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Michael K.h. Leung - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical modeling and parametric study of methane fed solid oxide fuel cells
Energy Conversion and Management, 2009Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:A mathematical model was developed to study the performance of methane (CH4) fed solid oxide fuel cells (SOFCs) considering the direct internal methane steam reforming (MSR) and water gas shift reaction (WGSR). An important feature of this model is that the effects of electrode structural parameters on both the exchange current density and gas diffusion coefficients are fully taken into consideration. The simulation results agreed well with literature data and thus validated the present model. Parametric analyses showed that all the Overpotentials decreased with increasing temperature. This finding is different from previous analyses on hydrogen (H2) fed SOFCs, in which the Concentration Overpotential is found slightly increasing with increasing temperature. This interesting phenomenon for CH4 fed SOFCs can be explained that the rate of MSR and WGSR increases with increasing temperature, leading to high rate of H2 production inside the porous anode and a high molar ratio of H2 to H2O. More simulation results were conducted to investigate the electrode’s microstructural effects on the performance of CH4 fed SOFCs. It is found that increasing electrode porosity or pore size decreases Concentration Overpotential but increases activation Overpotential of CH4 fed SOFCs. At low current densities, low porosity and pore size are desirable to reduce the electrode total Overpotentials as Concentration Overpotential is insignificant compared with activation Overpotential. At high current densities, the total Overpotentials can be minimized at optimal porosities and pore sizes. In order to further improve the performance of CH4 fed SOFCs, advanced electrodes with porosity graded and pore size graded structures are evaluated. It was found that both porosity grading and pore size grading were effective to increase the SOFC working potential due to reduced Concentration Overpotentials. The present study provided better understanding on the coupled transport and chemical reactions (i.e. MSR and WGSR) at the porous electrodes. The model developed can be used to conduct more analyses for design optimizations.
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Mathematical modeling of ammonia-fed solid oxide fuel cells with different electrolytes
International Journal of Hydrogen Energy, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the ammonia (NH3)-fed solid oxide fuel cells with proton-conducting electrolyte (SOFC-H) and oxygen ion-conducting electrolyte (SOFC-O). Different from previous thermodynamic analysis, the present study reveals that the actual performance of the NH3-fed SOFC-H is considerably lower than the SOFC-O, mainly due to higher ohmic Overpotential of the SOFC-H electrolyte. More analyses have been performed to study the separate Overpotentials of the NH3-fed SOFC-H and SOFC-O. Compared with the NH3-fed SOFC-H, the SOFC-O has higher anode Concentration Overpotential and lower cathode Concentration Overpotential. The effects of temperature and electrode porosity on Concentration Overpotentials have also been studied in order to identify possible methods for improvement of SOFC performance. This study reveals that the use of different electrolytes not only causes different ion conduction characteristics at the electrolyte, but also significantly influences the Concentration Overpotentials at the electrodes. The model developed in this article can be extended to 2D and 3D models for further design optimization.
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Electrochemical modeling of ammonia-fed solid oxide fuel cells based on proton conducting electrolyte
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the NH3-fed and H2-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H). The modeling results were consistent with experimental data in literature. It is found that there is little difference in working voltage and power density between the NH3-fed and the H2-fed SOFC-H with an electrolyte-support configuration due to an extremely high ohmic Overpotential in the SOFC-H. With an anode-supported configuration, especially when a thin film electrolyte is used, the H2-fed SOFC-H shows significantly higher voltage and power density than the NH3-fed SOFC-H due to the significant difference in Concentration Overpotentials. The anode Concentration Overpotential of the NH3-fed SOFC-H is found much higher than the H2-fed SOFC-H, as the presence of N2 gas dilutes the H2 Concentration and slows down the transport of H2. More importantly, the cathode Concentration Overpotential is found very significant despite of the thin cathode used in the anode-supported configuration. In the SOFC-H, H2O is produced in the cathode, which enables complete fuel utilization on one hand, but dilutes the Concentration of O2 and impedes the diffusion of O2 to the reaction sites on the other hand. Thus, the cathode Concentration Overpotential is the limiting factor for the H2-fed SOFC-H and an important voltage loss in the NH3-fed SOFC-H. How to reduce the Concentration Overpotentials at both electrodes is identified crucial to develop high performance SOFC-H.
