Kunal Karan - Academia.edu (original) (raw)

Papers by Kunal Karan

Research paper thumbnail of 287534 Multi-Physics Modeling of Auto-Thermal Diesel Surrogate Reforming

ABSTRACT Abundant supply and existing infrastructure makes diesel a favorable candidate for porta... more ABSTRACT Abundant supply and existing infrastructure makes diesel a favorable candidate for portable energy supply. Diesel generators are widely used in locations where there is no reliable electric grid, but they are noisy, have emission issues, and often have poor fuel efficiency in practical operations. Because of these drawbacks, there is interest in developing Solid Oxide Fuel Cell (SOFC) systems which use diesel fuel, but which deliver electricity quietly and with lower emissions and higher efficiency. The current study is part of a larger effort aimed at developing 1-5 kW diesel fed solid oxide fuel cells at SOFC-Canada and is mainly focused on understanding and deconvoluting the mechanism of diesel surrogate auto-thermal reforming in an experimental packed bed reactor. Gas phase kinetics play an important role during auto-thermal reforming and this study employs a detailed kinetic model developed using the automated Reaction Mechanism Generator (RMG) software. The generated model has about 9500 reactions and 450 species incorporating updated parameters from experiment and theory. The model has been validated against ignition delay data at different equivalence ratios and was found to perform reasonably well. The model has also been validated against the packed bed reactor steady state concentration data at different operating conditions. Coupling the fluid dynamics and heat transfer effects defined above with the large number of reactions and species was found to be very difficult using currently available commercial software such as Fluent and COMSOL. Hence an iterative approach was used in which simplified packed bed plug flow reactor model with heat transfer was solved using a finite element solver while the kinetics equations were solved using the CHEMKIN plug flow solver. The generated model shows the importance of entrance region effects for auto-thermal reformer design. Gas phase oxidation/pyrolysis consumes a large part of the hydrocarbon leading to lower molecular weight products that reach the catalyst surface and participate primarily in steam reforming reactions dominant on the surface of the catalyst.

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Research paper thumbnail of Fabrication of catalyst-coated membrane by modified decal transfer technique

Electrochemistry Communications, Mar 31, 2010

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Research paper thumbnail of CS 2 Formation in the Claus Reaction Furnace: A Kinetic Study of Methane−Sulfur and Methane−Hydrogen Sulfide Reactions

Ind Eng Chem Res, 2004

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Research paper thumbnail of An Experimental Investigation of Water Transport in PEMFCs The Role of Microporous Layers

Electrochemical and Solid State Letters, 2007

This experimental study was undertaken to resolve the contrasting viewpoints on the role of a mic... more This experimental study was undertaken to resolve the contrasting viewpoints on the role of a microporous layer (MPL), attached to carbon paper porous transport layer (PTL), on the net water transport in a polymer electrolyte membrane fuel cell (PEMFC). Experimental results on ...

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Research paper thumbnail of Solvent Composition (Isopropyl Alcohol/Water) effect on Self-Assembled Nafion Films

Meeting Abstracts, Mar 8, 2013

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Research paper thumbnail of Platinum Utilization in Thickness Controlled Catalyst Layers Prepared by Piezoelectric Printer

Meeting Abstracts, Aug 1, 2011

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Research paper thumbnail of 214231 Diesel Reforming Catalytic Kinetics - Experimental Results and Model Development

In regions where electricity is supplied using diesel generators (e.g., Northern territories of C... more In regions where electricity is supplied using diesel generators (e.g., Northern territories of Canada) and regions where diesel engines are used as a standby system when there is no electric power from grid (e.g., India, Pakistan), diesel reforming coupled with a Solid Oxide Fuel Cell (SOFC) system is a promising technology to efficiently convert the chemical energy of the fuel into electricity with less pollution issues. The present work will discuss the technical issues related to diesel reforming and research undertaken by SOFC Canada and SECA to address these issues. Experimental studies have been performed to characterize and screen two catalysts for diesel reforming. Fundamental surface science studies have been carried out using a Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) cell to study surface reactions as well as gas phase species formed during the catalytic reforming of small molecules such as methane and carbon monoxide. A blank reactor study us...

