The results strongly suggest the incorporation of caval offsets in future total cavopulmonary connections.

Computational models of Polymer Electrolyte Membrane (PEM) fuel cell have historically simulated the anode side reaction assuming the system is mass transfer limited. Specifically, the models assume that the hydrogen gas mass transfer rate is much slower than the reaction rate. Although this assumption makes computational simulations easier, the model does not accurately describe the system. This model introduces a novel method of simulating the anode side reaction. Specifically, the model uses the reaction rate law kinetics of hydrogen gas adsorption onto the platinum electrode and the subsequent ionization of the hydrogen atom to model the anode side reaction dynamics. The benefit is that the model is capable of predicting the actual behavior of the system at the electrode and polymer membrane interface. Because of the computational complexity of this system, the model assumes that a fraction of the hydrogen gas in contact with the polymer membrane dissolves into the polymer membrane and diffuses to the cathode side. The fraction of hydrogen, which is dissolved into the polymer membrane, is proportional to the Damko¨hler number (Da). Specifically, the model assumes that if the reactant is not completely consumed when it comes into contact with the polymer membrane that some fraction of the hydrogen gas will dissolve into the polymer membrane and will be diffused to the cathode side. In addition, because of the slight negative charge of the polymer membrane, the model assumes that no oxygen diffuses into the polymer membrane.

Modeling is increasingly widely used to optimization, improvement and cost reduction efforts of the fuel cell technology. Although there are many computational models in literature that describe the behavior of Polymer Electrolyte Membrane (PEM) fuel cell, there is a only few models that simulates the catalyst surface concentration of reactant gases at the catalyst-membrane layer interface. A modeling of a PEM fuel cell is presented to determine both the bulk reactant concentrations and the catalyst surface concentrations at the catalyst layer-membrane layer interface. The results suggest that the reactant deficiencies experienced at high current densities are localized to the catalyst surface. However, the bulk concentration of reactant is not zero, and, in most cases, the bulk concentration of the reactant gases is significantly greater than zero. In actuality, it is the catalyst surface, which is being depleted of reactant, and, at the limiting current density, the surface concentrations of reactant gases are zero. This treatment develops explicitly link between the fuel cell overpotentials and the movement of reactants. DOI: http://dx.doi.org/10.3126/jie.v9i1.10662Journal of the Institute of Engineering Vol. 9, No. 1, pp. 1–17