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Importance of pressure gradient in solid oxide fuel cell electrodes for modeling study
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract The pressure gradients in the electrodes of a solid oxide fuel cell (SOFC) are frequently neglected without any justification in calculating the Concentration Overpotentials of the SOFC electrodes in modeling studies. In this short communication, a comparative study has been conducted to study the effect of pressure gradients on mass transfer and the resulting Concentration Overpotentials of an SOFC running on methane (CH 4 ) fuel. It is found that the pressure gradients in both anode and cathode are significant in the fuel cell electrochemical activities. Neglecting the anode pressure gradient in the calculation can lead to underestimation of the Concentration Overpotential by about 20% at a typical current density of 5000 A m −2 and at a temperature of 1073 K. The deviation can be even larger at a higher temperature. At the cathode, neglecting the pressure gradient can result in overestimation of the Concentration Overpotential by about 10% under typical working conditions.
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Modeling of methane fed solid oxide fuel cells: Comparison between proton conducting electrolyte and oxygen ion conducting electrolyte
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the methane (CH 4 ) fed solid oxide fuel cell (SOFC) using proton conducting electrolyte (SOFC-H) and oxygen ion conducting electrolyte (SOFC-O). Both the internal methane steam reforming (MSR) and water gas shift (WGS) reactions are considered in the model. Previous study has shown that the CH 4 fed SOFC-H had significantly better performance than the SOFC-O. However, the present study reveals that the actual performance of the CH 4 fed SOFC-H is considerably lower than the SOFC-O, partly due to higher ohmic Overpotential of SOFC-H. It is also found that the CH 4 fed SOFC-H has considerably higher cathode Concentration Overpotential and lower anode Concentration Overpotential than the SOFC-O. The anode Concentration Overpotentials of the CH 4 fed SOFC-H and SOFC-O are found to decrease with increasing temperature, which is different from previous analyses on the H 2 fed SOFC. Therefore, high temperature is desirable for increasing the potential of the CH 4 fed SOFC. It is also found that there exist optimal electrode porosities that minimize the electrode total Overpotentials. The analyses provided in this paper signify the difference between the CH 4 fed SOFC-H and SOFC-O. The model developed in this paper can be extended to 2D or 3D models to study the performance of practical SOFC systems.
Meng Ni - One of the best experts on this subject based on the ideXlab platform.
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Mathematical analysis of SOFC based on co-ionic conducting electrolyte
Acta Mechanica Sinica, 2013Co-Authors: Keqing Zheng, Meng Ni, Li-yin ShenAbstract:In co-ionic conducting solid oxide fuel cell (SOFC), both oxygen ion (O2-) and proton (H+) can transport through the electrolyte, generating steam in both the anode and cathode. Thus the mass transport phenomenon in the electrodes is quite different from that in conventional SOFC with oxygen ion conducting electrolyte (O-SOFC) or with proton conducting electrolyte (H-SOFC). The generation of steam in both electrodes also affects the Concentration Overpotential loss and further the SOFC performance. However, no detailed modeling study on SOFCs with co-ionic electrolyte has been reported yet. In this paper, a new mathematical model for SOFC based on co-ionic electrolyte was developed to predict its actual performance considering three major kinds of Overpotentials. Ohm’s law and the Butler-Volmer formula were used to model the ion conduction and electrochemical reactions, respectively. The dusty gas model (DGM) was employed to simulate the mass transport processes in the porous electrodes. Parametric simulations were performed to investigate the effects of proton transfer number (tH) and current density (jtotal) on the cell performance. It is interesting to find that the co-ionic conducting SOFC could perform better than O-SOFC and H-SOFC by choosing an appropriate proton transfer number. In addition, the co-ionic SOFC shows smaller difference between the anode and cathode Concentration Overpotentials than O-SOFC and H-SOFC at certain tH values. The results could help material selection for enhancing SOFC performance.