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Research paper thumbnail of PEM Fuel Cell Bipolar Plate Reliability and Material Selection

1st International Fuel Cell Science, Engineering and Technology Conference, 2003

ABSTRACT

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Research paper thumbnail of Measurement of Waxy Crude Properties Using Novel Laboratory Techniques

SPE Annual Technical Conference and Exhibition, 2000

Copyright 2000, Society of Petroleum Engineers Inc. This paper was prepared for presentation at t... more Copyright 2000, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the 2000 SPE Annual Technical Conference and Exhibition held in Dallas, Texas, 1–4 October 2000. This paper was selected for presentation by an SPE Program Committee following ...

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Research paper thumbnail of Detailed Transport-Reaction Models for SOFC Ni-YSZ Patterned Anodes: A Critical Inquiry

ABSTRACT Understanding the detailed physicochemical mechanisms for the electro-oxidation of fuel ... more ABSTRACT Understanding the detailed physicochemical mechanisms for the electro-oxidation of fuel at the triple phase boundaries (TPBs) in solid oxide fuel cell (SOFC) anodes is a key step towards improving SOFC performance. Significant efforts have been directed toward this goal via both experimental and computational modeling studies. In particular, patterned Ni anode on a planar YSZ substrate has been examined because of its well-defined two-dimensional geometry that in principle offers the advantages of known TPB length and minimization of mass transport effects. A common formulation for such patterned anodes considers modeling of surface reactions and diffusion on both electrode and electrolyte surfaces, along with charge-transfer reactions at the TPBs based on elementary kinetics. In this study, we review the theoretical approaches proposed by several authors and offer a critique of their methods.

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Research paper thumbnail of Effect of Ionomer Loading in Inket Printed Catalyst Coated Membranes on PEFC Performance

ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology, 2012

ABSTRACT The effect of ionomer loading on ultra-thin polymer electrolyte membrane fuel cell (PEMF... more ABSTRACT The effect of ionomer loading on ultra-thin polymer electrolyte membrane fuel cell (PEMFC) electrodes fabricated using an inkjet printer is studied under a variety of temperatures and relative humidity conditions. Catalyst layer inks with varying amounts of Nafion were prepared and loaded in inkjet cartridges. The inks were then jetted on a Nafion membrane using an inkjet printer in order to produce fuel cell electrodes with low loadings. The Pt loading for the fabricated electrodes was estimated to be in the range of 0.009–0.01 mg/cm2 per printer pass. SEM imaging shows that the thickness of a catalyst layer fabricated using 10 passes is approximately 3 microns and the catalyst layer agglomerates are about 200nm in radius. In order to determine the optimal Nafion content for this fabrication method, the electrochemical active area and steady state performance for the fabricated catalyst coated membranes (CCMs) was measured and also compared to a conventional CCM fabricated using spray deposition. Results show that optimal performance is achieved with a 40wt% Nafion loading under the operating conditions tested. The improved performance can be attributed to decrease in cell resistance and increase in proton conductivity.

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Research paper thumbnail of COMMITTEE COMPOSITION

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Research paper thumbnail of The Analysis and Design of Microchannel Reactors

Advanced Materials Research, 2007

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Research paper thumbnail of Statistical Simulation of the Performance and Degradation of a PEMFC Membrane Electrode Assembly

ECS Transactions, 2013

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Research paper thumbnail of Effect of Relative Humidity on Electrochemical Active Area and Impedance Response of PEM Fuel Cell

ECS Transactions, 2008

ABSTRACT The influence of humidity of supplied gases on on electrochemically active surface area ... more ABSTRACT The influence of humidity of supplied gases on on electrochemically active surface area and charge transfer resistance in cathode process of PEM fuel cell was studied. Impedance spectra for cells operated with various gas stream combinations - H2/Air, H2/O2, H2/H2 and H2/N2 - was analyzed to determine the physical/chemical origin of the spectra features. Cathode charge transfer resistance increased with a decrease in the humidity of supplied gases. As well, a reduction in the electrochemically active surface area with a decrease in relative humidity was observed.

