Related Mcqs:

1. 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

2. 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

3. 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

4. Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is________________?

   A. 90
   B. 60
   C. 45
   D. 30

5. 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

6. For liquid flow through a packed bed, the superficial velocity as compared to average velocity through the channel in the bed is________________?

   A. More
   B. Less
   C. Equal
   D. Independent of porosity

7. 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

8. 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)

9. 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.

10. In Newton’s law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass varies as the ______________ of its diameter?

    A. Inverse
    B. Square root
    C. Second power
    D. First power