Heat Transfer MCQs

Question 1

If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

Accepted Answer

Decrease

Answer

Increase

Answer

Not affect

Answer

Increase the condensing film co-efficient as well as

Question 2

In forced circulation, the heating element is injected

Accepted Answer

Internally

Answer

Externally

Answer

Both A and B

Answer

Neither A nor B

Question 3

In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid

Accepted Answer

Varies directly as the area and the LMTD

Answer

Directly proportional to LMTD and inversely proportional to the area

Answer

Varies as square of the area

Answer

None of these

Question 4

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16 m is 10 W/m2. The temperature of the inside wall is -5°C. The outside wall temperature is

Accepted Answer

35°C

Answer

25°C

Answer

30°C

Answer

40°C

Question 5

The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as

Accepted Answer

$${\left( {\Delta {	ext{T}}} ight)^{\frac{3}{4}}}$$

Answer

$${\left( {\Delta {	ext{T}}} ight)^{\frac{1}{4}}}$$

Answer

$${\left( {\Delta {	ext{T}}} ight)^{\frac{1}{2}}}$$

Answer

$${\left( {\Delta {	ext{T}}} ight)^{\frac{5}{4}}}$$

Question 6

The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is

Accepted Answer

16.5 kW/m2

Answer

11.2 kW/m2

Answer

12.0 kW/m2

Answer

14.6 kW/m2

Question 7

Pick out the wrong statement.

Accepted Answer

The Colbum jH factor for heat transfer is given by Nst Npr

Answer

Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection

Answer

The ratio NNu/NRe . Npr is called the Stanton number

Answer

The Peclet number is a measure of the ratio of energy transport by convection to that by conduction

Question 8

Radiation energy is emitted by all the substances, which are above

Accepted Answer

0°K

Answer

0°C

Answer

100°C

Answer

Room temperature

Question 9

The purpose of floating head in a heat exchanger is to

Accepted Answer

Avoid buckling of tubes

Answer

Provide support for tubes

Answer

Decrease the pressure drop

Answer

Facilitate its lengthening, if needed