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Thermo Problem?
A steel pipe with the outside diameter of 0.15m carries steam at a temperature of 259 C is covered with two layers of 0.05 m thick, The thermal conductivities of the inner and outter layers are 0.082 and 0.054w/mK. The outer surface temp is 27C and there is no temp drop acorss the pipe
FIND : Heat loss per hour for a 40m pipe & find the interface temperaure
1 Answer
- ?Lv 74 years agoFavorite Answer
For each insulating layer, you have
Q = 2*pi*L*k*delta-T / ln(r2/r1).
Let "t" be the interface temperature. Then you have
(0.082 w/mK)(259 - t)/ln(0.20/0.15) = (0.054 w/mK)(t - 27)/ln(0.25/0.20).
You can use this to solve for "t," the interface temperature;
then go back to the "Q" equation above and put in L = 40m, as well as the k and the delta-T and the natural log for EITHER one of the two layers. I.e., the heat loss is the same for each layer, so it doesn't matter which layer you use in calculating the heat loss. Do note you'll multiply by 3600 s/hr to get to heat loss "per hour."
