The Experts below are selected from a list of 44325 Experts worldwide ranked by ideXlab platform
Shia-chung Chen - One of the best experts on this subject based on the ideXlab platform.
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Surface Visual Quality of Gas-Assisted Injection Molded ABS Parts with Various Gas Channel Designs
Journal of Reinforced Plastics and Composites, 2004Co-Authors: Shia-chung Chen, Rean Der Chien, Ming-chung Lin, Min-yu Teng, Chun-sheng ChenAbstract:Gas-assisted injection molding (GAIM) provides many more advantages than conventional injection molding (CIM), but its applications are limited to the surface visual quality problem. ABS plate parts designed with Gas Channels having five different types of cross-section but with the same section area were Gas-assisted injection molded. Furthermore, various plate thickness parts designed with semicircular Gas Channel of different radii were also molded. Surface visual quality of GAIM parts was investigated by gloss and chromatics measurements. Effects of processing parameters and geometrical factors, introduced by part thickness, shape, and associated dimensions of Gas Channels on glossy difference and chromatic aberration of GAIM parts were studied. Influence of mold with etching treatment on surface visual quality was also examined. Basically, it was found that glossy difference is very sensitive to the degree of crystallinity whereas Gas Channel residual skin melt thickness plays a dominant factor for chromatic aberration. The surface visual quality shows a strong dependence on processing conditions. In general, Gas Channel design of semicircular cross section (shape A) provides better surface effect than the other designs in visual quality. Meanwhile, to obtain best surface visual quality, the ratio of equivalent radius to plate thickness should be ranged from 2.2 to 2.4. Alternatively, the surface visual quality can be improved by etching treatment on mold core-side. The results of this research may provide part design guideline for choosing the most effective Gas Channel design to achieve the best surface visual quality.
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Effect of Gas Channel design on the molding window of Gas-assisted-injection-molded polystyrene parts
Journal of Applied Polymer Science, 2003Co-Authors: Rean Der Chien, Shia-chung Chen, Ming-chung Lin, Ping-hui Lee, Chun-sheng ChenAbstract:Gas Channel design plays a dominant role in determining the successful application of Gas-assisted injection molding. Although empirical guidelines for Gas Channel design have been proposed by the various equipment suppliers, quantitative criteria based on well-designed experiments have not been reported yet. In this study, transparent polystyrene plates designed with semicircular Gas Channels of different radii and with rectangular Gas Channels of different width-to-height ratios were Gas-assisted-injection-molded to investigate the geometrical effects on Gas penetration with various plate thicknesses. Plate parts designed with Gas Channels having four different types of cross sections but with the same section area were also examined. Molding windows and criteria for Gas penetration were properly chosen so that the design rule could be defined quantitatively. The moldability index was also classified into five levels (excellent, good, fair, poor, and bad) based on the relative areas of the molding windows. From a plot of the moldability index versus the ratio of the equivalent Gas Channel radius to the plate thickness, we found that the ratio should be approximately greater than 2 for an appropriate molding window (fair moldability index) to be obtained. The dimensional ratio of the width to the height for rectangular Gas Channels also affected the moldability index under the same equivalent radius. Meanwhile, for four Gas Channel designs, both Gas Channel designs attached to the top rib provided better moldability than the other designs. This investigation offers part designers preliminary quantitative design and molding guidelines for choosing an effective Gas Channel design that allows the parts to be molded under an appropriate molding window so that the uncertainty in both simulation and process control can be overcame. Furthermore, this study provides a methodology for the establishment of quantitative Gas Channel design guidelines. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2979–2986, 2003
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Investigations into moulding window of Gas assisted injection moulded polystyrene plates with various Gas Channel designs
Plastics Rubber and Composites, 2002Co-Authors: Rean Der Chien, Shia-chung Chen, Yen-chen ChenAbstract:AbstractThe design of the Gas Channel plays an important role in the successful application of Gas assisted injection moulding. Although empirical guidelines for Gas Channel design have been proposed by the various equipment suppliers, quantitative rules based on well designed experiments have not been reported previously. To investigate the effects of geometry on Gas penetration for two plate thicknesses, transparent polystyrene (PS) plates designed with semicircular Gas Channels of differing radii and with rectangular Gas Channels of differing width to height ratios have been produced using Gas assisted injection moulding. Moulding windows and criteria for Gas penetration were also chosen so that design rules could be defined quantitatively. The mouldability index was also classified into five levels (excellent, good, fair, poor, and bad) based on the relative areas of the moulding windows. From a plot of mouldability index against R eq , the ratio of equivalent Gas Channel radius to plate thickness, it...
