THEORY OF STRUCTURES QUIZ

In sub-cooled boiling,

Temperature of the heating surface is more than the boiling point of the liquid

Very large vapour space is necessary

Temperature of the heating surface is less than the boiling point of the liquid

Bubbles from heating surface are absorbed by the mass of the liquid

TRUE ANSWER : ?
YOUR ANSWER : ?

If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will

Decrease by 22

Increase by 1.8 times

Remain unchanged

Increase by 216

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YOUR ANSWER : ?

Calburn analogy is applicable for the value of Prandtl number from

0.001 to 1

0.6 to 120

0.5 to 5

120 to 400

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A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is

48000

24000

60000

6000

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Film condensation is promoted on a/an __________ surface.

dirty

clean & smooth

coated

oily

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Open pan evaporators are preferred to be used, when the solution to be concentrated is

Highly viscous

Scaling

Corrosive

Salty

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The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.

Decreases

Remains constant

Increases

May increase or decrease ; depends on the material

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Which of the following situations can be approximated to a steady state heat transfer system?

A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C

A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

10 kg of dry saturated steam at 8 kgf/cm² flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C

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What is the unit of thermal conductivity ?

Kcal/hr. m² °C

Kcal/hr. °C

Kcal/hr.m

Kcal/hr.m.°C

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Which of the following has the lowest overall heat transfer co-efficient?

Water

Molten sodium

Air

Dowtherm

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