Autocascade Drawings

Thanks for answer ! I understand all now.

For example, when I used R22/CO2 I can achieve really hard about -60*c idle, with R290/CO2 I can got easly -75*C @ 0bar without any problems. I don`t have to write, that with R290/CO2 I` ve got much better load results (about -65*C @ 160W), with R22/CO2 only ~ -55*C or more with that same load.

BTW, loaded temps on HX with R22 or R290 are very similar, but evap temp is different, so idea with oil, which is lowering heat transfer in HX, is really on place in that case

Cheers

mytekcontrols, can you write to me pm with you msn account name ?

Hmmm good point on oil being an insulator. I was going to avoid the propane due to the flammability but I may rethink that and use a bit for oil movement.

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Originally Posted by Unknown_road

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.

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Thanks a lot! :) would be great!!

@ cut-off valves: I'm sorry, but since my mothertongue is German, I meant some shut-off valves like these ones for example:

http://www.kaeltetechnik-shop.at/ima...ges/1254_0.jpg

The idea behind those was to be more flexible @ the captube lengths after building the unit! ;) New problem: I didn't think of the air which will be inside those captubes after changing its length! --> no more shut-off valves in my auto-c ... I'll edit mydrawing soon! :)

@ the solenoid valves:

The first one @ the direct connection between the bottom of the first phase-sep and the suction line was first plazed after a oilsep directly behind the desuperheater! But mytekcontrols gave me his advice to build it this way because a rotary with ~ > 2HP like this (2,5) should have no problems with a direct connection between HD and ND for about 5sec's per 2/3 minutes! Do you understand? :)

Second one will be used for a faster cool-down @ boot-up! :) It will we kept closed during the first 10-15 minutes and after that, I will open it to get the auto-c's full cooling-power! :D :) Right? ^^

btw.: Thx again for your help too! :)

regards
Patrick aka 404

shut off valves shouldn't be used in autocascade piping imo. too dangerous, forget one is closed and the high pressure gas will build up very fast with no where to go. Same goes for solenoids in high pressure gas piping, the one you placed there is very very dangerous!!

the other one below the phase sep; I still don't get it's function, seems to me like your routing liquid refrigerant directly in your suction, which is bad.

the solenoid for faster pull down should be placed from a liquid point (earlier phase sep) to the cpu evap,with some cap tube offcourse.

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Originally Posted by Unknown_road

shut off valves shouldn't be used in autocascade piping imo. too dangerous, forget one is closed and the high pressure gas will build up very fast with no where to go.

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Hmm .... OK! .. I agree! Didn't think of this! :rolleyes:

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Same goes for solenoids in high pressure gas piping, the one you placed there is very very dangerous!!

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A few people already told me that a solenoid @ this position would be the best solution! :) Except this one:

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the solenoid for faster pull down should be placed from a liquid point (earlier phase sep) to the cpu evap,with some cap tube offcourse.

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I know what you mean! ;) But my problem is (as mytekcontrols already wrote some posts above!), that I don't have any source for solenoid valves with an operation temp. below -40°C! :( So I'm afreiad of a leaking solenoid valve @ this position because of the temperature there! :( 2nd problem is, that it's a little bit difficult to reach the inside of the evap with 2 cap-tubes! (But I think finding a good solution shouldn't be too difficult! :))

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the other one below the phase sep; I still don't get it's function, seems to me like your routing liquid refrigerant directly in your suction, which is bad.

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Please read this Quote here first! :) :

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Originally Posted by mytekcontrols

On face value I would say it does, assuming that R290 and R600a are not good solvents for oil (I don't have this information available, so I am guessing on this part). If you can use at least 1 high boiling point refrigerant that is a great solvent for oil, then you can rely on the 1st phase separator to return it to the compressor for you without causing problems in the colder stages. If not, then a full flow oil separator is your best bet. [...]

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(... as you know: R600a and ESPECIALLY R290 are VERY good solvents for oil! :))

regards
-404

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Originally Posted by 404Power

Hmm .... OK! .. I agree! Didn't think of this! :rolleyes:



A few people already told me that a solenoid @ this position would be the best solution! :) Except this one:

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lots of people here talk without thinking(or even worse, they think they know it but it's actually total crap) , they are a danger for a whole lot off people. A solenoid there is very dangerous and doesn't help pull down. I have seen a few people here whining that walt talks to much about safety but walt is soooo right about this subject. Not enough people here grasp the dangers of high pressure gasses.
Hope I didn't offend to much people but the solenoid over there is uberdangerous.

