Heh easy to find yes, but only in 100lb drums as far as I've seen.
When I do my autocascade I'm using a Danfoss sc12mlx, and running r11, r134a, co2, r1150 if I can get some ethylene and avoid co2 problems.
Heh easy to find yes, but only in 100lb drums as far as I've seen.
When I do my autocascade I'm using a Danfoss sc12mlx, and running r11, r134a, co2, r1150 if I can get some ethylene and avoid co2 problems.
If you have a cooling question or concern feel free to contact me.
Won't it be quite difficult to go r134 -> r744?Originally Posted by n00b 0f l337
OT: Spoke with Cryo-tek earlier today. He says he'll try his best to stop by and see the recent happenings. He's been swamped at work and it's sounding like he may even be MORE busy in the coming weeks. Good for him and his business, bad for us and our autocascades
Nope because they generally use r134a to condense r508a. And then the r508a will help as well.
If you have a cooling question or concern feel free to contact me.
Yes R-11 was good stuffEven better was R-114 (also banned). Heck back in the CFC days you could get by with 4 refrigerants and easily achieve -150C or better. The charge: R-114, R-13, R-14, Argon. The HCFC replacement was as I described earlier R-22, R-123 (replaces R-114) R-23, Ethane (replaces R-13) R-14, Argon. The HFC only version gets even more complicated, and also requires POE oil as well as a very good oil separator. Of course if you don't mind using flammable gases you can still get away with a less finicky oil, and probably eliminate the oil separator, since most flammables are also excellent solvents for oil.
404Power I think you can do away with the solenoid valve coming out of the 1st phase separator, and check out the attached diagram for an even better trick for accelerating the initial cool-down.
Diverting liquid from the 2nd phase separator for the first 10-15 minutes after a warm start-up should speed up the cooling of the entire cascade-evap circuit without putting too much oil downstream in the process.
Moc on your question about which compressor to use, Rotaries are usually best when size is an issue. As for other advantages I'm not certain since I have no actual hands-on experience with anything other than a conventional hermetic. Perhaps someone else can jump with their experiences. Cap tubes vs. TXV, I would stick with cap tubes, since most TXV's were really only intended for a single refrigerant, and probably would be difficult (but not impossible) to match up with an auto cascade system.
Last edited by mytekcontrols; 01-09-2007 at 12:22 AM.
Michael St. Pierre
- Worked 15 years for Polycold Systems
- Now Self-Employed
- Manufacture Heat Load Controllers
- Also do contract service work on Polycold units
Side note: I usually don't respond to PM's or emails regarding the projects that I post in the forums. I feel it's much more fair to all, to answer questions within the forum topics themselves.
Very interesting post mytek !
You've confirm that I've supect about R14 / Ar.
Nice Schematics and very usefull information.
Sub cooler is used to create a SLHX where there are "no" incindence of charge put @ Evap, you can also use the "cold return" in the succion to make better T
Welcome in XS and have fun !
Overclocking-TV Staff
Ha, ha, ha.....NO WAY.....When I show someone preparing to take a shot, I hided the cigarette....
Thanks Steven
Hi, nice to meet you mytekcontrols
At last we have someone with big knowledge about autocascades (so bad that cryo-tek isn`t with us now).
Thanks for your answer!404Power I think you can do away with the solenoid valve coming out of the 1st phase separator, and check out the attached diagram for an even better trick for accelerating the initial cool-down.
Diverting liquid from the 2nd phase separator for the first 10-15 minutes after a warm start-up should speed up the cooling of the entire cascade-evap circuit without putting too much oil downstream in the process.
One more question: What do you mean with the term "liquid diversion valve"? I'm sorry but I don't know any valves like this!
TIA!
regards
Patrick aka 404
are there any good books you would recommend from which i can learn more about cascades.
I have some experience with autocascade and TXV, but it didn't work as I hoped, cappilairy is more efficient. Long ago, Redwolf posted some pictures of his autocascade on Teampuss, he also used a TXV and it worked rather well but I still think cappilairy is a lot easier, no hunting, no superheat screw adjustments everytime you change the charge etc.
