Surface Flame Spread for a Thermally Thick Solid

4 Surface Flame Spread for a Thermally Thick Solid 

Let us now turn to the case of a thermally thick solid. Of course thickness effects can be important, but only after the thermal penetration depth due to the flame heating reaches the back face, i.e. t = ff, 6j(t ) = d. As in the ignition case, if tf is relatively small, say 10 to even 100 s, the thermally thick approximation could even apply to solids of d 1 cm. Again, we represent all of the processes by a thermal approximation involving the effective properties of Tlg, k, p and c. Materials are considered homogeneous and any measurements of their properties should be done under consistent conditions of their use. Other assumptions for this derivation are listed below  

This approximation gives us a reasonable profile that satisfies the boundary conditions and allows us to perform the integration 

We have seen that a reasonable approximation for the penetration depth is 

FIRE SPREAD ON SURFACES AND THROUGH SOLID MEDIA 

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SURFACE FLAME SPREAD FOR A THERMALLY THICK SOLID 201... 

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