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Table 1 - The heat conductivity λ of various materials
Material λ W/(m K) Material λ W/(m K)

Diamond 2300 Brick 0.72

Silver 429 Water 0.613

Copper 401 Human skin 0.37

Gold 317 Wood (oak) 0.17

Aluminum 237 Helium (gas) 0.152

Iron 80.2 Soft rubber 0.13

Mercury 8.54 Glass fiber 0.043

Glas 0.78 Air 0.026

As you can see air does not conduct heat very well. This is the idea behind

styrofoam thermal insulation, the air pockets between the styrofoam beads do not

conduct heat very well. On the other hand, metals do conduct heat very well. This is

why metal seems cold when you touch it. The metal atoms are conducting your body

heat away from your hand quickly.

1.1.1 Steady-state conduction

Purely thermal conduction: in solid opaque bodies (opaque: not permeable for

radiation) the thermal conduction is the significant heat transfer mechanism

because the material doesn’t flow and there is no radiation.

Steady-state conditions: t = F(t) = constant

For steady-state heat conduction, in one dimension, the Fourier-law is

dt
I
Q  q  F    F, W ( 1.1)
dx
2
where q – heat transfer rate per unit area, W/m ;
λ – thermal conductivity or heat conduction coefficient, W/m·K;

2
F – cross sectional area normal to flow, m ;
dt/dx – temperature gradient, K/m.

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