Paper Reviews
Presentation file is attached for review papers presented at the group meeting only.
Numerical optimization of channel to land width ratio for PEM fuel cell
Mohammad Ziauddin Chowdhury a b, Omer Genc a b, Serkan Toros a b
a Nigde Omer Halisdemir University Prof. Dr. T. Nejat Veziroglu Clean Energy Research Center, Nigde, Turkey
b Mechanical Engineering Department, Faculty of Engineering, Nigde Omer Halisdemir University, Nigde, Turkey
Flow field plays a vital role in proton exchange membrane (PEM) fuel cell where channel geometry being the primary factor. Most of the channel geometry analyses were limited to few number of case studies, whereas in this study total 73 case studies were analyzed for the optimization of channel and land width. A three dimensional isothermal single phase flow mathematical model is developed and further validated with experimental study to optimize the channel and land width through parametric sweep function for a staggering 73 number of case studies. The optimization analyses are carried out for a straight channel geometry considering a fixed operating voltage of 0.4 V and channel depth of 1.0 mm. Due to the large number of case studies, the analyzed performance parameters i.e. current density and pressure drop are easily understandable for the change in different channel and land width. The numerical results predicted that the pressure drop is more dependent on channel width compare to the land width and anode pressure drop is less significant than cathode pressure drop. However, both channel and land width have an equal importance on the cell current density. Considering channel pressure drop and current density, the optimization analyses showed that the channel to land width of 1.0 mm/1.0 mm would be best suitable for PEMFC channel geometry.
Crossover effects of the land/channel width ratio of bipolar plates in polymer electrolyte membrane fuel cells
Aeri Jung a, Im Mo Kong a, Kyung Don Baik b, Min Soo Kim a
a Division of WCU Multiscale Mechanical Design, Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Republic of Korea
bAgency for Defense Development, Daejeon 305-152, Republic of Korea
The crossover effect of the land/channel width ratio of bipolar plates in polymer electrolyte membrane fuel cells is experimentally investigated in this study. To isolate the effect of the land/channel width ratio, three different types of bipolar plates of a fixed sum and channel width are specially prepared. With three different bipolar plates, measurements are taken of electrochemical performance, inlet pressure, and hydrogen crossover rate. When the stoichiometric ratio of hydrogen is 1.5, the standard type of bipolar plate, BP2 (land width = 0.75 mm, channel width = 1.05 mm) show the best performance. However, according to increasing stoichiometric ratio of hydrogen, BP3 (land width = 1.12 mm, channel width = 0.68 mm) has the best performance, especially at the medium and high current range. For the crossover rate, the biggest amount of hydrogen gas crossover to the cathode in BP3. This is because of the anode inlet pressure caused by the largest land/channel ratio of BP3.
Design optimization of proton exchange membrane fuel cell bipolar plate
Tabbi Wilberforce a, A.G. Olabi b d, Domenico Monopoli a, M. Dassisti c, Enas Taha Sayed e, Mohammad Ali Abdelkareem b d e
a College of Engineering and Physical Sciences, Department of Mechanical, Biomedical and Design Engineering, Aston University, Birmingham B4 7ET, UK
b Sustainable Energy & Power Systems Research Centre, RISE, University of Sharjah, P.O. Box 27272, Sharjah, United Arab Emirates
c Politecnico di Bari, DMM, Bari, Italy
d Center for Advanced Materials Research, University of Sharjah, 27272 Sharjah, United Arab Emirates
e Chemical Engineering Department, Faculty of Engineering, Minia University, Egypt
The bipolar plate geometry design is one of the fuel cell's key features that determines the cell's power. It equally has a direct correlation to the thermal and water management of the cell as it tends to regulate the amount of by-product water that can be expunged from the fuel cell. This study, therefore, explored the development of novel bipolar plate geometry designs, namely the square baffled channel, the rectangular baffled channel, the parallel channel design, and the double serpentine geometry design. This was further compared with the traditional serpentine design to ascertain the design with the optimum fuel cell performance. With the squared baffled channel presenting the best results, varying operating conditions that will influence the performance of the novel fuel cell channel design were also evaluated. It was observed that the hydrogen mass fraction increased by 22.6% for the square baffled channel design compared with the other geometry designs considered in the present study. The square baffle channel showed 12.11% increase in power density and 14.54% increase in current density compared to the rectangular baffle channel. In terms of the parallel channel design, the square baffle showed 18.941% increase in power density and 22.278% increase in current density. The least performing channel geometry design was the double serpentine design. Comparing the double serpentine channel geometry design to the square baffle channel geometry design, there was an increase in current density by 67.72% and 77.88% in terms of power density in favour of the square baffle channel geometry design. The square baffle channel also showed 50% increase in current density and 58.23% increase in power density compared to conventional serpentine channel flow plate geometry design. An adaptive neuro fuzzy inference system (ANFIS) was also adopted to predict the output power of the cell. This was then compared with Feed Forward Back Propagation Neural Network to determine the model with the most accurate results. The adaptive neuro-fuzzy inference model accurately predicted the non-linearities associated with fuel cell performance, hence recommended as ideal for Proton Exchange membrane fuel cell prediction. The main contribution for the study is the development of optimal flow plate geometry design that will ensure maximum fuel cell performance. The current study is aimed at providing technical information to policy makers and the fuel cell industry on how optimization of the flow plate design via the introduction of baffles could increase the cell performance hence accelerates its commercialization and widen their applications in various sectors beyond the automotive industry.
