Numerical simulation of effect of catalyst wire-mesh pressure drop characteristics on flow distribution in catalytic parallel plate steam reformer

Abstract

Steam reforming of hydrocarbons using a catalytic plate-type-heat-exchanger (CPHE) reformer is an attractive method of producing hydrogen for a fuel cell-based micro combined-heat-and-power system. In this study the flow distribution in a CPHE reformer, which uses a coated wire-mesh catalyst, is considered to investigate the effect of catalyst wire-mesh pressure drop characteristics on flow distribution in the CPHE reformer. Flow distribution in a CPHE reformer is rarely uniform due to inlet and exhaust manifold design. Poorly-designed manifolds may lead to severe flow maldistribution, flow reversal in some of the CPHE reformer channels and increased overall pressure drop. Excessive flow maldistribution can significantly reduce the CPHE reformer performance. Detailed three-dimensional models are used to investigate the flow distribution at three different catalyst wire-mesh pressure drop coefficients and at five different flow rates. Experiments are performed on a single CPHE reformer channel to evaluate the pressure drop characteristics of the catalyst wire-mesh in the current CPHE reformer design. The results are used in the numerical model where the catalyst zone is simulated as domains with momentum source to account for the pressure drop. The numerical model is verified experimentally, numerical and experimental results are found to be in good agreement. The study shows that severe flow maldistribution exists in the current reformer stack. At nominal load some channels in the CPHE reformer receive up to four times the average mass flow, while other channels have reversed flow. Flow maldistribution and flow reversal can be improved significantly by increasing the pressure drop characteristics of the catalyst wire-mesh.