huangyhg

heat dissipation - thermo problem
we have a very hot 12" diameter pipe (960 deg f) supported by the steel structure. is there a way to determine the heat dissipation or how long the supporting steel has to be to avoid heating the structural steel.
thanks

yes, but there are many variables, such as ambient temperature, wind speed, orientation of the supporting steel (vertical? horizontal?), paint (if any), type of connections, and more. imho, time to call a mechanical engineer.
sliderule is right..
but you can pick up an infra-red thermometer at radio shack or grainger, mcmaster etc for less than $100 that will tell what the temps really are. they say they are accurate to within a few degrees.
this is for an "emergency generator" exhaust that will not be installed or tested till later when the structure is up.
thank you
your supports can be a very important link and they can be made from appropriate materials. i suspect they may be sliding supports for 12" @ 960f if the length is substantial. - just the reverse of cryogentic piping.
if it is a hot exhaust gas a me should be able to get suggestions from the generator supplier based on similat installations.
thanks for the info.
fyi - the horizontal run is not a problem because it can be supported outside of the insulation (4" high density). however, the 10 floor riser has to be supported with some type of steel
you might also consider using a thermal break. we've provided an end plate moment connection in a beam with a korolath shim between the end plates to act as a thermal break.
do the bolts go through the korolath?
i had a similar project where i used steel pipe as my exhaust stack, which in turn was supported by a concrete wall. internet searches indicated that steel at 1000f has about half the strength of steel at room temp. i took this into account when calculating the stresses in the stack (dead, wind, seismic) as well as at the steel supports. but in my case the steel supports were attached to a concrete wall. it appears that you are attaching to a steel structure and are wondering if enough heat will dissipate in the stack & supports to prevent your structure from heating up and weakening? this is a heat transfer problem, not a thermo one. my heat transfer is too rusty to help you, but you may wish to transfer this post to the heat transfer section of the mechanical engineering forum. someone there should be able to help.
structural eit - what is "korrolath"?
yes, the bolts go through, but the amount of heat transfer through the bolts is nothing compared to the full section.
a korolate plate is a non-metallic pad (pad is a bit of a misnomer because it is pretty strong) that just takes bearing between the two end plates.

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