Weitong Pan a, Xueli Chen a, Fuchen Wang a, Gance Dai b
a Institute of Clean Coal Technology, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China
b State Key Laboratory of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China
A comprehensive understanding of gas channel (GC)-gas diffusion layer (GDL) interrelations incorporating the mass transfer coefficients, resistances, and areas provides guidelines for the flow channel design. This paper is based on the “flow field analysis scheme” that combines theoretical analysis and numerical simulation. In the analysis, transport-reaction interactions are clarified using multiple resistances in series approach. Results indicate that the external mass transfer resistance is primarily confined to the GDL; and instead, the GC-GDL interface should be highlighted for a uniform transport flux. It is further revealed that the reconciliation of the mass transfer area and coefficient is the key to enhanced transport capability. On this basis, the analytical solution of optimal channel width is obtained; and its coordination with the flow rate is established. Next, a typical single-channel fuel cell model is investigated with various geometric and operating parameters, further validating and quantifying the theoretical analysis.
Krystian L. Wlodarczyk a, Adam Brunton b, Phil Rumsby b, Duncan P. Hand a
a Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
b M-Solv Ltd., Oxonian Park, Landford Locks, Kidlington, Oxford OX5 1FP, United Kingdom
We investigate the feasibility of cutting and drilling thin flex glass (TFG) substrates using a picosecond laser operating at wavelengths of 1030 nm, 515 nm and 343 nm. 50 μm and 100 μm thick AF32®Eco Thin Glass (Schott AG) sheets are used. The laser processing parameters such as the wavelength, pulse energy, pulse repetition frequency, scan speed and the number of laser passes which are necessary to perform through a cut or to drill a borehole in the TFG substrate are studied in detail. Our results show that the highest effective cutting speeds (220 mm/s for a 50 μm thick TFG substrate and 74 mm/s for a 100 μm thick TFG substrate) are obtained with the 1030 nm wavelength, whereas the 343 nm wavelength provides the best quality cuts. The 515 nm wavelength, meanwhile, can be used to provide relatively good laser cut quality with heat affected zones (HAZ) of <25 μm for 50 μm TFG and <40 μm for 100 μm TFG with cutting speeds of 100 mm/s and 28.5 mm/s, respectively. The 343 nm and 515 nm wavelengths can also be used for drilling micro-holes (with inlet diameters of ⩽75 µm) in the 100 μm TFG substrate with speeds of up to 2 holes per second (using 343 nm) and 8 holes per second (using 515 nm). Optical microscope and SEM images of the cuts and micro-holes are presented.
Laser-perforated anode gas diffusion layers for direct methanol fuel cells
Abdullah Alrashidi, Hongtan Liu
Clean Energy Research Institute, Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL 33146, USA
Novel anode gas diffusion layers (AGDLs) with both hydrophobic and hydrophilic pathways are created to enhance transfer of both methanol and CO2. Such AGDLs are created by perforating PTFE-treated AGDLs with laser, so that the original pores/pathways in the AGDL are hydrophobic and the laser perforations are hydrophilic, thus providing easy transport paths for both the liquid methanol solution and CO2. One of the novel AGDLs has increased the cell performance by 32% over the non-perforated AGDL. Results of electrochemical impedance spectroscopy (EIS) show that the main reason for the performance enhancement is due to the reduction in mass transfer resistance. Additionally, there is a reduction in charge transfer resistances due to the enhanced methanol transfer to the catalyst layer. The results of linear sweep voltammetry (LSV) show that the perforations increase methanol crossover, thus if perforation density of the AGDL is too high, the cell performances are lower than that of the virgin AGDL.
