Part 1a: Refrigerant Basics:
by Richard C. Kozinski
From Nov/Dec 1997
© 2000 All Rights Reserved
¤ Part 1: The
VOV, is it the refrigerant control of the future?
¤ Part 2:
The VOV (Variable
Orifice Valve) versus the FOT (Fixed Orifice Tube)
3: The Flooded Evaporator
note: This section is intended to assist air conditioning
technicians to understand the operation, and advantages, of the VOV (Variable Orifice Valve)
Refrigerant may exist as a
liquid, a gas or both. It may be a subcooled liquid or a superheated
gas. But what does that actually mean? Here are some basics for your
Subcooling: The amount in °F that a
liquid is below its boiling pint. Water (212°F boiling point) at 200°F
is 12°F subcooled at atmospheric pressure.
Superheat: The amount in °F that a vapor
is above its condensation point. Steam at 220°F would be 8°F
Uncondensed gas: The gas leaving
the condenser mixed with liquid. This could be caused by an orifice that
is too large at idle for instance. A sight glass would show bubbles at
Liquid backup in the
condenser: By restricting orifice size, condensed liquid is
caused to backup in the condenser. This causes subcooling of this liquid
by the time it exits the condenser. This occurs at highway speeds with
the FOT today.
Have an a/c question? Ask Cool
Profit$. Maybe we can get Dick to provide the answer.
C. Kozinski Editor's note:
Mr. Kozinski is an automotive HVAC engineer with over 35 years
experience, including over 25 years in commercial HVAC. His masters
thesis in 1967 covered the fixed orifice tube system. He wrote this
while working for Chrysler Corporation. He co-invented the system with
Mr. Ed Bottum, owner of Refrigeration Research. In 1969 he and Ward
Atkinson spearheaded the FOT development while at General Motors. He
later helped develop the system at GM's Harrison Radiator Division. He
is currently the owner of a mechanical contracting firm and is also a
consultant to several companies involved in HVAC component development.
To move on to Part 2, click here.
To return to Part 1, click here.