4 stage cascade

[Sneil]

Hi Cold Ice, You want -160, is that C or F ?

Check out the Temprites at : http://www.temprite.com/main_catalog...y=288&item=965

Think out side the box... something like a mix in the R14 stage and a second separator after an added auxiliary condenser to trap the oil and the added high boiler. The oil will need to be miscible with the high boiler. Zerol would be a good choice for the oil. A cap tube could be used to control the feed of the high boiler back into the suction upstream of the auxiliary condenser. You could get some good suction cooling for the compressor and some precooling of the R-14 This would be sort of a hybrid of a cascade and an auto cascade. The high boiler, I'm not sure but my first thought is R-22. I need to think about what it might do when mixed with the R-14.

Another thought, R-14 will give you -120c with a 10 psi evap pressure. Try adding some argon to the R-14. This should lower the temp. but drive up the discharge pressure and temp. The added suction cooling provided by the high boiler will help overcome this.

Sounds wacked? I have systems that will do -170c with low loads. -135c with 2500 watts of heat load. Yes these are auto cascades.

Stay cool,

Wow, looks like a phase change god has just entered the forums...
wlcome to xs!

EDIT: and what kind of autocascade do you have running with temps @-135C on a 2500Watt load??? What size compressor?

[n00b 0f l337]

Are there any types of pressure refliefs that releive the pressure from highside into low side?

[Jort]

just a pressure cut-off and a solenoid valve parallel over the compressor...

[GuuZ]

what's a solenoid?

[Unknown_road]

what's a solenoid?

In our language we call it a "magneetventiel"

[GuuZ]

ok, but what's the exact function of a solenoid valve in this case?

[cold_ice]

Hi Cold Ice, You want -160, is that C or F ?

Check out the Temprites at : http://www.temprite.com/main_catalog...y=288&item=965

Think out side the box... something like a mix in the R14 stage and a second separator after an added auxiliary condenser to trap the oil and the added high boiler. The oil will need to be miscible with the high boiler. Zerol would be a good choice for the oil. A cap tube could be used to control the feed of the high boiler back into the suction upstream of the auxiliary condenser. You could get some good suction cooling for the compressor and some precooling of the R-14 This would be sort of a hybrid of a cascade and an auto cascade. The high boiler, I'm not sure but my first thought is R-22. I need to think about what it might do when mixed with the R-14.

Another thought, R-14 will give you -120c with a 10 psi evap pressure. Try adding some argon to the R-14. This should lower the temp. but drive up the discharge pressure and temp. The added suction cooling provided by the high boiler will help overcome this.

Sounds wacked? I have systems that will do -170c with low loads. -135c with 2500 watts of heat load. Yes these are auto cascades.

Stay cool,

-160°C is my aim, I've done -115°C with a two stage cascade already. I got the Henry oilseparators rather cheap, this is why I used them. My first choice are Danfoss oilseparators, never tried a Temprite.
Do you have pictures of your autocascades? -135° with 2500w is crazy, must be a real big unit. What are you cooling with this monster?

I fired up the cascade yesterday (first three stages). But the first stage seems to have a problem, high side pressure is pretty high with R404a when all stages are on (23bar!). Temp isn't good either, about -35° HX-Out. I'm not really happy with it. Shortened the captube two times, still the same problem. Will shorten it today for another time, if this still doesn't work I will try a Danfoss TEV instead. The other two stages seem to work fine, but I can't tune them when the 1.stage isn't working correctly...
Saw some temps in the -130°C range with alot R1150 in the 3.stage, just a few squirts of R50 in it. It's awesome when the whole suction line back to the compressor "smokes" because of the cold temps.

[Unknown_road]

I think chilly used temprite oil seps with R14 but they didn't work well enough either.

cold_ice: can you give more info about the first stage? condensor temperature, suction pressure and superheat ?

[cold_ice]

Top of condenser was warm/hot, bottom was ambient, discharge line was pretty hot. Suction pressure was 0,5-1bar, suction line was frosted back to the compressor until 3cm.
I know this is inaccurate, will note the exact temps and pressures today afternoon.

Also get another offer for R14, 1,2kg for 160€. 6kg for 500€ would be cheaper (per kilo) but 1,2kg should be enough for several cascades. Will order it.

[esdee]

Hi Cold Ice, You want -160, is that C or F ?

Check out the Temprites at : http://www.temprite.com/main_catalog...y=288&item=965

Think out side the box... something like a mix in the R14 stage and a second separator after an added auxiliary condenser to trap the oil and the added high boiler. The oil will need to be miscible with the high boiler. Zerol would be a good choice for the oil. A cap tube could be used to control the feed of the high boiler back into the suction upstream of the auxiliary condenser. You could get some good suction cooling for the compressor and some precooling of the R-14 This would be sort of a hybrid of a cascade and an auto cascade. The high boiler, I'm not sure but my first thought is R-22. I need to think about what it might do when mixed with the R-14.