HUALU WANG, 1,2 QIULING WEN, 1,2,* XIPENG XU, 1,2 JING LU, 1,2 FENG JIANG, 1,2 AND CHANGCAI CUI1,2
1 Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China
2 Fujian Engineering Research Center of Intelligent Manufacturing for Brittle Materials, Huaqiao University, Xiamen 361021, China
The microstructures on a diamond surface have attracted extensive attention in microelectronics, ultra-precision machining tools, and optical elements, etc. In this work, microgrooves were fabricated on a single-crystal diamond surface using ultraviolet nanosecond or infrared picosecond laser pulses. The surface and internal morphologies of the microgrooves were characterized. The chemical composition and phase transition of the diamond after laser irradiation were analyzed. Furthermore, the ablation threshold, ablation rate, and material removal rate of the diamond processed by nanosecond or picosecond lasers were also calculated. In addition, the temperature distributions of the diamond ablated by nanosecond or picosecond lasers were simulated. Finally, the material removal mechanisms of a single-crystal diamond processed by nanosecond or picosecond lasers were revealed. This work is expected helpful to provide a guidance for the laser fabrication of microstructures on diamond.
Development of bipolar plates with different flow channel configurations for fuel cells
Rajesh Boddu, Uday Kumar Marupakula, Benjamin Summers, Pradip Majumdar
Department of Mechanical Engineering, Northern Illinois University, DeKalb, IL 60115, USA
Bipolar plates include separate gas flow channels for anode and cathode electrodes of a fuel cell. These gases flow channels supply reactant gasses as well as remove products from the cathode side of the fuel cell. Fluid flow, heat and mass transport processes in these channels have significant effect on fuel cell performance, particularly to the mass transport losses. The design of the bipolar plates should minimize plate thickness for low volume and mass. Additionally, contact faces should provide a high degree of surface uniformity for low thermal and electrical contact resistances. Finally, the flow fields should provide for efficient heat and mass transport processes with reduced pressure drops. In this study, bipolar plates with different serpentine flow channel configurations are analyzed using computational fluid dynamics modeling. Flow characteristics including variation of pressure in the flow channel across the bipolar plate are presented. Pressure drop characteristics for different flow channel designs are compared. Results show that with increased number of parallel channels and smaller sizes, a more effective contact surface area along with decreased pressured drop can be achieved. Correlations of such entrance region coefficients will be useful for the PEM fuel cell simulation model to evaluate the affects of the bipolar plate design on mass transfer loss and hence on the total current and power density of the fuel cell.
Laser micro-milling of microchannel on copper sheet as catalyst support used in microreactor for hydrogen production
Wei Zhou a, Wenjun Deng b, Longsheng Lu b, Junpeng Zhang a, Lifeng Qin a, Shenglin Ma a, Yong Tang b
a Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China
b School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China
Microchannel structure as catalyst support has been widely used to construct numerous microreactors for hydrogen production. In this work, the laser micro-milling technique was introduced into the fabrication process of microchannels with different geometry and dimensions. The effects of varying scanning speed, laser output power and number of scans on the surface morphology and geometrical dimension of microchannels have been investigated based on SEM observations. It is found that the change of scanning speed and laser output power significantly affected the surface morphology of microchannel. Moreover, the depth of microchannel was increased when the laser output power and number of scans were increased. Subsequently, the microchannels on copper sheet fabricated by the laser micro-milling technique were used as catalyst support to conduct the methanol steam reforming reaction. The better reaction performance of methanol steam reforming in microchannels indicates that laser micro-milling process is probably suitable to fabricate the microchannel reactor for the commercial application.
Yu-Chih Lin a, Feng-Tang Chang b c
a Department of Environmental Engineering and Health, Yuanpei University, 306 Yuan-Pei Street, Hsin-Chu City 300, Taiwan
b JG Environmental Technology Co., Ltd., 3F, No. 70, Guangming 1st Road, Shihsing Village, Jhubei City, Hsinchu county 302, Taiwan
c College of Engineering, National Chiao Tung University, Taiwan
In this study, the authors attempted to enhance the removal efficiency of a honeycomb zeolite rotor concentrator (HZRC), operated at optimal parameters, for processing TFT-LCD volatile organic compounds (VOCs) with competitive adsorption characteristics. The results indicated that when the HZRC processed a VOCs stream of mixed compounds, compounds with a high boiling point take precedence in the adsorption process. In addition, existing compounds with a lowboiling point adsorbed onto the HZRCwere also displaced by the high-boiling-point compounds. In order to achieve optimal operating parameters for high VOCs removal efficiency, results suggested controlling the inlet velocity to <1.5 m/s, reducing the concentration ratio to 8 times, increasing the desorption temperature to 200–225 ◦C, and setting the rotation speed to 6.5 rpm.