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simulations of primary and secondary Gas penetration for a Gas assisted injection molded thin part with Gas Channel
Journal of Applied Polymer Science, 1998Co-Authors: Shia-chung Chen, Nien Tien Cheng, Shengyan HuAbstract:Numerical simulations and experimental studies concerning melt flow and primary as well as secondary Gas penetration during the filling and the postfilling stages in Gas-assisted injection molding of a thin plate with a semicircular Gas Channel design were conducted. Distribution of the skin melt thickness along the Gas-penetration direction was measured to identify primary and secondary Gas penetration. Melt and Gas flow within the Gas Channel of a semicircular cross section is approximated by a model which uses a circular pipe of an equivalent hydraulic diameter superimposed on the thin part. An algorithm based on the control-volume/finite-element method combined with a dual-filling parameter technique suitable for the tracing of two-component flow-front advancements is utilized and numerically implemented to predict both melt- and Gas-front advancements during the melt-filling and the Gas-assisted filling processes. A flow model of the isotropic melt-shrinkage origin combined with a gapwise layer tracing algorithm was implemented to assist the prediction of secondary Gas penetration and melt flow in the post-filling stage. Simulated results on the Gas front locations at the end of both primary and secondary penetration phases show reasonably good coincidence with experimental observations.
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Effect of Gas Channel design on bending properties of Gas-assisted injection molded Polystyrene parts
Journal of Reinforced Plastics and Composites, 1998Co-Authors: Rean Der Chien, Shia-chung Chen, Yuan Kang, Hsien-yang YehAbstract:Polystyrene (PS) thin plates designed with semicircular Gas Channel of different radius and with rectangular Gas Channel of different width to height ratio were Gas-assisted injection molded (GAIM). Effects ofgeometrical factors introduced by part thickness, various section shapes and the associated dimensions of Gas Channels on bending properties of GAIM parts were investigated via a bending test. It was found that Gas Channel design, introducing additional moment of inertia determined by the geometry of Channel section and the hollowed core, results in part structural reinforcement. Bending properties of GAIM parts. including maximum bending load and absorbed bending energy, are enhanced when part thickness and the sizes of semicircular and rectangular Gas Channel increase. Part stiffness and maximum bending load increases linearly with inertia moment and section modulus of the plate. respectively. Increasing Gas channcl height has the best effect on the enhancement ofbending stiffness. The present investigation provides part designers a guideline for choosing the most effective Gas Channel design to achieve a specific part bending structural performance.
Chih-yung Wen - One of the best experts on this subject based on the ideXlab platform.
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performance of a proton exchange membrane fuel cell stack with thermally conductive pyrolytic graphite sheets for thermal management
Journal of Power Sources, 2009Co-Authors: Chih-yung Wen, Yusheng LinAbstract:Abstract This work experimentally investigates the effects of the pyrolytic graphite sheets (PGS) on the performance and thermal management of a proton exchange membrane fuel cell (PEMFC) stack. These PGS with the features of light weight and high thermal conductivity serve as heat spreaders in the fuel cell stack for the first time to reduce the volume and weight of cooling systems, and homogenizes the temperature in the reaction areas. A PEMFC stack with an active area of 100 cm2 and 10 cells in series is constructed and used in this research. Five PGS of thickness 0.1 mm are cut into the shape of flow Channels and bound to the central five cathode Gas Channel plates. Four thermocouples are embedded on the cathode Gas Channel plates to estimate the temperature variation in the stack. It is shown that the maximum power of the stack increase more than 15% with PGS attached. PGS improve the stack performance and alleviate the flooding problem at low cathode flow rates significantly. Results of this study demonstrate the feasibility of application of PGS to the thermal management of a small-to-medium-sized fuel cell stack.
