A small disk of diameter D 1 = 50 mm and emissivity ε 1 = 0.6 is maintained at a temperature of T 1 = 900 K . The disk is covered with a hemispherical radiation shield of the same diameter and an emissivity of ε 2 = 0.02 (both sides). Tue disk and cap are located at the bottom of a large evacuated refractory container ( ε 4 = 0.85 ) , facing another disk of diameter D 3 = D 1 , emissivity ε 3 = 0.4 , and temperature T 3 = 400 K . The view factor F 2 3 of the shield with respect to the upper disk is 0.3. (a) Construct an equivalent thermal circuit for the above system. Label all nodes, resistances, and currents. (b) Find the net rate of heat transfer between the hot disk and the rest of the system.
A small disk of diameter D 1 = 50 mm and emissivity ε 1 = 0.6 is maintained at a temperature of T 1 = 900 K . The disk is covered with a hemispherical radiation shield of the same diameter and an emissivity of ε 2 = 0.02 (both sides). Tue disk and cap are located at the bottom of a large evacuated refractory container ( ε 4 = 0.85 ) , facing another disk of diameter D 3 = D 1 , emissivity ε 3 = 0.4 , and temperature T 3 = 400 K . The view factor F 2 3 of the shield with respect to the upper disk is 0.3. (a) Construct an equivalent thermal circuit for the above system. Label all nodes, resistances, and currents. (b) Find the net rate of heat transfer between the hot disk and the rest of the system.
Solution Summary: The author calculates the equivalent thermal circuit for the given system by labeling all nodes, resistance and currents.
A small disk of diameter
D
1
=
50
mm
and emissivity
ε
1
=
0.6
is maintained at a temperature of
T
1
=
900
K
. The disk is covered with a hemispherical radiation shield of the same diameter and an emissivity of
ε
2
=
0.02
(both sides). Tue disk and cap are located at the bottom of a large evacuated refractory container
(
ε
4
=
0.85
)
, facing another disk of diameter
D
3
=
D
1
, emissivity
ε
3
=
0.4
, and temperature
T
3
=
400
K
. The view factor F23of the shield with respect to the upper disk is 0.3.
(a) Construct an equivalent thermal circuit for the above system. Label all nodes, resistances, and currents. (b) Find the net rate of heat transfer between the hot disk and the rest of the system.
Calculate the net rate of energy exchange by thermal radiation between a gray convex body 1 and its gray enclosure 2. The surface area of the convex body is A1 of 0.8 m2, its temperature T1 is 410 K and emissivity ε1 is 0.6. The enclosure has a surface area A2 of 1.6 m2, temperature T2 of 330 K and emissivity ε2 of 0.9
How does radiosity for a surface differ from the emitted energy? For what kind of surfaces are these two quantities identical?
A thin aluminum sheet with an emissivity of 0.14 on both sides is placed between two very large parallel plates maintained at uniform temperatures of T1=720 K and T2=560 K. The emissivities of the plates are ɛ1=0.76 and ɛ2=0.85. Determine the net rate of radiation heat transfer between the two plates per unit surface area of the plates, and the temperature of the radiation shield in steady operation.
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