Minimum porosity for fluidisation is

An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture?

A

Cork

B

Saw dust

C

Sand

D

Chemically prepared foam

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 of the above

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 seggregation

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

In continuous fluidisation

A

Solids are completely entrained

B

The pressure drop is less than that for batch fluidisation

C

There is no entrainment of solids

D

Velocity of the fluid is very small

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

If the volume of voids is equal to the volume of solids in a soil mass, then the values of porosity and voids ratio respectively are

A

1.0 and 0.0

B

0.0 and 1.0

C

0.5 and 1.0

D

1.0 and 0.5

Select the correct relationship between porosity (N), specific yield (y) and specific retention (R)

A

N = y + R

B

y = N + R

C

R = N + y

D

R > (N + y)

The porosity of sediments in sewer pipes, is usually taken as

A

0.010

B

0.011

C

0.012

D

0.013

Porosity of silica bricks varies from __________ percent.

A

5 to 10

B

20 to 30

C

45 to 60

D

60 to 75

Minimum porosity for fluidisation is

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