A horizontal, opaque surface at a steady-state temperature of 77 ∘ C is exposed to an airflow having a free stream temperature of 27 ∘ C with a convection heat transfer coefficient of 28 W / m 2 ⋅ K . The emissive power of the surface is 628 W / m 2 , the irradiation is 1380 W / m 2 , and the reflectivity is 0.40. Determine the absorptivity of the surface. Determine the net radiation heat transfer rate for this surface. Is this heat transfer to the surface or from the surface? Determine the combined heat transfer rate for the surface. Is this heat transfer to the surface or from the surface?
A horizontal, opaque surface at a steady-state temperature of 77 ∘ C is exposed to an airflow having a free stream temperature of 27 ∘ C with a convection heat transfer coefficient of 28 W / m 2 ⋅ K . The emissive power of the surface is 628 W / m 2 , the irradiation is 1380 W / m 2 , and the reflectivity is 0.40. Determine the absorptivity of the surface. Determine the net radiation heat transfer rate for this surface. Is this heat transfer to the surface or from the surface? Determine the combined heat transfer rate for the surface. Is this heat transfer to the surface or from the surface?
Solution Summary: The author calculates the energy balance equation as per the incident radiation on a surface.
A horizontal, opaque surface at a steady-state temperature of
77
∘
C
is exposed to an airflow having a free stream temperature of
27
∘
C
with a convection heat transfer coefficient of
28
W
/
m
2
⋅
K
. The emissive power of the surface is
628
W
/
m
2
, the irradiation is
1380
W
/
m
2
, and the reflectivity is 0.40. Determine the absorptivity of the surface. Determine the net radiation heat transfer rate for this surface. Is this heat transfer to the surface or from the surface? Determine the combined heat transfer rate for the surface. Is this heat transfer to the surface or from the surface?
A furnace has the shape of a cylinder and has R = H = 2m as its dimensions. The temperatures on the base, top, and side surfaces of the furnace are kept constant at 500, 700, and 1200 K accordingly. All three surfaces are black. Determine the net rate of radiation heat transfer from or to the top surface when the system is operating at a steady state.
2. A thin aluminum sheet with an emissivity of 0.15 on both sides is placed between two very large parallel plates, which are maintained at uniform temperatures T1 = 900 K and T2 = 650 K and have emissivities ?1 = 0.5 and ?2 = 0.8, respectively. Determine the net rate of radiation heat transfer between two plates per unit surface area of the plates and compare the result with that without the shield
Two parallel planes measuring 1.2 x 1.2 m apart by a distance of 4 cm. The emissivities of the planes are 0.4 and 0.6 respectively and the temperatures are 760 and 300oC, respectively. A radiation shield measuring 1.2 x 1.2 m and having an emissivity of 0.05 and a temperature of 500oC is placed midway between the two planes. Calculate the heat transfer rate of the two planes if there is no shield!
INTERNATIONAL EDITION---Engineering Mechanics: Statics, 14th edition (SI unit)
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