2. Mathematical formulation
2.1. Geometry and assumptions
The schematic representation of the computational geometry
and physical size of the reactor is sketched in Fig. 1a where the
reaction is performed in a cylindrical tube. The physical size of the
reactor is constructed based on the experimental set-up of Horn
et al. [22]. The reactor can be partitioned into three zones. The
middle (second) zone is an Rh-based catalyst packed bed and it is
sandwiched by the first and third zones. The first and third zones
are empty for fluid flowing through.
The physical phenomena are related to fluid motion, heat and
mass transfer, and chemical reactions. To simplify the physical
problem, it is assumed that the flow field in the tube is
incompressible, laminar, and axisymmetric along the centerline
of the reactor. The porous media in the catalyst bed is assumed to
be homogeneous and local thermal equilibrium prevails at the
catalyst surface. This implies, in turn, that there is no temperature
difference at the interface of the catalyst and the fluid [22,30]. The
wall of the cylindrical tube is adiabatic so heat released from CPOM
will not penetrate through the wall. Meanwhile, it is postulated
that the gas mixture inside the reactor abides by the ideal gas law.