View Full Version : quick autocascade question
Sneil
09-06-2005, 03:07 PM
ive decided to have the oil separator directly following the compressor, althogh ive noticed many designs & people put the oil sep after the condensor to flow back with the first stage refrigerant. is this necessary? people then call it a phase seperator as well, why? isn't that the condensor's job?
also regarding oil flow back to the compressor, do i just stick a cap tube at the bottom of the sep, which is a 1-1/2' long by 2" diameter tube with steel wool, of a certain length connected to suction line and be done with it, or should i add a manual valve mid cap tube with a sight glass and open every so often?
thanks
Gray Mole
09-06-2005, 03:40 PM
In an Auto you don't particualrly need an additional oil separator if you use a carrier for the high stage like R290(carries anything) and a refrigerant that's not a carirer for the oil you're using in the Low stage.
IE R290/CO2 using POE oil, the oil will only be carried by the the R290 and will come out in the phase separator. (Hope I'm right on that, it might be mineral that most use, I can't remember if CO2 actually carries anything)
If you choose to use an oil sep, the following...
Compressor --> Oil Sep --> Condensor --> Phase Sep
The condensor's job is just to condense the High stage Refrigerant, which will come out as liquid from the phase sep, carrying the oil(or anything that's left of it if you use an oil sep) HX and then suction line and the low refrigerant carries on to the desuperheat coil and into the HX, condenses there and to the evap head then suction line.
Have you read through the stickies? There's a lot of help there. You only really need an oil sep for Cascade, in an Auto I suppose it's an option unless you're using refrigerants that both carry the oil you're using, then you'd have to. You would either need to run the oil sep with a manual valve that you open on occasion to flush(could put a sightglass there I suppose) or get an automatic one that releases as it's filled.
Hope that's all correct, I'm sure someone will pipe in if I've made any errors :D
Gray
chilly1
09-06-2005, 05:36 PM
exactly
if you use the oil seperator as a phase seperator you will have a more effecient oil removal using disimmilar refrigerants.
there are a few different ways to separate the different refrigerants in an autocascade.
You can feed the refrigerants into the middle of the condenser, higher pressure gas goes out the top of the condenser then to the hx
The lower pressure refrigerant will condense bottom part of the condenser and go to the hx to cool the 2nd stage refrigerant.
You could desupa heat all the refrigerants and separate them after the condenser.
Usally the gasses will be at room temp this situation.
The oil will then hopefully be carried with the high side to the hx (-40c or so) then back to the compressor.
You could place copper wool inside separator as well to facilitate the separation of the oil from the low stage refrigerant.
There are a few different ideas that refrigerant and oil separate at high temp better than low temps, some say it does it at cold temps. (I don’t know)
Then there is the idea that you don’t want oil sitting in the oil separator, (since its before the condenser) the oil will be quiet hot, and it may burn.
Again these are all ideas.
I say just try what you think is a good idea and see if it works.
There are also some good drawings in the stickies for different ideas.
Sneil
09-07-2005, 09:22 AM
thanks guys. yea ive read over the stickies. im using r290 & co2
You can feed the refrigerants into the middle of the condenser, higher pressure gas goes out the top of the condenser then to the hx
The lower pressure refrigerant will condense bottom part of the condenser and go to the hx to cool the 2nd stage refrigerant.
this is exactly what ive set up. i should have known about r290 being the oil carrier it is. :slap: I still dont know why you'd need a phase sep then since the two refrigerants are separating at the condensor... ? ill be adding it however since its already made and im guessing its obviously important.
and regarding desuperheating, is it just coiling the discharge line without active cooling (fan) before it gets to the condensor, or should i coil it around the suction line a few times... i should post some pics to show what ive done...
thanks for all the help :toast:
s7e9h3n
09-07-2005, 06:33 PM
...or should i coil it around the suction line a few times...
