A certain body at 20C is displayed on a top of a building during the night. The body sees nothing but the sky which has an effective temperature of 110K. Determine the heat transfer rate from the body to the sky if the body temperature is maintained at 23C, the surface emissivity of the body is equal to 0.92, and none of the radiation going out of the comes back

A certain body at 20C is displayed on a top of a building during the night. The body sees nothing but the sky which has an effective temperature of 110K. Determine the heat transfer rate from the body to the sky if the body temperature is maintained at 23C, the surface emissivity of the body is equal to 0.92, and none of the radiation going out of the comes back

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 1.47P: 1.47 A flat roof is modeled as a flat plate insulated on the bottom and placed in the sunlight. If...

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1.25 A spherical vessel, 0.3 m in diameter, is located in a large room whose walls are at 27°C (see sketch). If the vessel is used to store liquid oxygen at –183°C and both the surface of the storage vessel and the walls of the room are black, calculate the rate of heat transfer by radiation to the liquid oxygen in watts and in Btu/h.
Determine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.
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 .
11.41 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.
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.
1.47 A flat roof is modeled as a flat plate insulated on the bottom and placed in the sunlight. If the radiant heat that the roof receives from the sun is , the convection heat transfer coefficient between the roof and the air is 12 W/m2 K, and the air temperature is , determine the roof temperature for the following two cases: (a) Radiative heat loss to space is negligible, (b) The roof is black and radiates to space, which is assumed to be a black- body at 0 K.
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 long wire 0.7 mm in diameter with an emissivity of 0.9 is placed in a large quiescent air space at 270 K. If the wire is at 800 K, calculate the net rate of heat loss. Discuss your assumptions.
a certain body at 20 C is display on a top of a building during the night. the body sees nothing but the sky which has effective temperature of 110 k. determine the heat transfer rate from the body to the sky if the body temperature is maintained at 23 C. the surface to the sky emissivity of the body is equal to 0.92
Two parallel plates 0.5 m by 1.0 m are spaced 150 mm apart. One plate is maintained at 1,000 C and the other at 500 C. The emissivities of the plates are 0.20 and 0.50, respectively. The plates exchange heat with each other and only the plate surfaces facing each other are to be considered in the analysis. Find the net heat transfer rate to each other. Neglect other modes of heat transfer (conduction and convection). View Factor is based on the case shown below:
A thin square steel plate, 10 cm on the side, is heated in a blacksmiths forge to a temperature of 800°C. if the emissivity is 0.60, what is the total rate of radiation of energy in Watts?
Earth absorbs solar energy and radiates infrared energy. The intensity of the solar radiation incident on earth is J = 1350 Wm-2, also known as the solar constant. Assume earth’s surface (ground) temperature to be uniform at Ts, and that the ground and atmosphere are black (emissivity = 1) for infrared radiation. The radius of the earth is 6.378 x 106 m. The diagram shows the ground at the surface temperature Ts and the atmosphere, represented as a thin black layer, at temperature Ta . Suppose the atmosphere absorbs 100% of the infrared radiation emitted by the ground. Assume that the ground absorbs 47.5% of the incident solar energy, and that the atmosphere absorbs 17.5% of the incident solar energy (for a total of 65% absorbed by the planet). Calculate the "steady state” numerical values of the earth’s ground temperature Ts and the atmospheric temperature Ta taking into account the “greenhouse effect” of atmospheric infrared absorption and emission described above.