Heat Transfer MCQs

Question 1

At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical?

Accepted Answer

1

Answer

< 1

Answer

> 1

Answer

None of these

Question 2

Pick out the wrong statement.

Accepted Answer

In case of a 1 - 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs

Answer

The controlling resistance in case of heating of air by condensing steam is in the air film

Answer

The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature

Answer

Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

Question 3

A body is called grey if the monochromatic emissivity of the body is

Accepted Answer

Same for all wavelengths

Answer

Zero

Answer

Unity

Answer

Different for all wavelengths

Question 4

Rate of crystallisation does not depend upon the

Accepted Answer

None of these

Answer

Extent of supersaturation

Answer

Turbulence within the solution

Answer

Number and active surface area of the crystals

Question 5

Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is __________ law.

Accepted Answer

Wien's

Answer

Stefan's

Answer

Dalton's

Answer

Kirchoffs

Question 6

Stefan-Boltzman law applies to __________ body.

Accepted Answer

Black

Answer

White

Answer

Grey

Answer

Any colour

Question 7

__________ paint has the maximum absorption coefficient.

Accepted Answer

Black

Answer

Yellow

Answer

White

Answer

Grey

Question 8

A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun?

Accepted Answer

Black paint

Answer

Yellow paint

Answer

White paint

Answer

Grey paint

Question 9

The interchange factor for radiation heat transfer from surface 'x' to surface 'y' in case of an infinite parallel planes with emis-sivities $${\varepsilon _{	ext{x}}}$$ & $${\varepsilon _{	ext{y}}}$$ is given by

Accepted Answer

$$\frac{{{\varepsilon _{	ext{x}}} + {\varepsilon _{	ext{y}}}}}{{{\varepsilon _{	ext{x}}} + {\varepsilon _{	ext{y}}} - {\varepsilon _{	ext{x}}} \cdot {\varepsilon _{	ext{y}}}}}$$

Answer

$${\varepsilon _{	ext{x}}} + {\varepsilon _{	ext{y}}}$$

Answer

$${\varepsilon _{	ext{x}}} \cdot {\varepsilon _{	ext{y}}}$$

Answer

$$\frac{1}{{{\varepsilon _{	ext{x}}}}} + \frac{1}{{{\varepsilon _{	ext{y}}}}}$$