A small surface of area A1 = 5 cm? emits radiation as a blackbody, and part of the radiation emitted by A1 strikes another small surface of area A = 8 cm? oriented as shown in Fig. 4. If the rate at which radiation em itted by Ai that strikes Aa is measured to be 274 x 106 w, determine i the intensity of the radiation emitted by A1, and ii the temperature of A1. i. Az = 8 cm? 02 = 40°| 0, = 55° r=80 cm A = 5 cm? Fig 4

A small surface of area A1 = 5 cm? emits radiation as a blackbody, and part of the radiation emitted by A1 strikes another small surface of area A = 8 cm? oriented as shown in Fig. 4. If the rate at which radiation em itted by Ai that strikes Aa is measured to be 274 x 106 w, determine i the intensity of the radiation emitted by A1, and ii the temperature of A1. i. Az = 8 cm? 02 = 40°| 0, = 55° r=80 cm A = 5 cm? Fig 4

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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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.
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.
1.28 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.
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.
7. The emissive power of a blackbody, at 0.8 µm wavelength is measured as 1E5 W/m², µm. Find the blackbody temperature. [Ans. 1739 K]