Insulated Pipe Heat Loss Calculator
Calculate heat loss from insulated pipes using conduction through the insulation and outer surface convection. Results per metre, per line, surface temperature and yearly energy.
Download
- Calculator sheet with a worked example
- How to Use sheet with steps
- 52 built in formulas, no macros
- Yellow input cells, grey results
- Calculation sign off block
- Excel, Google Sheets and LibreOffice
Worked Example
These are the results of the example already filled in the workbook. Replace the yellow cells with your own data.
Lines
| Line | Pipe OD (mm) | Insulation (mm) | k (W/mK) | Fluid T (°C) | Ambient (°C) | Length (m) | Loss (W/m) | Surface T (°C) | Line loss (kW) | Energy (MWh/yr) | Bare pipe (W/m) | Remarks |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Steam 4" | 114.3 | 50 | 0.040 | 180 | 25 | 50 | 58.5 | 33.7 | 2.93 | 23.4 | 557 | |
| Condensate 2" | 60.3 | 40 | 0.040 | 120 | 25 | 30 | 26.5 | 31.0 | 0.79 | 6.4 | 180 | |
| Hot oil 3" | 88.9 | 75 | 0.045 | 250 | 25 | 40 | 62.0 | 33.3 | 2.48 | 19.8 | 628 |
About this Calculator
Heat loss sets insulation thickness, heat tracing and steam trap loads. This sheet gives quick, documented estimates for many lines together.
Basis: Steady state radial conduction plus outer film: Q/L = (Ti − Ta) ÷ [ln(r2/r1) ÷ (2πk) + 1 ÷ (2π r2 h)]. Pipe wall and inner film resistance neglected.
How to use
- Enter surface coefficient and hours.
- For each line enter OD, insulation thickness and conductivity, temperatures and length.
- Read loss per metre, surface temperature, total and annual energy.
- Compare with bare pipe to see the insulation saving.
Formulas used
- Q/L = ΔT ÷ [ln(r2/r1)/(2πk) + 1/(2π r2 h)].
- Surface T = Ta + (Q/L) ÷ (2π r2 h).
- Energy = kW × hours ÷ 1000 (MWh/yr).
Related tools
Frequently Asked Questions
Why ignore the pipe wall?
Steel wall resistance is tiny compared with insulation.
What k for mineral wool?
About 0.035 to 0.05 W/mK depending on temperature and density.
Is radiation included?
It is lumped into h; for hot bare surfaces radiation matters more.
Learn more on the blog
Thermocouple and RTD installation precautions
A practical guide on instrumentationblog.in that explains the engineering behind this workbook.
Read Full Article