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I know what you mean! ;) But my problem is (as mytekcontrols already wrote some posts above!), that I don't have any source for solenoid valves with an operation temp. below -40°C! :( So I'm afreiad of a leaking solenoid valve @ this position because of the temperature there! :( 2nd problem is, that it's a little bit difficult to reach the inside of the evap with 2 cap-tubes! (But I think finding a good solution shouldn't be too difficult! :))

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then use the solenoid for liquid propane which isn't -40. It's all about some pre-cooling of the heat exchangers. Problem is that the propane carries oil through the whole system.

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Please read this Quote here first! :) :

(... as you know: R600a and ESPECIALLY R290 are VERY good solvents for oil! :))

regards
-404

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and that's why you don't need a solenoid for the oil return, the propane will carry the oil back to the compressor after it has evaporated in the HX.

Ok ... I see! :)
So your advice is to LEAVE OUT the solenoid @ the bottom of the 1. phasesep. because propane carries the oil trough the whole unit back to the compressor?! ^^

2nd advice is to use the solenoid valve for a direct connection between the bottom of the 1st phasesep. (--> liquid propane) and the evap (with a captube of course! ^^) to get a good precooling? After 10-15mins this solenoid will be closed! Am I correct? :)
(SRY again for my "dumbness" @ undertsanding some of these things! :( Sometimes I just have problems to understand it since English isn't my mothertongue! :()
TIA!

regards
-404

EDIT: New Version! :D :)

http://img376.imageshack.us/img376/3...lannew3ug2.png

EDIT 2:
New problem??? Liquid propane goes through the captube to the evap --> as we know: propane carries oil --> "clogged" (right word?) captube?
Hmm .. don't know what to do now! :D :(

My german isn't that good unfortunatly, you don't speak Dutch by any change do you? mein Deutsch ist sehr slecht.

yes the propane and butane carry the oil through the r600a/r290/r23 HX so that it doesn't get in the lower temperature parts of the system. Problem with the solenoid positioned like this is that the propane carries the oil into the whole system, but since it's only for few minutes I geuss it'll be ok.

@ Unknown_road:

I see! :) OK ... I will do it that way then! :)
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I'm sorry, but I can't speak Dutch at all! :D :( I think we'll have to keep everything in English! ;)

btw: YGPM! :)

R022- NBP: -40.8C; Ct:096.2C; Cp:600psi; BTU/Lb:0,946
R290- NBP: -42.2c; Ct:096.7C; Cp:616psi; BTU/Lb:21,625

Ct = Critical Temperature
Cp = Critical Pressure
NBP = Normal Boiling Point

Aperantly R290 kicks R-22s ass just as I have all ways said, you can't beat nature!

Xeon, your forgetting an INSANELY large factor.
Latent heat of vaporization.

eh have to find that data again, but as I recall R-290 out performed R-22 in actual field tests and cycle energy over life time, For AC aplications it performs excelently, I'm going to do a 6,000BTU test run with it in a heat pump aplication. still awaiting parts to arrive though.


R-290 enthropy of vapourization @ -25C in Kj/Kg: 406
R-022 enthropy of vapourization @ -25C in Kj/Kg: 223

Sorry there it is.

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Originally Posted by Unknown_road

lots of people here talk without thinking(or even worse, they think they know it but it's actually total crap) , they are a danger for a whole lot off people. A solenoid there is very dangerous and doesn't help pull down. I have seen a few people here whining that walt talks to much about safety but walt is soooo right about this subject. Not enough people here grasp the dangers of high pressure gasses.
Hope I didn't offend to much people but the solenoid over there is uberdangerous.


then use the solenoid for liquid propane which isn't -40. It's all about some pre-cooling of the heat exchangers. Problem is that the propane carries oil through the whole system.



and that's why you don't need a solenoid for the oil return, the propane will carry the oil back to the compressor after it has evaporated in the HX.

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Thanks unknown,I appreciate the support it seems to me most skipped basic physics. Walt

Something as simple as a closed valve or closing one when it should not can cause a catastrophic failure, from a pressure rupture, to the meltdown of of nuclear reactor core like at three mile island ,all because a valve was closed supplying cooling water to the core. I know the difference between the outcome of the two situations, but in commercial operations certain places valves are not allowed to be placed,and if needed,a complete failsafe safety circuit must be designed. As we all know no matter how fail safe a design is, We don't trust our machines enough to take complete control from humans. With humans, comes Human ERROR.

