convert from heat transfer coefficient to thermal conductivity

[ChiefWildcat]

How do I convert from heat transfer coefficient of a material to its thermal conductivity?

 

[Latexman]

Heat transfer coefficient = thermal conductivity of material/thickness of heat flow path through material.

Good luck,
Latexman

 

[25362]

The heat transfer coefficient for conduction is k/[Δ]x
where k is the thermal conductivity and [Δ]x the thickness of the layer.

The th. conductivity is given, for example, in W/(m.K) which when divided by the thickness, in m, gives W/(m².K), the units of the coefficient of heat transfer.

Following Fourier's law, the heat flow, expressed in W, through the layer of thickness [Δ]x would be:

Q = k*A*[Δ]T/[Δ]x​

where A is the unit surface; [Δ]T, is the temperature gradient T₂-T₁.

This is for the case when the thermal conductivity is considered constant. If the thermal conductivity varies linearly with temperature as, for example, k = k_o(1+[β]T), the equation for heat flow becomes:

Q = (k_o*A[÷][Δ]x)[(T₂-T₁) + ([β]/2)(T₂²-T₁²)]​

 

[wavecrest]

h = k/delta

for gap contact coefficient

k of air

delta = average surface rougness