An opaque surface with the prescribed spectral, hemispherical reflectivity distribution is subject to the spectral irradiation shown. Find: 1.0 600 0.5 0 05 10 15 λ (μm) G₂(W/m²•μm) 300 0 0 5 10 15 20 20 λ (μm) (1) Find the spectral absorptivity distribution (αλ). (2) Determine the total irradiation G on the surface (3) Determine the radiant flux that is absorbed by the surface. (4) The total absorptivity a.

An opaque surface with the prescribed spectral, hemispherical reflectivity distribution is subject to the spectral irradiation shown. Find: 1.0 600 0.5 0 05 10 15 λ (μm) G₂(W/m²•μm) 300 0 0 5 10 15 20 20 λ (μm) (1) Find the spectral absorptivity distribution (αλ). (2) Determine the total irradiation G on the surface (3) Determine the radiant flux that is absorbed by the surface. (4) The total absorptivity a.

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.
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.
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.
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. G₁ 1.0 P₁ 0 5 10 15 λ(um) (a) Determine the total irradiation on the surface, in W/m². G = W/m² (b) Determine the radiant flux that is absorbed by the surface, in W/m². Gabs = i W/m² (c) What is the total, hemispherical absorptivity of this surface? α = i G₂(W/m².μm) 5 10 15 20 λ (um)
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)
Spectral hemispherical reflectivity distribution of an opaque surface is shown below. Surface is subjected to the spectral iradiation as shown. 1.0 400 a 0.4 200 10 15 0. 5 10 15 20 2 (um) 2 (um) Calculate the total irradiation on the surface in W/m2 Calculate the irradiation absorbed by the surface in W/m2 5750 6250 7500 3750 4250 5000 3250 1850 2000 1750 1600 1200 1400
A typical car's exterior consists of a thin layer of silica (SiO2) over an opaque painted metal panel. Silica is transparent in the visible wavelengths but offers high reflectance in the near- to mid- infrared wavelengths. The plot on the next page depicts the diffuse spectral reflectivity (pa) of the car's surface: Spectral reflectivity, P₂ 0.8 0.6 0.4 ལ 0.2 0 0.1 1 1 10 Wavelength, λ(μm) 100 If the car's exterior temperature is T₁ = 77°C, determine both the total absorptivity (a) and the total emissivity (a) of the silica-covered panel. Assume that the Sun's temperature is Tsun = 5800 K.
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.
Wien's law is stated as follows: AmT = C, where C is 2898 μmK and Am is the wavelength at which the emissive power of a black body is maximum for a given temperature T. The spectral hemispherical emissivity (Ex) of a surface is shown in the figure below (1Å= 10-¹0m). The temperature at which the total hemispherical emissivity will be highest is K (round off to the nearest integer). Ext n 5000 6000 7000 (A)
The spectral hemispherical absorptivity and irradiation profiles for an opaque surface are shown in the figure. Find the total hemispherical absorptivity.