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Exhaust pipe and cable tray temperature calculation? 1

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Mohamed.Shehab

Mohamed.Shehab

Mechanical
Joined
Jan 22, 2020
Messages
7
Location
AU
Gents,
Need Help,
we have a 6`` Exhaust pipe close to a cable tray, 150 mm top of the cable tray, the max exhaust temperature is 600 C, how can I calculate the temperature at the cables
 
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kindly advise what information needed, the pipe is uninsulated stainless steel
 
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How wide is the tray, etc. A drawing would be good. What is ambient temperature, A/C, etc.

A heat transfer problem usually involves ALL the relevant geometries, and you gave barely two.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Steel is 4 mm thick, No A/C only ventilation fans in the pump room, what I need to know/calculate is the temperature at the cable surface, think the cable insulation not really needed.
 
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The cable won't get much hotter than the temperature the sprinkler head is designed for.
 
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The primary mode of heat transfer will be radiation at 600 dC. So get you heat transfer textbook and apply the knowledge that you learned from that course. Forget the effects of convection on top of the cable tray.
Personally, I would forgo the heat transfer calculations as you have to determine a value for the view factor in the radiative heat transfer equation. On the other hand I would explore the installation of concave metal shields half way between the exhaust pipe and the cable tray. That concave metal shields would extend about a foot on both sides of the strut that supports the tray and the exhaust pipes. I would not suspend the concave metal shields from the exhaust pipes and I would not have a perforated shield either due to radiation leakage thru the perforation (unless one perforated shield is inside another perforated shield with their holes staggered and both shields are not in intimate contact). The shields will not get hot as there should be enough convection around them--- they'll be warm, though. The shape of the concave metal shields should provide only partial coverage of the exhaust pipes as you don't want the effect of convection around the exhaust pipes to be too diminished.
 
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Assuming the OP has the skills to do this radiant heat transfer calc, the key info on the view factor between the semi infinite length of vertical exhaust pipe and the horizontal plane of the cables is required - I dont see this info in Perry Chem Engg Handbook.
 
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You need to know the cable insulation to determine the emissivity of the cables, which will help get you the temperature at the cable surface.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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I found the references dealing with view(shape) factors for the concave protective metal shields that I mentioned in my original reply. The problem is that You have not identified which exhaust pipe in your picture gets to have a surface temperature at 600dC.
 
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If this is an existing and operational installation, can't you just stick a temperature probe up there or shoot the cables with an IR camera?
 
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