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

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
Better insulation should be put over pipe and better one over it
Both may be put in any order

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Heat and Mass Transfer
The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit)

tm = loge (Δt1 - Δt2)/ Δt1/Δt2
tm = loge (Δt1/Δt2)/ (Δt1 - Δt2)
tm = (Δt1 - Δt2)/ loge (Δt1/Δt2)
tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2)

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Heat and Mass Transfer
Film coefficient is defined as Inside diameter of tube

Equivalent thickness of film
Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
Thermal conductivity Equivalent thickness of film Specific heat × Viscosity
Film coefficient × Inside diameter Thermal conductivity

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