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Electrochemical modeling and parametric study of methane fed solid oxide fuel cells
Energy Conversion and Management, 2009Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:A mathematical model was developed to study the performance of methane (CH4) fed solid oxide fuel cells (SOFCs) considering the direct internal methane steam reforming (MSR) and water gas shift reaction (WGSR). An important feature of this model is that the effects of electrode structural parameters on both the exchange current density and gas diffusion coefficients are fully taken into consideration. The simulation results agreed well with literature data and thus validated the present model. Parametric analyses showed that all the Overpotentials decreased with increasing temperature. This finding is different from previous analyses on hydrogen (H2) fed SOFCs, in which the Concentration Overpotential is found slightly increasing with increasing temperature. This interesting phenomenon for CH4 fed SOFCs can be explained that the rate of MSR and WGSR increases with increasing temperature, leading to high rate of H2 production inside the porous anode and a high molar ratio of H2 to H2O. More simulation results were conducted to investigate the electrode’s microstructural effects on the performance of CH4 fed SOFCs. It is found that increasing electrode porosity or pore size decreases Concentration Overpotential but increases activation Overpotential of CH4 fed SOFCs. At low current densities, low porosity and pore size are desirable to reduce the electrode total Overpotentials as Concentration Overpotential is insignificant compared with activation Overpotential. At high current densities, the total Overpotentials can be minimized at optimal porosities and pore sizes. In order to further improve the performance of CH4 fed SOFCs, advanced electrodes with porosity graded and pore size graded structures are evaluated. It was found that both porosity grading and pore size grading were effective to increase the SOFC working potential due to reduced Concentration Overpotentials. The present study provided better understanding on the coupled transport and chemical reactions (i.e. MSR and WGSR) at the porous electrodes. The model developed can be used to conduct more analyses for design optimizations.
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Mathematical modeling of ammonia-fed solid oxide fuel cells with different electrolytes
International Journal of Hydrogen Energy, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the ammonia (NH3)-fed solid oxide fuel cells with proton-conducting electrolyte (SOFC-H) and oxygen ion-conducting electrolyte (SOFC-O). Different from previous thermodynamic analysis, the present study reveals that the actual performance of the NH3-fed SOFC-H is considerably lower than the SOFC-O, mainly due to higher ohmic Overpotential of the SOFC-H electrolyte. More analyses have been performed to study the separate Overpotentials of the NH3-fed SOFC-H and SOFC-O. Compared with the NH3-fed SOFC-H, the SOFC-O has higher anode Concentration Overpotential and lower cathode Concentration Overpotential. The effects of temperature and electrode porosity on Concentration Overpotentials have also been studied in order to identify possible methods for improvement of SOFC performance. This study reveals that the use of different electrolytes not only causes different ion conduction characteristics at the electrolyte, but also significantly influences the Concentration Overpotentials at the electrodes. The model developed in this article can be extended to 2D and 3D models for further design optimization.
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Electrochemical modeling of ammonia-fed solid oxide fuel cells based on proton conducting electrolyte
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the NH3-fed and H2-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H). The modeling results were consistent with experimental data in literature. It is found that there is little difference in working voltage and power density between the NH3-fed and the H2-fed SOFC-H with an electrolyte-support configuration due to an extremely high ohmic Overpotential in the SOFC-H. With an anode-supported configuration, especially when a thin film electrolyte is used, the H2-fed SOFC-H shows significantly higher voltage and power density than the NH3-fed SOFC-H due to the significant difference in Concentration Overpotentials. The anode Concentration Overpotential of the NH3-fed SOFC-H is found much higher than the H2-fed SOFC-H, as the presence of N2 gas dilutes the H2 Concentration and slows down the transport of H2. More importantly, the cathode Concentration Overpotential is found very significant despite of the thin cathode used in the anode-supported configuration. In the SOFC-H, H2O is produced in the cathode, which enables complete fuel utilization on one hand, but dilutes the Concentration of O2 and impedes the diffusion of O2 to the reaction sites on the other hand. Thus, the cathode Concentration Overpotential is the limiting factor for the H2-fed SOFC-H and an important voltage loss in the NH3-fed SOFC-H. How to reduce the Concentration Overpotentials at both electrodes is identified crucial to develop high performance SOFC-H.
