receiver volume

[cool-hvacer]

Hi all....

This a a divergence from another thread, but I thought it was relevant enough to warrent its own thread. The question is regarding the receiver.

1) When it is operating correctly, how full would you expect it to be with liquid. The numbers I have seen getting kicked around are between 20% and 80%.

(I personally was wondering why it wasn't 100%, but I think I have been convinced that this is not right)

2) And I guess that you would assume that what comes out of it is 100% liquid?!! Possibly even subcooled a bit

Now if these two things are true, then I think it would have to be a true statement that

3) what is entering it has to be a saturated mixture of vapor and liquid.

But if the geometry of your condenser is correct, would you not be getting subcooled liquid back from you condenser (bottom couple of coil rows would be liquid)??

Any help with these would be much appreciated (several people have tried to help in the other thread, but I think I am missing something)

[US Iceman]

The answers to your questions depends on the type of receiver you have. There are 2 types; flow-thru & surge.

The flow-thru type has a dip tube, which is connected to the main liquid line. A surge-type receiver is like an expansion tank. The excess liquid backs up into the vessel however the drain line from the condenser is also part of the liquid line.

No receiver should be filled more than 80% full. You need some vapor space to allow for expansion of the liquid.

In most cases a flow-thru receiver with the dip tube has to have a portion of the receiver filled with liquid to form a seal on the dip tube. Since this liquid occupies part of the receiver volume it is also part of the pump down volume. The manufacturers don't tell you that!

[johnyfreon]

Inside the receiver the volume of the liquid fluctuates with the evaporators load under high loads the TXV opens wide allowing for a greater mass flow as the loads diminish the TXV throttles decreasing the flow and increasing the liquid level of the receiver. Just because liquid and vapors coexist in the receiver it does not translates necessarily into a total loss of all or any subcooling, there most be some sort of heat gains or pressure loses for the refrigerant to loose its subcooling.