So do you want the high temp (high stage?) gasses to be as close as possible to the gas temp suction side, both entering and exiting?
Means that as much heat is bring transfered to the suction gas as possible, right?
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So do you want the high temp (high stage?) gasses to be as close as possible to the gas temp suction side, both entering and exiting?
Means that as much heat is bring transfered to the suction gas as possible, right?
Well entering.
And yes enough refrigerant that your getting down to as cold as possible :)
So you want the highside gas temp entering the HX to be as close as possible temp wise to the suction gas exiting the HX going back to the compressor? Just making sure... I coulda worded my question better before.
I was hoping this thread didnt die.
Otha side. The entering side doesnt really matter so much.
The temperature of the high side leaving the HX should be close to the temp of the suction right before the HX (basicaly where metering device is).
Ah, I see. High side leaving HX and suction side entering HX.
Any news, mytek? Every morning I am looking forward to see progress on your new AC, but I am a little in pre-chrismas stress also :)
just -80! i dont ask for too much:D, i will read and reread again all your post before starting up:)Quote:
Originally Posted by mytekcontrols
thank u!
PhilippF,Quote:
Any news, mytek? Every morning I am looking forward to see progress on your new AC...
I just got done fabricating all 4 heat exchangers last weekend, and I am now assembling them into a complete stack. Probably wont get a chance to do the brazing until my Christmas vacation. So far it's looking good, although I did have a fight with the 1/2" bender on Cascade #1 (and I think the bender won :( ). Nothing that will affect operation, but there are some deep grooves on some of the bends.
I'll post pictures when the stack has been brazed :)
quintus,
-80C can be obtained with only 2 refrigerants R600 (n-Butane) and R170 (Ethane), which are hydrocarbons, so might be easier to come by (and cheaper). Will probably work with only 2 heat exchangers (auxiliary condenser and cascade condenser), and a single phase separator. Just be sure to make the phase separator fairly large, and stuff the upper end with either steel or copper wool. Having fewer stages does require that you do a better job of phase separation, otherwise too much of the high boiling component gets through to contaminate the final stage. !!!Important Note!!! When fabricating your phase separator, be sure it is constructed to handle the working pressure on the discharge side of your system (350+ psi). Also implement a high side pressure switch to limit over pressure. Either 1 5/8" or 2 1/8" OD ACR hard drawn copper tubing with copper end caps works well.
Do you know a good source Michael for refrigerants like r600? I still cant seem to find it anywhere except at insane prices. Is butane really that price?
I cant get r600, maybe but not sure r600a, the same with r170.
I can get my hands easily on: r23 r22 and r11;)(even tomorow if i want to!) say an compresor like this: T-2180GK (Debit-3,89 m3/h, Volum cil.:22,4 cmc) is enought for removing 200watt at -80 with the above refrigerants(r23 r22 and r11)?I think is a bit on the big side:D what do you think?
10x,
q
Yes, I made the same experience here in Germany. Refrigerants are quite easy to get and also (if you now the right places) cheap but hydrocarbons are "special gasses" and very expensiv. For example 8kg R23 costs me 250€ - 3,7kg R1150 350€ .
Ah thats odd. Seems the opposite here except in butanes case. I'm thinking of alternative options at the moment. I have my r11 but sorta want to save it (my precioussssss). They have those tiny few ounce bottles and such and am thinking of a r134a can tap, maybe shim it to work with butane.
http://cgi.ebay.com/ebaymotors/ws/eB...m=310005940898
Ordered.
Okay why not ;)
if it's the lighter butane thats R-600a (Iso-Butane)
As I mentioned earlier, R11 and R23 are a viable combination for making a -75 to -80C autocascade system.Quote:
I can get my hands easily on: r23 r22 and r11
For small quantities it appears that Blazer Products has a possible solution in the highly refined n-Butane refills they offer for their Blazer tools. Here is the MSDS sheet, and it can be purchased on-line from various sources including Stan Rubenstein Assoc. Normally I wouldn't recommend using a fuel grade HC for a refrigerant, but this one might be pure enough to work OK. Ideally a refrigerant grade gas would be the better way to go, although this can get quite expensive.Quote:
Do you know a good source Michael for refrigerants like r600?
I am seriously thinking about using this for my first test charge. The only problem is, I'm not sure how best to extract it from the refill cartridge. Anybody got a good idea on this?
I also came across an interesting paper by L. Maclaine-cross and E. Leonardi called Comparitive Performance of HC Refrigerants that shows the distinct advantages to using HC refrigerants, over CFC's, HCFC's, or HFC's. It appears that not only do they excel from a COP point of view, but also have better heat conductive properties, and offer lower operating pressures (hence less energy consumption). And last but not least, HC refrigerants are highly miscible in virtually all the oils being used in standard refrigeration.
