A fraction of radiative energy leaving one surface that strikes the other surface is called

Emissive power of the first surface

If ε is the emissivity of surfaces and shields and n is the number of shields, introduced between the two surfaces, then overall emissivity is given by

\(\frac{1}{{n\left( {2 - \varepsilon } \right)}}\)

\(\frac{1}{{\left( {n + 1} \right)\left( {2 - \varepsilon } \right)}}\)

\(\frac{\varepsilon }{{\left( {n + 1} \right)\left( {2 - \varepsilon } \right)}}\)

In a radiative heat transfer, a gray surface is one

Which has reflectivity equal to zero

Whose emissivity is independent of wavelength

Which has reflectivity equal to zero

Which appears equally bright from all directions

Consider two infinitely long thin concentric tubes of circular cross section as shown in the figure. If D1 and D2 are the diameters of the inner and outer tubes respectively, then the view factor F22 is given by

\(\left( {\frac{{{D_2}}}{{{D_1}}}} \right) - 1\)

\(\left( {\frac{{{D_1}}}{{{D_2}}}} \right)\)

\(1 - \left( {\frac{{{D_1}}}{{{D_2}}}} \right)\)

A gray body is defined such that

Monochromatic emissivity of the body is dependent of wave length

Monochromatic emissivity of the body is independent of temperature

Monochromatic emissivity of the body is dependent of temperature

Monochromatic emissivity of the body is independent of wave length

Monochromatic emissivity of the body is dependent of wave length

A perfect black body is

One which absorbs total radiant energy

One which does not reflect the radiant energy

One which absorbs all radiant energy at all wavelengths

In a solar collector, the function of the transparent cover is to:

Absorb all types of radiation and protect the collector from dust

Protect the collector from dust

Decrease the heat loss from collector beneath to atmosphere

Absorb all types of radiation and protect the collector from dust

Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is R0 and that of the inner cylinder is Ri. The radiation view factor of the outer cylinder onto itself is

\(1 - \sqrt {\frac{{{R_i}}}{{{R_0}}}}\)

\(\sqrt {1 - \frac{{{R_i}}}{{{R_0}}}}\)

\(1 - {\left( {\frac{{{R_i}}}{{{R_0}}}} \right)^{1/3}}\)

\(1 - \frac{{{R_i}}}{{{R_0}}}\)

Radiation thermal resistance may be written as [where F, A, σ are shape factor, Area and Stefan-Boltzmann constant respectively]

\(\frac{1}{{FA\sigma \left( {{T_1} + {T_2}} \right)\left( {T_1^2 - T_2^2} \right)}}\)

\(\frac{1}{{FA\sigma \left( {{T_1} + {T_2}} \right)\left( {T_1^2 + T_2^2} \right)}}\)

\(\frac{1}{{FA\sigma \left( {{T_1} + {T_2}} \right)\left( {T_1^2 - T_2^2} \right)}}\)

\(\frac{1}{{FA\sigma \left( {T_1^4 - T_2^4} \right)}}\)

\(\frac{1}{{FA\sigma \left( {T_1^4 + T_2^4} \right)}}\)

Absorptivity of the grey body

varies with wavelength of the incident ray

varies with wavelength and temperature of the incident ray

does not vary with wavelength and temperature of the incident ray

For infinite parallel planes with emissivities ε1 and ε2, the interchange factor for radiation from surface 1 to surface 2 is given by

\(\frac{1}{{{\varepsilon _1}}} + \frac{1}{{{\varepsilon _2}}}\)

\(\frac{{{\varepsilon _1}{\varepsilon _2}}}{{{\varepsilon _1} + {\varepsilon _2} - {\varepsilon _1}{\varepsilon _2}}}\)

\(\frac{1}{{{\varepsilon _1}}} + \frac{1}{{{\varepsilon _2}}}\)

72 + Mcqs in Solar Radiation in Energy Engineering Page 1 McqOptions

1.	Which type of fuel is removed from the reactor core after reaching end of core life service?
A.	Burnt Fuel
B.	Spent fuel
C.	Engine oil
D.	Radioactive fuel
Answer» C. Engine oil