That's sub-cooling ;) If it'll help, I can try to get some pics of my autocascade for you and post them here....lmk :toast:
charlie
09-07-2005, 06:51 PM
That's sub-cooling ;) If it'll help, I can try to get some pics of my autocascade for you and post them here....lmk :toast:
Hehehe... all the "black magic" of your autocascade are buried under 10" of foam :D...
wdrzal
09-07-2005, 07:47 PM
Hehehe... all the "black magic" of your autocascade are buried under 10" of foam :D...
Its just like a "magician",if you knew the secrets it would ruin us "Warlocks" :D
chilly1
09-08-2005, 02:46 AM
Hehehe... all the "black magic" of your autocascade are buried under 10" of foam :D...
Yes especially that one and I am sure if you did get the foam off you still would not understand what it does. I got one here in the raw and I get dizzy looking at it.. The critical components are the tubes in the tubes in the tubes that are wrapped around the suctionline and soldered.
s7e9h3n
09-08-2005, 01:32 PM
Well, here's a couple of pics to help you out :p:
http://img394.imageshack.us/img394/8689/image0027us.jpg
http://img394.imageshack.us/img394/2659/image0037cn.jpg
LOL! And here's what you CAN actually see:
http://img394.imageshack.us/img394/9144/image0041yw.jpg
http://img394.imageshack.us/img394/5775/image0013ol.jpg
very nice, how cold does it get??
s7e9h3n
09-09-2005, 08:24 AM
very nice, how cold does it get??
Well, there's a little "plaque" on the back of the unit giving the specs for the unit and for temps it says "-120 to -140C", but I'm assuming that's @ a very low capacity. Charlie's told me that Chilly had the unit @ -100C but tuned it for a higher capacity @ -65. Then I asked Chilly about the unit and he told me that it has a capacity of 180W @ -50C, but I have a feeling his estimate may be a little conservative ;) . With my SD FX55 @ 1.64+ VCore, I've seen idle temps from a thermocouple attached to the side of the IHS as low as -55 and load temps max out @ ~-48.
http://img90.imageshack.us/img90/5787/11x290spi1m8ua.jpg
Sneil
09-09-2005, 09:19 AM
nice temps, but no, unfortunatly those pics don't help much :wth:
i added sub cooling to the discharge by coiling w/brazing to the suction. just gotta get some co2 and im ready to roll.
hey kayl, what were your load temps with that -82c auto of yours?
Gray Mole
09-09-2005, 10:21 AM
s7e9h3n that is just an amazing Auto you got yourself :toast:
Made me wish I was in the US, I'd have been jumping on it myself for what you got if for :slobber:
Gray
s7e9h3n
09-09-2005, 11:10 AM
Not only would you have to have been in the US, you'd have to have been Charlie's neighbor in order for the shippers to actually deliver it intact. I live only 250mi from Charlie, and the shippers managed to dent basically every panel on the unit, let it fall on it's side, break the tie-down straps, roll it over on it's power cord (and as a result snapping the conduit which was protecting it), and drop the pallet with the autocascade on it. And on top of that, they even tried to be lazy and wanted to deliver the unit 3 days after it was scheduled to arrive (we had paid for overnite delivery) :mad: Luckily, the internals seem to be fine though......
Redwolf
09-12-2005, 06:36 PM
Must have made a ticking noise :)
nice temps, but no, unfortunatly those pics don't help much :wth:
i added sub cooling to the discharge by coiling w/brazing to the suction. just gotta get some co2 and im ready to roll.
hey kayl, what were your load temps with that -82c auto of yours?
Never loaded it with -82c co2/r290 mix.
With extra r290 and less co2 I had it benching 3dmark2001 at -55c on me barton. changed evaps from 40mm to 30mm evap for me ati card (really small die)
-55c on me 9600xt, but I ran out of co2 with it benching the 9600xt so didn’t get to fine tune it as much.
Theres a hole lot of pics in me autocascde thread.
Ill get around to making another autocascade at a latter date with 1150 and load it this time.