A mathematical model based on fluid dynamics and heat-transfer theories was applied to predict gas dynamic pressure and temperature distribution in a coflow molten carbonate fuel cell (MCFC) stack. The mass balance was simplified to obtain exact solutions with an assumption of uniform current density in the cell. The simulations were compared with data from a pilot-scale MCFC stack. The effect Of internal geometry of gas channels was simulated to accurately, predict the gas-pressure drop. A close prediction of pressure drop was possible from a partially blocked gas channel model that approximates the significant flow resistance. The effect of external boundary conditions on stack temperature profile was also analyzed. Temperatures were accurately predicted from a boundary heat conduction model with a reasonable assumption of wet seal temperatures. The 2-D boundary conditions could be extended to 3-D simulations to predict temperature distribution with the same accuracy. The model was applied to see the effect of scale-zip on the maximum temperature rise and average cell potential. The result verified a significant effect of cell size on the maximum stack temperature.