Solve cylindrical heat transfer through pipe insulation. Choose units, coefficients, and materials for realistic results. Export CSV and PDF to share calculations confidently anywhere.
The calculator models steady, radial heat flow through a pipe wall and insulation, including convection on both sides. The heat loss is:
Once Q is known, temperatures at the boundaries follow from the cumulative drops across resistances:
Note: Radiation and axial conduction are not included here.
| Case | Thot (°C) | Tamb (°C) | Di (m) | tpipe (m) | tins (m) | kpipe (W/m·K) | kins (W/m·K) | hi (W/m²·K) | ho (W/m²·K) | L (m) | Q (W) | Q/L (W/m) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Example | 120 | 25 | 0.050 | 0.003 | 0.050 | 45 | 0.040 | 500 | 10 | 1 | 22.13 | 22.13 |
Your values may differ with material choice, thickness, and convection conditions.
Hot piping can waste surprising energy when left bare. As a rule of thumb, losses of 10–60 W/m are common in plant rooms, so 100 m of pipe can represent 1–6 kW of continuous load.
The calculation treats heat flow as a series of thermal resistances: convection at the inner fluid film, radial conduction through the pipe wall and insulation, then outer convection to ambient air. Radial conduction follows the cylindrical ln(r2/r1) relationship.
Temperature difference drives the load, while insulation thickness reduces it logarithmically. Outer convection is often 5–15 W/m²·K for still air and 15–50 W/m²·K with airflow. Inside convection for turbulent water commonly falls around 500–5,000 W/m²·K.
Steel pipe thermal conductivity is commonly near 45 W/m·K, while plastics can be 0.2–0.5 W/m·K. Typical insulation values are 0.035–0.045 W/m·K (fiberglass/mineral wool) and 0.022–0.030 W/m·K (high‑performance foams), with premium blankets approaching ~0.015–0.020 W/m·K.
For cylinders, adding a thin insulation layer can sometimes increase heat loss if the outer surface area grows faster than resistance. This “critical radius” effect is most noticeable for small diameters in very low external convection conditions.
The tool outputs heat loss per meter (W/m) and total loss (W) for the selected length. Use W/m to compare insulation options, then multiply by length to estimate the total thermal load that your heater, boiler, or chiller must cover. Results reflect steady-state conduction and convection.
Confirm diameters and thicknesses are realistic for your pipe schedule, and keep units consistent. Insulation thickness is radial, not an added diameter. A quick check: increasing insulation thickness should generally decrease heat loss, while doubling length doubles total loss.
Pick insulation thickness to meet a target W/m, safe touch temperature, or payback period. For hot lines, thicker insulation reduces losses and improves safety. For cold lines, keep the outer surface above dew point to limit condensation, and consider vapor barriers in humid spaces.
It is the heat leaving one meter of pipe under steady conditions. It helps compare insulation options without length. Total loss is simply (W/m) multiplied by pipe length.
Enter the inside diameter and pipe wall thickness so the calculator can determine inner and outer radii. If you only know outside diameter, convert it by subtracting twice the wall thickness.
Use the manufacturer’s k-value at your average insulation temperature. If unavailable, a practical range for fiberglass or mineral wool is 0.035–0.045 W/m·K, while high‑performance foams may be 0.022–0.030 W/m·K.
Run the first layer to get the outer radius, then rerun using that radius as the new “pipe” outer surface with the second layer thickness and conductivity. This mimics adding resistances in series.
The temperature difference becomes negative, meaning heat gain instead of loss. The magnitude still indicates how strongly the surroundings drive heat into the pipe, useful for chilled or cryogenic systems.
Outer convection often limits performance once insulation is thick. Natural convection around still air can be low, while wind can raise it significantly, increasing heat loss even with the same insulation thickness.
Yes. Use realistic humidity conditions separately to estimate dew point, then adjust insulation so the predicted outer surface temperature stays above dew point. Lower outer convection in still air generally helps reduce condensation risk.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.