why would the suction gas from the evap be any warmer then the evap itself? That's kind off impossible unless your insulation is insufficient.
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why would the suction gas from the evap be any warmer then the evap itself? That's kind off impossible unless your insulation is insufficient.
The suction gas will of course heat up as it begins its return path through the low pressure circuit, and through each heat exchanger picking up heat along the way. And you are correct in your observation that the only reason for any rise in temperature on the interconnecting line from the evap to the top of the cascade heat exchanger would be due to insulation losses (approximately 10 watts for a typical line).Quote:
Unknown_road stated... why would the suction gas from the evap be any warmer then the evap itself?
And this is all fine and well, but what I am suggesting, and that which has been proven over and over again, is that if we isolate what I call the subcooler heat exchanger from the evap return circuit, and we feed it with a small portion of the condensate that exits (about 20-30%), the subcooler itself will run at a colder temperature then the cascade that preceeds it (due to its isolation). This will subcool the condenstate that runs through the subcooler, and allow any uncondensed gases to either condense, or dissolve more readily into the condensate that is present. End result: we should see colder evap temperatures when this condensate is later expanded.
Now as to whether this will be needed on the suggested system that 404Power has shown, is debatable. I just know that in a system that utilizes Argon as part of its charge, we see a substantial improvement in using a subcooler as I have proposed. With the refrigerants as suggested in 404Powers design, and dependant upon the heat load, the subcooler may not yield much benefit.
Of course the only real proof would be to attach a thermocouple on each end of the subcooler (suction circuit or discharge circuit), and measure the difference. If things work as I say, you should see a colder temperature at the exit side of the subcooler v.s. the inlet side. So feel free to prove me wrong.
well I would agree with you if the system was designed for loads above 1kW or something but for a load of 200watt I would just shorten the cap tube to the evap so you have enough liquid comming out of the evap to cool the subcooler. Makes it a little easier I think.
But I have to admit I'm just talking theoretical because my autocascade still didn't reach below -80*C without load :D but this also has to do with that I only have r290/r507/r170 and r1150.
Probably would have been better wtih r290, r170, r1150. That and you have no auxillary cooling which does help with capacity.Quote:
r290/r507/r170 and r1150.
To say it would only benefit a system loaded to 1000 watts or higher is not really the case. It really has more to do with what refrigerants you are using, and how cold you want to get. Even a small system benefits if you want to go below -100C, and do so with a reasonable mass flow (not running the suction into a vacuum). Polycold's P-75 (3/4hp) and P-100 (1hp) units are equipped with subcoolers, and were intended to run at temperatures in the -130C to -140C range.
I meant I only posses these gasses, not that these gasses are in my autocascadeQuote:
Originally Posted by n00b 0f l337
@mytek: I'm not saying you should use a subcooler, just saying you can also feed the subcooler with liquid that didn't evaporate in the evap
This probably wouldn't buy you anything, since what you suggest makes it sound like the evaporator would be running in a "flooded" state, and therefore would also be at a warmer temperature as a result. In an ideal system you really want to completely expand the refrigerant that is feeding the evaporator, and you want this to occur within the evaporator itself. Expanding gases can generally carry away much more heat, then an unexpanded liquid would. This is what makes a refrigeration system really do its stuff.Quote:
Unknown_road stated... I'm not saying you should use a subcooler, just saying you can also feed the subcooler with liquid that didn't evaporate in the evap
Of course there is also a great possibility that I am simply misunderstanding what it is that you are trying to say :confused:
Anyway, I assure you that when a subcooler is implemented in the way that I previously showed, it will produce a colder liquid to enter the final captube, and do so better then any other method that has been suggested thus far. Of course the best way to prove this is to monitor the temperatures going into and out of the subcooler. If I get a chance, I'll do that very thing on one of the systems I service for a company I contract to.
Mytek, what do you think of using unfloated oil separators as phase separators?
@ n00b:
Look here! :) (one of cryo-tek's old "bad projects" - pics! ^^)
Looks like a Temprite 340 there I think! ^^
http://www.xtremesystems.org/forums/...7&d=1145658788
lol offcourse refrigerant is boiling in the evap but since we use very small evap's it very easy to flood them, no vaporisation means the evap is already colder then the boiling point which means the refrigerant doesn't boil off anyway no matter how much is in the evap.Quote:
Originally Posted by mytekcontrols
since the mass flow to the evap isn't much you also don't need that much refrigerant for the subcooler.
Thats what I thought since they're just baffled, plus I got a large box of em.
