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No clue, I've never run a cascade with R290 in both stages. I just use R290 to test the system as I can run the 2nd stage without requiring the 1st stage. I'll leave the R290 in the 2nd stage though and see how it'll perform, I imagine I might be able to hit -60C with it as it's more or less a single-stage with immense subcooling.
Hmm really, how could it only be -25C if it was in a deep vacuum? Back when I made a few cascades with propane in both stages my cheap thermometer would always be pegged at -50C/-58F. I am not exactly sure how cold it got, but I think it was somewhere around 20" of vac, and this was testing without a load. Here is a P/T chart to get an idea of the temperature in that kind of vacuum. http://www.glacierbay.com/ptchartpropane.aspQuote:
Originally Posted by [XC] gomeler
The low compression ratio is what really does it since you can achieve such a strong vacuum. But in order to make it work correctly you have to resize your 2nd stage cap tube, it has to be large I.D. cap tube or a CPEV. I was using some really big cap tube I got from a large window A/C unit, and very little of it. This is why I refer to it as somewhat of a "pump". The 1st stage keeps the 2nd stage so cold your head pressure will only be around 20-35psi or so, probably even less when done right as I never insulating anything well when playing with these, and it was when I was first learning about all of this.
But all in all it's a fun way to play with cascades without getting into the dangerous high pressure gasses. :)
Here is an old P/T chart for propane. http://www.glacierbay.com/ptchartpropane.asp
The -25C was a guess, the system hadn't been running long enough to even frost up the suctionline much. Insulating now and praying this looming storm doesn't start throwing lightning bolts.
Ground your unit :up:Quote:
Originally Posted by [XC] gomeler
Ah, well with that much of a vacuum I am sure it was nice and cold, even if the evap wasn't flooded. Good luck with that lightning storm! :eek::D
Rather not risk a surge protector not holding back a surge and blowing any of the electricals. Tornado warning in effect and lightning in the sky :( Oh well, good time as ever to work on non-tuning related stuff.
Nothing like funnel clouds and 3" hail eh Gom?
Are you getting hail out in the sticks? We've just got an immensely large cloud looming from the north and periodic lightening flashing from it. Very little rain and no hail. It is also quite warm, I'm in shorts and a t-shirt working :cool:
Bah, as long as you're not in a trailer park you'll be fine. :caution:
ahhh good ol' Canada in enjoying my -2C outside and no funnel clouds
ahhhh nice and sunny southern california. What is this rain and hail you speak of?
Just kidding been raining and hailing here for the past 2 weeks.
haha 76 and sunny today, but windy as hell. The storm Gom is getting is going south of me.
Man we had big down pours yesterday in the central valley, filled my pool up to the top !
Today nice and sunny, but clouds rolling in again.
The weather forcast tonight... mostly dark with scattered light in the morning :)
I would never say this myself but, as a child I was always told that the only good thing to ever come out of Alabama was I-20 :shrug:Quote:
Originally Posted by Gunslinger
Jus kiddin, hope all of us in the areas beseiged by Mother Nature stay safe.
And, Gom, the reported hail was all around us but none here at the house luckily. If we get enough I'll go out and get some and do a quick iced OCing run with it.
insulated the first stage last night. Briefly tested the first stage and decided I want to remove one of the filter driers and merge the two condensers into one single filter drier. The system in it's current form requires too much refrigerant to get liquid seals on both capillary tubes. Otherwise I'm satisfied with it. Later today I'm just going to precharge the second stage so I can start testing the insulation and be able to sufficiently load up the HX. This thing dumps a ton of heat from that condenser though, warms up the room nicely :up:
Chris get your camera out :)
I would really like to see some pictures of how this is turning out :--)
It's still too much of a mess. I just drained all the propane out of the two stages and snipped the filters off the 1st stage condensers. Going to braze in a new filter now and insert the two capillary lines into this single filter. This should halve the volume of my liquid-line and help reduce the static and operating pressures.
That should not reduce operating pressures.Quote:
Originally Posted by [XC] gomeler
A captube don't need liquid seal like TEVs do. Quite complicate to explain this so sorry I can't explain it in english.Quote:
Originally Posted by [XC] gomeler
Why aren't you using a TEV in the first stage? Here in Germany you can buy them for less money (don't know how the prices are in the US) on ebay and they are much better and less work than captubes. :)
I shouldn't have put operating pressures, but it will help reduce the static. As for TEV versus capillary, this cascade was build roughly 2 years ago and I'm simply chopping a few things, adding a few things, and pushing it out the door to fund a more advanced project.Quote:
Originally Posted by Moc
Regarding the liquid seal bit, there's a certain point where you just don't have enough liquid to feed the capillary correctly. My issue is the bottom row of my condensers are lower than my capillary tube entrance and I'm sure that bottom row is flooded with liquid refrigerant.
If anything it should reduce start-up operating pressures since more refrigerant = more load on system, so when it first starts up and has to condense all that refrigerant you get some nice warm condensers! Without having as much refrigerant it should lower the pressure on startup and of course condenser temperature as well, since the two are related. This brings me to the next point: static pressure. Since you're talking about the first stage, the static pressure won't change since it's only going to be as high as the vapor pressure of the propane at any given temperature, so static pressure isn't anything to worry about in this case.Quote:
Originally Posted by [XC] gomeler
By the way, why did you chose to go with 2 condensers and 2 cap tubes? Mainly curious about the cap tubes, since you might have gone with 2 small condensers instead of one large one because that's what you had.
any updates?
Well, the dual condensers still don't have enough capacity so I'm waiting on a larger condenser. It was supposed to be shipped on Monday, need to contact the guy to figure that out. The problem I have is the 1st stage discharge pressures under load still go up towards 300psi with suction around 10 psi. I'm not happy with such high discharge pressures so I'm dropping in a more appropriately sized condenser with aims of a 200psi to 225psi discharge.
don't forget if u need it i have a condenser that would put almost anything we use to shame
Ah, that's strange, seems like they should be able to handle it. Of course if they were in series and with one cap tube it would probably work better.Quote:
Originally Posted by [XC] gomeler
Yup, I had considered that but without stacking them vertical and making a tower of condensing power, I'd run into all sorts of liquid trapping problems.Quote:
Originally Posted by aenigma