10-8 W/M2K4. GATE-2. THE IRRADIATION (IN KW/M2) FOR THE UPPER PLATE (P...
10
-8
W/m
2
K
4
.
GATE-2. The irradiation (in kW/m
2
) for the upper plate (plate 1) is: [GATE-2009]
(a) 2.5
(b) 3.6
(c) 17.0
(d) 19.5
GATE-3. If plate 1 is also a diffuse and gray surface with an emissivity value of
0.8, the net radiation heat exchange (in kW/m
2
) between plate 1 and
plate 2 is:
[GATE-2009]
(a) 17.0
(b) 19.5
(c) 23.0
(d) 31.7
GATE-4. The following figure was generated from experimental data relating
spectral black body emissive power to wavelength at three
temperatures T
1
, T
2
and T
3
(T
1
> T
2
> T
3
). [GATE-2005]
Page 76 of 97
The conclusion is that the
measurements are:
(a)
Correct
because
the
maxima
in E
bλ
show the correct trend
(b) Correct because Planck's law
is satisfied
(c) Wrong because the Stefan
Boltzmann law is not satisfied
(d) Wrong because Wien's displacement law is not satisfied
Shape Factor Algebra and Salient Features of the Shape FactorGATE-5. A hollow encloser is formed between
two infinitely long concentric cylinders
of radii 1 m ans 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-
I). The radiating surfaces are diffuse
and the medium in the enclosure is
non-participating. The fraction of the
thermal radiation leaving the larger
surface and striking itself is:
[GATE-2008]
(a) 0.25
(b) 0.5
(c) 0.75
(d) 1
GATE-6. The shape factors with themselves of two infinity long black body
concentric cylinders with a diameter ratio of 3 are……… for the inner
and……… for the outer.
[GATE-1994]
(a) 0, 2/3
(b) 0, 1/3
(c) 1, 1/9
(d) 1, 1/3
GATE-7. For the circular tube of equal length and
diameter shown below, the view factor
F
13
is 0.17.
The view factor F
12
in this case will be:
(a) 0.17
(b) 0.21
(c) 0.79
(d) 0.83
[GATE-2001]
GATE-8. What is the value of the view factor for two inclined flat plates having
common edge of equal width, and with an angle of 20 degrees?
[GATE-2002]
(a) 0.83
(b) 1.17
(c) 0.66
(d) 1.34
Page 77 of 97
GATE-9. 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
F
11
is:
[GATE-2005]
(a) 0.375
(b) 0.625
(c) 0.75
(d) 1
Heat Exchange between Non-black BodiesGATE-10. The radiative heat transfer rate per unit area (W/m
2
) between two
plane parallel grey surfaces (emissivity = 0.9) maintained at 400 K and
300 K is:
[GATE-1993]
(a) 992
(b) 812
(c) 464
(d) 567
(Stefan Boltzman constant. σ = 5.67 × 10
–8
W/m
2
K
4
)
GATE-11. A plate having 10 cm
2
area each side is hanging in the middle of a room
of 100 m
2
total surface area. The plate temperature and emissivity are
respectively 800 K and 0.6. The temperature and emissivity values for
the surfaces of the room are 300 K and 0.3 respectively. Boltzmann's
constant
σ = 5.67 × 10
-8
W/m
2
K
4
. The total heat loss from the two
surfaces of the plate is:
[GATE-2003]
(a) 13.66 W
(b) 27.32 W
(c) 27.87 W
(d) 13.66 MW
Previous 20-Years IES Questions IntroductionIES-1.
Fraction of radiative energy leaving one surface that strikes the other
surface is called
[IES-2003]
(a) Radiative flux
(b) Emissive power of the first surface
(c) View factor
(d) Re-radiation flux
IES-2. Assertion (A): Heat transfer at high temperature is dominated by
radiation rather than convection. [IES-2002]
Reason (R): Radiation depends on fourth power of temperature while
convection depends on unit power relationship.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true but R is not the of A
(c) A is true but R is false
(d) A is false but R is true
IES-3.
Assertion (A): In a furnace, radiation from the walls has the same
wavelength as the incident radiation from the heat source.
[IES-1998]
Reason (R): Surfaces at the same temperature radiate at the same
wavelength.
(b) Both A and R are individually true but R is not the correct explanation of A
Page 78 of 97
IES-4.
Consider following parameters:
[IES-1995]