IIRC, those may not be 340's....they're actually custom made for him from TempriteQuote:
Originally Posted by 404Power
Well they seem to be about the same size as 340's, they have the same input, output, oil spots as temprite 340's, they're clearly steel, so they would only be different on the inside, but whats the difference? Who knows, 340's are just baffles and such to stop liquid from rising under pressure and collisionary forces. I already think they'd work well as phase seps, but thats sorta just a bit of confirmation.
I agree with you n00b! ^^ :)
I'll also use them as phaseseps I think ... can't think of any better solution! ^^
Surely oil seps are much more expensive to use as phase seperators than some copper pipe with a bit of wool inside? Empty MAPP gas bottles would probably be cheaper still for those who use it for brazing. Luke uses the MAPP bottles :).
Luke doesnt have temprites at $5 a pop ;)
Any suggestions on autocascade charging. Im going to pull my hair out soon lol.
The spec of the machine is as follows:
1HP rotary
R290/R23
HX is about 4 metres tube in tube
phase sep is a modified old accumulator about 1 litre capacity
captubes on both stages, 2.5m on evap and 2.5m on hx
I have no idea what pressures I should be running at high and low, also I have no idea how to go about charging it. My main problem is not getting the HX cold, I seem to be getting R290 temps on the evap, obviously the R23 is not condensing and somehowthe propane is making its way to the evap.
Im not sure but this seems weird, either the propane is not condensing (which I doubt) or it seems like the high stage captube is blocked somehow.
What do you guys think?
Check captubes first :)
It seems like blocked R290 captube for me...
Blocked captube makes sense, but if it was, the r290 would be having to build up to the top of the seperator wouldn't it?
True, but maybe he overcharged with R290 (although 1 liter is a pretty a big charge).
Nope, the pressure would force towards the unblocked.
Even if there was wool inside the seperator?
Yes.
Johann, as I said on MSN, try to add more R290 and more R23. You must have both gases inside system to have subzero HX temp.
Definitly!
With autocascades you should expect positive low side pressures, this will result in an evaporator temperature lower then that of the bp (@ 0 bar) of your final gas. With r23 you might expect around a -60C load in a good system? This begins to show its beauty when you have r14 or the like and we can get the -100C we strive for in 2 stagers.
Johann, doesn't the HX get cold at all or only a few degrees below room temperature?Quote:
Originally Posted by n00b 0f l337
Unknown, at first it was only a few c below room temp.
I had a chat with luke on MSN and it seems i was undercharged on the propane. I have now managed to get around 0c on the pipe exiting the hx going to the captube of the evap but still i see propane temps on the evap (around -35c) at 10psi or so lowside.
It seems the r23 is not condensing, and there is not proper seperation happening but at 0c it should be condensed shouldnt it?
What I do see, is frost all the way back to the rotary coming from the evap side. but nothing from the hx side.
Im thinking maybe the captube on the hx is too long or maybe too little R23 in the loop
Well all in all, it is getting better for sure, its not easy this.
At the moment both captubes is around 2.5m
what happens now it that when the HX cools down a bit the propane in the condensor sees no reason to condens in the condensor because it has found a colder place to condens. physics law: everything wants to go to it's lowest energy state .
to prevent this you need the r23, the r23 will "block" the HX entrance for the propane (it needs to fill the HX and large part of the phase sep) and raise the high side pressure making it easier for the propane to condens.
after adding some propane up to a few bar (3 or 4 or something)
try to get a high side pressure of around 10-15 bar with the r23. Then add propane again untill your HX gets cold. The r23 will start to condens so you need to add more r23 untill your evap is getting below propane temps. More r23 is more load on the HX so maybe you need to add some propane again. Keep doing this untill it works or untill you go crazy if it doesn't work :D
Excellent, thanks!
What would you say is a expected highside pressure with no load and say 200w load?
depends on your condensor offcourse but I would expect something like, 12-13bar without load and 15-17bar with.
Exacly, that same I told Johann :toast:Quote:
Originally Posted by Unknown_road
Quote:
Originally Posted by Unknown_road
thats excactly how i think i should tune my auto-c, it must be a nightmare tunning if you add another stage with r14/argon!
another stage with argon/R14 won`t work, you must have first something that boils at ~ -100*c, in that case ethylene, which is :banana::banana::banana::banana:ing hard to tune ;/Quote:
Originally Posted by esdee
geuss I'm not the only one having difficulties with ethylene in my autocascade.
R23 should be good to condense r14.
