Heat and Mass Transfer
A steam pipe is to be insulated by two insulating materials put over each other. For best results

Better insulation should be put over pipe and better one over it
Both may be put in any order
Inferior insulation should be put over pipe and better one over it
Whether to put inferior OIL over pipe or the better one would depend on steam temperature

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Heat and Mass Transfer
The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity)

Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁)
Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)]
Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁)
Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)

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