Re: air blowing out of an old mine

[jmclean@chem.ucsd.edu (James Mclean)]

Herbert H Gottlieb says:
> > The outside air is warm, but the mine shaft air is cool, and hence 
> > more dense. 
> But mine shafts are often hotter at the bottom than at the surface.
> Wouldn't the air become heated at the bottom and become
> less dense than the air at the surface? 
Oh, I see our communication block.  I'm suggesting an alternative mode of
operation, not a modification of your idea.  I don't know how common these
underground heat sources are, but even without them you can airflow going.
But my mechanism predicts alternating airflow with the seasons (but not
daily), while yours keeps the same direction year-round.

Someone else says:
> Hot bottoms are generally found only in deep mines which go well below any
> possible surface opening.  Therefore, there it is very difficult to get
> this hot air to participate in any natural circulation.

Is it possible that the air in the mine shaft would have a much higher
thermal conductivity than the earth, so that even though it doesn't
participate in the circulation, it does provide the heat source to drive
circulation in the air above?

-- 
--James McLean
jmclean@chem.ucsd.edu
post doc
UC San Diego, Chemistry