Don`t think so NoL, under load R23 will boil at -60*C, maybe less, it`s not enough for R14. To have "normal" discharge with R14 Hx temp should be around -75*C under load...Quote:
Originally Posted by n00b 0f l337
Eh...I don`t like ethylene, in autocascades...I got -85*C idle, then changed captubes to little bit longer and now "only" -75*C...god...really don`t know what I should do to get good results.:stick:Quote:
Originally Posted by Unknown_road
same here ;) I also reached something like -85*C idle but it was pretty unstable
I even tried condensing pressure regulators but nothing
Commercially r508a/b is used to condense r14/argon,
Or r13, is used to condense r14.
for us ethane would be a great choice!unless there is something with it that we don't know (except that its flamable)Quote:
Originally Posted by n00b 0f l337
Its very light like ethylene and has a low latent heat of vaporization sadly.
It should be a very good gas, but r508a or r23 (r23 for those who realize its half the price, just eco damaging if you people vent) should be a bit better. The big problem is to obtain temperatures neer a two stage cascade, we need r14, which is pricey as all hell and very eco damaging I"d imagine (CF4)
r508 is pricy as hell to, but its a great gas...Quote:
Originally Posted by n00b 0f l337
I got quoted at $78 a pound, 10 pound minimum, and $150 bottle rental that you get back later. R23 at $44 a pound, 20 pound minimum and the $150. The way I see it is I'll get r23 and have twice as much, plus the resell value on these gases at return is actually on the rise.
r508b it's about the same price here, ill try to get prices on both r508 and r23Quote:
Originally Posted by n00b 0f l337
i have a huge project comming up...
damn it, gasses are more expensive than the materials of the systems.
it's like DSLR cameras, you buy the body for 600euro and then you need 1k for a good lens!
(unluckily i have both hobbies...:slapass: )
Hahahah sounds about right SD, (new name for you :P)
Luckily for me I settled for a D50 with telephoto.
Unknown_road, what gases are you using in your Auto-c ?
I`m trying with R290/R600/CO2/R1150, but in next few days Johann should send to me some R23, maybe it will help. I think that CO2 isn`t the best gas for autocascades, is it ? :p
my nick actually comes from SD :DQuote:
Originally Posted by n00b 0f l337
D50 for me too, nikon 18-200mm VR, and soon 105mm macro :D
but i need gasses too :mad:
At last I am seeing some decent progress, autocascading is happening for sure, not great but at least I know its working.
I made the Propane captube a little shorter to get more flow down there and played with charge. At the moment still not great but evap is around -65c on 5psi low, high is too high, around 15bar and the hx-out temp is around -15c
Im getting a little too much flow from the evap side, so I think I will lengthen that captube a little.
Also I have to braze up some sort of manifold for the propane and r23 bottles to connect to, I cant swap the whole time. I think then I will get the charge better.
IIRC, it shouldn't be a problem.....at least it isn't in my auto ;)Quote:
Originally Posted by LukeXE
@latent heat of vaporization: You sure? My chart puts it at about half of that of r134a, and 3/4 of r507.
Hmmmm I think my charts wrong then!
*going to have take revise it over out of the air liquide library again!*
Quote:
Originally Posted by s7e9h3n
isn't that kinda the way argon helps the situation?mixing with r14 and giving higher suction pressure with better temps (IIRC)
Argon saturates like salt into water.
Im not too sure about this type of autocascade design with 2 stages and phase sep. I did not expect the lowside pressure to be this high. looking at what I did sofar you wont get lowside below 0 bar meaning idling temps in the -70's. What is load then? -55 -60c? By the way this rotary pulls vacuum with straigth R402a I should see -70c anyways and at least -50c -55c with 200w load.
Is this kind of design worth it?
For example, with 3/4HP rotary, R290/CO2 I`ve got -65*C @ 155W of load. Suction pressure - 1barQuote:
Originally Posted by johann
It may not seem worth it, but the unit itself would be more effieicient hopefully. THe true benefit I see comes in when you run a 3rd stage (not counting an auxillary cooling gas)
Luke i see in some other threads your hx temp is -50c how do you get it that cold? I cant get it close to that. I got it to -20c on the hx exit then it just goes up and up. Evnetually I could not get it colder than -5c. I gave more propane, more r23 until pressure n the highside was out of control. evap stays -65c at about .5 bar.Quote:
Originally Posted by LukeXE
I've tried r600/r507/r1150 I'll replace the ethylene with ethane and see if that works when I have some more time (probably about 10 years from now.)Quote:
Originally Posted by LukeXE
Maybe I'll make it r600/r290/r170 but maybe that's too much of an alkane party.
@Tom: KJ/kg doesn't say anything, you need "kJ/Liter".
@nol: salt disolves, the molecules fall apart :slap:
Okay okay you know what I mean,
As the r14 gets cold enough, and the argon gets cold enough, it dissolves into the r14. It then boils out when it enters the low side pressure.
Do you have SLHX before phase separator ? If not, install it. This will solve all your problems I think :)Quote:
Originally Posted by johann
Yeah the SLHX, or auxillary cooler, can increase your capacity and separation. I remember when Luke and I first chatted about that and it did turn out to help alot.
