- #1
Karol
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Homework Statement
A vertical steam pipe of outside diameter 7.5 cm and height 4 m has its outer surface at the constant temperature of 950C. The surrounding air is at atmospheric pressure and at 200C.
How much heat is delivered to the air by natural convection in 1 hr?
Homework Equations
[tex]\mbox{The heat convection current H: }H=hA\,\Delta t[/tex]
[tex]\mbox{Coefficient of naural convection in air at atmospheric pressure for a vertical pipe (diameter D): }h=1.00\times10^{-4\left(\frac{\Delta t}{D}\right)^{1/4}}[/tex]
The Attempt at a Solution
[tex]h=1.00\times10^{-4\left(\frac{75}{7.5}\right)^{1/4}=0.00018[/tex]
[tex]H=0.00018\cdot\frac{\pi\cdot 7.5^2}{4}400\cdot 75=235.7\left[Cal/Sec\right]=848,469\left[Cal/hr\right][/tex]
The answer, according to the book, should be 454,000.
If this isn't the place for this subject, please guide me to another sight that deals with those kind of problems.