First test run cascade: -72C / -98F

[DaBit]

http://www.icecoldcomputing.com/images/page_images/proj210k_lowtestrun1_72c.jpg

:)

I actually reached -74C before I pinched the captube totally shut. The 1.5 meter 1.2mm I.D. tube is way, and then I mean way too short. To increase restriction I pinched the tube almost closed over 30cm. And the last step was one too far, and even without the last step I was far from a solid liquid seal at the captube entrance.

Good insulation and better captube sizing would help a lot.

Some preliminary data (I didn't measure everything yet):

- Evap temp -74C
- Low stage refrigerant: R410A
- Low stage evaporation pressure: 0.25 bara (-77C)
- Low stage condensing pressure: 2.7 bara (-31C)
- Low stage discharge: 37C
- Interstage HX temp measured at the surface: -36C

No high stage measurements since I only have one gauge set and tempmeter.

I'm happy so far. Not bad for a first test run.

[ellsworth]

very very nice dabit. its good to see some numbers finally

[charlie]

Congratulations!
Very impressive....
Can't wait to see more.
C

[DaBit]

Neither can I :)
Mind you, it is still far from a useable system; a lot of optimization needs to be done. The high stage works correctly, but the low stage is still far from correct operation.

Damn, I hate those inflexible captubes. I wish I had not destroyed my needle valve on top of the evaporator.

[]JR[]

Inflexible captube?!?! my cap tube is bendy as anything?

]JR[

[DaBit]

With 'inflexible' I mean that I must open the system to adjust it. To solve this, I added a needle valve on top of the evaporator. But it proved impossible to braze a captube in without it blocking the needle path or being brazed shut.

But it wouldn't have made any difference; the captube is way, but then way too unrestrictive. More than my needle valve could adjust.

Back to the drawing tables. I'm investigating whether or not I could turn a TEV into a heat motor operated EEV :)

[berkut]

Great work Dabit !

Nice to see that more and more peapole run their cascades :D:D:D:D

With ethane and your skill'z (CS style ^^) if it comes to controll freon flow you will brake -100C first run ^^

And your needle valve inspired me to try 1 thing with one of my Golf II injectors

[DaBit]

Yup. Condensing and evaporation pressures are ridiculously low with R410A..

[bowman1964]

good going dabit.:toast:

looking nice:D

[DaBit]

Thanks Bowman :)

[bowman1964]

you should hit -57c loaded temps i am guessing with that 410.

that is looking good thou.

i was going to try some 410 also but not in the cascade.but i have 6 cans now of diff stuff in my small room,i cant put anymore with me unless i want a trip to the moon if something ever goes wrong.:D

[DaBit]

The problem with that R410A is that suction pressures drop too far.

On the other hand, the liquid is already very cold before it enters the captube. This should increase efficiency.

Bowman, what is the lowest suction pressure you have seen with a CPU load?

[bowman1964]

Originally posted by DaBit
.

Bowman, what is the lowest suction pressure you have seen with a CPU load?


Well a true load(actuall computer) as i am using either a p4 running 1.82v @4250mhz or a amd xp1700 @2.05v 2957mhz both will run between 0 to 5hg.

[DaBit]

Uh, what I asked made no sense since your comrpessor is larger. What about the prommie? That compressor is my low stage compressor.

[bowman1964]

Originally posted by DaBit
Uh, what I asked made no sense since your comrpessor is larger. What about the prommie? That compressor is my low stage compressor.


thats is with a prommie compressor.since i do so much work with them now, i work from those pressures.alot easier for me to keep track that way.

[DaBit]

Hmm, if a prommie can maintain that suction pressure, I have a good chance to stay in the -65C range with R410A

[bowman1964]

Originally posted by DaBit
Hmm, if a prommie can maintain that suction pressure, I have a good chance to stay in the -65C range with R410A

well it may be possable,
but i will bet on -57c to -60c

i think it will proberly run with 410c around 2psi to 3hg somewhere in that range.


but you know the numbers better than me.

i am a hands on guy on the spot thinker.

but if i havent said this before,you are one of the brightest minded people i have ever met.i am sure you will get it running as best it can:D

[DaBit]

Well, now I have to do the captube mumbo-jumbo :)

Suddenly I love TEV's :)

I will replace the crappy A/C compressor in the high stage for an 1.5hp R404a low temp unit (Tecumseh CAJ2464Z) which I can get for free. That should help temps also. I can also obtain an Danfoss SC15 for shipping cost only, but if that would work better than my current NL11F: i doubt it.

[berkut]

Dabit - that SC15 should work veeerryy good ^^

Right now im thinking of smth. i did when i started building phase change systems- i had service valves on the evap so i could measure the pressures very percise, right now im considering using a thick cap tube for this... (connected to a shrader valve somwhere else in the system- easy to connect)^^ I wont use this in my cascade, maybe later but its smth i wanted to share

the second thing is mounting the high side shrader valve on the discharge line- i think that that way we can fine tune the system much easyer and we loose much less freon, why:
-when we connect the mainfold some of the liquid freon is pumped to the mainfold and fills the lines- every connect destroys the balance in the system
-when we calibrate the system we get rid of vapour rather than liquid wich later evaporates- we can let freon out much more percise

I always mound the service valve on the discharge line beacause of the aspects i mentioned above

[DaBit]

I once did that also (~50cm of 0.8mm ID tube), mounting a schraeder through a captube on the evap, but pressure drop over the suction line proved to be insignificant.

And I always mount my high side schraeder on the discharge since I don't like liquid coming out of the valve when disconnecting.