Effects of geometry and operating conditions on hydrogen productivity of a fuel cell reformer

A 250-kW fuel cell reformer was numerically simulated with a user-defined function that was designed to simultaneously model reforming and combustion reactions. The calculation domain was a simplified 3-D configuration. To investigate the effects of geometry and operating conditions on the hydrogen productivity, the combustor outlet position, fuel ratio, equivalence ratio, and steam to carbon ratio were variable parameters. The numerical results show that the flow distributions in the furnace vary with respect to the combustor outlet position. The varied flow results in temperature distributions, which predicts the nonuniform hydrogen productivity in each reactor. Measuring the temperatures at reactor centers is an effective method for predicting the hydrogen productivity because the overall reforming reaction is affected by the average reactor temperature, which can be estimated by the temperature at the reactor center. The overall results for varying the operating conditions were summarized as a table by some nondimensional variables. By referring to the table, the proper operating conditions in similar reformer systems can be determined faster and more simply than by performing a conventional experiment.