فهرست مطالب

Iranian Journal of Hydrogen and Fuel Cell - Volume:1 Issue:4, 2015
  • Volume:1 Issue:4, 2015
  • تاریخ انتشار: 1393/12/23
  • تعداد عناوین: 7
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  • Mohammad Jafar Kermani, Asrin Ghanbarian Pages 199-207
    A three dimensional, compressible, steady, one phase flow of reactant-product mixture in the air side electrode of proton exchange membrane fuel cell (PEMFC) is numerically studied in this paper. The mixture is composed of three species: oxygen, nitrogen and water vapor. The performance of the cell is enhanced by partial blockage of the flow field channels. Various types of these blocks also called as dents in this study are considered. Examples of the dent profile shapes are: square (labeled as SQ case in this paper), semicircle (or SC) and trapezoid (or TR), and the enhancements are compared with that of no dent (or ND) case. It is observed that channel indentation can enhance the content of oxygen concentration at the face of catalyst layer up to 18%. It is noted that the content of oxygen at the face of catalyst is the driving moment for the kinetics of reaction within the catalyst layer. Hence channel indentation can be considered as a proper mechanism to enhance the performance of fuel cells. In this paper only the increasing of driving moment is discussed and the analysis of net power enhancement will be discussed later in another paper.
    Keywords: PEM Fuel Cell, CFD, Channel Indentation, Performance Enhancement
  • Mohammad Javad Vaezi, Ali Akbar Babaluo Pages 209-214
    The main goal of this work was to synthesize and evaluate the effect of dehydration temperature on the potential application of hydroxy sodalite zeolite membrane. Hydroxy sodalite zeolite membranes were synthesized via direct hydrothermal method onto a tubular alumina support without seeding in a hot air oven. The synthesized membranes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Permeation tests of H2 and CO2 were carried out in order to investige the applied dehydration temperature effect on the performance of the synthesized membranes. The performance of the synthesized membrane dehydrated at 100 ºC tended to high selectivity compared to that of the rest samples and the maximum separation factor (~21) was achieved with acceptable permeances about 3.810-8 and 1.8*10-9 mol.m-2.Pa-1.s-1 for H2 and CO2, respectively. The low selectivities observed for two other synthesized membranes (dehydrated at 150 and 200 ºC), indicating the formation of defects during the dehydration of these membranes at high temperatures.
    Keywords: Dehydration Temperature, Hydrogen Separation, Hydroxy Sodalite, Zeolite Membrane
  • Ali Reza Madram, Abolfazl Fathollahi Zonouz, Hamid Reza Pouretedal Pages 215-222
    The kinetics of hydrogen evolution reaction (HER) was studied in 1M NaOH at various temperatures (298 to 358 K) on Ni-P-C (composite electrodes. The electrochemical efficiency of the electrodes has been evaluated on the basis of electrochemical data obtained from the steady-state polarization Tafel curves, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) in 1M NaOH solution at 298, 323, 348 and 358 K. The HER rate constants were estimated using Tafel-impedance data assuming the Volmer Heyrovský path at various temperatures. The k2 values were smaller than those obtained for hydrogen adsorption rate constants (k1) at all temperatures. The average values of k2, which characterize the apparent activity of the electrodes for the HER on the Ni-P-C cathodes, are increased by factors of 4.0, 3.7 and 3.5 from temperatures of 298 to 323 K, 323 to 348 K and 348 to 358 K, respectively. Microstructure and composition of the investigated electrodes were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The kinetic parameters showed that the temperature plays an important role on increase of the activities of Ni-P-C composite cathodes toward the HER.
    Keywords: Hydrogen evolution reaction (HER), Ni P C, Electrochemical impedance spectroscopy, Electrocatalytic activity, Composite electrodes
  • Hossein Ghadamian, Leyli Ariyanfar, Mojtaba Baghban Yousefkhani, Hassanali Ozgoli Pages 223-231
    In the presented research, heat transfer of a mobile electrolyte alkaline fuel cell (AFC) (which the electrolyte has cooling role of system) has been considered. Proper control volumes of system with specific qualification have been chosen. Consequently, heat and mass transfer in control volumes have been assessed. Considerations on them and contributed models lead to approve a double tube heat exchanger as energy sink. Design of this heat exchanger is dependent on heat transfer conditions and related equations. A composite system of alkaline fuel cell and peripheral equipment has been used. Then the equations of all steps have been integrated. Furthermore, the optimization codes have been developed to propose best operation point of system, minimizing total cost and determining the heat exchanger dimensions, flow rates and temperatures and in this manner the software ‘GAMS’ was employed. In the results, optimum electrolyte inlet and outlet temperature obtained 73˚C and 40˚C respectively; and the heat exchanger total area with minimizing the cost model is rendered to 0.07 m2. Finally, parametric analysis for variation of temperature, length and diameter of heat exchanger, pressure drop, total cost and performance of planned combined system has been studied. It can be concluded that cooling of system is very important because the efficiency of system reduces with temperatures rising. A promising fact of increasing overall efficiency of system regards to reducing electrolyte temperature demonstrate reducing electrolyte temperature in the range of 70 to 40 oC, concluded 2% overall system efficiency increasing.
