(119i) A CFD Based Two-Fluid Model for a Dmfc

A number of physicochemical phenomena take place in a DMFC, including momentum and mass transfer, electrochemical reactions, and gas-liquid flow in anode and cathode channels. All these processes are coupled, resulting in difficulty on computing optimal cell design and operating conditions. A good understanding of this complex, interacting phenomena is essential in fuel cell design. Two?fluid model is suitable for the simulation of gas-liquid flow in a fuel cell [1, 2]. The presence of bubbles is reflected by the gas content and the source term that accounts for interphase mass transfer. The conventional two-fluid model uses non-equilibrium mass transfer model with the empirical coefficients for interphase transfer in multicomponent gas-liquid flow [2]. DMFC design with a new flow field requires a two-fluid model without empirical correlations. The objective of this research is to develop a new CFD model for a DMFC with a new method for estimating interphase source term and gas content without empirical correlations. We suggest a new equilibrium mass transfer model for interphase transfer in gas-liquid flow. The new equation for the source term was derived using the equilibrium flash equation for multicomponent gas-liquid stream. The developed CFD model is valuable in simulation of a DMFC with different flow fields. The CFD model was validated against the polarization curve for 5 cm2 DMFC. The primary advantage of the model is that it allows us to study the effect of flow field geometry on gas evolution, flow patterns and fuel cell performance. This study shows application of the 3D CFD model for exploring gas evolution in DMFC channels. The simulations of different flow field geometries provide a good illustration of the capability of the CFD model. As shown in this paper, the flow geometry of the anode side has important implication on gas evolution. The improved two-fluid model allows us to study the effect of flow field on the flow patterns in fuel cell design without empirical correlations. The new developed 3D CFD model includes all relevant phenomena and important factors and it is useful in DMFC design.

Acknowledgements This work was supported by a grant from Korean Federation of Science and Technology Societies and Korean Science and Engineering Foundation.

References [1] Pasaogullari U., Wang Ch.-Y. J. Electrochem. Soc. 2005, 152, A380-A390. [2] Wang Z. H., Wang C. Y. J. Electrochem. Soc. 2003, 150, A508-A519.