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/(m[sup]2[/sup].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 T[sub]2[/sub]-T[sub]1[/sub].

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[sub]o[/sub](1+[β]T), the equation for heat flow becomes:

Q = (k[sub]o[/sub]*A[÷][Δ]x)[(T[sub]2[/sub]-T[sub]1[/sub]) + ([β]/2)(T[sub]2[/sub][sup]2[/sup]-T[sub]1[/sub][sup]2[/sup])]​

 

[wavecrest]

h = k/delta

for gap contact coefficient

k of air

delta = average surface rougness