Figure 13 . The nondimensionalized mean and standard deviation
of bed height for LDPE and 100 wood pellets binary mixture with varying
initial bed height.
Figure 13 shows the effects of initial bed height on the mean and
standard deviation of bed height for LDPE and 100 wood pellets binary
mixture. After non-dimensionalizing the mean bed height and standard
deviation with the initial bed height (Hb0), both curves
are well collapsed on a straight line from 1.5Umf to
3Umf range, with both the nondimensionalized bed height
and standard deviation increase with the increase of the superficial gas
velocity. The experimental data above 3Umf is only
available for shallower bed cases due to pressure constraints for the
facility, which shows that the mean bed height remains almost constant
at 3.7 Umf. This trend is consistent with the pressure
drop data reported in Li et al.25. Figure 14 shows the
effects of initial bed height on the temporal evolution of the spatially
averaged vertical velocity. In presenting the data,
<v>FOV is non-dimensionalized
using the characteristic velocity (gΔH)1/2, where
ΔH=Hb-Hb0, is the difference between
expanded and initial bed height. The time is non-dimensionalized using
the characteristic time for the particle to travel ΔH, i.e.
τ=(2ΔH/g)1/2. The non-dimensionalized periods are at
~3. Specifically, it is 3.25 at 2Umf and
2.66 at 3Umf for the shallower bed and 2.89 at
2Umf and 3.10 at 3Umf for the deeper
bed. The non-dimensionalized amplitude is 1.71 and 1.36 at
2Umf and 3umf respectively for the deep bed. The value
decreases to 0.78 and 0.92 at 2Umf and
3Umf respectively for the shallow bed. In general, the
nondimensionalization works reasonably well for each static bed height
with varying superficial gas velocity, yet works less satisfactory when
static bed height is changed. This is possibly due to the internal flow
structure change due to the increase of the static bed height.