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Thermodynamics? number crunching thermal conductivity

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fastline
#1
Feb5-14, 05:56 PM
P: 24
I am working on some basic calcs for heat transfer from polyethylene pipe. My numbers are not working out right so I need a little refresher.

The PE pipe would have a TC of about .46 W/(m.*C). to get to BTU/(hr.ft.*F), I mult by .5779 to get .266.

Assuming 10sf of PE pipe, and lets say a dT of 10*F, how do I arrive at my BTU/hr? Wall thickness of piping is .120" but I am told that does not matter. IIRC, the unit is actualy per sf PER ft so I might actually divide by my thickness which gets me closer at around 2.22 BTU/hr/sf*F of pipe?
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Chestermiller
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Feb5-14, 06:50 PM
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Quote Quote by fastline View Post
I am working on some basic calcs for heat transfer from polyethylene pipe. My numbers are not working out right so I need a little refresher.

The PE pipe would have a TC of about .46 W/(m.*C). to get to BTU/(hr.ft.*F), I mult by .5779 to get .266.

Assuming 10sf of PE pipe, and lets say a dT of 10*F, how do I arrive at my BTU/hr? Wall thickness of piping is .120" but I am told that does not matter. IIRC, the unit is actualy per sf PER ft so I might actually divide by my thickness which gets me closer at around 2.22 BTU/hr/sf*F of pipe?
The formula for the heat load Q (BTU/hr) is:
[tex]Q=\frac{k}{d}ΔTA[/tex]
where d is the wall thickness.
fastline
#3
Feb5-14, 06:57 PM
P: 24
I guess I am second guessing the units here. Would you mind applying the math to my above figures? Would this indeed be

k=.266
d=.120

k/d = 2.22BTU?

Chestermiller
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Feb5-14, 09:49 PM
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Thermodynamics? number crunching thermal conductivity

Quote Quote by fastline View Post
I guess I am second guessing the units here. Would you mind applying the math to my above figures? Would this indeed be

k=.266
d=.120

k/d = 2.22BTU?
You need to use d expressed in feet. How many inches are there in 1 ft?


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