Heat Loss from PVC Pipe 1

[dxla]

How can I determine the heat loss from 2" PVC pipe (carrying H2SO4)at 100 deg F to the ambient air (assume 85 deg F) ? There is no wind and pipe length is 4265 ft. Is there any software available ?

thanks in advance

 

[TD2K]

Kern (page 215) for horizontal pipes gives the external film coefficent of 0.50 * (dT/do)^0.25 for the convective heat loss coefficient (US customary units, dT deg F, do inches, hc BTU/hrft2F). Don't forget to include the radation heat loss.

You said there is no wind so that is not an issue.

I'd first assume the temperature drop through the PVC pipe wall can be neglected.

Calculate Q using the outside film coefficent and radiation coefficient. Calculate the inside film coefficient for the acid and see if it's much larger than the outside coefficient. If it is, you can neglect it. If not, you really need to think about setting up a spreadsheet to do these calculations.

You now have a worse case Q based just on air loss coefficient, the area of the pipe and a 15F temperature drop. Check to see if this heat loss results in a dT drop across the pipe wall you need to take into account or if you can neglect it (my guess is that you can neglect it but I've not done calculations with PVC piping).

Also, if the heat loss (that you've calculated as a first past estimate assuming a constant acid temperature) results in a significant drop in the acid temperature at the end of your pipe, that needs to be factored into your spreadsheet. If that's the case, split the pipe up into short enough sections where the acid temperature change can be neglected for the Q loss for that section.

Basically, you'd start off with the first 100' section of pipe (or whatever length you want). Calculate the overall heat loss coefficient using the outside film coefficient, the thermal conducitivity and thickness of your pipe and the inside film coefficient. Calcalate Q over that 100' and calculate the dT of the acid.

Use 85F - dT just calculated to come up with an acid temperature for the next section to do the Q calculations for.

At the end of it, you have the arrival temperature of the acid.

For the second part of your question, one program I know that does this is Pipephase (not sure if acid is in its database), not sure what others ones are out there.

 

[stanier]

I would not neglect the dT across the pipe wall. You could consider it as a layer of insulation.

If you want software look at AFT's Fathom. This enable complex heat transfer analysis as well as fluid flow.

 

[CEM1]

Try

http://www.pipeinsulation.org/