Oil Accumulation

[ozankalkan]

hi everyone!
i'm very new in refrigeration and sometimes some big problems. this one is one of them well, i hope i could get my solution here.

during the refrigeration cycle, some oil of the compressor flows with the refrigerant.while it is flowing into evaporator from capillary tube, oil accumulation happens in the entry of the evaporator. i wonder how can i prevent the evaporator from oil accumulation.

i'm sorry for terminology
thanks.

[nike123]

hi everyone!
i'm very new in refrigeration and sometimes some big problems. this one is one of them well, i hope i could get my solution here.

during the refrigeration cycle, some oil of the compressor flows with the refrigerant.while it is flowing into evaporator from capillary tube, oil accumulation happens in the entry of the evaporator. i wonder how can i prevent the evaporator from oil accumulation.

i'm sorry for terminology
thanks.

Hi, ozankalkan. Welcome to RE.

By carefully designing system and maybe using oil separator.

Describe little more your problem and system layout.

[paul_h]

question:
Is the compressor and evaporator on the same level?
Problems normally occur on poorly designed systems or if the evap is below the compressor.
Refrigeration engineers solve this through careful design, the rest of us use oil separators!

[powell]

during the refrigeration cycle, some oil of the compressor flows with the refrigerant.while it is flowing into evaporator from capillary tube, oil accumulation happens in the entry of the evaporator. i wonder how can i prevent the evaporator from oil accumulation.

Until you give us more information as nike has suggested, Let's assume this is a freezer.

Take a look at the defrost operation of this unit to verify all is working well. I always like to see a minimum of 4 defrost cycles in a 24 hour period.

Proper defrost cycles are very important in low temperature applications. Excess frost restricts the airflow and reduces coil loading. This can cause oil to be trapped in the evap possibly causing floodback to the compressor.

[Gary]

during the refrigeration cycle, some oil of the compressor flows with the refrigerant.while it is flowing into evaporator from capillary tube, oil accumulation happens in the entry of the evaporator. i wonder how can i prevent the evaporator from oil accumulation.

What type of system are you working on and why do you believe that oil is accumulating in the entry of the evaporator?

[ozankalkan]

thanks for your replies.
well this problem occurs in refrigerators. there is a capillary tube with heat exchanger. capillary and evaporator tubes are jointed by welding. since capillary diameter size is too smaller than the evap tube diameter, the oil accumulates while flowing into the evaporator tube.
by the way compressor is below the evaporator, not on the same level.
how should i design the system? and what is the oil separator?

thanks again and again.

[Gary]

question:
Is the compressor and evaporator on the same level?
Problems normally occur on poorly designed systems or if the evap is below the compressor.
Refrigeration engineers solve this through careful design, the rest of us use oil separators!

Even the best separators allow some small amount of oil to pass, so eventually it ends up where it shouldn't be... and this brings us back to careful design.

[Gary]

well this problem occurs in refrigerators. there is a capillary tube with heat exchanger. capillary and evaporator tubes are jointed by welding. since capillary diameter size is too smaller than the evap tube diameter, the oil accumulates while flowing into the evaporator tube.

Why do you believe that oil is accumulating? What are the symptoms?

[ozankalkan]

Why do you believe that oil is accumulating? What are the symptoms?

This is what have been told to me by some experienced engineers. they also told me that they hear some oilish sound while refrigerant is flowing into evaporator.

[ozankalkan]

img91.imageshack.us/my.php?image=oilxd8.jpg
well this is what i try to tell

[paul_h]

Even the best separators allow some small amount of oil to pass, so eventually it ends up where it shouldn't be... and this brings us back to careful design.

Even the best compressor fitted with separators sometime seize up, I seem them and read about them all the time.
Ohh shi..

Seriously, it was a light hearted response because not much information was given
Forgive me, I shouldn't have. This is serious business, but it's 11.45pm here and not much to do
Sorry ozankalkan, at least I got you to tell us whether the compressor and evap where on the same level or not and find out whether you know what an oil separator is.

edit: this is his image from the above post. Saves people copy and pasting as I can hot link so I hope it makes it up to you.

[Gary]

This is what have been told to me by some experienced engineers. they also told me that they hear some oilish sound while refrigerant is flowing into evaporator.

Those experienced engineers are wrong. Any oil entering the evaporator is swept through the evaporator by the flow of refrigerant. Oil does not accumulate at the evaporator entrance.

[ozankalkan]

Those experienced engineers are wrong. Any oil entering the evaporator is swept through the evaporator by the flow of refrigerant. Oil does not accumulate at the evaporator entrance.

So why is there a patent which is named "oil separator for evaporator"?

[Gary]

So why is there a patent which is named "oil separator for evaporator"?

Because it is possible for oil to accumulate in other parts of the evaporator, not the entrance.

[Gary]

Would it be possible for a few drops of oil to accumulate as shown in the drawing? Yes. Would this affect the operation? No. It would not be enough to make any difference at all. It is not important.

[powell]

Would it be possible for a few drops of oil to accumulate as shown in the drawing? Yes. Would this affect the operation? No. It would not be enough to make any difference at all. It is not important.

I agree with Gary.

If it's an issue you have trying to have a 100% perfect system then just don't insert the cap tube too far in the evap inlet.

[nike123]

Do you maybe know what velocity of refrigerant you have in evaporator and what kind of refrigerant you using? Could you explain evaporator design?
Where is refrigerant injection, at top of evaporator or at bottom?
Do you have parallel circuits or serial circuits in evaporator?

[monkey spanners]

What problem is the oil accumilation at the entry to the evaporator causing? What are the symptoms?
Is the capiliary blocking up?

Cheers Jon