Looking at heat transfer the completely wrong way

[Plasmech]

I don't know what I was thinking...

During my recent calculations, I was worried about the thermal CONDUCTIVITY of my vessel wall, thinking, quite stupidly, that said wall would conduct heat away from the product at it's maximum rate, meaning that something on the outside skin of this wall would have to be taking that heat away at a VERY rapid rate, as IR had mentioned a large flow of chilled water or something.

What I should really do is NOT worry about the thermal conductivity of the wall material at all and instead worry about two things:

1. stopping convection

2. stopping radiation

I could make the vessel out of gold and, other than me getting fired, the ONLY thing that would happen assuming I had good convective and radiative blocks in place is: nothing.



-Plasmech

Mechanical Engineer, Plastics Industry

 

[IRstuff]

I wouldn't necessarily neglect conduction. There are supports, wires, etc., that cold away from cryosystems.

As general rule, you do want to start with a reasonable wall material, i.e., NOT aluminum or diamond, do the math on the convection and radiation and adjust as required. It's almost never a closed-form solution, and there are always plenty of iforgots.

TTFN

FAQ731-376

 

[Tunalover]

I've found that for large metal objects thicker than .19 inch the thermal conduction of the object is normally negligible when you have a high flux. One can usually say that the temperature is uniform through the metal at a given station away from the heat source. For a boiler one can says that the radial temperature distribution of any horizontal cross-section is simply a constant.




Tunalover