Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Chapter 11, Problem 11.3P
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
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determine the view factor, and the net heat transfer by radiation between two gray surfaces, A (εA= 0.88) and B (εB= 0.65) at temperatures 450°C and 50°C, respectively if d. surfaces A and B concentric cylindrical tubes with diameters of 400 mm and 200 mm, respectively e. both surfaces are discs of diameter 3 m one exactly above the other, 1 m apart
Determine the view factor between two gray surfaces A and B. Their emissivities are εA = 0.90 and εB = 0.25 at temperatures 450°C and 50°C, respectively, if (1) surfaces are infinite black parallel planes, (2) surfaces are infinite gray parallel planes, (3) surface A is a spherical shell 3 m in diameter and surface B is a similar shell concentric with A and 0.3 m in diameter, (4) surfaces A and B concentric cylindrical tubes with diameters of 300 mm and 275 mm, respectively, (5) both surfaces are discs with diameter 2 m one exactly above the other, 1 m apart.
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)
Chapter 11 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 11 - A tungsten filament is heated to 2700 K. At what...Ch. 11 - Determine the total average hemispherical...Ch. 11 - Prob. 11.4PCh. 11 - Prob. 11.9PCh. 11 -
11.31 A large slab of steel 0.1 m thick contains...Ch. 11 - Prob. 11.32PCh. 11 - 11.41 Determine the steady-state temperatures of...Ch. 11 - Three thin sheets of polished aluminum are placed...Ch. 11 - 11.68 Two infinitely large, black, plane surfaces...
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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_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_forward11.68 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_forward
- 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.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_forwardDetermine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.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_forwardConsider 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.arrow_forward
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