X² - V², my new Cascade

[Tyrou]

A few weeks ago, I made a R290/CO2 cascade, it worked, but not as efficiently as I would like, so Idecided to build a new one.

The parts :

- a CAJ2446Z, 1HP compressor, designed for R404A
- a SC21G, 3/4HP compressor, for R404A
- a modded Cu/Al condensor
- a TEV on the first stage
- a CPEV on the second stage
- a home made accumulator
- a home made receiver
- a home made oil separator
- two tube in tube HX (5 meters each, in parralel, ¼’inside ½ )
- driers, access valves, some flare nuts
- a metal armed hose, ½ ID, 3 ft
- a home made evap from a copper block, 32*32*25 mm
- a large fan for the condensor, and two papst 4550 for the compressors
- some PU foam and Armaflex

The improvements

- Condensor in the right position, cut in half
- HX with flare fittings to prevent brazing near PU foam
- 1st stage evaporates in the outer tube of the HX
- CPEV instead of cap tube on the second stage
- Receiver on the second stage
- Metal armed hose instead of charging hose
- Total size divided in half
- A nice enclosure
- Compressor are now aircooled with two fans
- Way better insulation

What I still have to do :

- Insulate the receiver with PU foam
- Make an acceptable fix for my evap on my DFI855
- Replace CO2 by Ethane

[Tyrou]

The pics :

The whole cascade










My evap, with his enclosure

[Tyrou]

The results :

Best temp for now :




HX temp :



Evap temp:




Pressures :

First stage :



Second stage

[Tyrou]

hope you'll have some xtreme advices for me

[Aphex_Tom_9]

whoa, nice unit. only -60 though??

[gclg2000]

wow 1HP and 3/4HP. Nice giant compressors. I really like that enclosure you have them in too.

[MaZeR]

Very impressive unit and compact too! It will be interesting to see load temps by comparison when you get the mount finished. Hopefully you won't have much of a drop leaving you a lot of room for tuning

[berkut]

finetune CO2 first

[Dissolved]

whoa, nice unit. only -60 though??

its only co2, and r290.

its not like ICE's triple stages :P

[Aphex_Tom_9]

its only co2, and r290.

its not like ICE's triple stages :P

yeah, good point. although with some tuning i think it could be lower.

[Tyrou]

my first cascade went down to -77.6, with CO2, so it's definetely a tuning issue

it's not so compact as it seems, it measures 62*50*60 cm, without wheels

I did a pressure test this night, the second stage is OK, but the first leaks I think it's an under-screwed flare nut which let the r290 go out, I have to fix that today, before finely tuning the two stages

I contated Air Liquide to buy some Ethane or Ethylene, they're OK to sell it, but they weren't able to give me the price, I have to wait 'til they call me

[Unseen]

nice project bro Well done.

[Tyrou]

thx

Now, i have to work, this leak must be fixed before the sun sets.

[hatemi]

See if your charging hoses leak. I have had 3 hoses that leak propane through even if there were no visible holes or scratches in the hoses. Braze a shcraeder sunt and put it to one of the hoses at a time and preasurize. Put the whole hose under water and see if there are any bubles comming.

[Tyrou]

I'll try this, but I don't think it's enough to explain the meraly 10 bar I lost this night :/

I used your method two weeks ago to ensure my metal hose is leak free :d

Leaks are really a pain, are leak detectors useful, do they "smell" CO2 ?

[Tyrou]

I tried a better blend of CO2 and R290, and my rig doesn't leak anymore

I went to -66.6°C unloaded, but as it's made to be used on a dothan, temps won't increase a lot :d

[Nazaar]

nice housing-job !

[Tyrou]

Thx

Here's today's best temp :



Tomorrow, I'll try to put it on my dothan

[Aphex_Tom_9]

cold day in hell

[Tyrou]

yeah

I would prefer 77.7, the number of boeing over 66.6 the number of evil

[kayl]

looking good.
do you know why the hx is only -20c, colder would help stage 2 a little.

[Tyrou]

I don't know, but I think it's more a temp probe issue than a real temperature problem, as my R290 evaporates at 1 bar in the HX, so it should be around -40°C instead of -20, moreover, the second stage's HP is around 14 bar, and at this pressure, CO2 condenses at -32°C

I'll try to improve the probe's fix, currently, I'm working on evap's housing and mobo's insulation, it shouls be done tonight, and the first tests should happen tomorrow

[berkut]

-66C is really bad. I think you should try increasing the flow.

I get -70C loaded with 2x weaker compressors. You probably have too much CO2.

I have ~5-7 bar condensing pressures (havent checked them for a long time), ~ -40C HX. The fun part is the fact CO2 cant condense at those pressures Still it works. I have to double check on my pressures / temps

The art of a fine tuned system: doing the impossible

[Tyrou]

I totally agree with your last sentence

I'll try a blend wtith more R290 in it, and maybe, open the CPEV a little bit more

[Tyrou]

I think my temp probes are out of order, I tried them on a well working PC, which runs R290 at 0.9bar, my old (broken) probe said -44c, now with these ones, I only measure something between -28c and -33c... I'll go to my electronics shop and ask for a refund :o

But I have another problem, I'm not sure if it's really a problem, but by limited experience with dual stage coolers makes me think that's not normal : I measure the hx temp on the copper tube which connects my HX to my compressor, one inch from the HX. When I turn on the first stage, it takes at least 5 minutes to reach a constant temp (no load, second stage off), it seems very slow, especially when I read fugger's thread about his three-stage which reaches -90c on the second stage in about 30 seconds... Is that normal ??

Thx