On the issue of oil sep, they're pretty useless in most cases. The refrigerant speed is very low in the phase sep so oil can't nearly get "upstream" and the other (low pressure) gasses are bigger in amount and liquid so they will carry the oil very good.
@n00b: SC12 is too small for an autocascade if you ask me. I've tried building one with an electrolux MP14FB but suction pressures just went up too high (3barg wasn't uncommon).
404Power... yes the "liquid diversion valve" is simply a solenoid valve followed by a cap tube which is sized probably about twice the flow of the one feeding into the top of the 2nd cascade (no exact science on this one, experiment and see what works best). It would be "opened" during the first 10-15 minutes (nothing exact about this either... experiment). However be sure that the solenoid is rated for cryogenic temperatures, since you will be seeing close to -60C at this point (most conventional solenoid valves are not designed to go below -40C without leaking). Something like an ASCO LN2 valve, or a Sporlan XUJ would do the trick.
I also got your email on the subject of how to size cap tubes. Since I feel it is of interest to all, I will answer the question here...
Unfortunately I don't have a clear cut answer on this one. Back in my development days, the approach taken was to base cap tube flows for a new design on an existing working system. Take the percentage of CFM difference between the existing system, and the new design, and then apply this percentage of change to the flow rates of the existing system's cap tubes. Since I was never a part of the development process for the very first system created and perfected, I do not possess the knowledge and/or the calculations that were used to create it, and thus fine-tune its cap tube flows for a working system. I also don't have access at this time to the original design paperwork for any of the units that I helped develop, and it has been nearly 20 years since I was doing this. My brain no longer retains the information
Last edited by mytekcontrols; 01-09-2007 at 09:31 AM.
Michael St. Pierre
- Worked 15 years for Polycold Systems
- Now Self-Employed
- Manufacture Heat Load Controllers
- Also do contract service work on Polycold units
Side note: I usually don't respond to PM's or emails regarding the projects that I post in the forums. I feel it's much more fair to all, to answer questions within the forum topics themselves.
LukeXE thanks for the compliment, but I am also equally impressed by what you have been doing as well (checked out some of your projects). I also loved how you recycled the MAPP gas cylinders into phase separators (now that's a GREEN machine!!!).Quoted from LukeXE... At last we have someone with big knowledge about autocascades (so bad that cryo-tek isn`t with us now).
I have a good feeling that cryo-tek will be back, and probably pretty soon (he better, before I give away all the goodies).
Michael St. Pierre
- Worked 15 years for Polycold Systems
- Now Self-Employed
- Manufacture Heat Load Controllers
- Also do contract service work on Polycold units
Side note: I usually don't respond to PM's or emails regarding the projects that I post in the forums. I feel it's much more fair to all, to answer questions within the forum topics themselves.
Hey mytekcontrols I also have a question
The AUX Condensers... are they made like heat exchangers? Or are they just an additional fanned condenser?
Thanks
the aux condenser is like normal heat exchanger, so it`s just SLHX before phase separator.
Aux if you look are heat exchangers, they need to be to be a heat exchange between high and low sides.
If you have a cooling question or concern feel free to contact me.
Cheers guys
What sorta size would a pipe-in-pipe SLHX be? For either an autocascade or just a standard cascade?
Personally I think the most economical from my own stand point is 3/8 in 1/2, of course you could do better and there are commercial ones. I think Ricky's five or six 1/8 in 1/2 or the like is great too, but a pain with all the little endings. All up to you. 3/8" in 1/2" is very tight though, tight enough to use 1/2" for a coupling sometimes (i do)
Really just need ot find a fitting combo without too much room inside the center pipe. 1/4" in 1/2" may leave to much room in the outside though.
If you have a cooling question or concern feel free to contact me.
What about in terms of total length?
Could a plate HX also be used?
I think that plate HX for aux condenser will be too big, no need for that efficent heat exchanger. For sure about 1,5 long HX (6mm in 12mm pipe) will be enough (IMHO).
@mytekcontrols, I just want to ask about R22/R290. I used both in normal autocascade, with CO2 or R23, and ALWAYS I got much better results with R290/R600 instead of R22. Why ? R22 should be better, but it`s not (in my case)
Last edited by LukeXE; 01-09-2007 at 12:10 PM.