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Importance of pressure gradient in solid oxide fuel cell electrodes for modeling study
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract The pressure gradients in the electrodes of a solid oxide fuel cell (SOFC) are frequently neglected without any justification in calculating the Concentration Overpotentials of the SOFC electrodes in modeling studies. In this short communication, a comparative study has been conducted to study the effect of pressure gradients on mass transfer and the resulting Concentration Overpotentials of an SOFC running on methane (CH 4 ) fuel. It is found that the pressure gradients in both anode and cathode are significant in the fuel cell electrochemical activities. Neglecting the anode pressure gradient in the calculation can lead to underestimation of the Concentration Overpotential by about 20% at a typical current density of 5000 A m −2 and at a temperature of 1073 K. The deviation can be even larger at a higher temperature. At the cathode, neglecting the pressure gradient can result in overestimation of the Concentration Overpotential by about 10% under typical working conditions.
Mark A. Douglas - One of the best experts on this subject based on the ideXlab platform.
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Performance comparison of Fick’s, dusty-gas and Stefan–Maxwell models to predict the Concentration Overpotential of a SOFC anode
Journal of Power Sources, 2003Co-Authors: R. Suwanwarangkul, Eric Croiset, Michael Fowler, Peter L. Douglas, Evgueniy Entchev, Mark A. DouglasAbstract:Models for mass transport inside a porous SOFC anode were developed based on Fick’s model (FM), the dusty-gas model (DGM) and the Stefan–Maxwell model (SMM) to predict the Concentration Overpotential. All models were validated with experimental data for H2–H2O–Ar and CO–CO2 systems. The effect of pore size on all model predictions was discussed. It was concluded that the dusty-gas model is the most appropriate model to simulate gas transport phenomena inside a SOFC anode. However, this model requires numerical solution, whereas Fick’s and Stefan–Maxwell’s do not. It was found that the SMM, rather than the FM, is a good approximation of the dusty-gas model for H2–H2O system, except in the case of high current density, low H2 Concentration and low porosity, where only the DGM is recommended. For the CO–CO2 system, there is no simple rule for selecting an alternate model to DGM. Depending on the CO Concentration, porosity and current density, the FM or the SMM could be used. The only restriction is for small porosities where only the DGM should be used. This paper also demonstrated that only the DGM is recommended for a multicomponent system (H2–H2O–CO–CO2).
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performance comparison of fick s dusty gas and stefan maxwell models to predict the Concentration Overpotential of a sofc anode
Journal of Power Sources, 2003Co-Authors: R. Suwanwarangkul, Eric Croiset, Michael Fowler, Peter L. Douglas, Evgueniy Entchev, Mark A. DouglasAbstract:Models for mass transport inside a porous SOFC anode were developed based on Fick’s model (FM), the dusty-gas model (DGM) and the Stefan–Maxwell model (SMM) to predict the Concentration Overpotential. All models were validated with experimental data for H2–H2O–Ar and CO–CO2 systems. The effect of pore size on all model predictions was discussed. It was concluded that the dusty-gas model is the most appropriate model to simulate gas transport phenomena inside a SOFC anode. However, this model requires numerical solution, whereas Fick’s and Stefan–Maxwell’s do not. It was found that the SMM, rather than the FM, is a good approximation of the dusty-gas model for H2–H2O system, except in the case of high current density, low H2 Concentration and low porosity, where only the DGM is recommended. For the CO–CO2 system, there is no simple rule for selecting an alternate model to DGM. Depending on the CO Concentration, porosity and current density, the FM or the SMM could be used. The only restriction is for small porosities where only the DGM should be used. This paper also demonstrated that only the DGM is recommended for a multicomponent system (H2–H2O–CO–CO2).
