oil recovery from flooded chillers

[lowtempref]

How to recover the oil from flooded chiller (operating with R134a/R 404a)?

[Andy]

Hi Lowtempref.

R404a or any 4 series refrigerant is not used in a flooded chiller, as the mixture will separate into layers of refrigerants bboiling at different temperature.

R134a chiller are normally DX, can't remember working on a flooded R134a chiller, but a presume you would take a sample of opil rich liquid off at the liquid level, heat it to boil off the refrigerant and return the oil to the compressor.

Kind Regards Andy

[lowtempref]

Hi Andy,

Thanks for your reply. Can we use jet pump also for this purpose?

[TXiceman]

I have downe several R-13a flooded chillers and used a gravity feed heated oil still. let it cycle on the heater thermostat to take batches and boil off the refrigerant. every few days, block in the still, pressurize it with discharge gas and blow the oil back to the compressor.

I don't carre for the eductor approach, as you can easily get liquid refrigerant into the compressor. The heated oil still insures warm refrigerant free oil to the compressor.

The 400 series refrigerants, are not suitable to use in a flooded design due to the temperature glide and different bubble points on the components.

Ken

[Andy]

Hi Andy,

Thanks for your reply. Can we use jet pump also for this purpose?

Hi Lowtempref

not sure what a jet pump is one of the hot gas driven pumps possibly.

Gravity two solinoides and some hot gas should do the job



Kind Regards Andy

[TXiceman]

I was calling it an eductor....probably the same as a jet pump. I don't like them as it is a cheap way to return oil, but you stand a chance to get some refrigerant liquid back to the compressor. When I have used them, I use discharge gas to drive the eductor and I take the tubing back to the compressor by taking a few tirns around the compressor discharge line to drive the refrigerant to gas and heat the oil a bit.

I believe that oil and R-134a are pretty we imessible and mix readily. so you wil get a mixture of oil and refrigerant. You really need to drive the refrigerant out of the oil and insure the compressor gets pretty warm and clear oil. So you need a heated oil still to batch distill off the reefrigerant. Takes a heated vessel (1.5KW electric heater) and 4 solenoid valves.

Ken

[US Iceman]

Yes, I would consider the jet pump the same as an eductor.

I have done this both ways as TXiceman suggested. However, I would only use the eductor on a screw compressor and even then make sure to try to burn off the liquid refrigerant.

If a recip compressor was being used I would make sure to use the gravity distillation method as it is much safer.

[joel]

hi.
we also use eductor...
and its doing good. just be sure in you have the proper refrigerant charge.
it might not push an oil, liquids are possible.

[TXiceman]

I too have used an eductor on a few systems, but only on screw compressors which were basically on a commerical applicaiton. It is a low cost way to return oil, but you must be very carefulto not over feed it and pull back too much liquid refrigerant. This type systems does not know the difference between oil and refrigerant liquid.

The amount of the charge does not really effect the operation unless you are running a critically charged, flooded system with high side float control.

Still the best and surest oil return is a heated oil still system.

Ken