OP-II-3

PP-II-56washcoat phases, and energy conservation equation for the steel wall. The reactivestreams are assumed to be incompressible Newtonian fluids. Simultaneous solutionof these equations is carried out using the method of finite elements under ComsolMultiphysics environment. Numbering-up the channels, i.e. sizing of themicrochannel reactor is handled by dividing the basis flow rate (which is 2.2×10 –2 mols -1 of hydrogen equivalent to 2-kW PEMFC power [3]) by the corresponding singlechannelflow rates due to the assumption of flow equipartition.Modeling of the reactors and heat exchangers involved in MAB system aredecoupled; one-dimensional, steady-state, pseudohomogeneous fixed-bed modelsare used to simulate adiabatically operating beds. The resulting set of ordinarydifferential equations is solved in MATLAB environment. The microchannel heatexchangers are of the same design as the microchannel reactor described above, i.e.alternating stack of hot- and cold-stream channels etched onto metallic plates, withthe single exception of catalytic washcoats, hence absence of species transport.Solution of the 2D steady-state transport equations is handled using ComsolMultiphysics. The design procedure is of trial-and-error nature; reactor array designthat involves sizing and numbering precedes interstage heat exchanger design [2].Saw-tooth shaped, controlled temperature profiles are obtained along the reactorarrays of the MAB system, while temperatures in the SR and combustion channels ofthe microchannel reactor equilibrate rapidly down the channel length due to high heattransfer rates. As for sizing, the MAB configuration consisting of 9 combustion beds,9 reforming beds and 9 microchannel heat exchangers, occupies a volume of1.39×10 –3 m 3 , 81% of which is contributed by the SR reactors. 14450 microchannelsrequired to produce the stated amount of hydrogen occupy a volume of1.04×10 –3 m 3 .References[1]. E.L.C. Seris, G. Abramowitz, A.M. Johnston and B.S. Haynes, Chem. Eng. J., 135S (2008) S9.[2]. A.K. Avci, D.L. Trimm, M. Karakaya, Catal. Today doi:10.1016/j.cattod.2009.01.046.[3]. O. Tan, E. Masalaci, Z.I. Onsan, A.K. Avci, Int. J. Hydrogen Energy, 33 (2008) 5516-5526.AcknowledgementsFinancial support is provided by Bogazici University through project BAP-09HA507D.A.K. Avci acknowledges TUBA-GEBIP program.436