Heat Transfer MCQs

Question 1

Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)

Accepted Answer

d2

Answer

$$\sqrt {	ext{d}} $$

Answer

d

Answer

d1.5

Question 2

The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe )

Accepted Answer

$$\frac{{	ext{K}}}{{{{	ext{h}}_0}}}$$

Answer

$$\frac{{2{	ext{K}}}}{{{{	ext{h}}_0}}}$$

Answer

$$\frac{{{{	ext{h}}_{	ext{i}}}}}{{	ext{K}}}$$

Answer

$$\frac{{2{{	ext{h}}_{	ext{i}}}}}{{	ext{K}}}$$

Question 3

In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface.

Accepted Answer

Local

Answer

Nucleate

Answer

Pool

Answer

Saturated

Question 4

Pick out the correct statement.

Accepted Answer

Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder

Answer

Higher is the temperature of the radiating body, higher is the wavelength of radiation

Answer

The wavelength corresponding to maximum mono-chromatic emissive power increases with rise in temperature

Answer

Solid angle subtended by the finite surface at the radiating element is called the angle of incidence

Question 5

Steady state one dimensional heat flow by conduction as given by Fourier's low does not assume that

Accepted Answer

Material is anisotropic

Answer

There is no internal heat generation

Answer

Boundary surfaces are isothermal

Answer

Constant temperature gradient exists

Question 6

Steam traps are provided in steam carrying pipelines to

Accepted Answer

Remove condensate and inert gases

Answer

Condense steam

Answer

Release excess steam pressure by bleeding steam

Answer

None of these

Question 7

In sub-cooled boiling,

Accepted Answer

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

Answer

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

Answer

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

Answer

Very large vapour space is necessary

Question 8

Presence of a non-condensing gas in a condensing vapour

Accepted Answer

None of these

Answer

Increases the rate of condensation

Answer

Decreases thermal resistance

Answer

Is desirable to increase the film co-efficient

Question 9

Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity?

Accepted Answer

Coke breeze

Answer

Aluminium foil

Answer

Refractory bricks

Answer

Iron plate