Rack system

[A.Mortezania]

Hi Friends,

I have a question. At photo below, Danfoss says for using several compressors together on rack system, One of the way to maintain oil level in compressors is Dynamic piping.
In this issue, By using gas restrictor P2 will be less than P1. This is clear.

But just this topic is not clear for me, Danfoss says while we use gas restrictor shown below, 90% of oil (coming in suction line) prefer go to upstream compressor. Then as result of higher P1 instead P2 (P1 > P2) extra oil will go to downstream compressor.

Why 90% of oil prefers go to upstream compressor ? Just for this reason than P1 is higher than P2 ? Gas restrictor is simple thing, Why it forces oil to go to upstream compressor ?

Thanks.
15357

[Brian_UK]

Please download this Danfoss document and see pages 15 and 21, they should explain more clearly than I can.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://files.danfoss.com/technicalinfo/dila/17/FRCC.PC.005.A7.02-SM-SY-SZ-Parallel-Nov2017.pdf&ved=2ahUKEwjU5LOcl-zgAhUWRBUIHcL8Cm8QFjALegQIAxAB&usg=AOvVaw1GIT_TYJmGscNtFyqiUxNP

[RANGER1]

Hi Friends,

I have a question. At photo below, Danfoss says for using several compressors together on rack system, One of the way to maintain oil level in compressors is Dynamic piping.
In this issue, By using gas restrictor P2 will be less than P1. This is clear.

But just this topic is not clear for me, Danfoss says while we use gas restrictor shown below, 90% of oil (coming in suction line) prefer go to upstream compressor. Then as result of higher P1 instead P2 (P1 > P2) extra oil will go to downstream compressor.

Why 90% of oil prefers go to upstream compressor ? Just for this reason than P1 is higher than P2 ? Gas restrictor is simple thing, Why it forces oil to go to upstream compressor ?

Thanks.
15357

Page 7 in Brian's link explains pressure drop in compressor P1 suction causes oil to migrate.