A furnace is located next to a dense array of cryogenic fluid piping. The ice-covered piping approximates a plane surface with an average temperature of T p = 0 ° C and an emissivity of ε p = 0.6 . The furnace wall has a temperature of T f = 200 ° C and an emissivity of ε f = 0.9 . To protect the refrigeration equipment and piping from excessive heat loading, reflective aluminum radiation shielding with an emissivity of ε s = 0.1 is placed between the piping and the furnace wall, as shown in the schematic. Assume all surfaces are diffuse-gray. If the temperature of the shield closest to the piping T s , N must be less than 30°C, how many radiation shields, N , must be installed between the piping and the furnace wall?
A furnace is located next to a dense array of cryogenic fluid piping. The ice-covered piping approximates a plane surface with an average temperature of T p = 0 ° C and an emissivity of ε p = 0.6 . The furnace wall has a temperature of T f = 200 ° C and an emissivity of ε f = 0.9 . To protect the refrigeration equipment and piping from excessive heat loading, reflective aluminum radiation shielding with an emissivity of ε s = 0.1 is placed between the piping and the furnace wall, as shown in the schematic. Assume all surfaces are diffuse-gray. If the temperature of the shield closest to the piping T s , N must be less than 30°C, how many radiation shields, N , must be installed between the piping and the furnace wall?
Solution Summary: The author calculates the number of radiation shields to be installed between piping and the furnace wall. The expression for heat flux without shield transfer is given by q_1A
A furnace is located next to a dense array of cryogenic fluid piping. The ice-covered piping approximates a plane surface with an average temperature of
T
p
=
0
°
C
and an emissivity of
ε
p
=
0.6
. The furnace wall has a temperature of
T
f
=
200
°
C
and an emissivity of
ε
f
=
0.9
. To protect the refrigeration equipment and piping from excessive heat loading, reflective aluminum radiation shielding with an emissivity of
ε
s
=
0.1
is placed between the piping and the furnace wall, as shown in the schematic. Assume all surfaces are diffuse-gray.
If the temperature of the shield closest to the piping Ts,Nmust be less than 30°C, how many radiation shields, N, must be installed between the piping and the furnace wall?
Consider a black spherical ball, with a diameter of 25 cm, is being suspended in air. Determine the surface temperature of the ball that should be maintained in order to heat 11.7 kg of air from 20°C to 30°C in the duration of 5 minutes.Given: cv = 718 J/kg∙K
Stefan-Boltzmann constant (σ) = 5.67 × 10–8 W/m2∙K
The surface temperature of the ball is Ts = _____ °C.
Two concentric spheres of diameters D1 = 15 cm and D2 = 25 cm are separated by air at 1 atm pressure. The surface temperatures of the two spheres enclosing the air are T1 = 350 K and T2 = 275 K, respectively, and their emissivities are 0.75. Determine the rate of heat transfer from the inner sphere to the outer sphere by (a) natural convection and (b) radiation.
A radiation shield that has the same emissivity 3 on both sides is placed between two large parallel plates, which are maintained at uniform temperatures of T1 = 650 K and T2 = 400 K and have emissivities of E1 = 0.6 and E2 = 0.9, respectively. Determine the emissivity of the radiation shield if the radiation heat transfer between the plates is to be reduced to 15 percent of that without the radiation shield
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