Work out pipe insulation thickness instantly with clear inputs, formula shown and shareable results.
Heat flow through pipe insulation is a cylindrical conduction problem in series with an outside air film. The conduction resistance is ln(r2/r1) / (2 pi k) per foot and the film resistance is 1 / (h x 2 pi r2), so heat loss is the temperature difference divided by their sum. The same result gives the jacket surface temperature, which is the personnel-protection criterion.
Cylindrical heat loss
q = ΔT / [ln(r2/r1) / (2 pi k) + 1 / (h x 2 pi r2)] per foot
Surface temperature
Ts = ambient + q x film resistance
Preliminary estimate only. Verify insulation thickness against the applicable energy code tables and the manufacturer's tested conductivity at operating temperature.
q = ΔT / [ln(r2/r1) / (2 pi k) + 1 / (h x 2 pi r2)] per foot. Heat flow through pipe insulation is a cylindrical conduction problem in series with an outside air film.
Returns diminish quickly because resistance grows with the logarithm of the radius ratio. On small pipes there is also a critical radius below which added insulation increases loss by enlarging the outer surface.
This calculator takes 4 inputs: Pipe outside diameter, Insulation thickness, Fluid temperature, Insulation conductivity. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.