Discussion

2.	Solar radiation received at any point of earth is called ______________
A.	Insolation
B.	Beam Radiation
C.	Diffuse Radiation
D.	Infrared rays
Answer» B. Beam Radiation

Discussion

3.	The scattered solar radiation is called ____________
A.	Direct Radiation
B.	Beam Radiation
C.	Diffuse radiation
D.	Infrared Radiation
Answer» D. Infrared Radiation

Discussion

4.	Solar radiation which reaches the surface without scattering or absorbed is called _____________
A.	Beam Radiation
B.	Infrared radiation
C.	Ultraviolet radiation
D.	Diffuse radiation
Answer» B. Infrared radiation

Discussion

5.	Complete the following reaction. H2O + CO2 → _______
A.	CH2O + O2
B.	CO2 + O2
C.	H + CO2 + O2
D.	CH2O + H2O + O2
Answer» B. CO2 + O2

Discussion

6.	Oil is estimated to last for ________ more.
A.	100 years
B.	500 years
C.	A decade
D.	800 years
Answer» B. 500 years

Discussion

7.	If 5 radiation shields are placed between two parallel plates, the rate of radiation heat transfer is reduced to:[ε = 1 for all surfaces]
A.	1/4 times
B.	1/5 times
C.	1/6 times
D.	1/10 times
Answer» D. 1/10 times

Discussion

8.	A fraction of radiative energy leaving one surface that strikes the other surface is called
A.	Radiative flux
B.	Emissive power of the first surface
C.	View factor
D.	Reradiation flux
Answer» D. Reradiation flux

Discussion

9.	A satellite floats in deep space with very high velocity. It will continuously lose heat by
A.	Convection
B.	Conduction and convection
C.	Radiation
D.	Radiation and convection
Answer» D. Radiation and convection

Discussion

10.	A radiator on a space capsule must dissipate heat generated inside the capsule, by radiating it into space. While on the bright side of the earth, the capsule sees the earth’s radiation and solar radiation. The radiator surface has a solar absorptivity of 0.5 and an emissivity of 0.9. What is the maximum equilibrium surface temperature of the radiator, if the maximum heat generated in the capsule is 800 W/m2?Assume earth’s radiation = 100 W/m2 and solar irradiation = 524 W/m2.Take Stefan Boltzmann constant as 5 × 10-8 W/m2-K4
A.	400°C
B.	100°C
C.	127°C
D.	160°C
Answer» D. 160°C

Discussion

11.	An isothermal cubical (10 m × 10 m × 10 m) blackbody at 200° C is suspended in air. The total radiation emitted by this body to its surroundings will be
A.	1702.9 kW
B.	1800.7 kW
C.	54.4 kW
D.	2832.1 kW
Answer» B. 1800.7 kW

Discussion

12.	For a hemispherical furnace with a flat circular base of diameter D, the view factor from the dome to its base is
A.	0.5
B.	1
C.	0
D.	0.32
Answer» B. 1

Discussion

13.	If ε is the emissivity of surfaces and shields and n is the number of shields, introduced between the two surfaces, then overall emissivity is given by
A.	\(\frac{1}{{n \epsilon}}\)
B.	\(\frac{1}{{n\left( {2 - \varepsilon } \right)}}\)
C.	\(\frac{1}{{\left( {n + 1} \right)\left( {2 - \varepsilon } \right)}}\)
D.	\(\frac{\varepsilon }{{\left( {n + 1} \right)\left( {2 - \varepsilon } \right)}}\)
Answer» E.

Discussion

14.	For an absolutely white or specular body-(where α = absorptivity, ρ = reflectivity, τ = transmissivity)
A.	α = 1, ρ = 0 and τ = 0
B.	ρ = 1 and α = τ = 0
C.	τ = 1 and α = ρ = 0
D.	α + τ = 1 and ρ = 0
Answer» C. τ = 1 and α = ρ = 0

Discussion

15.	According to Planck’s law, the wavelength corresponding to the maximum energy is proportional to
A.	T
B.	T2
C.	T3
D.	\(\frac{1}{T}\)
Answer» E.

