418
6 Applications: Two-Region Pebble Beds
Fig. 6.15 PSMI (a, c) and mixing entropy (b, d) for different particle discharge rates at (R D = 1.0,
R L = 3.0) (a, b) and (R D = 0.5, R L = 4.3) (c, d)
6.2.4.2 Effect of Discharge Rate and Flow Similarity
Under the condition of slow pebble flow, it will take a very long time to form the stable
two-region pebble bed. The discharge rate in the present simulation increases significantly. For investigating the effect of different discharge rates, a non-dimensional
time at different size ratios is defined as follows:
τ =
V (t)
100V 0
(6.4)
where V (t) is the total volume of discharged particles at time t starting from when
a particle begins to discharge, and V 0 is the volume of the type-1 particle (12 mm
in diameter). For R D = 1.0, the particle starts to discharge from the system at 3 s. If
the discharge rate is 100 particles per second, the non-dimensional time τ is equal to
t−3. Figure 6.15a and b show the results of particle-scale mixing index and mixing
entropy respectively, at the discharge rates of 100 particle/s and 1000 particles/s for
R D = 1.0 and R L = 3.0. It is found that the difference between them is negligible
(less than 5%). Thus, from a macroscopic point of view, the flow characteristics of
the two-region pebble bed are similar to each other under different discharge rates.
6 Applications: Two-Region Pebble Beds
Fig. 6.15 PSMI (a, c) and mixing entropy (b, d) for different particle discharge rates at (R D = 1.0,
R L = 3.0) (a, b) and (R D = 0.5, R L = 4.3) (c, d)
6.2.4.2 Effect of Discharge Rate and Flow Similarity
Under the condition of slow pebble flow, it will take a very long time to form the stable
two-region pebble bed. The discharge rate in the present simulation increases significantly. For investigating the effect of different discharge rates, a non-dimensional
time at different size ratios is defined as follows:
τ =
V (t)
100V 0
(6.4)
where V (t) is the total volume of discharged particles at time t starting from when
a particle begins to discharge, and V 0 is the volume of the type-1 particle (12 mm
in diameter). For R D = 1.0, the particle starts to discharge from the system at 3 s. If
the discharge rate is 100 particles per second, the non-dimensional time τ is equal to
t−3. Figure 6.15a and b show the results of particle-scale mixing index and mixing
entropy respectively, at the discharge rates of 100 particle/s and 1000 particles/s for
R D = 1.0 and R L = 3.0. It is found that the difference between them is negligible
(less than 5%). Thus, from a macroscopic point of view, the flow characteristics of
the two-region pebble bed are similar to each other under different discharge rates.