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Research paper thumbnail of Effective Transport Coefficients for Porous Microstructures in Solid Oxide Fuel Cells

ECS Transactions, 2009

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Research paper thumbnail of Investigating the role of a microporous layer on the water transport and performance of a PEMFC

ECS Transactions, 2006

ABSTRACT A test station was modified to collect water from the anode and cathode exhaust streams ... more ABSTRACT A test station was modified to collect water from the anode and cathode exhaust streams of a PEM fuel cell. Various combinations of cells were built and tested with (SGL10BA) and without microporous layers (SGL10BB) on the electrodes. Cells with a MPL at the cathode performed much better compared to cells with no MPL and the degradation rates were decreased. Water balance experiments were conducted with two combinations of inlet relative humidities (RH): 100% anode-60% cathode and 60% anode-100% cathode at current densities of 300, 500 and 700 mA/cm2. For the range of current densities studied, the net drag coefficient at 60{degree sign}C was -0.08-+0.08 mol H2O/mol H+ for RH 60% anode and 0.01-0.2 mol H2O/mol H+ for RH 100% anode. There was no significant change in the drag coefficient attributable to the presence of the MPL on the cathode. A MPL on the anode did affect the net water drag.

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Research paper thumbnail of Numerical Modeling of Nickel-Impregnated Porous YSZ-Supported Anodes and Comparison to Conventional Composite Ni-YSZ Electrodes

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Research paper thumbnail of 1 H Solid-State NMR Study of Nanothin Nafion Films

The Journal of Physical Chemistry C, 2015

ABSTRACT The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and ... more ABSTRACT The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and 160 nm (thin) were evaluated using variable-temperature and variable-humidity solid-state H-1 NMR spectroscopy. These unprecedented measurements of nanothin films stacked within an NMR rotor represent a remarkable experimental achievement and demonstrate that H-1 NMR spectroscopy of such minute amounts of ionomer might be possible within active catalyst layers in polymer electrolyte fuel-cell electrodes. This study was motivated by the observation, in a separate work, of thickness-dependent and highly suppressed conductivity in nanothin films of Nafion (4-300 nm) compared to counterpart free-standing Nafion membranes. Trends in the line width and, more precisely, the T2 relaxation, as probed using a Hahn echo, showed that the local mobility within the hydrogen-bonded domain is equivalent for 10 and 160 nm films and is governed by the fast exchange limit in terms of NMR time scales. Subtle differences in the chemical shift trends provide insight into the domain structures, where the 10 nm films show no changes whereas the thicker 160 nm films exhibit chemical shift trends that indicate a rearranging hydrogen-bonded network. Thus, it is inferred that domain structure formation is influenced by film thickness and that the interaction with the substrate becomes limiting as the film becomes thinner.

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Research paper thumbnail of Preparation of Ultra-Thin Catalyst Layers by Piezo-electric Printer for PEMFCs Applications

ECS Transactions, 2009

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Research paper thumbnail of 287534 Multi-Physics Modeling of Auto-Thermal Diesel Surrogate Reforming

ABSTRACT Abundant supply and existing infrastructure makes diesel a favorable candidate for porta... more ABSTRACT Abundant supply and existing infrastructure makes diesel a favorable candidate for portable energy supply. Diesel generators are widely used in locations where there is no reliable electric grid, but they are noisy, have emission issues, and often have poor fuel efficiency in practical operations. Because of these drawbacks, there is interest in developing Solid Oxide Fuel Cell (SOFC) systems which use diesel fuel, but which deliver electricity quietly and with lower emissions and higher efficiency. The current study is part of a larger effort aimed at developing 1-5 kW diesel fed solid oxide fuel cells at SOFC-Canada and is mainly focused on understanding and deconvoluting the mechanism of diesel surrogate auto-thermal reforming in an experimental packed bed reactor. Gas phase kinetics play an important role during auto-thermal reforming and this study employs a detailed kinetic model developed using the automated Reaction Mechanism Generator (RMG) software. The generated model has about 9500 reactions and 450 species incorporating updated parameters from experiment and theory. The model has been validated against ignition delay data at different equivalence ratios and was found to perform reasonably well. The model has also been validated against the packed bed reactor steady state concentration data at different operating conditions. Coupling the fluid dynamics and heat transfer effects defined above with the large number of reactions and species was found to be very difficult using currently available commercial software such as Fluent and COMSOL. Hence an iterative approach was used in which simplified packed bed plug flow reactor model with heat transfer was solved using a finite element solver while the kinetics equations were solved using the CHEMKIN plug flow solver. The generated model shows the importance of entrance region effects for auto-thermal reformer design. Gas phase oxidation/pyrolysis consumes a large part of the hydrocarbon leading to lower molecular weight products that reach the catalyst surface and participate primarily in steam reforming reactions dominant on the surface of the catalyst.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Fabrication of catalyst-coated membrane by modified decal transfer technique

