Browsing by Author "Lin, Jenn-Der"

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An Analysis of Extinction Coefficients of Particles and Water Moisture in the Stack after Flue Gas Desulfurization at a Coal-Fired Power Plant
(2011-08-01)
Tu, Wen-Fu
;
Lin, Jenn-Der
;
Wu, Yee-Lin
;
機械工程學系
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Department of Mechanical Engineering
Two important factors that affect in-stack opacity light extinction by emitted particles and that by water moisture after a flue gas desulfurization (FGD) unit are investigated. The mass light extinction coefficients for particles and water moisture, k(P) and k(w), respectively, were determined using the Lambert-Beer law of opacity with a nonlinear least-squares regression method. The estimated k(P) and k(w) values vary from 0.199 to 0.316 m(2)/g and 0.000345 to 0.000426 m(2)/g, respectively, and the overall mean estimated values are 0.229 and 0.000397 m(2)/g, respectively. Although k(w) is 3 orders of magnitude smaller than k(p), experimental results show that the effect on light extinction by water moisture was comparable to that by particles because of the existence of a considerable mass of water moisture after a FGD unit. The mass light extinction coefficient was also estimated using Mie theory with measured particle size distributions and a complex refractive index of 1.5-ni for fly ash particles. The k(p) obtained using Mie theory ranges from 0.282 to 0.286 m(2)/g and is slightly greater than the averaged estimated k(p) of 0.229 m(2)/g from measured opacity. The discrepancy may be partly due to a difference in the microstructure of the fly ash from the assumption of solid spheres because the fly ash may have been formed as spheres attached with smaller particles or as hollow spheres that contained solid spheres. Previously reported values of measured k(P) obtained without considering the effects of water moisture are greater than that obtained in this study, which is reasonable because it reflects the effect of extinction by water moisture in the flue gas. Additionally, the moisture absorbed by particulate matter, corresponding to the effect of water moisture on the particulates, was clarified and found to be negligible.
Influence of liquid hydrophobicity and nozzle passage curvature on microfluidic dynamics in a drop ejection process
(2010-01-01)
Lai, Jr-Ming
;
Huang, Chang-Yan
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Chen, Chih-Hao
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Kung Linliu
;
Lin, Jenn-Der
Employing methods of computational fluid dynamics, we investigated the physical phenomena and fluid dynamics of a microfluid during ejection of a droplet with a designed system of a nozzle plate connected to a flat-plate piezoelectric material. A comparison between experimental measurements and numerical simulations was devised to validate the theoretical model. The volume-of-fluid piecewise linear-interface construction (VOF-PLIC) interface-capturing method was adapted to represent the fluid domain and to track the evolution of its free boundaries whereas the continuous surface force (CSF) mode was chosen to model the interfacial physics. The results show that the curvature of the flow channel affects the velocity, period before disintegration, volume of the droplet and number of satellite drops. Increasing the diameter of the orifice increases the volume and decreases the velocity of the droplet. Increasing the amplitude or frequency of the nozzle plate raises the input energy, so increasing the velocity, decreasing the volume and hastening the disintegration of the droplet, but an increased amplitude or frequency increases the number of satellite drops. At the hydrophobic boundary, the velocity increases, the droplet volume decreases and the period before disintegration is abbreviated because of the decreased adhesive force between the fluid and the boundary surface.
Numerical investigation of the effect of a transducer pulse on the microfluidic control of a piezoelectric printhead
(2010-07-01)
Lai, Jr-Ming
;
Lin, Jenn-Der
;
Kung Linliu
;
機械工程學系
;
Department of Mechanical Engineering
Numerical calculations are performed to investigate the effect of the component of a single transducer pulse on the ejection of a drop for a drop-on-demand ink-jet printhead with a piezoelectric actuator. The flow field is governed by continuity and Navier-Stokes equations. A volume-of-fluid method with a piecewise-linear interface construction is used to track the complicated topological variation of the liquid-gas interface. The computer code is validated with experimental results present in the literature. The volume of the primary drop is closely related to the maximum displacement D(f) of chamber wall induced by the piezoelectric actuator in the forward stoke; the velocity of the primary drop depends on the ratio of Df to the time period of the forward stoke Delta tau(f) . Moreover, the fact that the formation of the primary drop depends weakly on the conditions of the backward stroke is considered. A decreased interval between forward and backward strokes might serve to suppress the formation of satellite drops owing to reducing the liquid thread length l(b) at pinching off to a value less than the upper limit lb l(b)*. The breaking up of the freely flying liquid thread from nozzle outlet has two modes-multiple breaking up and end pinching-and depends on the thread length at pinching off. (c) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3486201]
Transient Combined Conduction and Radiation with Anisotropic Scattering
(1990-01-01)
Tsai, Jen-Hui
;
Lin, Jenn-Der
;
機械工程學系
;
Department of Mechanical Engineering
The analysis of transient combined radiation and conduction heat transfer in an absorbing, emitting, and anisotropically scattering planar material is investigated theoretically. The medium boundaries are assumed with specified temperatures. Both specular and diffuse reflectivities are included. The Crank-Nicolson method is used to solve the transient energy equation, and the nodal approximation provides the solution for coupled radiative transfer. This solution method may be described as a finite-difference/nodal approximation method and would replace the governing energy and radiative transfer equations by a set of algebraic equations. Using the method, the present study examines the effect of scattering anisotropy on combined conduction and radiation heat transfer. Results are presented for temperature and heat-flux distributions, and results for isotropic scattering are compared to existing data. The agreement is excellent.