# Thermodynamics? number crunching thermal conductivity

by fastline
Tags: conductivity, crunching, number, thermal, thermodynamics
 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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PF Gold
P: 4,403
 Quote by fastline 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:
$$Q=\frac{k}{d}ΔTA$$
where d is the wall thickness.
 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?
HW Helper
Thanks
PF Gold
P: 4,403

## Thermodynamics? number crunching thermal conductivity

 Quote by fastline 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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