Thanks again for your reply!404Power... yes the "liquid diversion valve" is simply a solenoid valve followed by a cap tube which is sized probably about twice the flow of the one feeding into the top of the 2nd cascade (no exact science on this one, experiment and see what works best). It would be "opened" during the first 10-15 minutes (nothing exact about this either... experiment). However be sure that the solenoid is rated for cryogenic temperatures, since you will be seeing close to -60C at this point (most conventional solenoid valves are not designed to go below -40C without leaking). Something like an ASCO LN2 valve, or a Sporlan XUJ would do the trick.
I also got your email on the subject of how to size cap tubes. Since I feel it is of interest to all, I will answer the question here...
Unfortunately I don't have a clear cut answer on this one. Back in my development days, the approach taken was to base cap tube flows for a new design on an existing working system. Take the percentage of CFM difference between the existing system, and the new design, and then apply this percentage of change to the flow rates of the existing system's cap tubes. Since I was never a part of the development process for the very first system created and perfected, I do not possess the knowledge and/or the calculations that were used to create it, and thus fine-tune its cap tube flows for a working system. I also don't have access at this time to the original design paperwork for any of the units that I helped develop, and it has been nearly 20 years since I was doing this. My brain no longer retains the information
My problem is now that I don't have any source for "special" solenoid valves!
@ captube lengths:
Sounds quite interessting!
I just would need roughly estimated lenghts ... after that, we will see and go for a shorter/longer captube @ each stage!
regards
-404
btw:Agree with that!
Last edited by 404Power; 01-09-2007 at 01:21 PM.
the flow through a cap tube is dependent on the length, the ID and the pressure difference across it (and the refrigerant). Since you can estimate what load is applied to all the heat exchangers and you kind off now the compression ratio you can quess the cap length within a nice margin of error. Use the cap tube sizing rule that Gary Lloyd posted here few years back as an extra help. Cap tube sizing doesn't have to be rocket science, as long as the length is in the ball park your ok.
@ Unknown_road:
I know what you mean!
Anyway, I would be really thankful for any help from you, mytekcontrols and/or any other user here @ XS!
regards
-404
I really hope you're right, but I'm not sure how he'll find the time. He's trying to fill an order currently -> 16 x 10Hp autocascades "probably" can't be hammered out overnight...can they?
ok, I assume it is for the autocascade you posted a drawing off a few posts back? Why are there so many (high pressure?)cut-off valves? also the solenoids seem to be placed wrong, can you explain the reasoning behind these, I'll calculate something up when I now if these have any effect.@ Unknown_road:
I know what you mean!
Anyway, I would be really thankful for any help from you, mytekcontrols and/or any other user here @ XS!
regards
-404
Last edited by Unknown_road; 01-10-2007 at 07:46 AM.
If I understand the question right, my guess would be that you are getting superior oil return with the R290/R600 combination. If you look at the boiling points listed below, R22 and R290 are virtually the same. So like you mentioned there really shouldn't be a big difference in this regard. However due to the fact that R290 is probably far superior to R22 at returning oil, it doesn't surprise me that it would yield better performance (remember any oil left inside the heat exchangers, will tend to inhibit the heat exchange process, due to an insulating affect). R123 also has good oil returning properties, so when combined with R22, will probably produce similar results.Quoted from LukeXE... I just want to ask about R22/R290. I used both in normal autocascade, with CO2 or R23, and ALWAYS I got much better results with R290/R600 instead of R22. Why ? R22 should be better, but it`s not (in my case)
R22 boils at -41F
R290 (propane) boils at -44F
R600 (butane) boils at +31F
R123 boils at +82F
(sorry that the temps are not in degrees C, not on the chart I am using)
Michael St. Pierre
- Worked 15 years for Polycold Systems
- Now Self-Employed
- Manufacture Heat Load Controllers
- Also do contract service work on Polycold units
Side note: I usually don't respond to PM's or emails regarding the projects that I post in the forums. I feel it's much more fair to all, to answer questions within the forum topics themselves.
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