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application of a thermally conductive pyrolytic graphite sheet to thermal management of a pem fuel cell
Journal of Power Sources, 2008Co-Authors: Chih-yung Wen, Guowei HuangAbstract:This work experimentally investigates the thermal performance of a pyrolytic graphite sheet (PGS) in a single proton exchange membrane fuel cell (PEMFC). This PGS with high thermal conductivity serves as a heat spreader, reduces the volume and weight of cooling systems, and reduces and homogenizes the temperature in the reaction area of the fuel cells. A transparent PEMFC is constructed with PGS of thickness 0.1 mm cut into the shape of a flow Channel and bound with the cathode Gas Channel plate. Eleven thermocouples are embedded at different positions on the cathode Gas Channel plate to measure the temperature distribution. The water and water flooding inside the cathode Gas Channels, with and without PGS, were successfully visualized. The locations of liquid water are correlated with the temperature measurement. PGS reduces the maximum cell temperature and improves cell performance at high cathode flow rates. The temperature distribution is also more uniform in the cell with PGS than in the one without PGS. Results of this study demonstrate the promising application of PGS to the thermal management of a fuel cell system.
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A Study on Mass Transfer in the Cathode Gas Channel of a Proton Exchange Membrane Fuel Cell
Journal of Mechanics, 2007Co-Authors: K.-t. Jeng, Chih-yung Wen, L. D. AnhAbstract:A two-dimensional, transient mathematical model for the mass transfer of a reactant Gas in the cathode Gas Channel of a PEMFC is developed. This model accounts concurrently for Gas flow and multicomponent species (oxygen, water vapor and nitrogen) transport in the Gas Channel at specified cell current densities. The governing equations along with the boundary and initial conditions are solved numerically by using finite-difference methods. The numerical results show that the oxygen and water vapor concentrations in the Gas Channel are strong functions of stoichiometry. However, at a fixed stoichiometry, the current density has only a slight influence on the concentration variations. The fully-developed Sherwood number for oxygen mass transfer in the Gas Channel was found to be 6.0, which agrees well with the Sherwood number estimated from the correlation between mass and heat transfer. The current mathematical model and numerical results are confirmed by the experimental verification of the location of first appearance of liquid water at the Channel/GDL interface.
A M F R Pinto - One of the best experts on this subject based on the ideXlab platform.
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1D + 3D two-phase flow numerical model of a proton exchange membrane fuel cell
Applied Energy, 2017Co-Authors: Rui B. Ferreira, D S Falcao, Vânia Oliveira, A M F R PintoAbstract:Abstract In this work, a numerical model of a proton exchange membrane (PEM) fuel cell is presented. The volume of fluid (VOF) method is employed to simulate the air-water two-phase flow in the cathode Gas Channel, at the same time that the cell electrochemical performance is predicted. The model is validated against an experimental polarization curve and through the visualization of water distribution inside a transparent fuel cell. The water dynamics inside a serpentine Gas Channel is numerically analyzed under different operating voltages. Moreover, water content in different regions of the Channel is quantified. Current density and water generation rate spatial distributions are also displayed and it is shown how they affect the process of water emergence into the Gas Channel. Important issues on the simulation of the PEM fuel cells two-phase flow are addressed, especially concerning the coupling of the VOF technique with electrochemical reactions. Both the model and the numerical results aim to contribute to a better understanding of the two-phase flow phenomenon that occurs in these devices.
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1d 3d two phase flow numerical model of a proton exchange membrane fuel cell
Applied Energy, 2017Co-Authors: Rui Ferreira, D S Falcao, V B Oliveira, A M F R PintoAbstract:Abstract In this work, a numerical model of a proton exchange membrane (PEM) fuel cell is presented. The volume of fluid (VOF) method is employed to simulate the air-water two-phase flow in the cathode Gas Channel, at the same time that the cell electrochemical performance is predicted. The model is validated against an experimental polarization curve and through the visualization of water distribution inside a transparent fuel cell. The water dynamics inside a serpentine Gas Channel is numerically analyzed under different operating voltages. Moreover, water content in different regions of the Channel is quantified. Current density and water generation rate spatial distributions are also displayed and it is shown how they affect the process of water emergence into the Gas Channel. Important issues on the simulation of the PEM fuel cells two-phase flow are addressed, especially concerning the coupling of the VOF technique with electrochemical reactions. Both the model and the numerical results aim to contribute to a better understanding of the two-phase flow phenomenon that occurs in these devices.
