Thermal Science and Engineering
Online ISSN : 1882-2592
Print ISSN : 0918-9963
ISSN-L : 0918-9963
Volume 17 , Issue 4
Showing 1-2 articles out of 2 articles from the selected issue
  • Kazui FUKUMOTO, Yoshifumi OGAMI
    2009 Volume 17 Issue 4 Pages 133-145
    Published: 2009
    Released: January 18, 2010
    This research aims at building a turbulent diffusion combustion model based on chemical equilibrium and kinetics for simplifying complex chemical mechanism. This paper presents the combustion model based on chemical equilibrium combined with an eddy dissipation concept model (CE-EDC); the model is validated by simulating a H2-air turbulent diffusion flame. In the CE-EDC model, the reaction rate of fuels and intermediate species are estimated by using the equations of the EDC model. Then, the reacted fuels and intermediate species are assumed to be in chemical equilibrium; the amounts of the other species are determined by the Gibbs free energy minimization method by using the amounts of the reacted fuels, intermediate species, and air as reactants. An advantage of the CE-EDC model is that the amounts of the combustion products can be determined without using detailed chemical mechanisms. Moreover, it can also predict the amounts of the intermediate species. The obtained results are compared with Takagi′s experimental data and the data computed by the EDC model, which uses the complex chemical mechanisms. The mole fractions of H2, O2, H2O, temperature, and velocity obtained by using our CE-EDC model were in good agreement with these reference data without taking into account the chemical reaction rates of the O2 and H2O. Furthermore, the mole fractions of OH and H are in good agreement with the results of the EDC model at the high temperatures. On the other hand, the chemical equations involving OH and H were used for predicting the mole fractions of OH and H, which were similar to those obtained from the EDC model at low temperatures. Using the present CE-EDC model, amounts of combustion products can be calculated by using a reduced chemical mechanism and the Gibbs free energy minimization theory. The accuracy of this model is in the same order as that of the EDC model.
    Download PDF (785K)
  • Saiful HASMADY, Tomoyuki HATAKEYAMA, Manuel Philipp WACKER, Kazuyoshi ...
    2009 Volume 17 Issue 4 Pages 147-156
    Published: 2009
    Released: January 18, 2010
    Thermal and water management is a critical issue in PEFCs. In this research, the thermal behavior of PEFC is focused. The objective is to understand the influence of heat on cell performance both by experiment and theoretical analysis, as well as improving cell performance and reliability. In order to investigate the theoretical behavior, especially in the catalyst layer where the electrochemical reactions occur, a detailed modeling of heterogeneous surface reaction coupled with reactant transport is needed. In this paper, a theoretical model that improves the dependency of the exchange current density with reactant concentrations by applying data from a known surface reaction steps found in catalysis is developed. Further, we compared the results of calculation model with the experimental results. The results of calculation model showed good agreement with the experimental results, especially at low current densities and the model can estimate several properties in PEFC e.g. solid phase potential distribution, electron flow vector in GDL, hydrogen and oxygen mole fraction distribution at the membrane⁄catalyst layer interface. The calculation model served as a preliminary step before the thermal-electrochemical behavior of a PEFC can be fully understood.
    Download PDF (1266K)