Pipe Heat Loss Calculator

Steady-state convection and radiation from horizontal or vertical bare and insulated cylindrical pipework in air.

Design inputs

Unit system

Actual pipe outside diametermm — actual OD, not nominal bore

Common OD preset

Pipe lengthm

Orientation

Temperature basis

Pipe surface / fluid temperature°C

Ambient air temperature°C

Mean radiant surroundings°C

Air movement

Air velocitym/s; required for forced convection

Pipe material

External surface finish

Editable emissivityIndicative default; must be >0 and ≤1

Insulation

Insulation preset

Insulation thicknessmm

Thermal conductivityW/m·K

Fluid temperature is only a close bare-pipe surface approximation for highly conductive metallic pipe when internal film and wall resistances are small. Those resistances are not included.

Result

Total heat transfer——

Total for entered length—

Convection—

Radiation—

Outer surface temperature—

Convection coefficient—

Equivalent radiation coefficient—

Overall external coefficient—

Insulation resistance—

Insulation outside diameter—

Compare surface finishes

Finish	Conv.	Rad.	Total	vs baseline

Calculation method and limitations

Steady-state SI calculation. Radiation is evaluated directly using the Stefan–Boltzmann fourth-power relation. Horizontal natural convection uses Churchill–Chu’s all-range cylinder correlation; vertical pipework uses the Churchill–Chu vertical-surface form with pipe length as characteristic height. Forced crossflow uses Churchill–Bernstein. Natural and forced coefficients are combined by the cubic mixed-convection method. Air properties are evaluated at film temperature. Insulated surface temperature is solved by bisection so cylindrical conduction balances convection plus radiation.

Emissivities are indicative and can change materially with oxidation, dirt, paint, moisture and ageing. A silver colour is not inherently low-emissivity: the low value applies only to a clean bright metallic foil. Results exclude internal film resistance, detailed pipe-wall resistance, fittings, valves, supports, adjacent surfaces, enclosures and local currents. Independently check results before equipment selection or contractual use. No claim of BS 5422 or BS EN ISO 12241 compliance is made.