Electrochemistry Communications, Mar 31, 2010

Bookmarks Related papers MentionsView impact

Research paper thumbnail of CS 2 Formation in the Claus Reaction Furnace: A Kinetic Study of Methane−Sulfur and Methane−Hydrogen Sulfide Reactions

Ind Eng Chem Res, 2004

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An Experimental Investigation of Water Transport in PEMFCs The Role of Microporous Layers

Electrochemical and Solid State Letters, 2007

This experimental study was undertaken to resolve the contrasting viewpoints on the role of a mic... more This experimental study was undertaken to resolve the contrasting viewpoints on the role of a microporous layer (MPL), attached to carbon paper porous transport layer (PTL), on the net water transport in a polymer electrolyte membrane fuel cell (PEMFC). Experimental results on ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Solvent Composition (Isopropyl Alcohol/Water) effect on Self-Assembled Nafion Films

Meeting Abstracts, Mar 8, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Platinum Utilization in Thickness Controlled Catalyst Layers Prepared by Piezoelectric Printer

Meeting Abstracts, Aug 1, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of 214231 Diesel Reforming Catalytic Kinetics - Experimental Results and Model Development

In regions where electricity is supplied using diesel generators (e.g., Northern territories of C... more In regions where electricity is supplied using diesel generators (e.g., Northern territories of Canada) and regions where diesel engines are used as a standby system when there is no electric power from grid (e.g., India, Pakistan), diesel reforming coupled with a Solid Oxide Fuel Cell (SOFC) system is a promising technology to efficiently convert the chemical energy of the fuel into electricity with less pollution issues. The present work will discuss the technical issues related to diesel reforming and research undertaken by SOFC Canada and SECA to address these issues. Experimental studies have been performed to characterize and screen two catalysts for diesel reforming. Fundamental surface science studies have been carried out using a Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) cell to study surface reactions as well as gas phase species formed during the catalytic reforming of small molecules such as methane and carbon monoxide. A blank reactor study us...

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Research paper thumbnail of PEM Fuel Cell Bipolar Plate Reliability and Material Selection

1st International Fuel Cell Science, Engineering and Technology Conference, 2003

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Measurement of Waxy Crude Properties Using Novel Laboratory Techniques

SPE Annual Technical Conference and Exhibition, 2000

Copyright 2000, Society of Petroleum Engineers Inc. This paper was prepared for presentation at t... more Copyright 2000, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the 2000 SPE Annual Technical Conference and Exhibition held in Dallas, Texas, 1–4 October 2000. This paper was selected for presentation by an SPE Program Committee following ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Detailed Transport-Reaction Models for SOFC Ni-YSZ Patterned Anodes: A Critical Inquiry

ABSTRACT Understanding the detailed physicochemical mechanisms for the electro-oxidation of fuel ... more ABSTRACT Understanding the detailed physicochemical mechanisms for the electro-oxidation of fuel at the triple phase boundaries (TPBs) in solid oxide fuel cell (SOFC) anodes is a key step towards improving SOFC performance. Significant efforts have been directed toward this goal via both experimental and computational modeling studies. In particular, patterned Ni anode on a planar YSZ substrate has been examined because of its well-defined two-dimensional geometry that in principle offers the advantages of known TPB length and minimization of mass transport effects. A common formulation for such patterned anodes considers modeling of surface reactions and diffusion on both electrode and electrolyte surfaces, along with charge-transfer reactions at the TPBs based on elementary kinetics. In this study, we review the theoretical approaches proposed by several authors and offer a critique of their methods.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Effect of Ionomer Loading in Inket Printed Catalyst Coated Membranes on PEFC Performance

ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology, 2012

ABSTRACT The effect of ionomer loading on ultra-thin polymer electrolyte membrane fuel cell (PEMF... more ABSTRACT The effect of ionomer loading on ultra-thin polymer electrolyte membrane fuel cell (PEMFC) electrodes fabricated using an inkjet printer is studied under a variety of temperatures and relative humidity conditions. Catalyst layer inks with varying amounts of Nafion were prepared and loaded in inkjet cartridges. The inks were then jetted on a Nafion membrane using an inkjet printer in order to produce fuel cell electrodes with low loadings. The Pt loading for the fabricated electrodes was estimated to be in the range of 0.009–0.01 mg/cm2 per printer pass. SEM imaging shows that the thickness of a catalyst layer fabricated using 10 passes is approximately 3 microns and the catalyst layer agglomerates are about 200nm in radius. In order to determine the optimal Nafion content for this fabrication method, the electrochemical active area and steady state performance for the fabricated catalyst coated membranes (CCMs) was measured and also compared to a conventional CCM fabricated using spray deposition. Results show that optimal performance is achieved with a 40wt% Nafion loading under the operating conditions tested. The improved performance can be attributed to decrease in cell resistance and increase in proton conductivity.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of COMMITTEE COMPOSITION

