Re: IML: R-12 to R-134a Retrofit

[<50scars@xxxxxxxxxxxx>]

BASIC PRIMER ON THE WAY AIR CONDTIIONING AND REFRIGERATION WORK:

   All mechanical refrigeration works the same way.  You remove heat from
the cooled space by boiling a liquid in the evaporator at a low
temperature, then you compress that liquid so that the temperature that
it returns to a liquid is above ambient, and you do that in the
condenser.  You put that condensed liquid into a reciever, until the
evaporator calls for more refrigerant, where there is some device like
a thermal expansion valve, or a capillary tube that meters the high
pressure liquid into the evaporator and lets it become a low pressure
liquid, until it boils.
    This process takes advantage of the fact that by changing the pressure
on a gas that will condense to a liquid, you take advantage of the
latent heat of condensation/vaporization movement.  For instance,
water at 34 degrees can be a vapor, if there is a high enough vacuum. 
It takes 978 BTUs to change a LB of water to a LB of steam, no matter
what the temperature.  So it you have water at a 28 Inch vacuum it
will boil, removing that 978 BTUs from the air that is at a
temperature above 34 degrees.  At atmospheric pressure, water at any
temperature below 212 will condense to a liquid, after it dumps that
978 BTUs per LB.  So you can see how you can remove heat from a space
at 70 degrees and transfer it to a space that is 100 degrees.
There are 4 main parts to the air conditioning system.  The compressor,
Located on your engine, which sucks the hot low pressure gas out of the
evaporator, compresses it to a hot high presure gas, and sends it to the
condenser, located in front of your radiator.  There the hot high pressure
gas becomes a relatively cool high pressure liquid.  It then flows to the
reciever, which is usually located on the end of the condenser, and is
stored there, until the Thermal expansion valve opens and lets some into
the evaporator, both of which are located on the cowl, unless yours is
mounted in the trunk, where it boils and changes from a cold low pressure
liquid to a hot low pressure gas.


John









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