Temperature inside an enclosure

[vtmike]

Hi,

I have a setup with a hollow steel pipe and a heat source attached to it on its outer surface. The hollow steel pipe has another pipe centralized inside it & it is also sealed off from both ends. A heat flux is provided on the outer surface of the outer pipe to raise its temperature to 200 F.

If I understand this correct, the heat will be transferred to the ID of the outer tube by conduction and then the ID of the outer tube will radiate heat onto the inner tube. Also natural convection will keep the air moving and mixing.

Now, is it possible that the radiation and convection effects can raise the temperature of the inner tube above 200 F? If yes, then what is the driving cause for this? The radiation effects or maybe a rise in pressure due to heat?

Thanks,
Mike

 

[ginsoakedboy]

That wouldn't happen. Make sure that you don't have another heat source.

What are the ends like? How is the centralization achieved?

 

[vtmike]

Well the inner tube has a connection to the outer tube. This connection is used to centralize the inner tube. So, there is a conduction path from the outer tube to the inner tube. But, that should not increase the temp beyond 200 F.

This actually happened during our test. The inner tube temp was actually greater (210 F) than the outside tube temperature (200 F). I can't imagine what would cause this.

 

[ginsoakedboy]

Don't think that I am patronizing you, but have you made sure that your thermocouples are all working and their calibration is up-to-date?

Do you have any fluid with sharp variations in velocity flowing in the inner tube?

 

[IRstuff]

Then, you either are measuring the wrong thing, measuring the right thing with a bad instrument, or you have additional heat sources.

You can ask the same question however you want, but the result is the same; you cannot get something hotter that your source using passive means.

If you can repeatably do this, you need to patent it and sell it as a perpetual power source.

TTFN

FAQ731-376

 

[ginsoakedboy]

Another thing could be that you have a heat flux source, and not a constant temperature source. Now someone may have erroneously informed you that the heat source will maintain a constant temperature. You may wanna check that assumption too.

Did you mount TCs on outer pipe? Or, the temp on outer pipe was based on hearsay and assumptions based on experience or something?

Where was the test conducted? In shade, during a rain, in bright sunlight? Look at everything.

In short, IRstuff is right.