Here's some pics of the 1st Phase Separator, and the brazed stack assembly.
The First Phase Sep is 1 5/8" od x 8", and has the entry tubes coming in at an angle so as to create a spin on any liquids that make up the refrigerant stream. This should help separate the liquids from the gases using centrifugal force. There are also 2 pads of the copper wool stuffed into the top to further aid the phase separation.
The 2nd and 3rd phase separators are simply bullet strainers, whose internal volume is still large compared to the internal volume of the discharge tubes that feed them, so should still do a decent job of separation, especially considering the reduced amount of liquid in the refrigerant stream at these stages.
that looks amazing.....my jaw has dropped
...wow.
That is tight in there.
...wow.
Excellent job planning that out. Im not sure if someone just could "wing it" and pack everything in there so small without serious planning. :up:
2pipes as inlet and two as gas outlet out of phasesep? why not use bigger pipes instead?
regards
Tim
Nice work mytekcontrols
I cant wait to start on a autocascade again.
so all the hxs seem to be the same length and the aux tad longer.
Thanks for the compliments, and yes it was tight and did take some planning, but not as much as one would think. I just "layered it in" (see pics below).
My other choices were: Option #1 one 5/16" od (discharge) inside of 1/2" od (suction), or Option #2 one 3/8" od (suction -- reversed from previous) inside 1/2" od (discharge). Option #1 would not have yielded as much outer surface area as the dual 3/16" od tubes I did use, and Option #2 would have been extremely difficult to fabricate in order to stuff the 3/8" od tubing into the 1/2" od tubing. using anything larger for the outer tubing (such as 5/8" od tubing) would have been too much volume, and resulted in too large of a heat exchanger for what I needed.Quote:
2pipes as inlet and two as gas outlet out of phasesep? why not use bigger pipes instead?
Aux and Cascade #1 are identical, and Cascade #2 and #3 are identical.Quote:
so all the hxs seem to be the same length and the aux tad longer
Here is the nitrogen purging set-up I used to keep everything clean inside (nitrogen cylinder and regulator not pictured). The blue hose is connected to the suction return line from the stack, and the green hose connects to the distributed lines responsible for purging the discharge circuit(s).
I first brazed the stack as shown without any discharge connections. This required moving the distributed discharge purge tubes up as I brazed from the bottom up.
After the entire stack was brazed, I then proceeded to layer in the discharge circuitry as I described previously. When doing this, I only needed to purge from the bottom, since each assembled layer would automatically complete the discharge purging circuit for me.
Wow Michael. I've got to say, I think I'm in love with that pile of copper tubing. Might have some questions for you in a bit, still sourcing parts for my own projects. Looking forward to seeing this unit complete :up:.
Awesome! Now I am really excited to see how it performs :)
Having a little hard time following the heaps of copper but would it be safe to say you have decided to use SGHX for last stage? :)
SGHX? What does that stand for? I figure its some kind of heat xchanger (but what kind)
Suction Gas Heate Exchanger probably?
hmm could be that, come to think of it that would make sense since this is an autocascade, not just an ordinary ss
SLHX = SGHX (more proper term anyways).
You get better temp at cost of capacity in auto-c based on what mytek said in earlier thread :)
Quote:
Having a little hard time following the heaps of copper but would it be safe to say you have decided to use SGHX for last stage?
All the Heat Exchangers are all in essence "Suction Gas Heat Exchangers", and yes this is an AutoCascade without exception. Check out Post #107 for the complete piping diagram, which should help un-jumble the heap of copper tubing. You'll notice that I really haven't veered from my original course in this regard.Quote:
Suction Gas Heat Exchanger probably?
Me too :up:Quote:
Awesome! Now I am really excited to see how it performs
OMG, that's really awesome! :eek:
Wow looks amazing!
sorry for the noobness but will it work :)
Quote:
Originally Posted by HoriWanderFuLL
horri if anyone can do it, mytekcontrols is the man :yepp:
I supose you could easily make your own fractional distalation system to isolate the N-Butane (R-600)Quote:
Originally Posted by PhilippF
Cool the cylinder down to -10 then boil off all the gasses then very slowely raise the temp to a coulple degrees below the boiling point of the target gas. If you want to recover the other gases do so via tempriture gradient and the internal berometric pressure will drive flow.
Closer and tighter you control the temp raise to the boiling point of the target gas the more pur it will be.
Would a water cooled Condencer be too cold for a primary ? I'd be geting 20C leaving liquid refrigerant and even colder after the SGHX (An HX-50).
I have a 6,000BTU Coaxial condencer with a V46AA-1C head pressure modulated flow control valve to lock the condencing Temp (Pressure), I have it set to hold condencing to 110psi on a 3,000 btu compressor (SC12B, R-12, H/M temp w/ Oil cooler). Sensible cooling and subcooling will be insanely good even under max load conditions, thing is with such a topology it may effect phase seperation in an auto cascade type configuration or am I over stressing it?
