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Part 1a: Refrigerant Basics: Definitions
by Richard C. Kozinski
From Nov/Dec 1997 Cool Profit$ Magazine
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)
Part 3: The Flooded Evaporator

Editor's 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 review.

Subcooling: The amount in F that a liquid is below its boiling pint. Water (212F boiling point) at 200F is 12F subcooled at atmospheric pressure.

Superheat: The amount in F that a vapor is above its condensation point. Steam at 220F would be 8F superheated.

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 this point.

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.

Richard 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.

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