Thermodynamics: An Engineering Approach
9th Edition
ISBN: 9781259822674
Author: Yunus A. Cengel Dr., Michael A. Boles
Publisher: McGraw-Hill Education
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Chapter 2.8, Problem 105P
The outer surface of a spacecraft in space has an emissivity of 0.6 and an absorptivity of 0.2 for solar radiation. If solar radiation is incident on the spacecraft at a rate of 1000 W/m2, determine the surface temperature of the spacecraft when the radiation emitted equals the solar energy absorbed.
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A wood stove is used to heat a single room. The stove is cylindrical in shape, with a diameter of 26 cm and a length of 52 cm, and operates at a temperature of 490°F. If the temperature of the room is 60°F, and if the emissivity is 0.844, then
Calculate, the amount of radiant energy delivered to the room by the stove each second (KW)
Answer
Consider a room whose door and windows are tightly closed, and whose walls are well-insulated so that heat loss or gain through the walls is negligible.
The interior surface of a 25 cm thick wall has a temperature of 27 \deg C as shown in the figure. The outer surface is exposed to a solar radiation of 150 W/m^2 and exchanges heat by radiation and convection with the surroundings and the air that are at the same temperature of 40 \deg C. The coefficient of heat transfer by convection is 8 W/m^2* K, consider both the absorptivity (\alpha ) and emissivity (\epsi equal to 0.8. Assuming transfer of 1D heat and at steady state, determine the surface temperature outside and the heat flow by conduction in the wall in three conditions different: a) If the wall is made of brick (k=0.72 W/m*K) b) If the wall is made of wood (k=0.17 W/m*K) c) If the wall is made of rigid foam (polyurethane) (k=0.026 W/m*KMake a diagram of the corresponding thermal resistance circuit and a diagram of the variation of temperatures from the interior wall to the air abroad.
Chapter 2 Solutions
Thermodynamics: An Engineering Approach
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