Re: air blowing out of an old mine

["James W. Wheeler" <jwheeler@eagle.lhup.edu>]

A couple of thoughts.
1.  In the mountains, even in the summer, the surface temperature may be
higher than the cave or mine temperature during the day, and may be lower
than the cave or mine temperature during the night.

2.  Also in the mountains the peaks oftem heat up and cool down faster
than the valleys.  It is very common to have an uphill wind during the day
and a downhill wind at night.  For a mine or cave with multiple openings
this could set up Bernouilli effect induced flows.  

On Wed, 16 Sep 1998, James Mclean wrote:

> 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