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# Heat Loss to free air pipeline

## Heat Loss to free air pipeline

(OP)
Hi everyone,

Probably I've done it before but it wasn't my best subject at the university.

At work I had a question about the heat loss of oil flowing through a pipeline in free air.

I have the following known parameters:
Type of oil
Mass flow
Starting temperature of the oil
Air temperature
Length, diameter and wall thickness of the pipeline.

I've found countless examples about heat exchangers but I'm struggling to find the temperature drop along a bare straight pipe without insulation with a fluid flowing through the pipe.
Can someone help me with this?

### RE: Heat Loss to free air pipeline

Did you bother to open up your heat transfer book?

### RE: Heat Loss to free air pipeline

(OP)
I'm sorry if I used 10 seconds of your time. I'll search furthur

### RE: Heat Loss to free air pipeline

I forgive you. But seriously, that should be the first place you look as it not a complex issue you are dealing with.

That said, many heat trace companies (Thermon, Raychem, etc.) have design guides that have tables to estimate watt/ft for heat loss calcs. You could use something like that to calculate temp in versus temp out at the end of the line.

### RE: Heat Loss to free air pipeline

straight forward natural convection problem (or forced convection with max wind).
Numerous online calculators for this. Also check insulation companies.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Heat Loss to free air pipeline

and numerous articles in engineering periodicals.

### RE: Heat Loss to free air pipeline

Velocity of the air will also be a key item to know about or assume. When you say "bare"do you really mean nothing? Even 2 or 3 mm of PE coating can make a surprising difference.

Try engineering toolbox.

https://www.engineeringtoolbox.com/heat-loss-bare-...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Heat Loss to free air pipeline

Heat transfer in this case will consist of a convective component and a radiative component. If the pipe is painted, surface emissivity would depend on the type of paint applied. Wind speed infuences the mode of convective heat loss, as does pipe orientation ( horizontal / vertical). You'll find procedures that account for all of these in most heat transfer texts.

If you need some quick rough values, look up Perry Chem Engg Handbook 7th edition, page 5-14, table 5-2.

### RE: Heat Loss to free air pipeline

Also bear in mind that as the temperature of the oil falls so does the heat loSs and therefore temp vs distance is a curve. Either segment the line or make sure your results show this curve.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Heat Loss to free air pipeline

(OP)
It is for pipelines in hydraulic systems. Most of the times, the pipelines our inside without any wind velocity but then I don't have to calculate the heat loss. But for a machine ( and probably more machines in the future) I want to make an excel template for these situations.

The only thing covering the pipeline is epoxypaint. No insulation because it's located at the harbour and it would be a risk to have corrotion.
If I finish the excel-template I will post it here

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