**11.**A bed consists of particles of density 2000 kg/m^{3}. 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

- 25.61 kPa
- 11.77 kPa
- 14.86 kPa
- 21.13 kPa

Correct answer: (B)

11.77 kPa

11.77 kPa

**12.**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 × 10^{3} VOM + 10.94 × 10^{6} v^{2} 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?

- 0.2
- 0.5
- 0.7
- 0.8

Correct answer: (C)

0.7

0.7

**13.**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 × 10^{3} VOM + 10.94 × 10^{6} v^{2} OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is

- 12 mm/s
- 16 mm/s
- 24 mm/s
- 28 mm/s

Correct answer: (B)

16 mm/s

16 mm/s

**14.**A Bingham fluid of viscosity μ = 10 Pa.s and yield stress, η0 = 10 KPa, is shared between flat parallel plates separated by a distance of 10^{-3} m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is

- 10 KPa
- 20 KPa
- 30 KPa
- 40 KPa

Correct answer: (B)

20 KPa

20 KPa

**15.**A centrifugal pump designed to pump water is employed to pump a more viscous oil. In the later case, the pump

- Develops a lower head
- Capacity is reduced
- Requires more power
- All (A), (B) and (C)

Correct answer: (D)

All (A), (B) and (C)

All (A), (B) and (C)

**16.**A centrifugal pump has the following specifications:

Power = 4 H.P.; Speed = 800 rpm

Head = 8 metres

Flow = 1000 litres/minutes.

If its speed is halved, the new discharge will be _________ litres/minute.

- 500
- 200
- 1000
- 750

Correct answer: (A)

500

500

**17.**A centrifugal pump has the following specifications:

Power = 4 H.P.; Speed = 800 rpm

Head = 8 metres

Flow = 1000 litres/minutes.

If its speed is halved, the power consumed now will be _________ hp.

- 0.5
- 2
- 4
- 1

Correct answer: (A)

0.5

0.5

**18.**A centrifugal pump has the following specifications:

Power = 4 H.P.; Speed = 800 rpm

Head = 8 metres

Flow = 1000 litres/minutes.

If its speed is halved, then the new head will be _________ metres.

- 2
- 4
- 8
- 5.5

Correct answer: (A)

2

2

**19.**A centrifugal pump is called a turbine pump, if it is having a

- Turbine type impeller
- Vaned diffusion casing
- Rotating vaned volute
- None of these

Correct answer: (B)

Vaned diffusion casing

Vaned diffusion casing

**20.**A centrifugal pump loses prime after starting. The reason of this trouble may be

- Incomplete priming
- Too high a suction lift
- Low available NPSH and air leaks in the suction pipe
- All (A), (B), and (C)

Correct answer: (D)

All (A), (B), and (C)

All (A), (B), and (C)