The top surface of an L = 5 − m m − t h i c k anodized aluminum plate is irradiated with G=1000 W / m 2 while being simultaneously exposed to convection conditions characterized by h = 40 W / m 2 ⋅ K a n d T ∞ = 30 ∘ C . The bottom surface of the plate is insulated. For a plate temperature of 400 K as well as α = 0.14 and ε = 0 .76 , determine the radiosity at the top plate sur-face, the net radiation heat flux at the top surface, and the rate at which the temperature of the plate is changing with time.
The top surface of an L = 5 − m m − t h i c k anodized aluminum plate is irradiated with G=1000 W / m 2 while being simultaneously exposed to convection conditions characterized by h = 40 W / m 2 ⋅ K a n d T ∞ = 30 ∘ C . The bottom surface of the plate is insulated. For a plate temperature of 400 K as well as α = 0.14 and ε = 0 .76 , determine the radiosity at the top plate sur-face, the net radiation heat flux at the top surface, and the rate at which the temperature of the plate is changing with time.
Solution Summary: The author calculates the radiosity, the net radiation heat flux, and the temperature of the plate.
The top surface of an
L
=
5
−
m
m
−
t
h
i
c
k
anodized aluminum plate is irradiated with
G=1000
W
/
m
2
while being simultaneously exposed to convection conditions characterized by
h = 40
W
/
m
2
⋅
K
a
n
d
T
∞
=
30
∘
C
. The bottom surface of the plate is insulated. For a plate temperature of 400 K as well as
α
=
0.14
and
ε
= 0
.76
, determine the radiosity at the top plate sur-face, the net radiation heat flux at the top surface, and the rate at which the temperature of the plate is changing with time.
€ = 0.7
R = 50 cm
T = 500°C
Consider a furnace with a spherical cavity (R = 50 cm). If the walls of the cavity have an emissivity of 0.7 and a temperature
of 500 ˚C, calculate the total emmisive power, E, inside the cavity.
One of the given statement is true
Kirchoff's law shows that emissivity is the same as transmissivity for blackbodies
Incident radiation is the sum of the reflected and emitted radiation
The sum of the absorptivity, transmissivity and reflectivity can be more than 1 for real bodies
None of the given
Radiosity is another form of the Stefan-Boltzmann law
Planck's radiation law is given as:
8thv³
I = n(v)ɛ =-
c3
hv
ekBT – 1
8nhc
1
= n(1)ē =
25
hc
eAkgT – 1
(a) Show that it reduces to the Rayleigh-Jeans law as 2 –∞.
(b) Show that it reduces to Wien's law in the short wavelength limit (1 → 0).
Evaluate a and b.
(c) Derive the constant in the Wien's displacement law.
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