Heat & Mass Transfer True/False Quiz

01. 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.

A) True

B) False

02. The counter-current flow heat exchanger can transfer __________ heat than parallel flow heat

exchanger.

A) Less

B) More

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

A) Correct

B) Incorrect

04. 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.

A) Correct

B) Incorrect

05. 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.

A) True

B) False

06. The ratio of emissive power of a body to the emissive power of a perfectly black body is called

emissivity.

A) Agree

B) Disagree

07. 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).

A) True

B) False

08. Emissivity of a body will be equal to its absorptivity at all temperatures.

A) Yes

B) No

09. Prandtl number (PN) is given by PN = μ.Cp/k.

A) Yes

B) No

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

________ conductor of heat.

A) Good

B) Bad

11. The ratio of actual heat transfer to the maximum possible heat transfer is known as heat

exchanger effectiveness.

A) Agree

B) Disagree

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

incident ray.

A) True

B) False

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

A) True

B) False

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

A) True

B) False

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

A) True

B) False

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

A) Correct

B) Incorrect

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

difference.

A) Agree

B) Disagree

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

A) True

B) False

19. When there is an addition of water vapour to the air of enclosed space, a gain in ________ is

said to occur.

A) Sensible heat

B) Latent heat

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

A) True

B) False

Answers: Heat & Mass Transfer 

01. Answer: Option A 

02. Answer: Option B 

03. Answer: Option A 

04. Answer: Option A

05. Answer: Option A 

06. Answer: Option A 

07. Answer: Option A 

08. Answer: Option B

09. Answer: Option A 

10. Answer: Option B 

11. Answer: Option A 

12. Answer: Option A

13. Answer: Option A 

14. Answer: Option B 

15. Answer: Option A 

16. Answer: Option B

17. Answer: Option B 

18. Answer: Option A 

19. Answer: Option B 

20. Answer: Option B