Local Voltage Degradations (Drying and Flooding) Analysis Through 3D Stack Thermal Modeling

2010 ◽  
Vol 7 (4) ◽  
Author(s):  
J. Ramousse ◽  
K. P. Adzakpa ◽  
Y. Dubé ◽  
K. Agbossou ◽  
M. Fournier ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Temperature Distribution ◽  
Water Distribution ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Large Temperature ◽  
Strong Impact ◽  
Stoichiometric Ratio ◽  
Cell Efficiency ◽  
Drying Conditions

Temperature is a key parameter of fuel cell efficiency. In air cooled fuel cell stacks, large temperature disparities are observed. This temperature distribution has a significant influence on cell behavior in the stack, resulting in voltage disparities. The aim of this study, thus, is to correlate the temperature distribution in the stack to local voltage degradations, such as membrane drying and electrodes flooding. Indeed, the temperature has a strong impact on the water distribution in the cells because the saturation pressure is thermo-dependent. As a result, the hottest cells are prone to drying, whereas the coolest cells tend to be flooded, depending on the operating conditions. Measurements show that while drying, cell voltages decrease slowly and continuously until complete shutdown of the cells, whereas flooding results in quick voltage drops. Under drying conditions, voltage can be improved by increasing the inlet gas humidity or decrease in the stoichiometric ratio. In the case of flooding cells, purging the stack or reducing the inlet gas humidity is necessary to avoid complete shutdown of the cells. Consequently, small cell temperature variations through the stack can be responsible for large voltage variations from one cell to another. The cooling device must thus be optimized to reduce stack temperature nonuniformity.

Optimization of Purge Cycle for Dead-Ended Anode Fuel Cell Operation

2012 ◽  
Author(s):  
Jixin Chen ◽  
Jason B. Siegel ◽  
Anna G. Stefanopoulou
Keyword(s):  
Fuel Cell ◽  
Power Output ◽  
Proton Exchange Membrane ◽  
Flow Behavior ◽  
Molar Fraction ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Target Range ◽  
Nitrogen Accumulation ◽  
Cell Efficiency

This paper focuses on the optimization of the purge cycle for dead-ended anode (DEA) operation of a proton exchange membrane (PEM) fuel cell. Controling the purge interval at given operating conditions can optimize the fuel cell efficiency and hydrogen loss during the purge. For this optimization, a model capturing the liquid water and nitrogen accumulation in the anode and the purge flow behavior is presented. A target range of purge interval is then defined based on the minimal purge time that removes the plug of liquid and nitrogen in the channel end and the maximum purge interval beyond which hydrogen is wasted since hydrogen molar fraction all along the channel has been restored to one. If the purge is sufficiently long that all of the accumulated water and nitrogen are removed then the power output in the subsequent cycle (galvanostatic operation) would be highest, compared with incomplete purges which do not fully restore hydrogen concentration in the anode. Such purge schedule, however, is associated with certain amount of hydrogen loss. Therefore, there is a trade-off between hydrogen loss and power output, and a corresponding purge interval that produces the largest efficiency. The optimum purge intervals for different cycle durations are identified. The calculated DEA efficiencies are compared with flow-through (FT) operation. The analysis and model-based optimization methodology presented in this paper can be used for optimizing DEA operation of PEMFC with minimum experimentation and development time.

A Thermal Model for Reburning Fuel Injectors in Glass Furnaces

2000 ◽  
Author(s):  
L. W. Swanson ◽  
R. R. Koppang
Keyword(s):  
Temperature Distribution ◽  
Heat Source ◽  
Wall Temperature ◽  
Operating Conditions ◽  
Large Temperature ◽  
Transfer Model ◽  
Radiation Boundary Condition ◽  
Fuel Injectors ◽  
Highly Nonlinear ◽  
Glass Furnaces

