[TheForge] Building a propane forge

[Bruce Freeman]

I have to object to the following statement.  AFAIK, this is simply not
true.
 
For the sake of the scientifically bewildered, let me clarify that
there are only four phases of matter:  solid, liquid, gas, and plasma. 
(The last may be in dispute, but is characterized by parts of a flame,
so has some relevence.)  There is such a thing as a "supercritical
liquid" which has the properties of both liquid and gas, but there's
nothing magic about that - it can be viewed either as a gas compressed
till it has liquid-like properties or as a liquid heated till it has
gas-like properties.  The two phases converge at what is known as the
"critical point" (which is semantically related to, but very different
from, the various "critical points" of the solid-liquid steel diagram).

 
Back to the original point:  There is no "vapor" phase, distinct from
the "gas" phase.  At the temperatures and pressures of a burner, propane
will not be supercritical. The only remaining possibility would be a
mist, or "aerosol", in which liquid droplets are entrained in air.  I
submit that even this is highly unlikely under the conditions of
operation of any burner.
 
In fact, it would take quite an effort to develop an aerosol.  Consider
an air-driven paint sprayer.  At least part of the liquid is present as
an aerosol (though some it of may simply be liquid droplets - the
distinction may not be clear).  I doubt that propane drawn from the TOP
of a propane bottle, then passed through a regulator, hoses, etc., would
have any chance of containing entrained liquid.
 
All of this is not to say that no effort is required to mix gases.  Put
to gases in a chamber and go away for a while, and they'll thoroughly
mix by diffusion.  But diffusion takes time.  To speed up the process
takes energy.
 
Bruce
NJ

>>> Keporter@aol.com 2/16/2004 5:56:52 PM >>>


   Propane is a vapor, not a true gas. It forms miniature clumps that
must be 
broken down into individual molecules for proper mixing and combustion.