Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 12, Problem 12.72P
Consider an opaque, diffuse surface whose spectral reflectivity varies with wavelength as shown. The surface is at 750 K, and irradiation on one side varies with wavelength as shown. The other side of the surface is insulated
What are the total absorptivity and emissivity of the surface? What is the net radiative heat flux to the surface?
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Chapter 12 Solutions
Fundamentals of Heat and Mass Transfer
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Ch. 12 - Determine the fraction of the total, hemispherical...Ch. 12 - The spectral distribution of the radiation emitted...Ch. 12 - Consider a 5-mm-square, diffuse surface A0 having...Ch. 12 - Assuming blackbody behavior, determine the...Ch. 12 - The dark surface of a ceramic stove top may be...Ch. 12 - The energy flux associated with solar radiation...Ch. 12 - A small flat plate is positioned just beyond the...Ch. 12 - A spherical aluminum shell of inside diameter D=2m...Ch. 12 - The extremely high temperatures needed to trigger...Ch. 12 - An enclosure has an inside area of 100m2 , and its...Ch. 12 - Assuming the earth’s surface is black, estimate...Ch. 12 - A proposed method for generating electricity from...Ch. 12 - Approximations to Planck’s law for the spectral...Ch. 12 - Estimate the wavelength corresponding to maximum...Ch. 12 - A furnace with a long, isothermal, graphite tube...Ch. 12 - Isothermal furnaces with small apertures...Ch. 12 - For materials A and B, whose spectral...Ch. 12 - 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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.arrow_forwardDetermine 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.arrow_forwardTwo 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.arrow_forward
- 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.arrow_forward1.28 The sun has a radius of and approximates a blackbody with a surface temperature of about 5800 K. Calculate the total rate of radiation from the sun and the emitted radiation flux per square meter of surface area.arrow_forward11.41 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.arrow_forward
- 1.26 Repeat Problem 1.25 but assume that the surface of the storage vessel has an absorbance (equal to the emittance) of 0.1. Then determine the rate of evaporation of the liquid oxygen in kilograms per second and pounds per hour, assuming that convection can be neglected. The heat of vaporization of oxygen at –183°C is .arrow_forwardAn 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)arrow_forwardWien'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)arrow_forward
- Pravinbhaiarrow_forwardas fast as.arrow_forwardAn 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)arrow_forward
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