How to use the Heat Conduction Calculator
- 1. Pick the geometryPlane wall or pipe / cylinder.
- 2. Add the layersHot side first: thickness in mm and thermal conductivity k on each line.
- 3. Get the heat flowTotal resistance, heat flow, flux and the temperature after each layer.
Fourier's law and thermal resistance
For steady conduction through a plane wall, Q = kA(T1 − T2) / L. Writing it as Q = ΔT / R gives the wall resistance R = L / kA. Layers in series add up: ΣR = L1/k1A + L2/k2A + …, and convection adds 1/hA on each side.
For a cylinder, R = ln(r2 / r1) / (2πkL). The temperature after each layer is the previous temperature minus Q × R of that layer.
Worked example and exam tips
A 1 m² furnace wall has 200 mm firebrick (k = 1.2), 100 mm insulation (k = 0.15) and 100 mm brick (k = 0.9), with surfaces at 600 °C and 50 °C. ΣR = 0.167 + 0.667 + 0.111 = 0.944 K/W, so Q = 550 / 0.944 = 582 W. The insulation takes most of the temperature drop.
- Keep thickness in metres in the formula (the tool converts mm for you).
- The layer with the largest R has the largest temperature drop.
- For thin pipe insulation, adding insulation can raise heat loss below the critical radius k/h.
Frequently asked questions
What if I know fluid temperatures, not surface temperatures?
Enter the inside and outside heat transfer coefficients h. The temperatures you enter are then treated as fluid temperatures.
Can I name the layers?
Yes. Start the line with a word, for example: Brick 230 0.7.
Does it handle contact resistance?
Not directly. You can add it as an extra layer with a small thickness and matching k.
Is this calculator free?
Yes. You enter your name and WhatsApp number once to see your result, and all other Uncodemy tools then open without the form. Everything is calculated in your browser.