    Keywords: Alkaline fuel cell, Heat transfer, Sensitivity analysis, Energy efficiency, Cost model
  • Nahid Khandan, Mahmoud Ziarati, Reza Karkeabadi, Mohammad Ali Ghafouri Roozbahani Pages 233-238
    Steam reforming is one of the most important processes for producing hydrogen from hydrocarbon fuels such as LPG and has attracted much attention due to its high efficiency and economy. In this study, the LPG steam reforming reaction was investigated on nickel catalysts supported on four various zeolites (H-Y, Na-Y, HZSM5 and Ferrierite). The catalytic tests were performed in a tubular fixed bed stainless steel reactor (I.D. 10 mm) at 650°C. Results revealed that type of support and specific surface area have significant effects on the activity and selectivity of the prepared catalyst. In this way, Ni/Na-Y catalyst exhibited the highest surface area (696.4 m2/g) among the prepared catalysts. Also, this catalyst showed a low degree of coke formation and consequently, high stability in LPG steam reforming process. Ultimately, The catalytic results showed that the Ni/Na-Y catalyst possessed the highest LPG conversion (95.7 %), H2 yield (48.6%) and stability in this reaction.
    Keywords: Steam reforming, LPG, Ni, zeolite catalyst, Hydrogen production
  • Ebrahim Mostafavi, Alireza Babaei, Abolghasem Ataie Pages 239-246
    In this study the characteristics of two different kinds of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) powders, one in-house synthesized powder by a co-precipitation method and another one purchased from Fuel Cell Materials Co. (FCM Co., USA), were compared. The co-precipitated powder was prepared by using ammonium carbonate as precipitant with a NH4+/NO3- molar ratio of 2 and calcination at 1000C for 1 h. Phase composition, morphology and particle size distribution of powders were systematically studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and laser particle size analysis (LPSA), respectively. The synthesized and commercial LSCF powders were overlaid on Yttria-stabilized zirconia (YSZ) electrolyte having a gadolinium-doped ceria (GDC) interlayer. Electrochemical Impedance Spectroscopy (EIS) measurement was carried out at various operating temperatures in the range of 600-850C. XRD and FESEM analysis revealed that single phase nano-crystalline LSCF powder with a mean crystallite size of 14 nm and mean particle size of 90 nm is obtained after calcination at 1000C. The presence of hard agglomerated particles larger than few microns in the commercial powder and also sub-micron agglomerates in the co-precipitated LSCF powder might be related to the final mechanical milling process and high calcination temperature of powders, respectively. LPSA results show identical mean particle size of about 1.5μm for both LSCF powders. EIS results revealed almost identical polarization resistance for both LSCF powders.
    Keywords: LSCF, Nanoparticles, Co, precipitation, Cathodes, Solid Oxide Fuel Cells
  • Masih Karimi Alavijeh, Mohammad Mahdi Mardanpour, Soheila Yaghmaei Pages 247-260
    Microbial fuel cell and microbial electrolysis cell are two major types of microbial electrochemical cells. In the present study, we governed modeling of these systems by concentrating on the simulation of bioelectrochemical reactions in both biofilm and anolyte and considering the effect of pH on the microbial growth. The simulation of microbial fuel and electrolysis cells can be described by shifting the bioanode surface potential boundary conditions. Model validation was performed using experimental results from the MFCs fed with cheese whey wastewater and then it was switched to a supposed microbial electrolysis cell. The effect of applied voltage as well as poising the cathode surface potential on the anode surface potential and microbial population have been acquired. The results show that hydrogen production rate increases at the higher applied voltage and cathode potential, but the influence of cathode potential at the applied voltage of 0.9 V was much more tangible. The MFC was simulated in different pH values to optimize the power generation. The maximum of power output at 100 Ω was obtained in pH 7.5. In addition, the microbial behavior in the biofilm and anolyte was investigated as a strong function of pH. Due to the higher growth rate of electrogens, the optimum pH for the mixed culture of electrogens was the same for the pure culture (pH 7.7), but it is alterd for acetoclstic methanoges.
    Keywords: Microbial fuel cell, Microbial electrolysis cell, Simulation, Anode potential