Another thought, R-14 will give you -120c with a 10 psi evap pressure. Try adding some argon to the R-14. This should lower the temp. but drive up the discharge pressure and temp. The added suction cooling provided by the high boiler will help overcome this.

Sounds wacked? I have systems that will do -170c with low loads. -135c with 2500 watts of heat load. Yes these are auto cascades.

Stay cool,

are you working in a cryo cooler company?

Also get another offer for R14, 1,2kg for 160€. 6kg for 500€ would be cheaper (per kilo) but 1,2kg should be enough for several cascades. Will order it.

do you have a recovery unit?that would be ideal when dealing witch such expensive gases

[piotres]

cold_ice, maybe You should try CPEV on first stage ??

[Unknown_road]

A cpev on a first stage is a bad idea if you ask me. To much load changes.

[cold_ice]

TXV would be the best I think.
But I hadn't good results with valves in my previous units.

[Jort]

are you working in a cryo cooler company?




do you have a recovery unit?that would be ideal when dealing witch such expensive gases

R14 with a recovery

and like U_K saids, a 4stage with cpev on the first stage is asking for trouble

[Unknown_road]

you guys seem like the mythbusters, you only want big boom!

btw cold_ice TXV's are sometimes hard to handle indeed but when they work it is ideal! Make sure the bulb is placed on a horizontal piece of piping and the let the pipe go upward after the bulb so the liquid wants to stay there. I think this will improve reaction time and prevent floodback most efficiently.

[404Power]

Plz explain why CPEV @ first Stage isn't a rly good idea! ^^

[Jort]

because the first stage needs to transport VARIABLE loads

go figure, a cpev keeps the pressure CONSTANT

[cryo-tek]

Cold_Ice, Have you tried R-22 in your first stage? Another thought is to try adding some R123 along with the R-404a. The 123 will Reedley condense and reject lots of heat at the condenser. What can I say, I'm an auto cascade guy and I like to mix my gas.
When I start with a proto type I use 6 to 8 cap tubes to get to my expected flow. This gives me the ability to pinch closed some to adjust the flow on the fly.

The temprite 900 series are coalescing separators and should remove most of the oil. Are you putting the 4th stage oil separator someplace were the discharge gas has been cooled?

Do you have a drawing of your system?

I'm off to my mom's this weekend but when I get back I'll draw up something else you can play with. What gasses do you have? Do you have a spare compressor in the 1/20 hp low back range?

Stay well,

[Unknown_road]

why try r22? R404a should work fine. why trow in r123? it isn't logical that it will reject heat at the condensor, it will probably vaporise in the compressor just adding extra heat to the condensor.

[esdee]

R14 with a recovery

i know you can't recover r14 in it's original bottle. (cause you cant get it liquid again) but in several regular freon bottles... i do this all the time to save as much ethylane i can

[jinu117]

Ethylene? Lol... at least that is cheap gas that is natural forming for sure... Cheaper than most refrigerant out there anyway...
And here I am sitting wondering how can I recover r508 lol... good luck... maybe i need those 100lbs recovery cylinder instead of 30lbs ones here for some decent amount of recovery...

[cold_ice]

I can get R22, buts not allowed to use in new units here in Europe. I don't get the idea of using R22 instead of R507 but ok...
I don't have a drawing, but the circuit is nothing special. Almost the same as 2 stage cascade only with 4 stages.
Ethylene is not that cheap here, about 45$ for one kg.

[cold_ice]

Did some more testing today, shortened the captube down to the half (1,8m). It got a little bit better, but I'm not happy up to now. Maybe I'll replace the whole captube, or I will try a TEV.
Blending the methane with the ethylene is like a game, sometimes it droops very fast to the lowest temps, than it gets 5° warmer again. I this mix wouldn't hold load well, R14 is the better choice here for sure.
And maybe R23 in the second stage instead of the R1150 would be better. This gets expensive...

Some pics:











Pressure 1.stage


Pressure 2.stage


Pressure 3.stage










Here a little video: http://www.extremecooling.net/random...stage_test.mpg

[n00b 0f l337]

Welcome to -100C club :P
Nice shooting there mate. Amazing setup. Don't you need to start worrying about co2 in the air and other such gases condensing onto your evap?
I can't wait to see the insulation.

[esdee]

Ethylene? Lol... at least that is cheap gas that is natural forming for sure... Cheaper than most refrigerant out there anyway...
And here I am sitting wondering how can I recover r508 lol... good luck... maybe i need those 100lbs recovery cylinder instead of 30lbs ones here for some decent amount of recovery...

i know it's rather cheap, and you need way to many bottles to recover a high pressure gas in air form, but i usually save small ammounts of ethylane that i need to release or charge the system while finetunning... nothing special but with so many tests i have made i guess i would have need twice the ammount of ethylane i have already consumed