AS unknown eluded too some of what is being posted is made up as a thread s progresses by some members ,and that can be dangerous.

I going to stay out of this auto cascade thread unless I see someone doing something way to dangerous, but I don't have time to follow every post.

Mytekcontrols, I'm going to ask the same basic question as I did to cryotek, these drawings been around for many years, may I ask why technical engineering information is not added to the drawings,Even, basic cap tube sizes,tube lengths and diameters ,separator volumes,pressures and mass flows don't accompany them? Most guys here are DIY type and between them all tens of thousands of dollars will be wasted trying to figure out a working circuit from scratch.

Is you reason here to teach other members how to build auto-cascades? as by your stated resume you are the man after 30 years R & D, and if so why not give above mentioned data as patents to original models have expired long ago. that would sure help a lot and save these guys funds from failures & possible dangers from experimenting.

Also As far as I know, a zero O.D.P. replacement charge has not been found for the older polycolds,could you comment on that also.

I'm sure the guys here would be thrilled with specfic information.

Boy does this stuff get out of hand, or out of context very easily. Just to be clear on this, I was not familiar with the refrigerants specified when I was first asked about utilizing R290 and R600 as refrigerants (never used these before). After looking up the information on these (thanks to an additional observation and question by LukeXE), it became readily apparent that these were excellent oil carriers, which as many of you know, is a good thing to have in an auto cascade system.

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Quoting 404Power... The first one @ the direct connection between the bottom of the first phase-sep and the suction line was first plazed after a oilsep directly behind the desuperheater! But mytekcontrols gave me his advice to build it this way...

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As for the additional valves that 404Power showed in his first drawing... these were not based on any of my ideas. My suggestion (which has been both proven and patented), was to add a "time or temperature controlled" solenoid valve (what I called a "liquid diversion valve") with a serially connected cap tube from the bottom of the 2nd phase separator, to the entrance of the evaporator. This valve would only be opened for a very short period of time on start-up, in order to initially pre-cool the upper stages, and thereby speed up the ability for the upper stages to decrease to a working temperature.

The way this works is based on the fact, that condesates that initially form directly following a warm start-up, will most likely be separated from the gas stream predominately in the 1st and 2nd phase separators. It takes a while longer until substantial condensates are available for use in the upper stages. If we take some of the condensate formed in the 2nd phase separator and feed it to the top (via the liquid diversion valve and associatted cap tube), we will jump start the cooling of the upper stages. Since the diversion valve's source is being taken from the 2nd phase separator, and assuming the oil has been virtually eliminated through separation in the 1st phase separator (as well as other good oil control practices like a temprite oil separator, and a good oil carrying refrigerant such as R290), there should be no problem with oil contamination of the upper cooling stages. In fact a system of this design was proven to work reliably, and has the added benefit of being a variable capacity system, through precise cyclic control of the liquid diversion valve (e.g.; warmer temperature operation with higher wattage capability v.s. colder temperature operation with lower wattage loads). You could also think of this as being akin to a transmission in a car, where you can shift gears to suit the load requirements.

If anyone is interested, I can probably find a copy of the liquid diversion patent for all to see.

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Quoted from Wdrzal... Mytekcontrols, I'm going to ask the same basic question as I did to cryotek, these drawings been around for many years, may I ask why technical engineering information is not added to the drawings,Even, basic cap tube sizes,tube lengths and diameters ,separator volumes,pressures and mass flows don't accompany them? Most guys here are DIY type and between them all tens of thousands of dollars will be wasted trying to figure out a working circuit from scratch.

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I have a simple answer to this. I don't have this information to give, and it is never something that was ever part of a public disclosure such as a patent. In fact to this day, much of this information is considered to be a trade secret, and I can't speak for cryo-tek, but I am still obligated to keep this secret for another 2 years because of a signed non-disclosure agreement I made with a previous employer (sorry). As for the statement that these drawings have been around for years, all I can really say is that this particular part of the forum was labeled as "Auto Cascade Drawings", and I didn't see anything posted here that remotely looked like the drawings that I posted, so I presumed that this would be of interest to someone. I figure any information given on this subject should be usefull to someone first starting out, even if it isn't useful to a veteran such as your self.