Discussion

16.	In a radiative heat transfer, a gray surface is one
A.	Which appears gray to the eye
B.	Whose emissivity is independent of wavelength
C.	Which has reflectivity equal to zero
D.	Which appears equally bright from all directions
Answer» C. Which has reflectivity equal to zero

Discussion

17.	A solid cylinder (surface 2) is located at the centre of a hollow sphere (surface 1). The diameter of the sphere is 1 m, while the cylinder has a diameter and length of 0.5 m each. The radiation configuration factor F11 is
A.	0.375
B.	0.625
C.	0.75
D.	1
Answer» C. 0.75

Discussion

18.	A hemispherical furnace of radius 1.0 m has a roof temperature of T1 = 800 K and emissivity e1 = 0.8. The flat floor of the furnace has a temperature T2 = 600 K and emissivity e2 = 0.5. The view factor F12 from surface 1 to 2 will be
A.	0.3
B.	0.4
C.	0.5
D.	0.6
Answer» D. 0.6

Discussion

19.	Hot surface at temperature 400 K having an emissivity of 0.5 dissipates heat by radiation into a surrounding of 375 K. Its radiation heat transfer coefficient (W/sqm K) is
A.	14.6
B.	6.6
C.	1.83
D.	9.4
Answer» C. 1.83

Discussion

20.	A radiation shield should have
A.	high emissivity
B.	low reflectivity
C.	high reflectivity
D.	none of the above
Answer» D. none of the above

Discussion

21.	Intensity of solar radiation in kW/sqm is about
A.	1
B.	3
C.	5
D.	2
Answer» B. 3

Discussion

22.	Absorptivity of a body is equal to its emissivity
A.	For a polished body
B.	Under thermal equilibrium
C.	At one particular temperature
D.	At shorter wave lengths
Answer» C. At one particular temperature

Discussion

23.	Consider two infinitely long thin concentric tubes of circular cross section as shown in the figure. If D1 and D2 are the diameters of the inner and outer tubes respectively, then the view factor F22 is given by
A.	\(\left( {\frac{{{D_2}}}{{{D_1}}}} \right) - 1\)
B.	Zero
C.	\(\left( {\frac{{{D_1}}}{{{D_2}}}} \right)\)
D.	\(1 - \left( {\frac{{{D_1}}}{{{D_2}}}} \right)\)
Answer» E.

Discussion

24.	For an opaque surface, the absorptivity (α) , transitivity (τ) and reflectivity (ρ) are related by the equation
A.	α + ρ = τ
B.	ρ + α + τ = 0
C.	α + ρ = 1
D.	α + ρ = 0
Answer» D. α + ρ = 0

Discussion

25.	Incident radiation of 1000 W / m2 falls on the object. The energy absorbed by the object is 400 W / m2 and energy transmitted is 350 W / m2. What will be the value of reflectivity?
A.	0.4
B.	0.35
C.	0.75
D.	0.25
Answer» E.

Discussion

26.	A gray body is defined such that
A.	Monochromatic emissivity of the body is independent of temperature
B.	Monochromatic emissivity of the body is dependent of temperature
C.	Monochromatic emissivity of the body is independent of wave length
D.	Monochromatic emissivity of the body is dependent of wave length
Answer» D. Monochromatic emissivity of the body is dependent of wave length

Discussion

27.	A radiator in a domestic heating system operates at a surface temperature of 55°C. Assuming the radiator behaves as a black body, the rate at which it emits the radiant heat per unit area is (assume σ = 5.67 × 10-8 W/(m2K4))
A.	0.66 kW/m2
B.	0.0005 kW/m2
C.	0.5 kW/m2
D.	66 kW/m2
Answer» B. 0.0005 kW/m2

Discussion

28.	If the temperature of the sun is doubled, the rate of energy received on earth will be increased by a factor of
A.	2
B.	4
C.	8
D.	16
Answer» E.

Discussion

29.	A perfect black body is
A.	One which absorbs total radiant energy
B.	Black in colour
C.	One which does not reflect the radiant energy
D.	One which absorbs all radiant energy at all wavelengths
Answer» E.

