| A steady-state computer model has been developed to simulate the thermal and electrochemical performance of an internal-reforming, cross-flow, solid oxide fuel cell concept that was previously under development at the Idaho National Engineering and Environmental Laboratory. Mass and energy balances are calculated for the methane, steam, hydrogen, carbon monoxide, and carbon dioxide in the fuel channel, interconnect and anode, and for the oxygen and nitrogen in the air channel, cathode and electrolyte. The endothermic reforming occurs on the nickel catalyst which is found in both the interconnect and anode. The exothermic carbon monoxide plus steam shift reaction is assumed to be in chemical equilibrium and also occurs both within the interconnect and anode. The exothermic hydrogen oxidation occurs at the anode-electrolyte interface. Nernst voltage and empirical overpotential models establish the electrochemical balances. The system of partial differential equations is solved by partitioning it into inner and outer loops for efficient computation.; Scoping studies have been performed to investigate reforming models, overpotential models, temperature profiles, fuel utilization, and electric current and power generation. Because the interconnect, which is a cermet, has relatively high thermal conductivity, the resulting temperature profile is nearly constant and tends to flatten the temperature throughout the fuel cell. Further, most of the reforming is completed in the first 10% of the fuel channel length, thus lowering the temperature of the entire fuel cell. Air to fuel flow ratios greater than ten are required to provide sufficient convective energy to counterbalance the quenching due to the reforming and bring the overall temperature profile into a more acceptable range.; The model is useful for design analyses and to determine fuel cell performance under a variety of operating conditions, fuel mixtures, material combinations, and geometries. The largest uncertainties arise from the constitutive models used to calculate the reforming and the electrochemical overpotential. Experimental work is needed in these areas to resolve these questions.; This work includes multi-region, multi-species, mass and energy balances with both homogeneous and heterogeneous electrochemical kinetics. The extensive model features enable a wide range of scoping studies to be performed with a minimum of a priori assumptions. |
