# Thermodynamics? number crunching thermal conductivity

1. Feb 5, 2014

### 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?

2. Feb 5, 2014

### Staff: Mentor

The formula for the heat load Q (BTU/hr) is:
$$Q=\frac{k}{d}ΔTA$$
where d is the wall thickness.

3. Feb 5, 2014

### 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?

4. Feb 5, 2014

### Staff: Mentor

You need to use d expressed in feet. How many inches are there in 1 ft?