Overall heat loss pipes

[LaughingGearhead]

Hello all,

I am interested in calculating heat loss in insulated/uninsulated pipes. There are a few infos I found on the net. Some of it seems quite simple, like this one here:

https://www.engineeringtoolbox.com/conductive-heat-loss-cylinder-pipe-d_1487.html

And more complicated calculations like this:

https://cheguide.com/heat_loss_insulation.html

My question now would be. What to go for to have a result that comes close to the reality?

regards

 

[GBTorpenhow]

First method is simple radial conduction through the pipe/insulation layers. To use this you need to know or assume the pipe/insulation surface and ID temperatures.

Second method incorporates convection and radiation transfer, and will be more accurate in the sense that all the relevant convection and radiation coefficients are accounted for, with the inputs being easily measured ambient conditions and bulk fluid properties.

Simulating reality is not usually the interest of real life engineering applications. The goal of these calculations is usually to determine worst case heat loss and/or design insulation for the piping system in question. In practice, something closer to the second method is used. Often the bulk fluid temperature is taken as the pipe ID temperature by assuming that the internal convection coefficient is very large compared to the conduction and external convection/radiation coefficients.

ASTM C680 standardizes the computational approach to this problem. If interested in playing with it yourself, 3E Plus is a free software tool created by the insulation industry trade group NAIMA that utilizes the ASTM C680 method.

 

[IRstuff]

The first link shows an incomplete problem, since it does not include how the heat gets from the surface of the pipe into the environment. The second link shows a complete solution, which you can ostensibly derive, based on conservation of energy through each thermal interface, starting with the heat convection from the fluid to the inside wall of the pipe, to the convection and radiation from the outer surface of the insulation. Not sure why they factored the D_3 term the way they did; it seems to obscure the physics a bit, since the last factor has no diameter associated with it.

TTFN (ta ta for now)
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[pierreick]

Hi,
Consider this resource to support your work.
Pierre