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| Teaching Since: | May 2017 |
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| Questions Answered: | 66690 |
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MCS,PHD
Argosy University/ Phoniex University/
Nov-2005 - Oct-2011
Professor
Phoniex University
Oct-2001 - Nov-2016
12.125Â Â
The neighborhood cat likes to sleep on the roof of our shed in the backyard. The roofing surface is weath- ered galvanized sheet metal (s = 0.65, aS = 0.8). Consider a cool spring day when the ambient air tem- perature is 10°C and the convection coefficient can
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be estimated from an empirical correlation of  the          Ts
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Plate
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1.0
0.7
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form
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h = 1.011T1/3, where 11T is the  difference
0.2
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between  the  surface  and  ambient  temperatures.
Assume the sky temperature is -40°C.
(a)Â Â Â Assuming the backside of the roof is well insu- lated, calculate the roof temperature when the
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Insulation
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Electrical heater
0
0Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2
l (mm)
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solar irradiation is 600 W/m2. Will the cat enjoy sleeping under these conditions?
(b)  Consider the case when the backside of the  roof is not insulated, but is exposed to ambient air with the same convection coefficient  relation and experiences radiation exchange with the ground, also at the ambient air temperature. Cal- culate the roof temperature and comment on whether the roof will be a comfortable place for the cat to snooze.
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