Heat Transfer Engineering Quiz Questions

Thank you very much for taking test

Test your caliber

1. The thermal diffusivities for solids are generally
less than those for gases	jess than those for liquids
more than those for liquids and gases	more or less same as for liquids and gases

2. Thermal diffusivity of a substance is _____.
directly proportional to thermal conductivity	inversely proportional to density of substance
inversely proportional to specific heat	all of the above

3. The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as
Krichoff's law	Stefan's law
Wien' law	Planck's law

4. According to Stefan's law, the total radiation from a black body per second per unit area is proportional to
absolute temperature	T2
T5	t

5. According to Wien's law, the wavelength corresponding to maximum energy is proportion to _____.
absolute temperature (T)	I2
f	t

6. Depending on the radiating properties, a body will be white when
p = 0, x = 0 and a = 1	p=l,T = 0anda = 0
p = 0, x = 1 and a = 0	x = 0, a + p = 1

7. Depending on the radiating properties, a body will be black when
p = 0, x = 0 and a = 1	p= l,T = 0anda = 0
p = 0, x = 1 and a = 0	x = 0, a + p = 0

8. Depending on the radiating properties, a body will be opaque when
p = 0, x = 0 and a = 1	p=l,x = 0anda = 0
p = 0, x = 1 and a = 0	x - 0, a + p = 1

9. The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit
temperature	thickness
area	time

10. The ratio of the energy absorbed by the body to total energy falling on it is called
absorptive power	emissive power
absorptivity	emissivity

11. 40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is
0.45	0.55
0.40	0.75

12. The amount of radiation mainly depends on
nature of body	temperature of body
type of surface of body	all of the above

13. The emissive power of a body depends upon its
temperature	wave length
physical nature	all of the above

14. Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by
convection	free convection
forced convection	radiation

15. Absorptivity of a body will be equal to its emissivity
at all temperatures	at one particular temperature
when system is under thermal equilibrium	at critical temperature

16. In regenerator type heat exchanger, heat transfer takes place by
direct mixing of hot and cold fluids	a complete separation between hot and cold fluids
flow of hot and cold fluids alternately over a surface	generation of heat again and again

17. A perfect black body is one which
is black in colour	reflects all heat
transmits all heat radiations	abslprbs heat radiations of all wave lengths falling on it

18. Planck's law holds good for _____.
black bodies	polished bodies
all coloured bodies	all of the above

19. If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of
3	6
9	81

20. Depending on the radiating properties, body will be transparent when
p = 0, x = 0 and a = 1	p=l,x = 0,and a = 0
p = 0, T= l,and a = 0	X = 0, a + p = 1