PDA

View Full Version : Flooded R404a oil question







Superfridge
08-12-2014, 08:30 AM
Hi all,
I'm working on a Geneglace ice maker that has a flooded evaporator and is on R404a. This is something new to me.

My question is can this type of system operate on your standard run-of-the-mill refrigeration oils that you would use on a DX system or should it be on something a bit different?

My thoughts are that the oil should be not miscible with the R404a.

Thanks in advance.

sterl
08-12-2014, 04:11 PM
Miscible is relative but its largely academic: refrigerant circuits using immiscibles still have oil accumulating in low side heat exchangers as per most ammonia circuits. The separation process there is simple: the oil is lighter than the refrigerant and at the low velocities in a barrel like the G-Glace it simply falls to the bottom and can be readily extracted. With any of the halocarbons this is reversed and with a drum type ice maker warm at the top is NOT a good thing.
So the G-Glace needs an extraction arrangement. This can take a variety of forms and may rely on the temperature of the high pressure liquid to drive it.

If this to be used in a gravity flooded arrangement there is a separate pressure vessel (surge drum, but GEA calls it a Flooding Bottle) which will be a player in that "kit". If its a pumped arrangement the extraction/separation can best be done at the recirculator, though that implies that the piping between the ice machine and the vessel has to be implemented specifically and laid out appropriately.

Grizzly
08-12-2014, 05:34 PM
Hi sterl.
An Impressive reply and worthy of recognition.
Rep point given.
Grizzly

Superfridge
08-12-2014, 07:16 PM
A sterling reply sterl, thank you.
The unit is a stand-alone package using system differential as HP liquid supply and equipped with the Flooding Bottle. It appears to be returning oil satisfactory but I would like to know what type of oil should be used in this type of unit and what it looks like inside.
I have tried to obtain drawings of the internals without success. I'm imagining some sort of oil skimmer or a vertical sparge pipe that collects oil at various levels as it has to return oil with very little differential probably just using the head of the liquid.

With a lot of vessels, we as fridge's, don't know how the internal arrangement is configured until drawing are obtained. We need to be Superman to see inside!

joe-ice
09-12-2014, 03:58 PM
I think these just use a pick up tube in the drum .It would pick up liquid and oil and boil off the liquid in the heat exchanger on route to the top of the suction pipe.I think theres a valve on the oil line to control the flow .The pick up must be near top of drum because i know they suffer poor oil return if drum isnt fully flooded such as low in gas.