A. That corresponding to static bed
B. That corresponding to completely fluidised bed
C. The porosity of the bed when true fluidisation begins
D. Less than that of the’ static bed
Related Mcqs:
- A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun’s equation for the above fluid-particle system (in SI units) is given below : Δ P/L = 375 × 103 VOM + 10.94 × 106 V2 OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is_________________?
A. 12 mm/s
B. 16 mm/s
C. 24 mm/s
D. 28 mm/s - Umf is the minimum fluidisation velocity for a bed of particles. An increase in the superficial gas velocity from 2 Umf to 2.5 Umf results in (all velocities are smaller than the entrainment velocity of the particles) no change in the_______________?
A. Drag on particles
B. Drag on column walls
C. Bed height
D. Bed voidage - Minimum fluidisation velocity for a specific system depends upon the___________________?
A. Particle size
B. Fluid viscosity
C. Density of both the particle & the fluid
D. All A., B. and C. - A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun’s equation for the above fluid-particle system (in SI units) is given below: Δ P/L = 375 × 103 VOM + 10.94 × 106 V2 OM (SI units) If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed ?
A. 0.2
B. 0.5
C. 0.7
D. 0.8 - With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity___________________?
A. Widens
B. Squeezes
C. Does not change
D. Unpredictable from the data - Which of the following is not an advantage of fluidisation from transfer operation point of view ?
A. Intimate contact of the fluid with all parts of the solid particles
B. Lower fluid pumping power requirement
C. Minimisation of temperature variation
D. Prevention of particle segregation - A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is________________?
A. 4.4 KPa
B. 2.94 KPa
C. 3.7 KPa
D. None of these - When larger particles e.g., grains are subjected to fluidisation, the corresponding bed produced is termed as the _______________ bed?
A. Spouted
B. Sluggish
C. Boiling
D. Teeter - Hydraulic mean radius for flow through packed bed of spherical particle of size, ‘Dp, with porosity ‘ε’ is________________?
A. (Dp/6) (ε/1- ε)
B. (Dp/6) (1- ε/ε)
C. ⅔Dp (1- ε/ε)
D. ⅔Dp (ε/1- ε) - A bed consists of particles of density 2000 kg/m3. If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is_________________?
A. 25.61 kPa
B. 11.77 kPa
C. 14.86 kPa
D. 21.13 kPa