Discussion

30.	A good approximation of the measured solar spectrum is made by
A.	black-body energy distribution
B.	Planck’s energy distribution
C.	inverse square law
D.	solar constant
Answer» C. inverse square law

Discussion

31.	In a solar collector, the function of the transparent cover is to:
A.	Transmit solar radiation only
B.	Protect the collector from dust
C.	Decrease the heat loss from collector beneath to atmosphere
D.	Absorb all types of radiation and protect the collector from dust
Answer» D. Absorb all types of radiation and protect the collector from dust

Discussion

32.	Gases have poor
A.	transmissivity
B.	absorptivity
C.	reflectivity
D.	emissivity
Answer» D. emissivity

Discussion

33.	Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is R0 and that of the inner cylinder is Ri. The radiation view factor of the outer cylinder onto itself is
A.	\(1 - \sqrt {\frac{{{R_i}}}{{{R_0}}}}\)
B.	\(\sqrt {1 - \frac{{{R_i}}}{{{R_0}}}}\)
C.	\(1 - {\left( {\frac{{{R_i}}}{{{R_0}}}} \right)^{1/3}}\)
D.	\(1 - \frac{{{R_i}}}{{{R_0}}}\)
Answer» E.

Discussion

34.	For the same type of shapes, the value of Radiation Shape Factor will be higher when surfaces are
A.	More closer only
B.	Moved further apart
C.	Smaller and held closer
D.	Larger and held closer
Answer» E.

Discussion

35.	If a body is at 2000 K, the wavelength at which the body emits maximum amount of radiation is
A.	1.45 μm
B.	1.45 cm
C.	0.345 cm
D.	0.345 μm
Answer» B. 1.45 cm

Discussion

36.	A 1m diameter spherical cavity is maintained at a uniform temperature of 500 K. The emissivity of the material of the sphere is 0.5; One 10 mm diameter hole is drilled. The maximum rate of radiant energy streaming through the hole will be
A.	2782 W
B.	0.139 W
C.	1392 W
D.	0.278 W
Answer» C. 1392 W

Discussion

37.	For a surface, the direct and diffuse components of the solar radiation are 400 and 300 W/m2 and the direct radiation makes 60 deg angle with the normal. If the surface temperature is 300 K and effective sky temperature is 200 K, calculate the net rate of radiation heat transfer. (Assume solar absorptivity and emissivity as 0.1 each; For calculation Take Stefan Boltzmann's constant as 6 × 10-8 W/m2.K4)
A.	11 W/m2
B.	45 W/m2
C.	33 W/m2
D.	64 W/m2
Answer» B. 45 W/m2

Discussion

38.	Radiation thermal resistance may be written as [where F, A, σ are shape factor, Area and Stefan-Boltzmann constant respectively]
A.	\(\frac{1}{{FA\sigma \left( {{T_1} + {T_2}} \right)\left( {T_1^2 + T_2^2} \right)}}\)
B.	\(\frac{1}{{FA\sigma \left( {{T_1} + {T_2}} \right)\left( {T_1^2 - T_2^2} \right)}}\)
C.	\(\frac{1}{{FA\sigma \left( {T_1^4 - T_2^4} \right)}}\)
D.	\(\frac{1}{{FA\sigma \left( {T_1^4 + T_2^4} \right)}}\)
Answer» B. \(\frac{1}{{FA\sigma \left( {{T_1} + {T_2}} \right)\left( {T_1^2 - T_2^2} \right)}}\)

Discussion

39.	A solid sphere of radius r1 = 20 mm is placed concentrically inside a hollow sphere of radius r2 = 30 mm as shown in figure.The view factor F21 for radiation heat transfer is
A.	2/3
B.	4/9
C.	8/27
D.	9/4
Answer» C. 8/27

Discussion

40.	For infinite parallel planes with emissivities 0.4 and 0.2, the interchange view factor for a radiation from surface 1 to surface 2 is about
A.	0.4
B.	0.6
C.	0.2
D.	0.15
Answer» E.

Discussion

41.	Absorptivity of the grey body
A.	varies with temperature
B.	varies with wavelength of the incident ray
C.	varies with wavelength and temperature of the incident ray
D.	does not vary with wavelength and temperature of the incident ray
Answer» E.

