Help finding insulation thickness needed for industrial furnace
Help finding insulation thickness needed for industrial furnace
(OP)
I'll start by saying I am on my first job since graduating, and it feels like forever since I took my heat transfer class, so I'm sitting here at my desk with 2 textbooks and still having trouble remembering how to do what feels like a fairly simple problem, haha.
My first assignment is to design a test furnace. The max temperature inside is 2000F, and the surface temperature on the outside needs to be less than 150F. I was wondering how to determine the insulation thickness needed to have the outside temp of 150F.
The equation if found was heat transfer rate, q = (T1 - T2)/[ (width of insulation/k insulation) + (width of steel wall/k steel wall) ]
I have the width and thermal conductivity, k, values for the outside steel walls, and my temperatures. I'm not really sure where to go from there, without the q value. I will have the k value for the insulation as soon as I decide on what I am using, I just needed help setting up the rest of the problem.
Like I said I feel like this is something I should easily know how to find, but it has been a while and I seem forgotten some of my heat transfer.
Thanks for the help
My first assignment is to design a test furnace. The max temperature inside is 2000F, and the surface temperature on the outside needs to be less than 150F. I was wondering how to determine the insulation thickness needed to have the outside temp of 150F.
The equation if found was heat transfer rate, q = (T1 - T2)/[ (width of insulation/k insulation) + (width of steel wall/k steel wall) ]
I have the width and thermal conductivity, k, values for the outside steel walls, and my temperatures. I'm not really sure where to go from there, without the q value. I will have the k value for the insulation as soon as I decide on what I am using, I just needed help setting up the rest of the problem.
Like I said I feel like this is something I should easily know how to find, but it has been a while and I seem forgotten some of my heat transfer.
Thanks for the help





RE: Help finding insulation thickness needed for industrial furnace
This gives you 333 W/m^2, by conservation of energy, that must be the same heat transferred through the insulation, so:
(333W/m^2)/(2000F-150F) = 0.324W/m^2-K That's the quantity that the insulation plus steel wall must provide.
You'll need to provide some sort of engineering margin, of course, since mileage may vary.
TTFN
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RE: Help finding insulation thickness needed for industrial furnace
Hence you need to work out what should be allowable heat loss through furnance wall & work backwards to calculate minimum thickness required.
Generally heat loss through furnance wall accounts for 10-15 % of total heat input of the furnace.
so calculate the total heat loss through furnace wall ( BTU/HR) = 0.15 (Worst case) x Total Heat Input of furnace.
once you found Q (heat loss through furnace wall) then calculate the Insulation thickness required.
RE: Help finding insulation thickness needed for industrial furnace
RE: Help finding insulation thickness needed for industrial furnace
IR is on the money with how you do this.
Or you find real furnaces and see what they used.
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Plymouth Tube
RE: Help finding insulation thickness needed for industrial furnace
Therefore, as indicated above, assume 15% "cost" of heat loss is industry standard. Don't make the insulation much thicker than that: unless the cost of your fuel goes down: Natural gas-fired furnace will be less expensive over time (now that fracking has increased supplies in most areas) compared to an electric-heated furnace.