Temperature rise of a 2.2 m diameter pipeline in the sun

[Citruskid]

Hi all, I'm new to this forum and I am a new chemical engineering graduate that has been practising for about a year now.

My boss wants me to work out the temperature rise per hour of a 2.2m diameter transfer pipeline. There is an aluminium shade covering the pipeline that is about 2cm thick and the shade "hugs" the shape of the pipe, where we have 5cm of air space between the pipe and the shade. The pipe is empty and it is a mild steel, concrete lined pipe. I have assumed an ambient temperature of 45'C (hot summer's day).

The reason for this calculation is for pipe stress analysis purposes.

I am having difficulty coming up with a reasonable answer for this problem. Any help would be greatly appreciated!

 

[Citruskid]

I forgot to add, would a pipeline this big typically get very hot especially if there is an aluminium shade over it that would reflect most of the heat?

The mild steel layer has a thickness of about 2cm and the concrete lining has a thickness about 2.5 cm (These values are just a guess, I am not sure what the thicknesses would typically be for a pipe of this size).

I don't think the pipe would get too hot, but I am having difficulty coming up with the number to prove this to my boss.

 

[BigInch]

Unshaded, above ground pipe temperatures in Saudi Arabia for an empty line in the sun can reach 60 to 75C.

Temperatures of full pipes with no flow would depend on the volume of fluid and its heat capacity, the diurnal heating and cooling cycle superimposed on the average temperature of the environment, either in winter or summer and the wind speed reaching the pipe, often nominally considered as 1 m/s

If the line was flowing, the heating or cooling affect of the fluid would have to be considered.

Offhand, I wouldn't think temperatures of a typical shaded pipeline would reach much more than highest ambient temperature + 5 C.



**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[FMJalink]

Citruskid,
In order to achieve an indication of the temperature rise per hour, you will have to put up a heat balance: Accumulation of heat (per time unit) = Input of heat (per time unit) – Loss of heat (per time unit).

You stated that the pipe is empty, ruling out the cooling effect of the contents, as air (assumption) in the pipe has only a very limited heat capacity. The accumulation is then only in the steel pipe and concrete lining. The heat transfer in the concrete lining will be slow compared to that of the steel piping.

As there is a sun shed covering the pipe, your subject appears to be in a sunny location. You can use sun radiation data of the location to determine heat input to the sunshade. Below the sunshade you will have to put up a radiation heat balance between sun shed and pipe.

The ambient temperature can have a heating and a cooling effect. If the ambient temperature is above the pipe temperature it will have a heating effect. With the ambient temperature and wind speed (both can vary significantly during a day) you can determine this heat input or heat loss.

 

[rconner]

Welcome to these forums. Wow, the preceding post sounds like some interesting (quite hairy?) calculations, and with assumptions maybe not for the timid!

I noticed however that the original inquiry stated, “There IS an aluminium shade covering the pipeline…” While what this literally says may well not be the case, there would appear to be an outside chance that this shade/pipeline (or one similar to it, in similar conditions?) may already be in existence. If so, maybe someone could take a laser thermometer (a sort of non-contact pyrometer), out there and fire it at different parts of the piping, perhaps in the shade and not, along with ambient (reading regular thermometer.ambient) at different times of the day? If none are available, it might be worthwhile to haul one (a pipe, and shade?) out there! [If and when this is done, I wouldn’t be a bit surprised however if you end up with readings basically in the range Mr. BigInch stated.] I suspect at least in the sun you may be able to “cook and egg on it” (let us know what you find)!



“One test result is worth one thousand expert opinions…” or,
“Basic research is what I’m doing when I don’t know what I’m doing.”
(I think both attributed to Wernher Von Braun)

 

[BigInch]

Or a regular oven stick-in-the-meat cooking thermometer.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[saplanti]

I agree with the reflection from the shiny surface. I attached three files in a zip file to show the surface colour effect on the heat transfer in the building materials.

If the surface exposed to the radiation, in the long term, the shiny surfaced -aluminium or stainles steel- material temperature will still raise until a heat balance occur because the emission of these materials is very low although the reflection is highest. Painting surface white gives the best solution due to the reasonable reflection and large heat emission. Some of you may say the graphs does not show this. Unfortunately, graphs are up to 15 minutes only.

In your case there is a gap between reflective surface and the mild steel pipe skin. Defenitely, I can say, the system is very effective to reduce the radiation heat effect. The only problem is the effectiveness of the gap between reflective aluminium and the pipe skin to allow the convective cooling by air. From my experience there are some LPG road tankers use the same method to keep the LPG contacted skin at below the design temperature 50 deg C. They are mainly in motion, however, some times they are motionless and they keep the surface temperature under the design temperature in hot climates as you have.

Everything may be depend on how large cover you can provide to reduce the exposed surface to the direct sun light.

Hope it helps.

Ibrahim Demir

 

[Citruskid]

Hey guys! Thanks for the replies, they were quite helpful. At the moment I was told to assume for a worst case scenario and hence to remove the aluminium cladding which means I have to put the radiative heat from the sun back into the equation. Where can I find reliable radiative heat transfer coefficient data based on geographical region? Can you guys recommend any books or references that may help me with this? At the moment I am tempted to buy some of this data from the local bureau of meteorology.

 

[SJones]

Google 'solar insolation maps' and then use the ASHRAE Handbook of Fundamentals, Chapter 4, to guide you in the calculation considerations, including values of the Steffan-Boltzmann constant.

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[SJones]

PS - You could always participate in this group

forum391

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04