Discussion

42.	A body 1 in the form of a sphere of 2 cm radius at temperature T1 is located in body 2, which is a hollow cube of 5 cm side and is at temperature T2 (T2 < T1). The shape factor F21 for radiation heat transfer becomes:
A.	0.34
B.	0.43
C.	0.57
D.	0.63
Answer» B. 0.43

Discussion

43.	A hollow enclosure is formed between two infinitely concentric cylinders of radii 1 m and 2 m respectively. Radiative heat exchange takes place between the inner surface of the larger cylinder (surface 2) and the outer surface of the smaller cylinder (surface 1) the radiating surfaces are diffuse and the medium in the enclosure is non-participating. The fraction of the thermal radiation leaving the surface and striking itself is
A.	0.25
B.	0.5
C.	0.75
D.	1
Answer» C. 0.75

Discussion

44.	A metallic surface is maintained at 1000 K, the wavelength at which maximum spectral intensity occurs
A.	289.8 μm
B.	28.98 μm
C.	0.2898 μm
D.	0.002898 mm
Answer» E.

Discussion

45.	A 40 cm diameter disk with an emissivity of 0.65 is placed in a large enclosure at 30°C and is effectively a black body. If the disc has a temperature of 55°C, calculate the radiosity of its upper surface.
A.	604 W/m2
B.	594 W/m2
C.	560 W/m2
D.	749 W/m2
Answer» C. 560 W/m2

Discussion

46.	For a glass plate, transmissivity and reflectivity are specified as 0.86 and 0.08 respectively, the absorptivity of the plate is
A.	0.86
B.	0.08
C.	1.00
D.	0.06
Answer» E.

Discussion

47.	A wave of radiation falls on a body, 35% of the radiation is reflected back. If transmissivity of the body is 0.25, then emissivity is:
A.	0.35
B.	0.45
C.	0.40
D.	0.25
Answer» D. 0.25

Discussion

48.	For infinite parallel planes with emissivities ε1 and ε2, the interchange factor for radiation from surface 1 to surface 2 is given by
A.	\(\frac{{{\varepsilon _1}{\varepsilon _2}}}{{{\varepsilon _1} + {\varepsilon _2} - {\varepsilon _1}{\varepsilon _2}}}\)
B.	\(\frac{1}{{{\varepsilon _1}}} + \frac{1}{{{\varepsilon _2}}}\)
C.	ε1 + ε2
D.	ε1 ε2
Answer» B. \(\frac{1}{{{\varepsilon _1}}} + \frac{1}{{{\varepsilon _2}}}\)

Discussion

49.	Flat plate collectors are used to heat the water upto the temperature of
A.	70 – 90°C
B.	100 - 200°C
C.	200 – 300°
D.	300 – 400°C
Answer» B. 100 - 200°C

Discussion

50.	During very cold weather conditions, cricket players prefer to wear white woolen sweaters rather than colored woolen sweaters. The reason is that white wool comparatively:1. Absorbs less heat from the body2. Emits less heat to the atmosphereWhich of the above statements is/are correct?
A.	1 only
B.	2 only
C.	Both 1 and 2
D.	Neither 1 nor 2
Answer» C. Both 1 and 2

Discussion

Explore topic-wise MCQs in Energy Engineering.

Which type of fuel is removed from the reactor core after reaching end of core life service?

Solar radiation received at any point of earth is called ______________

The scattered solar radiation is called ____________

Solar radiation which reaches the surface without scattering or absorbed is called _____________

Complete the following reaction. H2O + CO2 → _______

Oil is estimated to last for ________ more.

