Spectral hemispherical reflectivity distribution of an opaque surface is shown below. Surface is subjected to the spectral iradiation asshown.1.0400a 0.420010150.51015 202 (um)2 (um)Calculate the total irradiation on the surface in W/m2Calculate the irradiation absorbed by the surface in W/m25750625075003750425050003250185020001750160012001400

Total irradiation in surface, Gtotal = Area under irradiation curve Gtotal = A1+A2+A3 Gtotal…

Spectral hemispherical reflectivity distribution of an opaque surface is shown below. Surface is subjected to the spectral iradiation as shown. 1.0 400 ã 0.4 200 10 15 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 6250 7500 5750 3750 4250 5000 3250 001400 1600 1750 1850o 2000 5

Spectral hemispherical reflectivity distribution of an opaque surface is shown below. Surface is subjected to the spectral iradiation as shown. 1.0 400 ã 0.4 200 10 15 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 6250 7500 5750 3750 4250 5000 3250 001400 1600 1750 1850o 2000 5

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.28P: 1.28 The sun has a radius of and approximates a blackbody with a surface temperature of about 5800...

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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.
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 .
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.
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.
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.
1.28 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.
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.
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.
Spectral hemispherical reflectivity distribution of an opaque surface is shown below. Surface is subjected to the spectral irradiation as shown. 1.0 400 a 0.4 200 5 10 15 20 a (um) 5 10 15 2 (um) Calculate the total irradiation on the surface in W/m2 Calculate the irradiation absorbed by the surface in W/m2 3250 || 3750 || 4250|| 5000 || 5750|| 6250|| 7500 1050 || 1200 1400|| 1600|| 1750| 1850 || 2000
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.
! Required information 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, Determine the absorptivity of the medium. The absorptivity of the medium is 0.75 X