Abstract A quasi-steady multi-mode heat-transfer model for retraining fuel injectors in glass furnaces has been developed that predicts the effect of geometry, furnace heat source and heat sink temperatures, radial and axial injector wall conduction, and coolant flow rate on the injector wall temperature distribution. The model imposes a radiation boundary condition at the outlet tip of the injector, which acts as a heat source. A parametric study has been conducted to investigate effects that the furnace gas temperature, reburning methane fuel and purge-air flow rates, and furnace wall temperature have on the injector wall temperature distribution. For nominal operating conditions, highly nonlinear temperature distributions were observed throughout the injector. Operation with methane as the coolant produced an extremely large temperature gradient near the injector tip that could cause excessive thermal stresses in the injector wall. The results also showed that nominal injector operating conditions should prevent alkali deposition at the injector tip and produce injector/metallic disconnect temperatures well below the initial deformation temperature for stainless steel.

scholarly journals Flexible Five-in-One Microsensor for Real-Time Wireless Microscopic Diagnosis inside Electric Motorcycle Fuel Cell Stack Range Extender

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 103
Author(s):  
Chi-Yuan Lee ◽  
Chia-Hung Chen ◽  
Ti-Ju Lee ◽  
John-Shong Cheong ◽  
Yi-Cheng Liu ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Bipolar Plate ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Strong Impact ◽  
Energy Regulation ◽  
Fuel Cell Stack ◽  
Range Extender ◽  
Microscopic Diagnosis

The focus of research and development on electric motorcycle range extender are system integration and energy regulation and management but the present fuel cell stack range extender still has defects, such as large volume, heavy weight and high cost. Its volume and weight will have a strong impact on the endurance of electric motorcycle. The bipolar plate takes most volume and weight of a proton exchange membrane fuel cell (PEMFC) stack and it is the key component influencing the overall power density and cost. Therefore, how to thin and lighten the bipolar plate and to enhance the performance and life of PEMFC stack is an urgent research subject to be solved for the moment and will be the key to whether the PEMFC stack range extender can be put in the electric motorcycle or not. In addition, the internal temperature, humidity, flow, voltage and current in the operation of PEMFC stack will influence its performance and life and the overall performance and life of fuel cell stack will be directly influenced by different external operating conditions. As nonuniform distribution of temperature, humidity, flow, voltage and current will occur in various regions inside the fuel cell stack, this study will use micro-electro-mechanical systems (MEMS) technology to develop a flexible five-in-one microsensor, which is embedded in the PEMFC stack range extender for real-time wireless microscopic diagnosis and the reliability test is performed, so that the actual operating condition inside the fuel cell stack range extender can be mastered instantly and correctly and the internal information is fed back instantly, the fuel cell stack range extender control system can be modified to the optimum operating parameters immediately, so as to enhance the performance and prolong the lifetime effectively.

Effects of Operating Conditions on Direct Methanol Fuel Cell Performance Using Nafion-Based Polymer Electrolytes

2014 ◽  
Vol 11 (6) ◽  
Author(s):  
Shingjiang Jessie Lue ◽  
Wei-Luen Hsu ◽  
Chen-Yu Chao ◽  
K. P. O. Mahesh
Keyword(s):  
Fuel Cell ◽  
Flow Rate ◽  
Direct Methanol Fuel Cell ◽  
Methanol Solution ◽  
Operating Conditions ◽  
Methanol Concentration ◽  
Cell Performance ◽  
Stoichiometric Ratio ◽  
Direct Methanol ◽  
Methanol Fuel Cell

Systematic experiments were carried out to study the effects of various operating conditions on the performances of a direct methanol fuel cell (DMFC) using Nafion 117 and its modified membranes. The cell performance was studied as a function of cell operating temperature, methanol concentration, methanol flow rate, oxygen flow rate, and methanol-to-oxygen stoichiometric ratio. The experimental results revealed that the most significant factor was the temperature, increasing the cell performance from 50 to 80 °C. We achieved the maximum power density (Pmax) of 86.4 mW cm−2 for a DMFC at 80 °C fed with 1 M methanol (flow rate of 2 ml min−1) and humidified oxygen (80 ml min−1). A methanol concentration of 1 M gave much better performance than using 3 M of methanol solution. The oxygen and methanol flow rates with the same stoichiometric ratio had a beneficial effect on cell performance up to certain values, beyond which further increase in flow rate had limited effect. The Voc using argon plasma-modified Nafion was higher than the pristine Nafion membrane for the cell operated on 3 M methanol solution, which was due to the lower methanol permeability of the Ar-modified Nafion.

