It is worth to note that the fast heat transfer time periods is due
to the proper mixing of the particles in the bed. In Fig. 6 the time
evolution of the particulate phase volume fraction is shown. Particles
are very well mixed in the bed and the snapshots of the bed
through time show that after about 2.0 s the bed tends to be uniform
with respect to phase fraction distribution. This means that all
of the portions of the particles in the bed are in proper contact with
the liquid phase. On the other hand, snapshot of the bed velocity
vector field in Fig. 7 qualitatively shows that particles are very well
mixed in the bed so, for example, during the cold period the warm
particles can return to the lower sections of the bed and have
efficient contact with cold inlet fluid.