Dennis Y.c. Leung - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical modeling and parametric study of methane fed solid oxide fuel cells
Energy Conversion and Management, 2009Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:A mathematical model was developed to study the performance of methane (CH4) fed solid oxide fuel cells (SOFCs) considering the direct internal methane steam reforming (MSR) and water gas shift reaction (WGSR). An important feature of this model is that the effects of electrode structural parameters on both the exchange current density and gas diffusion coefficients are fully taken into consideration. The simulation results agreed well with literature data and thus validated the present model. Parametric analyses showed that all the Overpotentials decreased with increasing temperature. This finding is different from previous analyses on hydrogen (H2) fed SOFCs, in which the Concentration Overpotential is found slightly increasing with increasing temperature. This interesting phenomenon for CH4 fed SOFCs can be explained that the rate of MSR and WGSR increases with increasing temperature, leading to high rate of H2 production inside the porous anode and a high molar ratio of H2 to H2O. More simulation results were conducted to investigate the electrode’s microstructural effects on the performance of CH4 fed SOFCs. It is found that increasing electrode porosity or pore size decreases Concentration Overpotential but increases activation Overpotential of CH4 fed SOFCs. At low current densities, low porosity and pore size are desirable to reduce the electrode total Overpotentials as Concentration Overpotential is insignificant compared with activation Overpotential. At high current densities, the total Overpotentials can be minimized at optimal porosities and pore sizes. In order to further improve the performance of CH4 fed SOFCs, advanced electrodes with porosity graded and pore size graded structures are evaluated. It was found that both porosity grading and pore size grading were effective to increase the SOFC working potential due to reduced Concentration Overpotentials. The present study provided better understanding on the coupled transport and chemical reactions (i.e. MSR and WGSR) at the porous electrodes. The model developed can be used to conduct more analyses for design optimizations.
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Mathematical modeling of ammonia-fed solid oxide fuel cells with different electrolytes
International Journal of Hydrogen Energy, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the ammonia (NH3)-fed solid oxide fuel cells with proton-conducting electrolyte (SOFC-H) and oxygen ion-conducting electrolyte (SOFC-O). Different from previous thermodynamic analysis, the present study reveals that the actual performance of the NH3-fed SOFC-H is considerably lower than the SOFC-O, mainly due to higher ohmic Overpotential of the SOFC-H electrolyte. More analyses have been performed to study the separate Overpotentials of the NH3-fed SOFC-H and SOFC-O. Compared with the NH3-fed SOFC-H, the SOFC-O has higher anode Concentration Overpotential and lower cathode Concentration Overpotential. The effects of temperature and electrode porosity on Concentration Overpotentials have also been studied in order to identify possible methods for improvement of SOFC performance. This study reveals that the use of different electrolytes not only causes different ion conduction characteristics at the electrolyte, but also significantly influences the Concentration Overpotentials at the electrodes. The model developed in this article can be extended to 2D and 3D models for further design optimization.
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Electrochemical modeling of ammonia-fed solid oxide fuel cells based on proton conducting electrolyte
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the NH3-fed and H2-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H). The modeling results were consistent with experimental data in literature. It is found that there is little difference in working voltage and power density between the NH3-fed and the H2-fed SOFC-H with an electrolyte-support configuration due to an extremely high ohmic Overpotential in the SOFC-H. With an anode-supported configuration, especially when a thin film electrolyte is used, the H2-fed SOFC-H shows significantly higher voltage and power density than the NH3-fed SOFC-H due to the significant difference in Concentration Overpotentials. The anode Concentration Overpotential of the NH3-fed SOFC-H is found much higher than the H2-fed SOFC-H, as the presence of N2 gas dilutes the H2 Concentration and slows down the transport of H2. More importantly, the cathode Concentration Overpotential is found very significant despite of the thin cathode used in the anode-supported configuration. In the SOFC-H, H2O is produced in the cathode, which enables complete fuel utilization on one hand, but dilutes the Concentration of O2 and impedes the diffusion of O2 to the reaction sites on the other hand. Thus, the cathode Concentration Overpotential is the limiting factor for the H2-fed SOFC-H and an important voltage loss in the NH3-fed SOFC-H. How to reduce the Concentration Overpotentials at both electrodes is identified crucial to develop high performance SOFC-H.
