Subcooling

[Kh1971]

Hi, can you explain again the foaming issue on the sight glass

[nike123]

Hi, can you explain again the foaming issue on the sight glass

Why again? Does the explanation gone somewhere, or missing?

[chillyblue]

Back to subcooling

I've been experimenting again, as follows. just to add the freezer is working fine, i'm just experimenting.

Copeland condensing unit operating a freezer

refrigerant R22
room temperature minus 17deg C
air on temp 16deg C
air off temp 21deg C
discharge pressure 135psi / 24deg C
suction pressure 16psi / minus 24deg C
temperature reading taken at condenser outlet or reciever outlet (did not seem to change between the two) around 24deg C with a clear sight glass.
One thing i did notice which is very strange, the outlet temperature of the condenser/receiver went higher than the condensing pressure/temperature relationship (is this possible).

Why can i never achieve any subcooling, i feel that i am being robbed of the privilege.

Thanks in advance for your assistance.

CB

[SteinarN]

Back to subcooling

the outlet temperature of the condenser/receiver went higher than the condensing pressure/temperature relationship (is this possible).

Why can i never achieve any subcooling, i feel that i am being robbed of the privilege.

Thanks in advance for your assistance.

CB

In real life you can not have a higher outlet tempereature than is the condensing temperature. It's probably measuring error, either your thermistor, your gauge or both.

Regarding the amount of subcooling it is several threads here where that subject has been discussed lively. Some argues you always have (measurable) subcooling and often a large subcooling. My opinion is that you never have any (measurable) amount of condenser outlet subcooling in a simple, stable running system with receiver as you describe.
This is assuming no non-condensables in the system, not any measurable pressure loss between condenser outlet and receiver, and the receiver not mounted significantly higher than the condenser.

[chillyblue]

Regarding the amount of subcooling it is several threads here where that subject has been discussed lively. Some argues you always have (measurable) subcooling and often a large subcooling. My opinion is that you never have any (measurable) amount of condenser outlet subcooling in a simple, stable running system with receiver as you describe.
This is assuming no non-condensables in the system, not any measurable pressure loss between condenser outlet and receiver, and the receiver not mounted significantly higher than the condenser.

Sorry i don't quite understand what you are trying to say.

CB

[SteinarN]

I ment to say I have trouble to understand how it can be possible with substantial subcooling on most systems. Thus I find your measurments where you dont have any subcooling absolutely normal.

[chillyblue]

I ment to say I have trouble to understand how it can be possible with substantial subcooling on most systems. Thus I find your measurments where you dont have any subcooling absolutely normal.

Thanks, i'm glad i'm not the only one i have never experienced large amounts of subcooling unless it is produced artifically via a vessel pre cooling the liquid or condensers with a dedicated subcooling circuit.
Most books refer to 4 to 7 degC of subcooling or the system is undercharged.
I've charged many systems that run perfect(in my opion), with full sight glasses and no subcooling. i would guess that if you continued to charge the system with refrigerant perhaps the subcooling will come??? but at a cost of reducing the condensing surface area and causing excessively high discharge pressures, and electrical current.
Is it that the manufacturers reduce condenser and reicever sizes???

Most condensing units i work with the receiver sits infront of the condenser fan so is subject to the air off temperature, would that make a difference??

Cheers CB

[Gary]

One thing i did notice which is very strange, the outlet temperature of the condenser/receiver went higher than the condensing pressure/temperature relationship (is this possible).

No, it isn't possible. You need to calibrate your instruments.

[US Iceman]

Another possibility for warmer liquid lines is if the liquid seal is lost somewhere and warm gas flows with the liquid.

[chillyblue]

No, it isn't possible. You need to calibrate your instruments.

I assume when you say that it is not possible, you mean because there is liquid present.
Am i right in saying that when a liquid is present the temperature cannot rise above the
temperature/pressure, and when there is no liquid present the temperature cannot drop below temeperature/pressure relationship

Hope that makes sense
Cheers CB

[SteinarN]

I assume when you say that it is not possible, you mean because there is liquid present.
Am i right in saying that when a liquid is present the temperature cannot rise above the
temperature/pressure, and when there is no liquid present the temperature cannot drop below temeperature/pressure relationship

Hope that makes sense
Cheers CB

That's a good understanding of the temp/pressure relation limits.