Heat Transfer MCQs

Question 1

Pick out the wrong statement:

Accepted Answer

With change in temperature, the radiant energy emitted by a black body remains unchanged

Answer

Absorptivity of a body approaches unity in case of diffuse reflection

Answer

Absorptivity of a perfectly black body is unity

Answer

Value of Stefan-Boltzman constant is 4.876 × 10-8 kcal/m2.hr.°K4

Question 2

Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is

Accepted Answer

Finned tube heat exchanger with air outside and steam inside

Answer

Finned tube heat exchanger with air inside and steam outside

Answer

Shell and tube heat exchanger with air inside tubes and steam on shell side

Answer

Shell and tube heat exchanger with air on shell side and steam inside tubes

Question 3

The steam ejector is used to

Accepted Answer

Create vacuum

Answer

Remove condensate from the steam pipelines

Answer

Superheat the steam

Answer

None of these

Question 4

Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is

Accepted Answer

< 1

Answer

1

Answer

> 1

Answer

> 5

Question 5

Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is

Accepted Answer

0.6

Answer

0.2

Answer

0.4

Answer

0.8

Question 6

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

Accepted Answer

Decreases

Answer

Increases

Answer

Remains unchanged

Answer

Increases exponentially

Question 7

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

Accepted Answer

Increases

Answer

Decreases

Answer

Remains constant

Answer

May increase or decrease, depends on the vacuum

Question 8

One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300°C. The major heat consumption in the process will be to

Accepted Answer

Evaporate the water

Answer

Heat the water from 0°C to 100°C

Answer

To superheat the steam

Answer

Data insufficient, can't be predicted

Question 9

jH factor for heat transfer is not a function of the __________ number.

Accepted Answer

Both B & C

Answer

Reynolds

Answer

Nusselt

Answer

Grashoff