Yes, it`s helping a lot with good separation. The best in this idea is that some of condensed lowstage gas (CO2/R23 etc) is going to the HX, lowering its temperature a lot at idle ! At load maybe not that much, but still it helps with capacity, like NoL said. You will see only good sides of that solution, it won`t hurt the unit for sure :)
Hmm, try to change R507 with something else, I tried with it but no good results at all...I`m preffering R290 :toast: I will try to do some tests with R22.Quote:
Originally Posted by Unknown_road
R600/R290/R22/R23/R1150/R14 mix, hehe, what results I should expect with that mix in 2 stage autocascade ? (two separators) :toast: :banana:
Only one other thing I dont think you've tried yet Luke, the subcooler? Or possibly the solenoid on/off switch which should definitly help.
EDIT: More separators I think, one to get the r600 liquid out to the auxillary cooler, one for hte r290/r22 to the hx, one for liquid r23/r1150. Then possibly a subcooler stage.
I still can`t understand the subcooler idea :|
Hop on AIM or msn :)
Ok, I got it. Thank you :*
No problemo Luke ;)
So, when we will do next autocascade competition ? :toast:
Hahha itll be co2 again Luke if we do, and I can't wait as this time Ive got parts and such.
I would start new competition on 1 of April and end on 1 of September. 6 months of fun :p I must talk about that with Jinu and Runmc.
Of course, CO2 will be ! It must !
I'd be in, nothing colder in the units then co2 though, anything warmer than that call it fair game? That excludes r23, r508a-b, and r13 and most other normal 2 stage gases.
We should stay with only CO2. It`s the most fair low stage gas for everybody, everyone can buy/got it for really funny money and with it everybody can obtain some good results. No dry ice problems when unit will be properly designed.
Yup! But that doesnt mean we should limit ourselves from things like r600, r11, or r21.
I'm sure I can take you on Luke :P
Of course, all gases are OK, mixes are always good. But lowstage = CO2 only :).
Hehe
O I think this year might be very eventful. Maybe we'll see some cleaner units :P
I hope, that we will see a lot of wonderfull builds in this year :) Can`t wait to start competition btw. :woot:
Quote:
Originally Posted by LukeXE
only problem is with each autocascade compertition only a handful enter and only 1-3 actually get them working and holding load:mad:
We should have our first cascade comp using small compressors.
couple 1/3hp units or 1/2hp and tune to 250w ;)
Specially with quad core cpus, and 8 cores around the corner
also if we look at even the single stage comp, baxz is the only one with a finished entry,little sad really.
I would love to try a standard 2 stage cascade competition as I plan on building a unit around two 1/3HP Embraco compressors, everyone says it can't be done but I want to give it a shot. Another AutoC competition would be fun though but considerably more difficult, I'm going to experiment with an AutoC next month. Learned a lot from reading this thread, keep talking guys :)
edit: CO2 as the 2nd stage gas would be perfect also as I can't even find a supplier of R1150 in Atlanta, all the places say they haven't stocked it in years :(
Air gas has R1150 and they have a place outside atlanta I think...Quote:
Originally Posted by gomeler
Order a small bottle.
I have a working -105C cascade at 265 watts cooling that is using two 1/3 hp tecumsehs I have also a working cascade at 200 watts at -90c made with two 1/4 hp compressors. IT is all in the tuning... the HX has to be perfect and you cant use a captube of it will not tolerate large fluxuations in load.
I am working on a 24Vac controller for an electronic TXV for cascade use... this will allow you to have a fully adjustable first and second stage.. tune on the fly ..
O forgot to mention th -105C is a factory unit used to dehumidify air ina process machine.. however teh chamber works fine to chill alchol to -90c and at 3 liters it takes about 2 hours to get there.Quote:
Originally Posted by chilly1
I'll have to continue my search, I've only checked 2 distributors within the perimeter. That eletronic TXV sounds like fun but sounds expensive, I'll have to stick with more common metering devices. Thanks for the heads up!Quote:
Originally Posted by chilly1
I know but lot's of people here say "refrigerant A has a latent heat of 200 kJ/kg and refrigerant B has a latent heat of 100kJ/kg so refrigerant A is better" As long as density isn't taken into consideration kJ/kg doesn't say anything about how the substance will work as a refrigerant. I know that you know this but since lots of people don't I mentioned it for clarity ;) (and because I'm a pain in the *ss probably :lol: )Quote:
Originally Posted by SoddemFX
Does anyone know a number or preferably an email to get a quote from Air Gas or Air Liquide for r1150 in small quantities? (Preferably less then 20 pounds)