Wall Heat Conduction Calculator (Multi Layer)
Calculate heat flow through a flat wall made of up to three layers, such as steel, refractory and insulation, with inside and outside film coefficients. The calculator gives the U value, heat flux and interface temperatures.
- Rtotal = 1/hi + ΣL/k + 1/ho = 2.12 m²·K/W
- q = ΔT ÷ Rtotal = 176.9 W/m²
- Each interface: T = previous T − q × R of the layer
Temperature profile
| Position | Temperature °C | Resistance before m²·K/W |
|---|---|---|
| Inside surface (layer 1 hot face) | 396.5 | 0.02 |
| Layer 1 / layer 2 | 396.4 | 0.000222 |
| Layer 2 / layer 3 | 42.69 | 2 |
| Outside surface | 42.69 | 3.13 × 10^−6 |
Conduction Through Layers
U = 1 ÷ Rtotal
Tnext = Tprevious − q × Rlayer
L is each layer thickness, k its thermal conductivity, hi and ho the inside and outside film coefficients. This is one dimensional steady conduction through flat layers; for pipes use the pipe heat loss calculator. Typical k: carbon steel about 45, stainless about 16, mineral wool about 0.04 to 0.05 W/m·K.
Worked example
A 10 mm steel wall at 400 °C inside, with 100 mm of mineral wool (k 0.05) and 0.5 mm aluminium cladding, loses about 176 W/m²; the cladding is at about 43 °C.
Frequently Asked Questions
What is a U value?
The overall heat transfer coefficient of the wall: heat flow per square metre per degree of temperature difference.
Why include film coefficients?
Heat must pass from the fluid into the wall and from the wall to the air. These surface resistances can be significant, especially outside.
Can I use it for a tank wall?
Yes for large tanks, where the wall is nearly flat. For pipes and small vessels use the cylindrical formula.
Learn more on the blog
Thermocouple and RTD installation precautions
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
Read Full Article