Just keep an eye on your sub-cooling on your first stage. As long as your condensing refrigerant your ok.
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Just keep an eye on your sub-cooling on your first stage. As long as your condensing refrigerant your ok.
Thx for the help. I will look which condenser I'll get next week.
Although today I had some more time for the cascade. The first stage is running much better now. I let out some refrigerant, otherwise the compressor would had been an ice cube without load within some minutes :D
Highside pressure is 15-16bar now, lowside about 1bar. HX-Temps are in -30° range , -28° on suction line after HX (measured with Dixell thermostat). Today the condenser didn't get that hot as yesterday, liquid line was a little above ambient, but rather cool. Although ambient was a bit lower today, 22°C
So the first stage is running fine...
I also tried to get the HX temps of the second stage down. Got it to about -73° on "load" with only 3rd stage running. Although when I start the third stage the HX-out warms up, up to -30°C! After 3 minutes back to -73°. So when the temperature rises, the condensing pressure in third stage is rising too, pressure switch kicks in at 24bar, and relief valve at 25bar (factory setting).
Thus I will get a soleneid valve, which opens the high side to the suction when a certain pressure is reached (for example at 23bar). So hot gas enters the suction, then the heatload on the HX isn't that high on one time. This should allow a slow cooling down of third stage. I hope this works.
Because when I add more R23 to second stage so that the temp is rock stable when starting the third stage, best load temps are around -66°. Which less refrigerant its -75° loaded.
The third stage is running too. Gets down to -120°. But maybe I'll change the captube for a CPEV. I will also drop Alco an email, because I heard that the make TEVs for R14 on request. But I think they will be very expensive, but worth a try....
http://www.extremecooling.net/random...4stage/175.jpg
http://www.extremecooling.net/random...4stage/176.jpg
Very interesting project! -120 is already a nice number :D Good luck!
Wow, -120 on the third stage it's great!
Can't wait to see the forth in action!
Big work!:toast: :clap:
What makes you think you need a condensor?
To replace the small 1,1kw condenser?
1.1 kw@what discharge,ambiant air temp ,fan speed, ? all these affect rating you may be able to pusk 2kw out of it depeng on how it was rated.
check your sub-cooling :measure temp at bottom exit of condensor accuratly.
then measure low side pressure and look on p/t chart of your refrigerant for temperature and subtract. the differance is your subcooling
all you need is 2 to 3 degrees to be sure you have liquad at metering device., see where your at before deciding you need a new condensor.
do you have condensor rating info???
as long as your comfortable the head pressure is not to high and discharge temperature is ok and you have sub-cooling your all right.
watch you discharge temps so you don't cook the oil,thus your compressor. take a amp reading and see how close your compressor is to its FLA. that tells you how hard your stressing things.
your using a TXV on your first stage right? How come the compressor flooded when unloaded? Is your superheat set improperly? Seems like the high pressure from your previous run was because of floodback. Turn the superheat screw a bit clockwise (I think. screw must go more inside the valve) untill the superheat is about 5-10K. If the discharge pressure is keeps below 20bar I won't worry to much about a bigger condensor.
weird that the r23 TXV doesn't react fast on the load change, 3minutes is a long time for a txv.
congratulations with the -120 ;)
-120C with R14 ?
are you using an expansion tank in the 3 stage ?
do you have enough R23 ?
superheat factory settings will make our small systems overflooded, this will reduce capacity instead of increasing it
EDIT: actually, all TXV industrial systems must have their superheat screw tuned, at least if you have a good HVAC tech hehehe
he is using expansion tanks in all stages except the first. since the temperature is restoring I think there is enough r23 in the system.Quote:
Originally Posted by berkut
maybe at start up the load is to much for the orifice to handle?
@blaster: indeed every time I work with a TXV I turn the screw in.
The first thing wich cold ice could do would be connecting the expansion tanks using a capilary tube. This would decrease the heatload during startup as now not all the gases would be pumped once at a time (thus being condensed).Quote:
Originally Posted by Unknown_road
The temperture is being restored once you pull the temp down and all the gas from the expansion tank has flowed in to the system.
If i had to judge how much heat load there is during startup of a normal cascade's 2 stage comparing to normal work it would be 2-3x
@wdrzal: I don't have a datasheet of the condenser, only written 1,1kw on the invoice. I'll try to get some more information. Will check subcooling next time, do you really mean low side pressure because it must be high side pressure and condenser out temp? Typo?
`
@Unknown_road: Yes I use TS2 with 01 orifice in first stage. I let out some gas, now it doesn't flood the compressor. High side pressure is lower now, at about 16bar, what seems fine to me. So the first stage is running good.
I use 00 orifice in second stage, this should give me 1400 watts capacity with R23 condensing at -20°C and evaporating at -60°C (written in Danfoss catalog).
@berkut: Yes -120° is with R14. I will change the captube for a CPEV, I don't feel comfortable with the captube in 3rd stage. As said all stages except first stage have an expansion tank connected with about 1m 0,9mm captube to the suction lines.
Static charge in 2nd stage with R23 is 10bar, I want to keep the pressure low, so that I can get down to -75° loaded. When I add more R23 so that the HX-out doesn't warm up that much when the 3rd stage starts I only get down to -65° loaded.
ya high side pressure,for sub-cooling, I was up all night , sorry
I like as this surrendering the impressive one:), I want to see a final result to see the maximum thing to what this cascade can arrive :D
Greetings luf1c3r
:O someone make cold_ice a -100C clubmember
AMAZING! looks awesome!
Agreed....IIRC, he should have made the club a LONG time ago with another cascade of his :confused:Quote:
Originally Posted by Waus-mod
better wait till he hits -150 :)
what is holding you back to update?
I'll hope its time, and not more trouble
I'm working to get this unit done. Installed a solenoid valve in the third stage. Replacing the condenser in the first stage with a Luve STVF-193 when I have time.
Any UP Cold Ice?
I'm curious to see this beast in action!:woot:
I'm working on it. I hope to get a TEV for R14, otherwise I will use a CPEV. I have a lot of other units to finish, so my personal unit is not so important right now. Must finish all the other first :(
wouldnt it be easier to just buy a huge tank of liquid nitrogen? Is there a way to use liquid nitrogen then recapture the gas as it heats up recompress the gas back into a liquid and use it again? pressures are too high? How cold is liquid nitrogen? how cold is a 4 stage cascade? Just trying to learn
Thanks
Lee
If we could re-compress LN2, then we could build a LN2 phase change ;) -194C...temps on a 4 stager should be ~-150+C depending on gases/charge.....Quote:
Originally Posted by lross78550