Three Stage Cascade

[chilly1]

The beginnings of a beautiful thing... -150C

[JetForcegeminiX]

looks real nice good luck

[saratoga]

I never get tired of looking at system pics. Its amazing what people can build in their spare time.

[hatemi]

What size capline you use from the valve to the evap? Looks sooouu nice A Pro is always a Pro no mater what, and it raly is visible in this sytem.

[chilly1]

The tubing supplying the refrigerant to the evap is a 0.060 ID tube the metering device is the PEV which in this case will regulate the input pressure into the tube...

[JSU]

looks realy nice! btw what kind of brazeing rods do you use?

[chilly1]

looks realy nice! btw what kind of brazeing rods do you use?

On the block I use 56% silver solder and on teh copper to copper I use 15% silver brazing alloy. With teh 56% you must use a floride paste flux with simmilar melt point to the solder. For teh 15% no flux is nessassary.

[cold_ice]

This looks very very good!

It is a bad idea to take copper/phosphor brazing rods? Because I can get 5 c/p rods for the same price as for one silver rod

[Dissolved]

Looks Neat. Wish i had one or 2 of those laying around.

[SlackeR]

not bad, chilly
will it be r507, r1150, and then methane??

[kayl]

do you remember care50 post a few weeks back
r290 50% ethane for -50c at 1 atompshere and lower pressure than r410a
i recond if you got some ethane and played around a little could get a really cold first stage going

[hatemi]

Phosphorous copper is good for copper to copper joints and dont need flux. Easy to use and cheap. With propper Silver rods you can braze almoste anything (exept aluminum) and you can get the rods that are covered with flux so no need for manual fluxing. Propper silversolder costs helluva lot but you realy don't need it unless you solder stainles to copper etc.

[chilly1]

not bad, chilly
will it be r507, r1150, and then methane??

First stage R507, Second R1150 + 2 oz R12, Third R50 +25% R740 + 2 oz Ethlyene + 2 oz R12, This will be the first Range of refrigerant I will try. I am going with R12 instead of propane because of its misicibility with the oil.

[runmc]

1. How do u measure 2 oz?

2. What the heck is R740 and why are u using it?

3. How are you going to add 25%?

[craig588]

2. R740 is argon, it has a boiling point of -182C.

[chilly1]

Argon= R740 instrument grade, R50= Methane CP grade, R 290= Propane instrument grade.. Instrument grade is 99.997% pure , CP grade is 99.95% pure, My propane does not small (No mercaptian)

[pythagoras]

Are those plate HX's expensive?

And is the schematic for that 3 stage in your cascade drawings thread?

Cant wait to get some numbers on that beauty when you fire her up

Regards

John.

[chilly1]

This is my three stage design. There are a few things in the block not shown... But basically thats it. Plate HX's of this size (originally for a 1/2 ton chiller) are 195 US plus shipping. This is my first cascade with plate HX's..

[chilly1]

Update.The Argon needs a colder condensing temp (-130) to operate properly at load. The methane needs -100C to condense, On first run we found we had a dead first stage compressor, changed and restarted, third stage compressor started and hammered then tripped the breaker, Bent rod or broken poiston "Hammered it to 600 PSI" Danfoss compressors destroy them selves at 600+ psi. Changed this compressor charged third with ethlyene temps down to -112C on block... First at top of HX (outlet) -20C second HX (outlet) -70C Minimum for operation with methane is -95C , Working on it, I will post the answers asap... Probably remove the HX's and redesign the interstsage... Need more capacity. Maybe move up to a 2 hp for first and a 1hp for second. Tried a few blends only more of the same Temps stay the same but pressure rises with blend,, no Gains, Blew up a capacitor, dont stand over a start cap on a system.. Covered in Oil from the cap,,, More to follow...

[iboomalot]

ouch well atleast you are making some progress and gathering info.

you guys sure live on the razors edge

***OT***

here after awhile when money if gathered and wife won't notice I will be contacting you via PMs on a nice -60+ single stage setup.

[captaincascade]

Anything over 2 stages requires some seriouse thought. Designing a system so that interstage temperatures are just enough to condense the next stage is foolish. You always need to alow plenty of room for error. When designing a 3+ stage system I will always be sure my 1st stage is nearly twice the size of my second. If designing a 4 stage, use the same logic... like Biggest, bigger, big, 4th stage. lol get me? Also an excellent way to minimize interstage loads is to pipe a completely seperate condenser with a fan, as a desuperheater. Use say, the first 5 or 6 loops to desuperheat the 1 stage. then the next 4 or 5 for the second desuperheater and so on. This will allow the bulk of the heat from each stage to be blown off prior to entering the interstage. This minimizes the desuperheaters physical space, while maximizing surface area.

C.C.

[Unseen]

keep going chilly!!

[chilly1]

Captain Long time no see, I am close to being able to condense methane the bottom of the HX (brazed plate) was -95C. The Metering device is an expermential valve from sporlan, The first compressor I had was 2X times the second but it was a DOA. I used a 1 hp R22 in its place and My condenser is a little small, I am instaling a larger one. Also I need to install a larger second stage air coil before the oil seperator, The discharge temp of the second stage was 215F which is about the limit of the compressor I had there, THe Third stage compressor has the same displacment as the second but with methane the BTU that it will dissipate is nearly half that of the previous stage. So With a few tweaks it should work...With methane.

[pythagoras]

Are you thinking a fourth stage may be required to condense the Argon? I dont know if you can get plate HX's that have 3 routes, can take three gases in seperate paths. Hope that makes sense. You could maybe run the discharge from the fourth stage and route it through all the HX's then.

That way the first two HX's would desuperheat the argon at it could then condense in the third? Probably damn expensive though, even if such a thing exists

Regards

John.

[chilly1]

Are you thinking a fourth stage may be required to condense the Argon? I dont know if you can get plate HX's that have 3 routes, can take three gases in seperate paths. Hope that makes sense. You could maybe run the discharge from the fourth stage and route it through all the HX's then.

That way the first two HX's would desuperheat the argon at it could then condense in the third? Probably damn expensive though, even if such a thing exists

Regards

John.

I am a little dissapointed at the preformance of the Plates but I can work with them. I did a few calculations on the enthalpy and critical temperatures of argon and we will need -140C to condense it at anywhere near resonable pressures.