Constant Fuel Utilization Operation of a SOFC System: An Efficiency Viewpoint

2010 ◽  
Vol 7 (4) ◽  
Author(s):  
P. Vijay ◽  
A. K. Samantaray ◽  
A. Mukherjee
Keyword(s):  
Fuel Cell ◽  
Recursive Algorithm ◽  
Second Law Of Thermodynamics ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
System Efficiency ◽  
Fuel Utilization ◽  
Control Laws ◽  
Cell Efficiency ◽  
Control Volumes

The operating conditions of a solid oxide fuel cell (SOFC) system that result in maximum efficiency needs to be studied by considering the whole closed circuit system because operating at maximum cell efficiency may not lead to maximum system efficiency. In this paper, this study is performed with the aid of a comprehensive steady state model of the SOFC, the after-burner, and the heat exchangers. In order to account for the large irreversibilities, the SOFC model is derived by the application of the second law of thermodynamics to the fuel cell control volumes. The SOFC system efficiency is maximized by employing a recursive algorithm with two cascaded optimization loops, which also gives the corresponding cell operating conditions. Complex control laws are required for controlling the SOFC system for maximum efficiency. On the other hand, it is found that an appropriately chosen constant fuel utilization operation closely approximates the maximum efficiency operation of the fuel cell in its operating range.

Modeling of a Proton Exchange Membrane Fuel Cell With a Large Active Area for Thermal Behavior Analysis

2008 ◽  
Vol 5 (4) ◽  
Author(s):  
Dohoy Jung ◽  
Sangseok Yu ◽  
Dennis N. Assanis
Keyword(s):  
Fuel Cell ◽  
Temperature Distribution ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Active Area ◽  
Coolant Temperature ◽  
Electric Resistance ◽  
Large Active Area ◽  
Exchange Membrane

A numerical model of a proton exchange membrane fuel cell has been developed to predict the performance of a large active area fuel cell with the water cooling thermal management system. The model includes three submodels for water transport, electrochemical reaction, and heat transfer. By integrating those submodels, local electric resistance and overpotential depending on the water and temperature distribution can be predicted. In this study the effects of the inlet gas temperature and humidity on the fuel cell performance are explored, and the effect of the temperature distribution at different coolant temperatures is investigated. The results show that the changes in local electric resistance due to temperature distribution cause fuel cell power decrease. Therefore, the coolant temperature and flow rate should be controlled properly depending on the operating conditions in order to minimize the temperature distribution while maximizing the power output of the fuel cell.

Computational Analysis of Heat Transfer in Air-Cooled Fuel Cells

2011 ◽  
Author(s):  
S. Shahsavari ◽  
M. Bahrami ◽  
E. Kjeang
Keyword(s):  
Heat Transfer ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Temperature Distribution ◽  
Proton Exchange Membrane ◽  
Gas Diffusion ◽  
Cell System ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Heat Management

Temperature distribution in a fuel cell significantly affects the performance and efficiency of the fuel cell system. Particularly, in low temperature fuel cells, improvement of the system requires addressing the heat management issues, which reveals the importance of developing thermal models. In this study, a 3D numerical thermal model is presented to analyze heat transfer and predict the temperature distribution in air-cooled proton exchange membrane fuel cells (PEMFC). In the modeled fuel cell stack, forced air flow supplies oxidant as well as cooling. Conservation equations of mass, momentum, and energy are solved in the oxidant channel, whereas energy equation is solved in the entire domain, including the gas diffusion layers (GDLs) and separator plates, which play a significant role in heat transfer. A parametric study is done to investigate the effect of various operating conditions on maximum cell temperature. The results are further validated with experiment. This model provides a theoretical foundation for thermal analysis of air-cooled stacks, where temperature non-uniformity is high and thermal management and stack cooling is a significant engineering challenge.

