For given operating conditions some simulations were carried out with both the
2D and the 3D models. Figure 5 shows the temperature distribution over a slice of
the 3D geometry lying on a x-y plane intersecting the reactor in the middle of its
height along z. Such a temperature distribution diagram reflects that obtainable
with a simulation performed through the 2D model. In principle, a plane 2D
geometry represents a slice of the reactor where the z dimension is greatly
prevalent with respect to the y dimension. Actually, the model reactor has not
such characteristics, the length in the z dimension being only 5 times the
reforming channel width (see Table 2). This means that the effects of the presence
of the boundary walls in the z direction might have a significant influence on the
velocity, temperature and species concentration profiles and, then, on the overall
reactor performance.
Figures 6 shows the reactor temperature longitudinal profiles on the
centrelines of the combustion and the reforming channels, and on the centrelines
of the combustion and reforming catalysts calculated with the 3D model under the
operating conditions of the reference case. Such temperature profiles are those
lying over a x-y plane intersecting the reactor in the middle of its height along z,
as shown in Figure 5. Comparing these profiles with those reported in Figure 2 b
for the corresponding 2D model, they appear closely similar: the temperatures in
the combustion section (catalyst and channel) are always slightly higher than the
corresponding in the reforming section. However, a closer inspection reveals
some significant differences. In the 2D case the temperature, after an initial slow
growth, increases steadily from 800 K at the reactor inlet up to 900 K at the
reactor outlet while in the other case it grows faster, but reaches only 896 K at the
reactor outlet. Another difference is represented by the larger transverse