insulated pipe heat loss 3

[bencpv]

hi,

I wonder if anyone can help me.....

I have been tasked to find out the heat loss of buried insulated pipework. I have spent ages looking online for help in this and managed to find an equation (attached) that takes into consideration the service pipe, insulation, and jacket pipe.

In my efforts to find such an equation, I found other (more complex) equations that contain things like Reynolds number.... I think this will be too complex for what I need. I just would like something relatively simple, relatively accurate. Does anybody know of such an equation? Ideally one that considers flow and return pipes at x distance apart.

Now, going back to the attached example, I worked through this and expected to reach a result of 33.7 Btu/h lf. Instead I came up with the answer of 41.6 Btu/h lf! I would be grateful to hear if anyone can get 33.7.....and how! Where am I going wrong?!!!

Thank you in advance,

Ben

 

[IRstuff]

I thought you were asking why there were only 3 terms in the U1-U2 in the second set of calculations. Comparison with the first set shows that the two lowest resistances were dropped, presumably because they were negligible compared to the 2.979 mK/W term.

TTFN
faq731-376

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[bencpv]

ok, thanks for explanation.

In you opinion IRstuff, in theory I could take the method on the PDF (first example), plug in the appropriate values and and up with an approximate value for the heat loss? i.e. do the equation(s) look ok and does it match your MathCAD program?

I would like your opinion before venturing forth with this!

 

[IRstuff]

The equations are basically comparable, with the exception that these calculations involve two pipes, although some of the explanation of how the two heat loss coefficients are derived.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[bencpv]

Thank you IRstuff,

As the pipe work which our company supplies does (99% of the time) involve 2 pipes (flow and return), I shall use the equation shown in the first example of the PDF to obtain a figure for approximate heat loss.

I'll adjust the coefficients for different materials etc.

Thank you everyone, you have been most helpful.