Pipe Insulation Heat Loss Calculator
How much heat does this pipe lose, and how much does insulation save?
Single calculationv1.0.0Verified 2026-11-01Runs in your browser
Spec sheet
cylinder_conduction_natural_convection · v1.0.0Method
Cylindrical conduction + Churchill–Chu natural convection + grey-body radiation
- 01
R_ins = ln(D_o/D_p) / (2π k) per metre (ht.R_cylinder) - 02
Nu = [0.60 + 0.387 Ra^(1/6) / (1 + (0.559/Pr)^(9/16))^(8/27)]² (ht, Churchill–Chu) - 03
h_rad = ε σ (T_s² + T_a²)(T_s + T_a) - 04
Solve T_s: (T_p − T_s)/R_ins = (h_conv + h_rad) π D_o (T_s − T_a)
Limits — read before relying on it
- Indoor still air only (no wind); wind can multiply bare-pipe losses.
- Pipe wall and inside film resistances are neglected (pipe surface = fluid temperature), which slightly overstates bare-pipe loss.
- Constant insulation conductivity; real k rises with temperature — use the value at the mean insulation temperature.
- Not a personnel-protection or condensation-control design check.
Sources
- ht (MIT) — R_cylinder, Nu_horizontal_cylinder_Churchill_Chu, ported to TypeScript ↗library
- Churchill & Chu (1975), Int. J. Heat Mass Transfer 18, 1049–1053standard
- Air viscosity and conductivity by Sutherland's law (White, Viscous Fluid Flow)textbook