Wall Segment Cross-section 5% Active Particles

For the particle in this figure, only the outer 5% of the radius was active, to simulate conditions closer to the "egg-shell" nature of the diffusion/reaction situation in the catalyst. The temperature fields inside the wall particles are less symmetric in this case. Significant temperature incursions appear inside the spheres, and the influence of the wall is strongly felt. The spheres are warmer close to the hot wall than on the side facing the center of the segment. This is not so for the interior particles, which still appear to be quite symmetrical in temperature. The proximity of the wall intruded only a little on the particle temperature fields for 100% active particles, and we may conclude that particle gradients dominate for the near-wall spheres under these conditions. It is noticeable that the particles are considerably lower in temperature than the surrounding gas, except possibly near a contact point with the wall. Especially where the entire particle is uniformly active, temperatures are quite low in the interiors of the particles. The volume average particle temperature for the uniformly active particle is 723 K, whereas for the particles in the figure above, it is 799 K.