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Quoted from Wdrzal... Also As far as I know, a zero O.D.P. replacement charge has not been found for the older polycolds,could you comment on that also.

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A zero O.D.P. charge is used on their 552, 662, and 1102 models, but to use it in an older series unit would require that POE oil be substituted for the original Zerol 150, as well as installing dual serial fed full-flow oil separators directly following the compressor discharge (standard in the 552, 662, and 1102 models). It would also require flushing out the system to get rid of the remaining Zerol 150 which is not compatible with the new refrigerants. This can be done, but it is costly.

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Have you used methane in any of your autocascaded systems? If so, what (if any) problems did you have?

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Yes Methane was used in a now discontinued model that Polycold use to sell called the PFC-100. It was found to be very beneficial at bridging the gap between refigerants being used in the upper stage, and thus provided more load capacity. However just to be clear, the improvement in performance was small, but it was enough to warrant the addition. Also it was found that whereas a small percentage of the charge being made up from Methane yielded good results, trying to increase its ratio substantially actually ended up degrading the coldest temperature obtainable.

@ mytekcontrols:

Thanks for your answer! :)

One more question @ newest diagramm:

http://img376.imageshack.us/img376/3...lannew3ug2.png

New problem (:D): Since I don't have any source for solenoid valves which can operate in a temp range BELOW ~ -40°C, I think I'll have to do it this way and connect a "liquid diversion valve" with the bottom of the FIRST phase-sep (since liquid propane + R600a aren't that cold as liquid R23!) ... so .. what to do now with oil? Go back to the roots and build in a third temprite 340 (I will use these oil-seps also as phaseseps ;)) directly behind the desuperheater and connect it to the suction with a 2nd solenoid which opens every (let's say) 5-10mins for about 5secs? Or what would be the best solution in your opinion? :)

regards
-404

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Quoted from 404Power... Since I don't have any source for solenoid valves which can operate in a temp range BELOW ~ -40°C, I think I'll have to do it this way and connect a "liquid diversion valve" with the bottom of the FIRST phase-sep (since liquid propane + R600a aren't that cold as liquid R23!) ... so .. what to do now with oil? Go back to the roots and build in a third temprite 340 (I will use these oil-seps also as phaseseps ) directly behind the desuperheater and connect it to the suction with a 2nd solenoid which opens every (let's say) 5-10mins for about 5secs? Or what would be the best solution in your opinion?

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Yes a Temprite used for oil separation should improve your chances for success considerably, if diverting liquid from the 1st Phase Separator, instead of the recommended 2nd Phase Separator is your only viable option. I'm assuming that the Temprite 340 does not have an internal float valve to regulate oil return (unlike a Temprite 900 series), so that is the reason you are suggesting the use of a second valve. This seems reasonable, although you could also get by with a very small (low flow) cap tube to keep it simple.

Ok, I've got to ask... what does SLHX stand for? I know it's being used as what I called the Sub-Cooler, but cannot figure out specifically what the SL part stands for (the HX part is obviously Heat Exchanger). Please excuse my dumb question, because I have seen others use this term also.

Opps!! I think I just figured it out. Is it Subcooled Liquid Heat Exchanger?

Ya ... You are right! :) The temprite 340's don't have an internal floating valve ....
But I REALLY like your idea of using a captube for oil-return ... I'll think about this! :)

"SLHX" stands for suction line heat exchanger! :)
As you already told me ... there are no "dumb" questions! ;) :)

404Power, Thanks for the heads up on the question (now I get it :rolleyes: ).

Just curious, but what kind of temperatures and watt capacity are you after? I noticed that your system is a 2 cascade system, which is quite capable of very low temperature operation (assuming the load is small). So for instance, I'm guessing hypothetically that a 1hp 2 cascade system with Sub-Cooler, should be able to do -150C at around 30-50 watts. However as the wattage increases, a third cascade would probably be needed to maintain such temperatures.

:fact: Just so someone doesn't jump all over me, I do not consider myself an expert , let me repeat that, I am not an expert when it comes to auto cascade system design. Now that I have cleared that up, I'll go on to say that yes I do have many years experience in this field, and yes many of those years were spent doing Research and Development on these kind of systems (although much larger). However I never went to college, and instead learned on the job, mostly through empirical methods. I will offer my advice, but I don't want anyone to think that my answers are absolute truths. I would always hope that everyone here would also apply their own experience and education, and sort through the information available, before making any firm decisions on the approach that they will take in designing such systems.

