AutoCascade

[mike8913]

Hi everyone. I've been doing a lot of experimenting with single stages lately but i wanted something a little more capable. I've been looking at auto cascades alt especially over a UTI (funny acronym) but I still don't understand how it works fully. The major confusion comes from the phase separator. I can't quite comprehend how it is constructed and many of the guides on UTI are incomplete or broken.

So I was hoping that the more experienced among you might not mind giving really clear definitions as to how the autoC works. Pictures would be amazing too. Thanks in advance if you so choose to help me (and presumably others) out.

[tiborrr]

Autocascade refrigeration system consists of two or more stages (n), therefore you need (n-1) phase separators. Every stage represents at least one refrigerant (or refrigerant blend) phase change. The phase separator is practically a receiver which has a job to separate the liquified refrigerant (high temperature stage) from gaseous refrigerant (low temperature stage). Basic physics and gravity does the trick with the separation of liquid and gas in the phase separator - liquified refrigerant leaves the phase separator at the lowest point of the separator while gaseous refrigerant exits at the top. The already liquified refrigerant is routed through metering device which causes pressure drop and eventually leads to low evaporation temperature. The gaseous refrigerant exiting at the top will later enter the interstage heat exchanger where it will (hopefully) condense.

The low temperature refrigerant flow of e.g. 1. stage gas (like R290 - Propane) is then used to condense the 2. stage gas (e.g. R23 - Trifluoromethan) in the interchange heat exchanger (just like in normal cascades).

I would not recommend even trying to build an autocascade as your first multi-stage refrigeration system since the discharge pressures can go dangerously high in a very short amount of time, i think it's a lot better and safer to start with the normal mini cascade project (e.g. R404A/CO2). You have to take the learning curve slowly.

To sum up, there is no real science in making the home-made phase separator. Make sure it has enough volume (some builders suggest using empty MAPP fuel bottles with aditional brazed-on outlet.

[wdrzal]

Auto-c is very complex, that said Mytek controls has the most inforitive thread I've ever seen.He did a goog job documenting his build from a ac to a cold trap. Keep in mind that the ac unit he used won't hold 300 watts. the design would be very similiar but a larger compressor wouldbe needed.
Ask mytek if you have any auto cascade questions.

below is his build.

http://www.xtremesystems.org/forums/showthread.php?t=144007

[wdrzal]

One more thing, unlesss your very experienced and have a deep understanding of thermodynamics,your project will probably FAIL.

No one has built a unit to hold 300 watts @ -150c like the polycolds did,@ least not that I'm aware of.

Myteks's was a great example but it held 50 watts (great for the purpose he built it for) but would not cool a CPU for overclocking.

[teyber]

One more thing, unlesss your very experienced and have a deep understanding of thermodynamics,your project will probably FAIL.

No one has built a unit to hold 300 watts @ -150c like the polycolds did,@ least not that I'm aware of.

Myteks's was a great example but it held 50 watts (great for the purpose he built it for) but would not cool a CPU for overclocking.

i think most peoples goal is to hold ~ 230w at temps colder then a ss considering how bad the auto-c's of the bast have done... i havn't seen a successful one on the forum... nol claims he built many but never gave any facts/info/pics/evidence so...

[n00b 0f l337]

Built two, one as proof to self, not for CPU holding, since the 1/6hp compressor I used was too small, and one a bit larger which I found I needed lower HX temps, and resulted to parting out due to a lack of isobutane or ethane. (Butane propane and ethylene was decent though, really wish I had isobutane for that one)

[wdrzal]

Built two, one as proof to self, not for CPU holding, since the 1/6hp compressor I used was too small, and one a bit larger which I found I needed lower HX temps, and resulted to parting out due to a lack of isobutane or ethane. (Butane propane and ethylene was decent though, really wish I had isobutane for that one)

Simple question,did you build a auto-cascade yet capable of holding the load of a modern CPU ?????

Answer NO......so the rest is just BS


Noob don't get yourself into a spot like Luke did, auto's at -100c to -150c are very difficult. Don't make promises you can't keep.


Just words of advice. :yepp:

[n00b 0f l337]

Actually I have Walt, holding 200W, but the discharges were a bit higher then I would have liked, though well within decent operating range. I am not selling autocascades, or even units, so take your words of advice ;)