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numerical simulations of two phase flow in an anode Gas Channel of a proton exchange membrane fuel cell
Energy, 2015Co-Authors: Rui Ferreira, D S Falcao, V B Oliveira, A M F R PintoAbstract:In this work, the two-phase flow in an anode Gas Channel of a PEM (proton exchange membrane) fuel cell is numerically investigated using the VOF (volume of fluid) method. Water movement in the Gas Channel is analyzed and the effects of hydrogen inlet velocity, operating temperature and Channel walls wettability are investigated. Results reveal that for hydrophilic Channel walls water moves as films in the upper surface of the Channel (surface opposite to the GDL (Gas diffusion layer)) whereas it moves as a droplet when the Channel walls are hydrophobic. Moreover, increasing hydrogen inlet velocity, operating temperature and Channel walls wettability results into a faster water removal. However, for the case when hydrogen velocity is increased, a considerable increment on pressure drop is also observed. Results from the present work provide important quantitative information that complements experimental data from literature.
Hua Meng - One of the best experts on this subject based on the ideXlab platform.
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lattice boltzmann simulations of liquid droplets development and interaction in a Gas Channel of a proton exchange membrane fuel cell
Journal of Power Sources, 2012Co-Authors: Bo Han, Hua MengAbstract:Abstract Liquid water transport in Gas Channels may influence and even prevent Gas supply in a proton exchange membrane (PEM) fuel cell, so significantly affect cell operation. A two-phase two-dimensional lattice Boltzmann model is employed in this paper to simulate the development and interaction of two liquid droplets in a Gas Channel of a PEM fuel cell, focusing mainly on parametric effects, including the Gas flow velocity, initial droplet distance, different micropore combinations, and the Gas diffusion layer (GDL) surface wetting properties, on liquid droplet transport behaviors. Results confirm that an increased Gas stream velocity and liquid pore distance may prevent liquid droplet interaction and enhance liquid water removal. Numerical simulations further indicate that different pore size combinations may promote droplet interaction, particularly with a large pore in front of a small one. On the contrary, a more hydrophobic GDL surface can decrease liquid droplet interaction, benefit liquid water removal, and consequently improve PEM fuel cell water management.
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A PEM fuel cell model for cold-start simulations
Journal of Power Sources, 2008Co-Authors: Hua MengAbstract:Abstract In this paper, a transient multiphase multi-dimensional PEM fuel cell model has been developed in the mixed-domain framework for elucidating the fundamental physics of fuel cell cold start. Cold-start operations of a PEM fuel cell at a subfreezing boundary temperature of −20 °C under both constant current and constant cell voltage conditions have been numerically examined. Numerical results indicate that the water vapor concentration inside the cathode Gas Channel affects ice formation in the cathode catalyst layer and thus the cold-start process of the fuel cell. This conclusion demonstrates that high Gas flow rates in the cathode Gas Channel could increase fuel cell cold-start time and benefit the cold-start process. It is shown that the membrane plays a significant role during the cold-start process of a PEM fuel cell by absorbing the product water and becoming hydrated. The time evolutions of ice formation, current density and water content distributions during fuel cell cold-start processes have also been discussed in detail.
Yusheng Lin - One of the best experts on this subject based on the ideXlab platform.
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performance of a proton exchange membrane fuel cell stack with thermally conductive pyrolytic graphite sheets for thermal management
Journal of Power Sources, 2009Co-Authors: Chih-yung Wen, Yusheng LinAbstract:Abstract This work experimentally investigates the effects of the pyrolytic graphite sheets (PGS) on the performance and thermal management of a proton exchange membrane fuel cell (PEMFC) stack. These PGS with the features of light weight and high thermal conductivity serve as heat spreaders in the fuel cell stack for the first time to reduce the volume and weight of cooling systems, and homogenizes the temperature in the reaction areas. A PEMFC stack with an active area of 100 cm2 and 10 cells in series is constructed and used in this research. Five PGS of thickness 0.1 mm are cut into the shape of flow Channels and bound to the central five cathode Gas Channel plates. Four thermocouples are embedded on the cathode Gas Channel plates to estimate the temperature variation in the stack. It is shown that the maximum power of the stack increase more than 15% with PGS attached. PGS improve the stack performance and alleviate the flooding problem at low cathode flow rates significantly. Results of this study demonstrate the feasibility of application of PGS to the thermal management of a small-to-medium-sized fuel cell stack.