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Analysis and Design of Microchannel Reactors

Advanced Materials Research, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Statistical Simulation of the Performance and Degradation of a PEMFC Membrane Electrode Assembly

ECS Transactions, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Effect of Relative Humidity on Electrochemical Active Area and Impedance Response of PEM Fuel Cell

ECS Transactions, 2008

ABSTRACT The influence of humidity of supplied gases on on electrochemically active surface area ... more ABSTRACT The influence of humidity of supplied gases on on electrochemically active surface area and charge transfer resistance in cathode process of PEM fuel cell was studied. Impedance spectra for cells operated with various gas stream combinations - H2/Air, H2/O2, H2/H2 and H2/N2 - was analyzed to determine the physical/chemical origin of the spectra features. Cathode charge transfer resistance increased with a decrease in the humidity of supplied gases. As well, a reduction in the electrochemically active surface area with a decrease in relative humidity was observed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Effective Transport Coefficients for Porous Microstructures in Solid Oxide Fuel Cells

ECS Transactions, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Investigating the role of a microporous layer on the water transport and performance of a PEMFC

ECS Transactions, 2006

ABSTRACT A test station was modified to collect water from the anode and cathode exhaust streams ... more ABSTRACT A test station was modified to collect water from the anode and cathode exhaust streams of a PEM fuel cell. Various combinations of cells were built and tested with (SGL10BA) and without microporous layers (SGL10BB) on the electrodes. Cells with a MPL at the cathode performed much better compared to cells with no MPL and the degradation rates were decreased. Water balance experiments were conducted with two combinations of inlet relative humidities (RH): 100% anode-60% cathode and 60% anode-100% cathode at current densities of 300, 500 and 700 mA/cm2. For the range of current densities studied, the net drag coefficient at 60{degree sign}C was -0.08-+0.08 mol H2O/mol H+ for RH 60% anode and 0.01-0.2 mol H2O/mol H+ for RH 100% anode. There was no significant change in the drag coefficient attributable to the presence of the MPL on the cathode. A MPL on the anode did affect the net water drag.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical Modeling of Nickel-Impregnated Porous YSZ-Supported Anodes and Comparison to Conventional Composite Ni-YSZ Electrodes

Bookmarks Related papers MentionsView impact

Research paper thumbnail of 1 H Solid-State NMR Study of Nanothin Nafion Films

The Journal of Physical Chemistry C, 2015

ABSTRACT The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and ... more ABSTRACT The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and 160 nm (thin) were evaluated using variable-temperature and variable-humidity solid-state H-1 NMR spectroscopy. These unprecedented measurements of nanothin films stacked within an NMR rotor represent a remarkable experimental achievement and demonstrate that H-1 NMR spectroscopy of such minute amounts of ionomer might be possible within active catalyst layers in polymer electrolyte fuel-cell electrodes. This study was motivated by the observation, in a separate work, of thickness-dependent and highly suppressed conductivity in nanothin films of Nafion (4-300 nm) compared to counterpart free-standing Nafion membranes. Trends in the line width and, more precisely, the T2 relaxation, as probed using a Hahn echo, showed that the local mobility within the hydrogen-bonded domain is equivalent for 10 and 160 nm films and is governed by the fast exchange limit in terms of NMR time scales. Subtle differences in the chemical shift trends provide insight into the domain structures, where the 10 nm films show no changes whereas the thicker 160 nm films exhibit chemical shift trends that indicate a rearranging hydrogen-bonded network. Thus, it is inferred that domain structure formation is influenced by film thickness and that the interaction with the substrate becomes limiting as the film becomes thinner.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Preparation of Ultra-Thin Catalyst Layers by Piezo-electric Printer for PEMFCs Applications

ECS Transactions, 2009

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