A small circular surface of area A1=2 cm2located at the center of a 2-m-diameter sphere emits radiation as a blackbody at T1= 1000 K. Determine the rate at which radiation energy is streaming through a D2=1-cm-diameter hole located (a) on top of the sphere directly aboveA1and (b) on the side of the sphere such that the line that connects the centres of A1 and A2 makes 45° with surface A1. (c) Repeat it for a 4-m diameter sphere.

A small circular surface of area A1=2 cm2located at the center of a 2-m-diameter sphere emits radiation as a blackbody at T1= 1000 K. Determine the rate at which radiation energy is streaming through a D2=1-cm-diameter hole located (a) on top of the sphere directly aboveA1and (b) on the side of the sphere such that the line that connects the centres of A1 and A2 makes 45° with surface A1. (c) Repeat it for a 4-m diameter sphere.

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.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.44P

See similar textbooks

Similar questions

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.
11.31 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.
Determine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.
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.
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.
Consider a 20-cm-diameter spherical ball at 800 K suspended in air. Assuming the ball closely approximates a blackbody, determine (a) the total blackbody emissive power, (b) the total amount of radiation emitted by the ball in 5 min, and (c) the spectral blackbody emissive power at a wavelength of 3 mm.
Daylight may be approximated as a blackbody at the effective surface temperature of 5800 K. Determinethe fraction of radiation emitted that falls in the UV (0.1 – 0.4 μm) and visible (0.4 – 0.76 μm) region.(Ans: 0.1245, 0.4243)