The suitable evaporator for concentration of foaming liquids is a __________ evaporator.

Agitated film evaporator is suitable for concentrating __________ liquids.

A

Foaming

B

Viscous

C

Very thin

D

Corrosive

Foaming and priming in boiler operation can be reduced by reduction in __________ in feed water.

A

Turbidity

B

Color (Hazen)

C

Total solids

D

All of the above

Vapor velocity in a distillation column for non-foaming mixture is in the range of __________ times the flooding velocity.

A

0.1 to 0.3

B

0.6 to 0.7

C

0.85 to 0.95

D

1.5 to 2

In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.

A

Increases

B

Decreases

C

Remains constant

D

May increase or decrease, depends on the vacuum

For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally

A

Decreases

B

Increases

C

Remains unchanged

D

Increases exponentially

For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is

A

3

B

0.33

C

1

D

1.33

The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is

A

Same

B

More

C

Less

D

More or less depending on ambient conditions

A multiple effect evaporator as compared to a single effect evaporator of the same capacity has

A

Lower heat transfer area

B

Lower steam economy

C

Higher steam economy

D

Higher solute concentration in the product

A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because

A

Total heat transfer area of all the effects is -less than that in a single effect evaporator system

B

Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect

C

Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system

D

Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system

A forced circulation long tube vertical evaporator as compared to the natural circulation evaporator

A

Is economical in operation

B

Employs high velocity, high heat transfer rate and less heating surface requirement

C

Employs a centrifugal pump placed between external downtake from vapor drum and inlet to tube bundle

D

Both B & C

The suitable evaporator for concentration of foaming liquids is a __________ evaporator.

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