For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as

For pipes, turbulent flow occurs when Reynolds number is

A

Less than 2000

B

Between 2000 and 4000

C

More than 4000

D

Less than 4000

In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of

A

Relative roughness

B

Absolute roughness

C

Friction co-efficient for flows at equal Reynold number

D

All of the above

A tank is fitted with 8 pipes, some of them that fill the tank and others that are waste pipe meant to those that empty the tank can empty it in 6 hours. If all the pipes are kept open when the tank is full, it will take exactly 6 hours for the tank to empty. How many of these are these are fill pipes?

A

2

B

4

C

6

D

5

For pipes, laminar flow occurs when Reynolds number is

A

Less than 2000

B

Between 2000 and 4000

C

More than 4000

D

Less than 4000

In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

A

Convection

B

Radiation

C

Conduction

D

Both convection and conduction

For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of

A

1

B

1.74

C

6.1

D

37

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is

A

Free convection

B

Entry length problem in laminar forced conduction (developing thermal boundary layer)

C

Mixed convection (both free and forced)

D

Forced convection

According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity)

A

D

B

D²

C

D^0.5

D

$$\frac{1}{{\text{D}}}$$

Overall mass transfer co-efficient in case of absorption of __________ in water is based on the gas film co-efficient only, as the mass transfer process is gas film (phase) controlling.

A

CO₂

B

SO₂

C

NH₃

D

None of these

For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is

A

Calculated

B

Unknown

C

Known

D

Not required

For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as

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