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Importance of pressure gradient in solid oxide fuel cell electrodes for modeling study
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract The pressure gradients in the electrodes of a solid oxide fuel cell (SOFC) are frequently neglected without any justification in calculating the Concentration Overpotentials of the SOFC electrodes in modeling studies. In this short communication, a comparative study has been conducted to study the effect of pressure gradients on mass transfer and the resulting Concentration Overpotentials of an SOFC running on methane (CH 4 ) fuel. It is found that the pressure gradients in both anode and cathode are significant in the fuel cell electrochemical activities. Neglecting the anode pressure gradient in the calculation can lead to underestimation of the Concentration Overpotential by about 20% at a typical current density of 5000 A m −2 and at a temperature of 1073 K. The deviation can be even larger at a higher temperature. At the cathode, neglecting the pressure gradient can result in overestimation of the Concentration Overpotential by about 10% under typical working conditions.
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Modeling of methane fed solid oxide fuel cells: Comparison between proton conducting electrolyte and oxygen ion conducting electrolyte
Journal of Power Sources, 2008Co-Authors: Meng Ni, Dennis Y.c. Leung, Michael K.h. LeungAbstract:Abstract An electrochemical model was developed to study the methane (CH 4 ) fed solid oxide fuel cell (SOFC) using proton conducting electrolyte (SOFC-H) and oxygen ion conducting electrolyte (SOFC-O). Both the internal methane steam reforming (MSR) and water gas shift (WGS) reactions are considered in the model. Previous study has shown that the CH 4 fed SOFC-H had significantly better performance than the SOFC-O. However, the present study reveals that the actual performance of the CH 4 fed SOFC-H is considerably lower than the SOFC-O, partly due to higher ohmic Overpotential of SOFC-H. It is also found that the CH 4 fed SOFC-H has considerably higher cathode Concentration Overpotential and lower anode Concentration Overpotential than the SOFC-O. The anode Concentration Overpotentials of the CH 4 fed SOFC-H and SOFC-O are found to decrease with increasing temperature, which is different from previous analyses on the H 2 fed SOFC. Therefore, high temperature is desirable for increasing the potential of the CH 4 fed SOFC. It is also found that there exist optimal electrode porosities that minimize the electrode total Overpotentials. The analyses provided in this paper signify the difference between the CH 4 fed SOFC-H and SOFC-O. The model developed in this paper can be extended to 2D or 3D models to study the performance of practical SOFC systems.
M Pourkashanian - One of the best experts on this subject based on the ideXlab platform.
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comparison of the multicomponent mass transfer models for the prediction of the Concentration Overpotential for solid oxide fuel cell anodes
Journal of Power Sources, 2010Co-Authors: Yasemin Vural, D B Ingham, M PourkashanianAbstract:Abstract In this study, multicomponent mass diffusion models, namely the Stefan–Maxwell model (SMM), the Dusty Gas model (DGM) and the Binary Friction model (BFM) have been compared in terms of their predictive capabilities of the Concentration polarization of an anode supported solid oxide fuel cell (SOFC) anode. The results show that other than the pore diameter, current density and Concentration of reactants, which have a high importance in Concentration polarization predictions, the tortuosity (or porosity/tortuosity) term, has a substantial effect on the model predictions. Contrary to the previous discussions in the literature, for the fitted value of tortuosities, SMM and DGM predictions are similar, even for an average pore radius as small as 2.6e−07 and current density as high as 1.5 A cm −2 . Also it is shown that the BFM predictions are similar to DGM for the case investigated in this study. Moreover, in this study, the effect of the pressure gradient term in the DGM and the BFM has been investigated by including and excluding this term from the model equations. It is shown that for the case investigated and model assumptions used in this study, the terms including the pressure coefficient have an insignificant effect on the predictions of both DGM and BFM and therefore they can be neglected.