2. (a) i. Freshly painted flat panels are cured by placing them under a planer radiation source as shown in the diagram below. The panel and source may be approximated as blackbodies at temperatures of Tp = 227 °C and T, = 627 °C, respectively. The panel and source are of widths Wp= 300 mm and W, = 150 mm, very long (in the direction perpendicular to the paper). and are separated by a distance of L = 150mm. If the region between the panel and source is not enclosed, but is exposed to large surroundings at 27 °C, what is the rate at which electric power must be supplied to the radiation source per unit length? (a = 5.67 x 10* W/m² K*). Discuss the rational used to model the situation described in ure ii. question above and explain the assumptions made. sur 0.15 m Wp Figure Q 5(a) (b) i. Determine the shape factor F12, for the rectangles shown in the Figure Q 5(b) below. ii. Substantiate any additional areas used in the analysis. 1 m 0.5 m 2

2. (a) i. Freshly painted flat panels are cured by placing them under a planer radiation source as shown in the diagram below. The panel and source may be approximated as blackbodies at temperatures of Tp = 227 °C and T, = 627 °C, respectively. The panel and source are of widths Wp= 300 mm and W, = 150 mm, very long (in the direction perpendicular to the paper). and are separated by a distance of L = 150mm. If the region between the panel and source is not enclosed, but is exposed to large surroundings at 27 °C, what is the rate at which electric power must be supplied to the radiation source per unit length? (a = 5.67 x 10* W/m² K*). Discuss the rational used to model the situation described in ure ii. question above and explain the assumptions made. sur 0.15 m Wp Figure Q 5(a) (b) i. Determine the shape factor F12, for the rectangles shown in the Figure Q 5(b) below. ii. Substantiate any additional areas used in the analysis. 1 m 0.5 m 2

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.

Chapter11: Heat Transfer By Radiation

Section: Chapter Questions

Problem 11.13P

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Similar questions

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.
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.
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.
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.
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.
For a pair of blackbodies surrounded by an adiabatic wall and separated by vacuum, show if and that the net entropy increase
Example..6.1 A glass plate 30 cm square is used to view radiation from a furmace. The transmissivity of the glass A foom 0.2.03.5 jm, The emissivity may be assumed to be 0.3 up to 3.5 im and 0.9 above {hat. The tranamissivity of th glassis ero, except inthe range from 0.2 10 3.5 . Assuming that i furmace is a blackbody at 2000°C, calculate the energy absorbed in the glass and the energy transmitted.
Consider a cubic body 20 cm × 20 cm × 20 cm at 750 K suspended in air.Assuming that the body closely approximates a black body, determine (a) the ratio of thewhich the cube emits radiation energy, in W, and b) the spectral emission power of bodyblack at a wavelength of 4 mm.As =?Eb =?Ebλ =?