Average oil return??

[girina]

Good morning!
I'm working on a little research about refrigerants and lubricants.
I've searched everywhere, but I can't find data about oil return or oil transportation in refrigeration system.

Anyone can tell me if there is a study of oil return in refrigerating system using R422D?

I just want to know if the average of oil transported by R422 is around 20% or 80% or 100%.

Thank you very much!

[Sandro Baptista]

Good morning!
I just want to know if the average of oil transported by R422 is around 20% or 80% or 100%.
Thank you very much!

I don't understand quite well your answer...every oil is circulating on the plant and back to the compressor. The oil mass flow carry over can be more or less depending on: oil separator or not, and its design, compressor regimen, compressor capacity, discharge pressure, discharge temperature, etc...

[girina]

Mmm..ok.
So it isn't possible to quantificate how much oil return at the compressor?.
I found a patent where is measured the % of a oil charge return at the compressor with a refrigerant mixture containing DME and I'd like to compare the % of oil return with the normally oil return with R422D.

But as you said, I think that will be 100% for a good functioning, no?

Thank you

[NoNickName]

The oil return is by definition always 100% otherwise the compressor would starve after minutes or hours. It is called continuity equation.
What you are looking for are miscibility diagrams. For that, you would contact the refrigerant supplier or producer.

[girina]

Ok! It's what I'm thinking about this all time! Now I have to explain it to my chief! ;-)
thank you very much!

[Lodiev]

What you are looking for are miscibility diagrams. For that, you would contact the refrigerant supplier or producer.[/QUOTE]

The oil supplier is the best to speak to because they design the oil to be miscible with different gases or not.
Like for instance on a ammonia plant with screw compressors we do not want the oil to have a high miscibility, but with a ***** plant with semi hermetic compressors u do want this aspect of the oil to be high.

[girina]

Mmm..
This is my other doubt...
If lubricant has poor miscibility with my refrigerant, it isn't transportated by refrigerant, so the oil transportation could be lower...or not?

I don't know if I'm clear.

[Sandro Baptista]

Mmm..
This is my other doubt...
If lubricant has poor miscibility with my refrigerant, it isn't transportated by refrigerant, so the oil transportation could be lower...or not?

I don't know if I'm clear.

On a R717 plant with flooded system (industrial system) the oil cannot be returned to the compressor by the suction line unless there is automatic mechanisms installed for that (which even on the modern days they exist albeit little people mount their). So the oil accumulated on the drums will be purged out on the lower points. So it is essential that almost all the oil be below level the R717 liquid level.

[NoNickName]

Mmm..
If lubricant has poor miscibility with my refrigerant, it isn't transportated by refrigerant, so the oil transportation could be lower...or not?

Yes, you are right. And in that case you would realise very soon your compressor will be low on oil, unless you have a very large oil reservoir for feeding oil to the compressor and purge it or skim it from the evaporator from time to time

[girina]

Yes, you are right. And in that case you would realise very soon your compressor will be low on oil, unless you have a very large oil reservoir for feeding oil to the compressor and purge it or skim it from the evaporator from time to time

Ok, so the lubricant "migrate" from compressor to evaporator in any case (good miscibility or poor miscibility with refrigerant) then the point is to return the oil at the compressor and the good miscibility is essential... right?

[girina]

And the oil transportation must be 0% or 100%. But the 0% isn't possible, so the oil transportation has to be near 100%.
I've understand?

[NoNickName]

The oil leaves the compressor at high temperature. As you know, warm oil is more liquid than cold oil, so it is easily transported even when the miscibility is low.
Then the oil leaves the condenser and enters the evaporator. Here it gets colder and clogs the evaporator. In low miscibility conditions, the oil remains trapped in the evaporator.

For what concerns your idea of 0% miscibility, it is a good idea, but the high turbulence of refrigerant in the compressor, the high temperature and the moving organs in the compressor, cause the oil to be splashed and sprayed, and finally carried away, even if the oil is not miscible.
Also, most compressors rely on oil returning from the suction to make sure that the suction side bearings and journals are lubricated properly.

Being 0% miscibility technically and mechanically impractical, it is therefore essential to have the highest possible miscibility and circulation of oil.

[girina]

thank you!
You have explained very well what I'd have in my mind! :-)
Thank you very much, now (I think) is all clear!

[NoNickName]

Please add to my reputation points.

[girina]

What you are looking for are miscibility diagrams. For that, you would contact the refrigerant supplier or producer.

The oil supplier is the best to speak to because they design the oil to be miscible with different gases or not.
Like for instance on a ammonia plant with screw compressors we do not want the oil to have a high miscibility, but with a ***** plant with semi hermetic compressors u do want this aspect of the oil to be high.[/quote]


New day, new doubt!
I'm studing and reading a lot of things about refrigerants and lubricants.
Refrigerants.com publish a reference guide about refrigerants and blends for drop in porpouse. In this Guide is explain that R416A is used, without change of oil, with mineral oil. I'ts also explaned that " Although the blend does not mix with mineral oils the addition of
hydrocarbon thins the oil for satisfactory oil return."

So miscibility diagrams wouldn't be enought for establish if a refrigerant blend transport efficacily mineral oil? This tip have to be clarified only in the system in use and with the blend interested?

[NoNickName]

Firstd of all, if you want to speak our native language, please drop me a pm with your email address.

Secondly, as far as drop in replacements are concerned, the refrigerant producer claims are not completely true. Basicly what they say is: "Yes, our drop in are HFC and as such are not miscible with MO, but if you add some HC, then it will be transported along with refrigerant.".

This is ridiculous, and in fact it is possible with any other refrigerant, for that matters, not just those described as "drop ins".

To my customers, I suggested to stay and stick to R22 until at least 2015. Then, we'll see...
Of course, miscibility diagrams are not available for blends between drop ins and hydrocarbons of some percentage.

[Lodiev]

For normal selections of oil with gas u have a table to do the selections. i am trying to attach it but am unsuccessful. give me a private mail and i will forward it to u. The oil u should select is according to the gas mixture and this is pre-determent from the oil manufacturer.
Newer mix gases to get oil return.

[girina]

mmm.. I don't know how I can send PM.. :-S

Ok, I agreed with you, but there are refrigerant blends that already contain a little bit of HC and is said that the HC don't turn the blend miscible with mineral oil, but it enhance the capacity of blen of tranposrt the mineral oil.
It's also said that it depend on the system in use (long tubing, complexed tube) too.

(sorry for my english, maybe will be better in Spanish!)

[girina]

For normal selections of oil with gas u have a table to do the selections. i am trying to attach it but am unsuccessful. give me a private mail and i will forward it to u. The oil u should select is according to the gas mixture and this is pre-determent from the oil manufacturer.
Newer mix gases to get oil return.

Thank you, but I've already seen it.
What I'm searching for is to know how much oil is sufficient to return to the compressor by the refrigerant (100% or less) and how the presence of a little quantity of Hydrocarbon can influence it.
Thank you!

[NoNickName]

mmm.. I don't know how I can send PM.. :-S

Top right corner of the page. PRIVATE MESSAGES.

It's also said that it depend on the system in use (long tubing, complexed tube) too.

Yeah, and that is a disclaimer in my eyes, that frightens the **** out of me. I keep well clear of such ****tails.

EDIT C O C K tails is a totally legitimate word.

[girina]

Ok, so, is a "scaricabarile" and they wash their hands like Pilato!
I like drink ****tails!
thank you!