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Fourier's law

Conduction is the transport of heat through a substance without the substance itself moving. Fourier's law says the heat flow through a plane layer is proportional to the temperature difference and the area, and inversely proportional to the thickness. The thermal conductivity tells you how well the material conducts heat.

\dot Q = \dfrac{kA\Delta T}{L}

heat flow through a plane layer

Symbols

$k$	thermal conductivity	W/(m·K)
$A$	area perpendicular to the heat flow	m²
$L$	thickness	m

Example

A layer with $L = 50$ mm, $k = 0.04$ W/(m·K) and $A = 10$ m² has $\Delta T = 30$ K. $\dot Q = 0.04\cdot 10\cdot 30/0.05 = 240$ W.

Do not confuse

k

(thermal conductivity, W/(m·K)) with

h

(heat transfer coefficient, W/(m²·K)) – they describe different mechanisms.

Practise conduction for free →

Thermal resistance in series →

Part of Heat Transfer: Conduction.