Bottomline... I agree with wdrzal and Unknown_road, that this stuff can be very dangerous, so always get a 2nd or 3rd opinion, and if it still doesn't seem clear, then hold off until it does. Don't ever accept something as gospel just because some one tells you so (like weapons of mass destruction :woot: ).

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Originally Posted by mytekcontrols

404Power, Thanks for the heads up on the question (now I get it :rolleyes: ).

Just curious, but what kind of temperatures and watt capacity are you after? I noticed that your system is a 2 cascade system, which is quite capable of very low temperature operation (assuming the load is small). So for instance, I'm guessing hypothetically that a 1hp 2 cascade system with Sub-Cooler, should be able to do -150C at around 30-50 watts. However as the wattage increases, a third cascade would probably be needed to maintain such temperatures.

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No problem! :)
Hmm ... I'm after lowest temps @ about 150-180watts I would say! :D :)
But ... as you can see @ my diagramm ... I'm NOT using a 1HP comp or something like this! ;) My Mitsubishi rotary here is somewhere between 2,5 and 3 HP! :cool: :) So ... which temps @ about 150-180W's should be possible in your oppinion? :)

regards
-404

use a seperate HX for the r600a and the r290, I don't really know if this works well since r290 might be tempted to condens in the condensor but in my experience with autocascades I'd say lots of the r290 will condens in the other HX (dependent on temperatures offcourse)

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404Power said... Hmm ... I'm after lowest temps @ about 150-180watts I would say!

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Silly me, of course you want lowest temps (this is XtremeSystems afer all).

3hp should get you 200-240 watts, but only if you use 3 cascades (with 3 phase separators). I'm basing this on a 10hp 37cfm system (Polycold PFC-1100LT) that will do about 800 watts at around -150C. So proportionally speaking a 3hp compressor should do approximately 30% as well. This also assumes that your 3hp compressor is close to 11cfm. If it is less, then of course either you will get less watts, or a warmer temperature (depending upon how you want to look at it). This is because it's really all about cfm, and not strickly related to a compressor's horsepower.

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Originally Posted by mytekcontrols

Silly me, of course you want lowest temps (this is XtremeSystems afer all).

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dito! :D

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3hp should get you 200-240 watts, but only if you use 3 cascades (with 3 phase separators). I'm basing this on a 10hp 37cfm system (Polycold PFC-1100LT) that will do about 800 watts at around -150C. So proportionally speaking a 3hp compressor should do approximately 30% as well. This also assumes that your 3hp compressor is close to 11cfm. If it is less, then of course either you will get less watts, or a warmer temperature (depending upon how you want to look at it). This is because it's really all about cfm, and not strickly related to a compressor's horsepower.

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Ah .. OK .. I see! :) ... So ... which other gasses would you add to get to a 3rd stage? :)

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Ah .. OK .. I see! ... So ... which other gasses would you add to get to a 3rd stage?

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R14 and Argon, with the subcooler running at around -125 to -135C (final strainer temperature before refrigerant is expanded into the evaporater). This is where the subcooler really kicks A*s! Allowing an appreciable amount of the Argon to dissolve into the R14 for an obviously lower expanded temperature then what R14 could ever do alone, especially at the suction side pressure you will most likely be operating at (probably 20-30 psi under full load).

Opps! gotta get to work, chat with you later :)

@ mytekcontrols:

Hmm ... but as you know ... I already (want to) use R14 + Argon! ;)
But you talked about a 3rd stage ... so .. what do you mean? :( Sry don't understand what the subcooler has to do with a 3rd stage! :(

@ Chating: I would like to ... but ... unfortunaly it's 1h before midnight here atm! :D ;)

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Originally Posted by 404Power

@ mytekcontrols:

Hmm ... but as you know ... I already (want to) use R14 + Argon! ;)
But you talked about a 3rd stage ... so .. what do you mean? :( Sry don't understand what the subcooler has to do with a 3rd stage! :(

@ Chating: I would like to ... but ... unfortunaly it's 1h before midnight here atm! :D ;)

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As subcooler mytekcontrols mean slhx on 3 stage, if I understand well.