Date:         Fri, 8 Aug 2003 20:41:21 EDT
Reply-To:     Willolyn99@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Bill Marshall <Willolyn99@AOL.COM>
Subject:      Re: repost - basic a/c hose connection question.
Content-Type: text/plain; charset="US-ASCII"

So if we look at the equation

PV=nrT

Where P is the pressure, V is the volume, nr is basically the amount of stuff
in the gas, and T is temperature, we find that there is an equivalence, or
proportionality, between PV and T:

PV~T

So, if one of these variables remains the same, then the other 2 will change,
and in a way that follows this ratio.  So, for example, if the pressure
increases and the volume does not, the the temperature will increase:

P(x)V~T(x)

Not necessarily a direct ratio, but they will change in a similar way.  So,
at the compressor, the pressure is increased by the pump.  The volume remains
constant, so the temperature goes up.  That explains the heat on the DIScharge
side of the compressor.  This hot, compressed gas goes to the condensor in the
front of the van.  Here, the air in the atmosphere cools the compressed freon
through a convective current.  Now, we have subtracted heat from our PV~T
system, yet we are still pressurized, so we will find that the volume has been
reduced -- the gas becomes a liquid.  The phase change is often accompanied by a
big change in energy to the system.

Still under high pressure, the liquid is sent to the evaporator in the rear
of the van.  Through a small orifice, the pressure is allowed to escape.  At
this point, the reducton in pressure causes the liquid freon to evaporate,
increasing in volume.  This phase change causes the freon to cool considerably --
the pressure loss is reflected in the temperature loss.  The cooled freon gas
is sent through the evaporator coils, and exchanges heat with the air on the
inside of the van.  This heat is brought to the compressor, to be compressed and
sent to the condensor in the front again.

Continuous cycle -- the heat is grabbed at the evaporator, is collected at
the compressor, and is sent to the condensor to have the heat released to the
atmosphere.

Easy.  It's all in the motions of molecules.  It's like a party -- sometimes
you have to go outside to cool down.  Then you come back in and heat up again.

Bill Marshall
'85 GL Tiico "Pandora"
Aurora, IL