Heat and Mass Transfer Mechanical Engineering Online Quiz - ObjectiveBooks

# Heat and Mass Transfer Mechanical Engineering Online Quiz

1. The process of heat transfer from a hot body to a cold body, in a straight line, without affecting the intervening medium, is called radiation.
True
False

2. The counter-current flow heat exchanger can transfer __________ heat than parallel flow heat exchanger.
Less
More

3. For a white body, absorptivity (α) = 0, reflectivity (ρ) = 1 and transmissivity (τ) = 0.
Correct
Incorrect

4. According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.
Correct
Incorrect

5. According to Prevost's theory of exchanges, everybody irrespective of its temperature continuously emit heat radiations to the surrounding bodies and at the same time receives heat radiations from the surrounding bodies.
True
False

6. The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity.
Agree
Disagree

7. The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (h₀).
True
False

8. Emissivity of a body will be equal to its absorptivity at all temperatures.
Yes
No

9. Prandtl number (PN) is given by PN = μ.Cp/k
Yes
No

10. The space between the two walls of a thermos flask is evacuated because vacuum is a ________ conductor of heat.
Good

11. The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness.
Agree
Disagree

12. A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray.
True
False

13. The average value of thermal conductivity for water at 20° C saturate is about 0.51
True
False

14. In a black body, all radiations are rejected.
True
False

15. A device used for transferring heat from one fluid to another is called heat exchanger.
True
False

16. The temperature below which a gas is always liquefied is known as critical temperature.
Correct
Incorrect

17. Logarithmic mean temperature difference is the same as the arithmetic mean temperature difference.
Agree
Disagree

18. Planck's law holds good for all coloured bodies.
True
False

19. When there is an addition of water vapour to the air of enclosed space, a gain in _______ is said to occur.
Sensible heat
Latent heat

20. The thermal diffusivity for solids is generally less than those for liquids and gases.
True
False

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