Entropy Generation When A Gas Mixed With A Solid

Markus

30th August 2009 - 07:48 AM

What is the entropy generation associated with mixing a gas with a solid? Assuming that no mass is tranfered between two phases (heat is transfered).

Typical example of this kind of scenario is pneumatic transport of a solid (eg.cement, grains, etc) with air.

I know that entropy is increased when two different gases (even in same pressure and temperature) are mixed in a closed container.

But I don't have an idea how should I calculate it for solid and gas case.

Thanks in advance..

rpenner

30th August 2009 - 06:37 PM

It depends if the gas interpenetrates the solid or not.
Assuming the solid is models as impenetrable sphere of a few microns or more, the gas which has molecules massing 1 million times smaller has entropy high enough that you can ignore the change in the uncertainty of position of the solid. So it breaks down as a ourethermal equilibrium problem.

If the solid is palladium and the gas is hydrogen, then the gas slightly "expands" into the volume occupied by the solid.

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