If 5 radiation shields are placed between two parallel plates, the rate of radiation heat transfer is reduced to:[ε = 1 for all surfaces]

A fraction of radiative energy leaving one surface that strikes the other surface is called

A satellite floats in deep space with very high velocity. It will continuously lose heat by

An isothermal cubical (10 m × 10 m × 10 m) blackbody at 200° C is suspended in air. The total radiation emitted by this body to its surroundings will be

For a hemispherical furnace with a flat circular base of diameter D, the view factor from the dome to its base is

If ε is the emissivity of surfaces and shields and n is the number of shields, introduced between the two surfaces, then overall emissivity is given by

For an absolutely white or specular body-(where α = absorptivity, ρ = reflectivity, τ = transmissivity)

According to Planck’s law, the wavelength corresponding to the maximum energy is proportional to

In a radiative heat transfer, a gray surface is one

A solid cylinder (surface 2) is located at the centre of a hollow sphere (surface 1). The diameter of the sphere is 1 m, while the cylinder has a diameter and length of 0.5 m each. The radiation configuration factor F11 is

A hemispherical furnace of radius 1.0 m has a roof temperature of T1 = 800 K and emissivity e1 = 0.8. The flat floor of the furnace has a temperature T2 = 600 K and emissivity e2 = 0.5. The view factor F12 from surface 1 to 2 will be

Hot surface at temperature 400 K having an emissivity of 0.5 dissipates heat by radiation into a surrounding of 375 K. Its radiation heat transfer coefficient (W/sqm K) is

A radiation shield should have

Intensity of solar radiation in kW/sqm is about

Absorptivity of a body is equal to its emissivity

Consider two infinitely long thin concentric tubes of circular cross section as shown in the figure. If D1 and D2 are the diameters of the inner and outer tubes respectively, then the view factor F22 is given by

For an opaque surface, the absorptivity (α) , transitivity (τ) and reflectivity (ρ) are related by the equation

Incident radiation of 1000 W / m2 falls on the object. The energy absorbed by the object is 400 W / m2 and energy transmitted is 350 W / m2. What will be the value of reflectivity?

A gray body is defined such that

A radiator in a domestic heating system operates at a surface temperature of 55°C. Assuming the radiator behaves as a black body, the rate at which it emits the radiant heat per unit area is (assume σ = 5.67 × 10-8 W/(m2K4))

If the temperature of the sun is doubled, the rate of energy received on earth will be increased by a factor of

A perfect black body is

A good approximation of the measured solar spectrum is made by

In a solar collector, the function of the transparent cover is to:

Gases have poor

Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is R0 and that of the inner cylinder is Ri. The radiation view factor of the outer cylinder onto itself is

For the same type of shapes, the value of Radiation Shape Factor will be higher when surfaces are

If a body is at 2000 K, the wavelength at which the body emits maximum amount of radiation is

A 1m diameter spherical cavity is maintained at a uniform temperature of 500 K. The emissivity of the material of the sphere is 0.5; One 10 mm diameter hole is drilled. The maximum rate of radiant energy streaming through the hole will be

Radiation thermal resistance may be written as [where F, A, σ are shape factor, Area and Stefan-Boltzmann constant respectively]

A solid sphere of radius r1 = 20 mm is placed concentrically inside a hollow sphere of radius r2 = 30 mm as shown in figure.The view factor F21 for radiation heat transfer is

For infinite parallel planes with emissivities 0.4 and 0.2, the interchange view factor for a radiation from surface 1 to surface 2 is about

Absorptivity of the grey body

A body 1 in the form of a sphere of 2 cm radius at temperature T1 is located in body 2, which is a hollow cube of 5 cm side and is at temperature T2 (T2 < T1). The shape factor F21 for radiation heat transfer becomes:

A metallic surface is maintained at 1000 K, the wavelength at which maximum spectral intensity occurs

A 40 cm diameter disk with an emissivity of 0.65 is placed in a large enclosure at 30°C and is effectively a black body. If the disc has a temperature of 55°C, calculate the radiosity of its upper surface.

For a glass plate, transmissivity and reflectivity are specified as 0.86 and 0.08 respectively, the absorptivity of the plate is

A wave of radiation falls on a body, 35% of the radiation is reflected back. If transmissivity of the body is 0.25, then emissivity is:

For infinite parallel planes with emissivities ε1 and ε2, the interchange factor for radiation from surface 1 to surface 2 is given by

Flat plate collectors are used to heat the water upto the temperature of

During very cold weather conditions, cricket players prefer to wear white woolen sweaters rather than colored woolen sweaters. The reason is that white wool comparatively:1. Absorbs less heat from the body2. Emits less heat to the atmosphereWhich of the above statements is/are correct?