Volume of circulating receiver

[SNi]

Please advise me - how to calculate needed volume of circulating receiver?

[US Iceman]

I am assuming you mean a receiver that has refrigerant pumps to circulate the liquid refrigerant...

The size is based on several critical elements:

1. The volume of liquid to be stored
2. The maximum liquid level desired
3. The volume needed for separating liquid from vapor before the compressor

The usual method for a horizontal is to fix the vessel volume at 1/2 full. In this case you use the top half of the vessel for the liquid/vapor separation.

The volume of liquid to be stored determines how much volume you need below the maximum liquid level of 1/2 of the vessel diameter.

In addition you need a minimum liquid level to ensure the refrigerant pumps can prime and operate.

These are the basic fundamentals for either a vertical or horizontal vessel.

This is a complex subject and will stretch over many replies from others also. This is just a starting point.

[SNi]

US Iceman

Thanks for you reply. Yes i wrote about receiver that has refrigerant pumps. I think it`s a very interesting subject too. From one side it`s very simlpe, but from other it`s have some features. How do you calculate needed volume for calculating receiver?

[US Iceman]

The more difficult problem is estimating the volume of the evaporators that will be in defrost at any one time. If the evaporators are using hot gas defrost, the volume of liquid in the coils has to be stored in the receiver during defrost. This is what I call the surge volume.

This volume occupies the area between the normal operating liquid level and the maximum liquid level (before the compressors are de-energized due to high liquid levels).

[SNi]

The more difficult problem is estimating the volume of the evaporators that will be in defrost at any one time. If the evaporators are using hot gas defrost, the volume of liquid in the coils has to be stored in the receiver during defrost. This is what I call the surge volume.

This volume occupies the area between the normal operating liquid level and the maximum liquid level (before the compressors are de-energized due to high liquid levels).

But in this case you can prohibit the simultaneous defrost. What do think about retention time?

[US Iceman]

I think the pump retention time should be based on the liquid volume to re-fill the evaporators after defrost. However, you also have the surge volume from the evaporator defrost liquid (and pumpdown) providing a lot of liquid in the vessel.

I have seen some recommendations that say you need at least five minutes of retention time for the pumping rate.

As a point of argument I would say it is more important to make sure the liquid make-up supply can maintain the minimum pump liquid level during normal operation.