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NiCuZn · Black Owl — Engineering calculation sheet

Pipe insulation heat loss.

Estimate heat loss and surface temperature for an insulated pipe, the saving against bare pipe, and the annual energy lost.

Pipe and insulation
mm

114.3 mm is 4″ pipe.

mm
W/m·K

Mineral wool is roughly 0.035–0.05 at moderate temperatures; use the manufacturer’s value at the mean temperature.

W/m²·K

About 8–12 in still air including radiation; higher outdoors in wind.

Conditions
°C
°C
m
h/year

Results

Heat loss58.5 W/m
Surface temperature33.7 °C
Bare pipe heat loss557 W/m
Saving against bare pipe89.5 %
Annual loss over 100 m46.8 MWh/year
Annual loss if bare445.3 MWh/year

Preliminary estimate for early engineering. Check against your design basis, standards and vendor data.

Method

How it is calculated

Heat flows through the insulation layer and then from the outer surface to ambient, two resistances in series per metre of pipe:

Q / L = (Tprocess − Tambient) / ( ln(r₂ / r₁) / (2π k) + 1 / (2π r₂ h) )

The surface temperature follows from the heat flow through the outer resistance. The pipe wall and inner film resistances are neglected, which slightly overstates the loss. The bare-pipe comparison uses the same surface coefficient on the pipe outside diameter.

Thickness for personnel protection, condensation control or economics is usually set by company standards and insulation suppliers; this tool gives the first numbers.

All engineering tools →Size equipment from your own balance in Black Owl ↗

Calculated with the free engineering tools at nicuzn.com/tools. Preliminary estimate for early engineering; check against your design basis, applicable standards and vendor data before use.