Banned
yep, the tank would have to be all liquid to get the pressure up to 200 PSI wouldn't it ? thought about that after I posted it, I should have used 121.4 PSI, the saturation pressure of R 22 at 70 degrees, once settled the pressure would be no higher than that, however at 50 PSI at 70 degrees the refrigerant would all be in a vapor state.Originally Posted by BBeerme
Membership Chair/ARP Committee / Professional Member*
It's beyond possible - it's very real. <g>
To create liquid refrigerant from refrigerant vapor you can remove sufficient heat or add sufficient pressure. Either will work, although in an operating refrigeration system - both are used at the same time.
And no; the vessel does not have to be 100% liquid. By that logic every cylinder Not 100% full of liquid - would be 100% vapor. <g>
PHM
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PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
Professional Member
First off...refrigerant in the condenser of a running system will not condense unless heat is removed, even when the fan cycles off. Second, the recovery cylinder example is a completely different situation. We start with a cylinder with no pressure and a cylinder at saturated pressure. If we add it as liquid up to 50# pressure in the recovery cylinder, all the liquid boils off due to being introduced to a lower pressure and not adding enough to allow it to reach saturation. As we continue to add liquid, the refrigerant in the recovery cylinder will eventually reach saturation and liquid will build in the cylinder. This does not relate to fan cycling. Fan cycling builds pressure for the metering device, not so refrigerant will condense. In fact, fan cycling causes less refrigerant to condense due to the bubbles that occur every fan cycle.
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Skills wanted the bottle at 70 degrees Fahrenheit.
So once you got over 120 PSI, then you would need to refrigerate the bottle. Then you would continue adding refrigerant until the bottle was 100% full of liquid. Then that pressure would begin increasing and you would have a supercooled liquid at a temp of 70* and a pressure of 200 PSI.
I do a triple evac with nitro to remove non condensables.
Banned
that is how I see it also, technically you could argue that it is the drop in temperature that causes the refrigerant to condense, however, you could also argue that it is the act of compressing the gas which creates a rise in pressure that initiates the entire sequence.
Professional Member
We can all agree that the compressor raising the pressure is what initiates the sequence. The thing is, if you don’t remove heat in the condenser, or somewhere else, the refrigerant will not condense.
Banned
I can agree with that.
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duplicate
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to roughly word it, see if I get this right
when using a fan cycling control, during the fan off cycle, the rise in pressure has to match or exceed the amount of heat dissipated by the coil and associated piping, according tho the refrigerants pressure / temperature relationship, in order for the refrigerant to condense.
Last edited by hvacskills; 08-17-2019 at 01:15 PM. Reason: added the word ' match '
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the fan shutting off has nothing to do with a rise in pressure!
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reason being, when using a fan cycling control, if removing heat from the refrigerant was the only condition that has to be met in order for the refrigerant to condense, then why are there bubbles in the sight glass when the fan is in the on cycle ? obviously pressure plays a significant factor.
or, I suppose we could remove the compressor completely from the system and just cause the refrigerant to change state strictly by changing the refrigerants temperature.
Professional Member*
It's difficult for me to wrap my head around your thought process. Somehow it just doesn't compute.
Maybe if you said the rise in pressure will match the saturation temp, that's easy to understand.
I do a triple evac with nitro to remove non condensables.
Professional Member*
Because the pressure was reduced below the temp of the refrigerant.
So, after any subcooling, the refrigerant needs to boil in order to cool itself to match the new pressure.
Freons are good little soldiers. They, by their very make up, will sacrifice themselves to allow their other Freon buddies to continue on to get the job done. After all, they know they will have another chance to be the Freon that gets the job done the next time around. Maybe another Freon buddy will sacrifice themselves next time around.
I do a triple evac with nitro to remove non condensables.
Banned
yep, thought about using that terminology after the fact, suppose I was wanting to describe the two as constantly changing, but sure, that terminology is more appropriate, but have to include the word exceed, or probably just use the word exceed, otherwise the refrigerant would be at saturation and with R 22 the refrigerant would be neither fully a vapor or liquid.
Banned
so are you saying that pressure plays a roll in the condensing of refrigerant in the condensing coil Bbeerme ?
Professional Member*
The word exceed comes into play when you what to reject the heat, assuming we're on the high side.
I do a triple evac with nitro to remove non condensables.
Professional Member*
The role of the compressor is to pump up the pressure above the ambient [T/P relationship], that's how we remove the heat.
I do a triple evac with nitro to remove non condensables.
Banned
in fairness to differing HVACR technicians, sure terminology is important and should be pretty much universal In order for people to be able to hold conversation, but not only do
differring people have differing terminology,
differing people also have differimg perspectives, so differing people take differing approaches, with perhaps neither side being wrong, just different.
also, always think of it as kind of funny how differing people can have differing areas of expertise.
Professional Member*
Regarding terminology, and engineering, all of the terminology has to be consistent with no variation. Otherwise, Engineers would not be able to speak with each other and have meaningful discussions or results.
Same thing here. When someone wants to call TD the difference between the entering and leaving air of a coil. If you do not use the right terminology, you will not get the right answers to your questions or thoughts. Quite simply put, you will not be communicating.
I do a triple evac with nitro to remove non condensables.
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