An opaque surface with the prescribed spectral, hemispherical reflectivity distribution is subjected to the spectral irradiation shown Assume that p₁ = 0.5 and G₁ = 650 W/m²-μm. 1.0 P₁ 5 10 15 λ (um) (a) Determine the total irradiation on the surface, in W/m². G = i W/m² (b) Determine the radiant flux that is absorbed by the surface, in W/m². Gabs W/m² (c) What is the total, hemispherical absorptivity of this surface? a = i G₂(W/m² μm) G₁ 5 10 15 20 λ (μη)

An opaque surface with the prescribed spectral, hemispherical reflectivity distribution is subjected to the spectral irradiation shown Assume that p₁ = 0.5 and G₁ = 650 W/m²-μm. 1.0 P₁ 5 10 15 λ (um) (a) Determine the total irradiation on the surface, in W/m². G = i W/m² (b) Determine the radiant flux that is absorbed by the surface, in W/m². Gabs W/m² (c) What is the total, hemispherical absorptivity of this surface? a = i G₂(W/m² μm) G₁ 5 10 15 20 λ (μη)

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter11: Heat Transfer By Radiation

Section: Chapter Questions

Problem 11.3P: Determine the total average hemispherical emissivity and the emissive power of a surface that has a...

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11.31 A large slab of steel 0.1 m thick contains a 0.1 -m-di- ameter circular hole whose axis is normal to the surface. Considering the sides of the hole to be black, specify the rate of radiative heat loss from the hole. The plate is at 811 K, and the surroundings are at 300 K.
11.68 Two infinitely large, black, plane surfaces are 0.3 m apart, and the space between them is filled by an isothermal gas mixture at 811 K and atmospheric pressure. The gas mixture consists of by volume. If one of the surfaces is maintained at 278 K and the other at 1390 K, calculate (a) the effective emissivity of the gas at its temperature, (b) the effective absorptivity of the gas to radiation from the 1390 K surface, (c) the effective absorptivity of the gas to radiation from the 278 K surface, and (d) the net rate of heat transfer to the gas per square meter of surface area.
Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 816C and 260C, respectively. Determine the rate of heat transfer by radiation between the plates in W/m2 and the radiative heat transfer coefficient in W/m2K.
Determine the total average hemispherical emissivity and the emissive power of a surface that has a spectral hemispherical emissivity of 0.8 at wavelengths less than 1.5m, 0.6 at wavelengths from 1.5to2.5m, and 0.4 at wavelengths longer than 2.5m. The surface temperature is 1111 K.
A tungsten filament is heated to 2700 K. At what wavelength is the maximum amount of radiation emitted? What fraction of the total energy is in the visible range (0.4to0.75m)? Assume that the filament radiates as a graybody.
Determine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.
11.41 Determine the steady-state temperatures of two radiation shields placed in the evacuated space between two infinite planes at temperatures of 555 K and 278 K. The emissivity of all surfaces is 0.8.
An opaque surface with the prescribed spectral, hemispherical reflectivity distribution is subjected to the spectral irradiation shown. Assume that p₁ = 0.5 and G₁ = 700 W/m².um. 1.0 P₁ 5 10 15 λ (um) (a) Determine the total irradiation on the surface, in W/m². G = i W/m² G₂ (W/m².um) (b) Determine the radiant flux that is absorbed by the surface, in W/m². W/m² Gabs i (c) What is the total, hemispherical absorptivity of this surface? α = i G₁ 10 5 10 15 20 λ (um)
Irradiation on a semi-transparent medium is at a rate of 640 W/m². If 160 W/m² of the irradiation is reflected from the medium and 130 W/m² is transmitted through the medium, 1) Determine the absorptivity of the medium. 2) Determine the reflectivity of the medium. 3) Determine the transmissivity of the medium.