Chemical Engineering - Fluid Mechanics - Discussion
Discussion Forum : Fluid Mechanics - Section 12 (Q.No. 24)
24.
With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity
Discussion:
2 comments Page 1 of 1.
Taisir said:
2 months ago
(B) squeezes :
In fluidization, a bed of solid particles behaves like a fluid when a gas or liquid flows through it at sufficient velocity.
There are two key velocities in fluidization:
Minimum fluidization velocity (Uₘ): The lowest velocity at which the bed just starts to fluidize.
Terminal velocity (Uₜ): The velocity at which the particles are carried away by the fluid (i.e., elutriation occurs).
The operating range of fluidization is between these two limits:
Um < Ufluidization < Ut.
Effect of Particle Size:
As particle size decreases :
Minimum fluidization velocity Um decreases — smaller particles are easier to lift.
Terminal velocity Ut also decreases — small particles are more easily entrained by the fluid.
However, Ut decreases faster than Um , so the difference between them becomes smaller.
Thus, the range of velocities over which fluidization can occur becomes narrower — we say the operating range "squeezes".
In fluidization, a bed of solid particles behaves like a fluid when a gas or liquid flows through it at sufficient velocity.
There are two key velocities in fluidization:
Minimum fluidization velocity (Uₘ): The lowest velocity at which the bed just starts to fluidize.
Terminal velocity (Uₜ): The velocity at which the particles are carried away by the fluid (i.e., elutriation occurs).
The operating range of fluidization is between these two limits:
Um < Ufluidization < Ut.
Effect of Particle Size:
As particle size decreases :
Minimum fluidization velocity Um decreases — smaller particles are easier to lift.
Terminal velocity Ut also decreases — small particles are more easily entrained by the fluid.
However, Ut decreases faster than Um , so the difference between them becomes smaller.
Thus, the range of velocities over which fluidization can occur becomes narrower — we say the operating range "squeezes".
KRR said:
4 years ago
A is the right answer.
(1)
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