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Free download in PDF Heat Transfer Objective Type Questions and Answers for competitive exams. These short objective type questions with answers are very important for competitive exams like IIT-JEE, AIIMS, NEET etc. as well as Board exams. These short solved questions or quizzes are provided by Gkseries.
(21)
A non-dimensional number generally associated with natural convection heat transfer is
[A]
Grashoff number
[B]
Nusselt number
[C]
Weber number
[D]
Prandtl number
(22)
In counter flow heat exchangers
[A]
both the fluids at inlet (of heat ex¬changer where hot fluid enters) are in their coldest state
[B]
both the fluids at inlet are in their hot¬test state
[C]
both the fluids .at exit are in their hottest state
[D]
one fluid is in hottest state and other in coldest state at inlet
Answer: both the fluids at inlet are in their hot¬test state
(23)
Fourier’s law of heat conduction is valid for
[A]
one dimensional cases only
[B]
two dimensional cases only
[C]
three dimensional cases only
[D]
irregular surfaces
Answer: one dimensional cases only
(24)
All radiations in a black body are
[A]
Reflected
[B]
Refracted
[C]
Transmitted
[D]
Absorbed
(25)
The unit of overall coefficient of heat transfer is
[A]
kcal/m2
[B]
kcal/hr °C
[C]
kcal/m2 hr °C
[D]
kacl/m hr °C
(26)
Joule sec is the unit of
[A]
universal gas constant
[B]
kinematic viscosity
[C]
thermal conductivity
[D]
Planck’s constant
Answer: Planck’s constant
(27)
The value of the wavelength for maximum emissive power is given by —
[A]
Wien’s law
[B]
Planck’s law
[C]
Stefan’s law
[D]
Fourier’s law
(28)
The energy distribution of an ideal reflector at higher temperatures is largely in the range of
[A]
Shorter Wavelength
[B]
Longer Wavelength
[C]
Remains Same At All Wavelengths
[D]
Wavelength Has Nothing To Do With It
Answer: Shorter Wavelength
(29)
According to Stefan-Boltzmann law, ideal radiators emit radiant energy at a rate proportional to
[A]
absolute temperature
[B]
square of temperature
[C]
fourth power of absolute temperature
[D]
fourth power of temperature
Answer: fourth power of absolute temperature
(30)
Which of the following property of air does not increase with rise in temperature
[A]
Thermal Conductivity
[B]
Thermal Diffusivity
[C]
Density
[D]
Dynamic Viscosity
31
The unit of Stefan Boltzmann constant is
[A]
watt/cm2 °K
[B]
watt/cm4 °K
[C]
watt2/cm °K4
[D]
watt/cm2 °K4
32
In free con-vection heat transfer, Nusselt number is function of
[A]
Grashoff no. and Reynold no.
[B]
Grashoff no. and Prandtl no.
[C]
Prandtl no. and Reynold no.
[D]
Grashoff no., Prandtl no. and Reynold no.
Answer: Grashoff no. and Prandtl no.
33
The thermal diffusivities for gases are generally
[A]
more than those for liquids
[B]
less than those for liquids
[C]
more than those for solids
[D]
dependent on the viscosity
Answer: more than those for liquids
34
Thermal diffusivity of a substance is
[A]
directly proportional to thermal con¬ductivity
[B]
inversely proportional to density of substance
[C]
inversely proportional to specific heat
[D]
all of the above
35
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
[A]
Krichoff’s law
[B]
Stefan’s law
[C]
Wien’ law
[D]
Planck’s law
36
According to Wien’s law, the wavelength corresponding to maximum energy is proportion to
[A]
absolute temperature (T)
[B]
I2
[C]
f
[D]
All Of The Above
Answer: absolute temperature (T)
37
Depending on the radiating properties, a body will be white when
[A]
p = 0, x = 0 and a = 1
[B]
p=l,T = 0anda = 0
[C]
p = 0, x = 1 and a = 0
[D]
x = 0, a + p = 1
Answer: p=l,T = 0anda = 0
38
Depending on the radiating properties, a body will be black when
[A]
p = 0, x = 0 and a = 1
[B]
p= l,T = 0anda = 0
[C]
p = 0, x = 1 and a = 0
[D]
none of the above
Answer: p = 0, x = 0 and a = 1
39
Depending on the radiating properties, a body will be opaque when
[A]
p = 0, x = 0 and a = 1
[B]
p=l,x = 0anda = 0
[C]
p = 0, x = 1 and a = 0
[D]
x – 0, a + p = 1
40
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
[A]
0.45
[B]
0.55
[C]
0.40
[D]
0.75
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