[NedFlanders]

.........

Rceivers are never 100% full during normal operation. They can't be or they would serve no purpose.

The subcooling of liquid is most often done in the lower tubes of a condenser.

Yes the condenser may subcool the liquid,but I think the theory is the receiver tank itself is made warm by its surroundings.



Do a search about this...I did within the last few minutes and it seems to be a common theory.

 

[icemeister]

Here we go again about the damned ole subcooling arguement in the receiver.

Precisely my thought as well.

What Dow is referring to is a very long thread from a while back here on H-Talk which covers this issue quite thoroughly:

http://www.hvac-talk.com/vbb/showthread.php?t=56495&highlight=subcooling+receiver

 

[NedFlanders]

F-that thread....... too long....who won?...I gave up.
Just check subcooling before metering device.

Who cares....

 

[nwrscold]

I agree with Ned that there is subcooling back to the receiver, but his point is a great one, if outdoor ambient temp. is low and return liquid to the receiver is lower than the ambient in the mech. room and receiver is running at 50% the liquid in the receiver is being heated before it leaves the receiver. Liquid temp. at inlet of receiver will be colder than outlet temp. of receiver or liquid header temp. Tyler envirogaurd systems run at 0% and use the receiver as a surge tank, they take full advantage of the subcooled liquid right out of the receiver to the expansion valves of a system. If a receiver is a subcooler than why do we use mechanical subcoolers and, why don't you have to insulate liquid lines on a reservoir type system without a mechanical subcooler??

 

[icemeister]

I agree with Ned that there is subcooling back to the receiver, but his point is a great one, if outdoor ambient temp. is low and return liquid to the receiver is lower than the ambient in the mech. room and receiver is running at 50% the liquid in the receiver is being heated before it leaves the receiver. Liquid temp. at inlet of receiver will be colder than outlet temp. of receiver or liquid header temp. Tyler envirogaurd systems run at 0% and use the receiver as a surge tank, they take full advantage of the subcooled liquid right out of the receiver to the expansion valves of a system. If a receiver is a subcooler than why do we use mechanical subcoolers and, why don't you have to insulate liquid lines on a reservoir type system without a mechanical subcooler??

There's a general misconception in this industry that rests on the theory that refrigerant must lose its subcooling when in a receiver because there is liquid and vapor present within. The thread I provided a link for, if you read it, attempts to explain why in the real world this is not necessarily true. The answer lies with the dynamic nature of an operating system vs, a static, isolated vessel as well as an understanding of the vapor/liquid interface concept. Granted, most of us would shrug our shoulders and say so what?...but it's always a good thing to be open to learning some more involved basics of this business which supports us all.

As for the receiver being a subcooler...that was never stated or implied that I'm aware of. The major thrust of this debate is how subcooling can be maintained within a receiver...not that subcooling is actually created there.

 

[Poodle Head Mikey]

NedFlanders -

You wrote: "Yes the condenser may subcool the liquid,but I think the theory is the receiver tank itself is made warm by its surroundings"

This may be true in a more industrial setting where the condenser is alone in a cold outdoors while the compressor package and receiver are inside a warm mechanical room. But even then, given the typical refrigerant 'pounds pumped per hour' numbers I doubt that much heat gain would take place in a simple container vessel with minimal surface area.

But what I originally meant was say; on a refrigeration condensing unit - that most often the liquid receiver is in the air stream of the air flow entering the condenser. And this air would always be a lower temperature than the subcooled refrigerant existing the condenser - because of the inefficiencies inherent in the condenser coil's heat exchange.

Plus; we have the same problem with heat exchange at the vessel as with a seperated industrial system: no surface area. The condenser would have hundreds of square feet of surface area while the receiver vessel would have a tiny fraction of that.

I just can't see that in a typical application that any subcooling is lost in the receiver.

 

[Dowadudda]

well answer me this. I have tested this theory on a unit awhile back because of this subject on here in prior threads. I did a subcooling measurment on a running system, both before and after receiver. They were the same when a full cloumn of liquid was there, and reduced when flashing. Reduced. Not gone. These facts reitterated by comparing measurments and montioring the liquid sight glass.

So thats all I know. Proving to me, that subcooling remains. I realize fully there is vapor in the reciever, above the liquid. And thats at saturation. Theory in it's basic form, would argue that this is impossible, that liquid and vapor can't have this relationship. But the line at which these two phases of refrigerant meet, that boundary if you will is there and it has proved out to be that's just the effin way it is. So let's move on.

 

[NedFlanders]

well answer me this. I have tested this theory on a unit awhile back because of this subject on here in prior threads. I did a subcooling measurment on a running system, both before and after receiver. They were the same when a full cloumn of liquid was there, and reduced when flashing. Reduced. Not gone. These facts reitterated by comparing measurments and montioring the liquid sight glass.

So thats all I know. Proving to me, that subcooling remains. I realize fully there is vapor in the reciever, above the liquid. And thats at saturation. Theory in it's basic form, would argue that this is impossible, that liquid and vapor can't have this relationship. But the line at which these two phases of refrigerant meet, that boundary if you will is there and it has proved out to be that's just the effin way it is. So let's move on.

Moving on

If you verified it ..I believe.