGP carbon anode material) to 292.51 mA h/g (semi-battery with MGP/nano-Fe2O3 composite particles carbon anode material).