Single-stage auto-cascade build

[tiborrr]

So, it has finally begun. Phase separator was already build few months ago:


Today I coiled one of the two coaxial heat-exchangers and braze it to the phase sep:


Second (cascade) HX, waiting to be coiled :


Compressor for test run - Danfoss FR7.5, scrapped from a working freezer. Already grinded down some rust, now it just need some primer + coat love:


I'm going out for a beer or two now!
Best Regards,
N.

[-EC-UnRockStar]

i think the Compressor is to small to handle a load ~200W

Gases?

Subcooler?

[tiborrr]

Hi,

Compressor is just for first run to test out everything. There are some rotaries standing by Subcooler is seen on the second picture, the gases will be n-butane R-600 & R-744.

Best Regards,
N.

[[XC] gomeler]

Best of luck with this, I hope it works

[[486]]

You purge the lines so far? I gave up on my auto mostly because of that, the HX and phase sep has so much oxide in it...

Why not mix in a little propane for the high temp stage, it'll help cool off the co2 in the second. Or are you hoping to avoid dry ice by having a higher HX temp. It has been a while since I've been into this stuff, so sorry if my questions seem dumb...

[captaincascade]

Hi,

Compressor is just for first run to test out everything. There are some rotaries standing by Subcooler is seen on the second picture, the gases will be n-butane R-600 & R-744.

Best Regards,
N.

If you have the compressor your planning to use, then use it. these things are finicky enough without tuning them to work, then changing a part and tuning again

[tiborrr]

@Gomeler: Thank you, buddy. I try to keep my expectations low, but still I'm excited as the project is about to enter the 'charging phase'

@[ 486 ]: Yeah, I purged the lines with nitrogen shielding gas. Used about 1/5 of the 10kg tank just for purging and pressure testing. I'll try to avoid R-290 in the charge as it will 'contaminate' the CO2 charge, making the final CPU evaporator temperatures warmer. I think Mytekcontrol's topic explains this the best.

See, almost emptied my N2 tank :


@captaincascade: I'll keep that in mind, sir!

Here is the final auto-cascade HX assembly with SLHX (refered as 'auxillary' HX by Mytekcontrols), main cascade HX and a liquid/gas phase separator. Had a few leaks at the T-joints, repaired them quickly and now the assembly appears to be leak-proof (still under nitrogen charge):



The long horizontal lines are compressor discharge (condenser) and compressor suction. The port, which is at the moment brazed shut, coming from phase separator's gaseous line is for the direct bypass (of gaseous refrigerant directly to expansion tank).

Best Regards,
Niko

[[486]]

@[ 486 ]: Yeah, I purged the lines with nitrogen shielding gas. Used about 1/5 of the 10kg tank just for purging and pressure testing. I'll try to avoid R-290 in the charge as it will 'contaminate' the CO2 charge, making the final CPU evaporator temperatures warmer. I think Mytekcontrol's topic explains this the best.

I mean R290 in the first stage rather than the butane. Or is it that dry ice problems can be avoided if you keep the co2 closer to it's critical temperature, dropping it in temperature just enough to allow it to condense with reasonable pressures.

If your nitrogen tank runs empty, I always use propane, there isn't enough air in the lines at any time for it to ignite, so it is pretty safe, so long as you are outside. It also gives a nice visual indicator of how fast the purge gas is going through the tube, I keep the flame at the outlet end around 3" tall, good amount of gas going through, but not so much as to waste it.

[tiborrr]

R-600 is probably more suitable than R-290 because butane will absorb more CO2 in the newly formed solution. Can't explain it properly since English isn't my native language, but this is the post that will probably explain this a tad better - link!.

I tend to avoid purging with propane, I can recharge the Nitrogen tank for less amount of money than buying a 5kg propane tank. But thanks for your input, [ 486 ]!

[[486]]

R-600 is probably more suitable than R-290 because butane will absorb more CO2 in the newly formed solution. Can't explain it properly since English isn't my native language, but this is the post that will probably explain this a tad better - link!.

Oops! I forgot you were talking about an autocascade, I was trying to figure out why the refrigerants would be mixed in a 2 stage cascade! Sorry for any confusion I caused!

[tiborrr]

No harm done, [486]!

Just ordered a single-row 0.72kW condenser with 230mm fan /w 10W Papst motor. Hope it will do well with 9400BTU/h L'Unite Hermetique R-22 rotary I will use (I am skipping the Danfoss FR7.5 as per captaincascade's advice). Rotary uses AB oil, R-600 is compatible with mineral and AB so no issues there I think.

[tiborrr]

Pipeline finished, but I ran out of both fuel & oxygen for my brazing torch. Will have to wait until Thursday but in the meanwhile I will manufacture the base plate, the HX housing and bolt down all the components.





Best Regards,
N.

[Turrican]

wow, looks awesome bro
would be great if mine could be tuned a bit if possible.

[Patrickclouds]

hast this flex pipe pvc in it?
or is this only stainless steel?

[tiborrr]

Ofcourse stainless steel, I have never used PVC tubing before.

[tiborrr]

Auto-cascade assembled, currently pressure tested. Tommorow - if no leaks are to be found - I will vacuum the system using the standard triple-vacuum method and charge it with R-600/R-744 for the first time. I may need to charge a bit of R-507 to blend with the CO2 and help flushing dry ice.



Brazed shut port is the so-called wdrzal safety expansion port It will be used for HPCO.




Gas (CO2) line bypass with ball valve connected to expansion device:

[tiborrr]

Update: The rest of the piping appears to be leak-free during the night, will leave it another day just to be sure!

[Turrican]

wow, looks very nice.

trust me guys, i've seen it myself live.

[SAE]

Wow, eager to see how it performs.

[K404]

IM an outsider to phase change but its good to see an autoc again

Hope it goes right first time tiborr

[ruffus]

looks real nice man can't wait to see how it works out as i got my self a real big scroll compressor to make mine from when or if i ever get that far as i still have to get this cascade out that i have been building for the last 9 months

[tiborrr]

Thanks, guys!

First charging went well, although I already ran out of butane. Damn can, two charges and it's over... I'll get re-stashed on thursday, but in the meanwhile I'll insulate the whole auto-cascade, especially the HX stack. I think I can get another 10-15°C just by adding insulation.



First charge - too much of R-600:


Uninsulated auto-c @ R-600/shot of R-507/R-744:


Best Regards,
Niko

[quintus]

Hell yeah! you go men

[bartx]

Nice bulid. Looks very neat

[[XC] gomeler]

Very nice start. Can't read the gauges too well when blowing up the image, what pressures are you running? Looks like 2 bar suction and 11 bar discharge?