Latest Trends and Challenges In Proton Exchange Membrane Fuel Cell (PEMFC)

2017 ◽  
Vol 10 (1) ◽  
pp. 96-105 ◽  
Author(s):  
Mohammed Jourdani ◽  
Hamid Mounir ◽  
Abdellatif El Marjani
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Total Cost ◽  
Cell Efficiency ◽  
Technical Advances ◽  
Exchange Membrane

Background: During last few years, the proton exchange membrane fuel cells (PEMFCs) underwent a huge development. Method: The different contributions to the design, the material of all components and the efficiencies are analyzed. Result: Many technical advances are introduced to increase the PEMFC fuel cell efficiency and lifetime for transportation, stationary and portable utilization. Conclusion: By the last years, the total cost of this system is decreasing. However, the remaining challenges that need to be overcome mean that it will be several years before full commercialization can take place.This paper gives an overview of the recent advancements in the development of Proton Exchange Membrane Fuel cells and remaining challenges of PEMFC.

scholarly journals A Numerical Investigation into the PAT Hydrodynamic Response to Impeller Rotational Speed Variation

2021 ◽  
Vol 13 (14) ◽  
pp. 7998
Author(s):  
Maxime Binama ◽  
Kan Kan ◽  
Hui-Xiang Chen ◽  
Yuan Zheng ◽  
Daqing Zhou ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Distribution Systems ◽  
Water Distribution ◽  
Production Efficiency ◽  
Operating Conditions ◽  
Energy Regulation ◽  
Speed Increase ◽  
Energy Field ◽  
Long Run ◽  
Study Results

The utilization of pump as turbines (PATs) within water distribution systems for energy regulation and hydroelectricity generation purposes has increasingly attracted the energy field players’ attention. However, its power production efficiency still faces difficulties due to PAT’s lack of flow control ability in such dynamic systems. This has eventually led to the introduction of the so-called “variable operating strategy” or VOS, where the impeller rotational speed may be controlled to satisfy the system-required flow conditions. Taking from these grounds, this study numerically investigates PAT eventual flow structures formation mechanism, especially when subjected to varying impeller rotational speed. CFD-backed numerical simulations were conducted on PAT flow under four operating conditions (1.00 QBEP, 0.82 QBEP, 0.74 QBEP, and 0.55 QBEP), considering five impeller rotational speeds (110 rpm, 130 rpm, 150 rpm, 170 rpm, and 190 rpm). Study results have shown that both PAT’s flow and pressure fields deteriorate with the machine influx decrease, where the impeller rotational speed increase is found to alleviate PAT pressure pulsation levels under high-flow operating conditions, while it worsens them under part-load conditions. This study’s results add value to a thorough understanding of PAT flow dynamics, which, in a long run, contributes to the solution of the so-far existent technical issues.

scholarly journals Modeling Bacterial Regrowth and Trihalomethane Formation in Water Distribution Systems

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 463
Author(s):  
Gopinathan R. Abhijith ◽  
Leonid Kadinski ◽  
Avi Ostfeld
Keyword(s):  
Distribution Systems ◽  
Water Distribution ◽  
Mechanistic Model ◽  
Water Distribution Systems ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Growth Rate Constant ◽  
Model Parameters ◽  
Bacterial Regrowth ◽  
The Impact

The formation of bacterial regrowth and disinfection by-products is ubiquitous in chlorinated water distribution systems (WDSs) operated with organic loads. A generic, easy-to-use mechanistic model describing the fundamental processes governing the interrelationship between chlorine, total organic carbon (TOC), and bacteria to analyze the spatiotemporal water quality variations in WDSs was developed using EPANET-MSX. The representation of multispecies reactions was simplified to minimize the interdependent model parameters. The physicochemical/biological processes that cannot be experimentally determined were neglected. The effects of source water characteristics and water residence time on controlling bacterial regrowth and Trihalomethane (THM) formation in two well-tested systems under chlorinated and non-chlorinated conditions were analyzed by applying the model. The results established that a 100% increase in the free chlorine concentration and a 50% reduction in the TOC at the source effectuated a 5.87 log scale decrement in the bacteriological activity at the expense of a 60% increase in THM formation. The sensitivity study showed the impact of the operating conditions and the network characteristics in determining parameter sensitivities to model outputs. The maximum specific growth rate constant for bulk phase bacteria was found to be the most sensitive parameter to the predicted bacterial regrowth.

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