Question's on Scroll Compressor's

[ruffus]

so chilly i have to ask again if i was to use a scroll in a high vacuum i would need a oil sep now all i have is a couple of non floated ones and u were saying something about how i could use a non floated oils sep with out a valve i just need to use a length of cap to as a oil return office could u tell us what size and length that we would use to make this work right without the low side riseing in PSI's because i have to short of a cap tube

[chilly1]

so chilly i have to ask again if i was to use a scroll in a high vacuum i would need a oil sep now all i have is a couple of non floated ones and u were saying something about how i could use a non floated oils sep with out a valve i just need to use a length of cap to as a oil return office could u tell us what size and length that we would use to make this work right without the low side riseing in PSI's because i have to short of a cap tube

basically you can't, you need to inject enough liquid back into the suction side of the scroll to cool it, currently a special TXV is used it senses the temperature on the top of the compressor this is a DTC liquid injection valve as the compressor heats up it opens the valve feeding more refrigerant, some scrolls have built in protection for high superheat and high discharge pressures both resulting in the internal relief opening up and bypassing refrigerant from discharge to suction, so if you were to use a conventional scroll without the internal protection and ran it under high superheat say R507 @ 10 inches vacuum and suction line temp of say 50 you super heat is over 100 these are designed to run at superheat of 8 to 12, there are very few compressors that can run any higher than 20F so any system running in a vacuum is at risk. The only exception is some open frame compressors oil cooled vacuum pumps etc.
So back to scroll compressors, OK say you are running at 10 inches vacuum, your internal surfaces are not getting cooling and lubrication so well add a DTC these inject refrigerant into the compressor enough to cool it say, this will raise the suction pressure to 10 to 40 psi defeating the purpose you wish to use it for... SO then say you hermetically jacket the compressor and use a second scroll to run the compressor at 70F and you use a small pump to lubricate it, you still have huge power consumption to deal with,
Why not design an auto cascade that will better utilize the capacity of the scroll, you can get larger gains in temperature by selecting a high boiler that will give you say -200 to 240F... Nice to experiment with but it would be destructive testing.. fun but not really particle