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A dynamic model of a stationary proton exchange membrane (PEM) fuel cell system has been developed in MATLAB-SIMULINK®. The system model accounts for the fuel processing system, PEM stack with coolant, humidifier with anode tail-gas oxidizer, and an enthalpy wheel for cathode air. Four reactors are modeled for the fuel processing system: (1) an autothermal reformation (ATR) reactor, (2) a high temperature shift (HTS) reactor, (3) a low temperature shift (LTS) reactor, and (4) a preferential oxidation reactor. Chemical kinetics for ATR that describe steam reformation of methane and partial oxidation of methane were simultaneously solved to accurately predict the reaction dynamics. The chemical equilibrium of CO with H2O was assumed at HTS and LTS reactor exits to calculate CO conversion corresponding to the temperature of each reactor. A quasi-onedimensional PEM unit cell was modeled with five control volumes for solving the dynamic species and mass conservation equations and seven control volumes to solve the dynamic energy balance. The quasi-one-dimensional cell model is able to capture the details of membrane electrode assembly behavior, such as water transport, which is critical to accurately determine polarization losses. The dynamic conservation equations, primary heat transfer equations and equations of state are solved in each bulk component, and each component is linked together to represent the complete system. The model predictions well matched the observed experimental dynamic voltage, stack coolant outlet temperature, and catalytic partial oxidation (CPO) temperature responses to perturbations. The dynamic response characteristics of the current system are representative of a typical stationary PEM fuel cell system. The dynamic model is used to develop and test a proportional-integral (PI) fuel flow controller that determines the fuel flow rate to maintain the uniform system efficiency. The dynamic model is shown to be a useful tool for investigating the effects of inlet conditions, load, and fuel flow perturbations and for the development of control strategies for enhancing system performance. Copyright © 2009 by ASME.

The ion transport membrane (ITM) reactor has been developed as a potential novel syngas production technology that includes both air separation and fuel conversion. To successfully commercialize the ITM reactor, it is necessary to optimize its operation. In this study, a spatially resolved physical model of the ITM reactor for syngas production has been developed to investigate the ITM reactor characteristics using Aspen Plus®, which will be extended to the system level simulation. The approach captures spatial variations in the crucial physics of heat transfer, oxygen permeation and reaction kinetics in a manner that is simple enough to make the model amenable to ITM reactor system simulations development. To simulate the partial oxidation of methane (POM), methane oxidation, steam reforming of methane, and dry reforming of methane have been considered. By varying the carbon space velocity, CH 4 conversion, CO selectivity, H 2 –CO ratio, and species molar flow rates have been calculated. Moreover, oxygen partial pressure and temperature distribution on the feed and sweep sides are presented in the paper. This study provides the basic insight to establish the optimal system designs and operating schemes of the ITM reactor by analyzing the reaction kinetics distribution of the POM and oxygen permeation rates. • Development of a two dimensional ITM reactor model. • Current model can be extended to the system level simulation. • Thermodynamic analysis of the ITM reactor by varying the carbon space velocity. • Capturing the distributions of the POM reaction kinetics and oxygen permeation rates. • Establishing the optimal designs and operations for the ITM reactor. [ABSTRACT FROM AUTHOR]

Highlights: [•] Proposes the scale-up strategy to develop a large-scale coupled reactor. [•] Investigation of performance of steam reformer coupled with catalytic combustor. [•] Experimental parameters are inlet temp., air excess ratio, SCR, fuel utilization. [•] Evaluation of the heat transfer distribution along the gas flow direction. [•] The mean value of methane conversion rate is approximately 93.4%. [Copyright &y& Elsevier]

Abstract: Water management is a crucial factor in determining the performance of proton exchange membrane fuel cell (PEMFC) for automotive application. The shell-and-tube water-to-gas membrane humidifier is useful for humidifying the PEMFC due to its good performance. Shell-and-tube water-to-gas membrane humidifiers have liquid water on one side of the tube wall and a dry gas on the other. In order to investigate humidifier performance, a two-dimensional dynamic model of a shell-and-tube water-to-gas membrane humidifier is developed. The model is discretized into three control volumes – shell, tube and membrane – in the cross-sectional direction to resolve the temperature and species concentration of the humidifier. For validation, the dew point temperature of the simulation result is compared with that of experimental data and shows good agreement with only a slight difference. The distribution of humidification characteristics can be captured using the discretization along the air-flow direction. The humidification performance of two different flow configurations, counter and parallel, are compared under various operating conditions and geometric parameters. Finally, the dynamic response of the humidifier at the step-change of various air flow rates is investigated. These results suggest that the model can be used to optimize the inlet flow humidity of a PEMFC. [Copyright &y& Elsevier]

Abstract: A first principles dynamic model of the physical, chemical, and electrochemical processes at work in a proton exchange membrane fuel cell has been developed. The model solves the dynamic equations that govern the physics, chemistry and electrochemistry for time scales greater than about 10ms. The dynamic equations are solved for a typical but simplified quasi-three dimensional geometric representation of a single cell repeat unit of a fuel cell stack. The current approach captures spatial and temporal variations in the important physics of heat transfer and water transport in a manner that is simple enough to make the model amenable to PEMFC system simulations and controls development. Comparisons of model results to experimental data indicate that the model can well predict steady state voltage–current relationships as well as the oxygen, water, and nitrogen spatial distribution within the fuel cell. In addition, the model gives dynamic insight into the distribution of current, water flux, species mole fractions, and temperatures within the fuel cell. Finally, a control system test is demonstrated using the simplified dynamic model. [Copyright &y& Elsevier]