Frictionless Calc

Pipe Insulation Calculator

Estimate heat loss or gain, insulation surface temperature, and the effect of insulation thickness.

1. Pipe and insulation

Model a uniform layer around a pipe held at a known outer-wall temperature.

Use actual outside diameter, not nominal pipe size.

Temperature at the pipe/insulation interface. Fluid temperature is only an approximation when internal film and pipe-wall drops are negligible.

Use manufacturer data at the mean insulation temperature. The example value is not a material specification.

Enter convection alone, or an effective convection + radiation coefficient if air and radiant surroundings are at the same temperature.

2. Heat-transfer results

Enter inputs and calculate.

Insulation around a pipeCross section with pipe outside radius r1 and insulation outside radius r2. Insulation thickness equals r2 minus r1.r₁r₂Insulationt = r₂ − r₁Pipe wallAmbient airCross section · not to scale

Calculation method

r₁ = pipe OD / 2; r₂ = r₁ + thickness
R′ins = ln(r₂/r₁) / (2πk)
R′surface = 1 / (2πr₂h)
q′ = (Tpipe − Tambient) / (R′ins + R′surface)
Tsurface = Tambient + q′ R′surface
Q = q′ L

Resistances per unit length are in m·K/W, q′ is W/m, and Q is W. At zero insulation thickness, the model reduces to the bare-pipe surface resistance.

Steady, one-dimensional radial conduction with uniform properties and full circumferential coverage. The entered pipe outer-wall temperature is fixed. Internal convection and pipe-wall resistance are not included. Neither are supports, valves, seams, wet insulation, solar heating, axial cooling, or end losses. Radiation is included only if you supply a suitable combined surface coefficient; the calculator does not calculate that coefficient.

The critical insulation radius is k/h for this constant-coefficient model. On sufficiently small pipes, adding a thin layer can increase heat transfer. A negative savings result is therefore possible. Surface temperature alone does not establish burn protection or condensation control.

Check the reported mean insulation temperature against your conductivity data. Actual conductivity and external heat transfer vary with temperature and installation conditions. For a planar stack, use Multi-Layer Heat Transfer.

References