The above plant is still a blank and I'm thinking of making it to an Auto cascade but thedegree of over cooling I've designed into it is a ocncern to me for the 1st seperation stage.
Actually water cooling is even better. This is the method commonly used for most of the mid-to-large sized systems that Polycold has made (it was also used on some smaller 1HP systems, but not as common). However if you are using chilled water (or just happen to live in a very cold place), and/or anticipate condenser refrigerant outlet temperatures will be much below 18C, then it is wise to run a crankcase heater on the compressor. This will prevent refrigerant saturation in the oil, and save the compressor from having it's cylinder walls stripped of oil on start-ups.Quote:
Would a water cooled Condencer be too cold for a primary ? I'd be geting 20C leaving liquid refrigerant and even colder after the SGHX (An HX-50).
Having a lower liquid line temperature (condenser outlet) will help produce colder temps in all the following stages, and improve phase separation as a result.
I sure hope so, otherwise I really will have nothing but a useless heap of copper :eek:Quote:
sorry for the noobness but will it work
On the more optimistic side, I'm pretty darn sure it will work, and it will achieve -110 to -120C temps (or colder with a tad bit of Argon added). The only question in my mind is how much load can it take. I might also need to boost the compressor displacement from what I'll be initially using. Basically this stuff is difficult to calculate, when it comes to full blown autocascades such as the one I am building.
Oh Ok well I live in a cold climate, Canada when it hits absalute 0 we consider wearing a coat here ;) But I've designed the system so the compressor is all ways the warmest part of the system (Puting the control electonics snug against it all the waste heat keeps it warm :D ) and I'll be using a snap disk thermal cut in to keep it between 50C and 39c.
Ok so thanks I may seriously retask that plant when I have the money to make some HX's
Quote:
Originally Posted by mytekcontrols
Would a Tempright 350 series oil seperator work as a phase sep for this aplication?
Should be, though with higher flows might want a taller and larger volume phase sep.
Thats why I'm asking, and don't forget need to factor in the lighter mass of the Hydrocarbon refrigerants. My system is being engineered for low temp not capacity thus flow rates won't be as high, it is all so on a 3,000btu system. It will only have rughley 700 btu/m latent load at 100 microns chamber vacuum. So evap load will be realitively tiny as all I'm doing is recondensing ice.
H2O at -30 has a partial vapour pressure of.0035 psia
Latent heat:
-fussion: 172.63 BTU/Lb
-Sublimination: 1221.2 BTU/Lb.
Density in F^3:
-Ice= 57.5
-Vapour 14^10-4
Product load: 4Lb apx @ apx 85% water (Ice cream sandwich bars)
It is for my vacuum freeze drying unit that I've been designing!
It's been a while since I posted anything, so here's an update.
Virtually all the refrigerant circuit has been assembled and brazed, including gauges, and expansion tank. The expansion tank was quite a deal, which I got for free when it came off of a customer's unit due to a bad access valve. I simply chopped off the valve and silver soldered in a 3/16" OD tube for connection to my expansion captube.
In one of the pictures you can see my evaporator. This is mainly to be used for doing calibrated heat load tests, and not actually meant to be a permanent fixture. The 50 OHM wire-wound ceramic resistor will be slid inside around the center tube connection. The entire thing will then be wrapped with aluminum foil to radiate any escaping heat back towards the center, and the outside will be insulated very well (I'll probably foam it). This design is called a radiation style heat load v.s. a direct contact heat load. Basically a miniature version of what we use for testing the big Polycold units. Check out my Avatar
My next order of business will be to connect up to 13 thermocouples for temperature profiling the entire HXC Stack, and then insulation + charging.
I'm starting to get excited :D
Oh my god.
Wow.
Seriously Michael; wow. If anyone finds your contact info you might put us all out of business. If I had the cash I'd buy that off you in a heart beat. I wish my work was nearly that good. Maybe the next one will be. I really do like the condensers quite a bit. They really are quite perfect for this sorta application.
Wow.
Also: Still what, 3/4hp rotary? Wow. Love what looks like a hell of a gas selection in the backgroud.
And that a true expansion tank? I've always prefered a suction accumulator since there easier to find.
Also2 (P.P.S.) You have email :)
Also3:
http://img233.imageshack.us/img233/4853/stackat2.jpg
Your work in red as well? Looks like some more nice HX stacks ;)
And finally (but no promises) Also4:
Still using 6500 BTUH rotary? (Just looked back) Damn wish I had more r14 quite badly now (and r170 or r23). I need an investor hahaha :)
Appreciate it, but this one's not for sale.Quote:
If I had the cash I'd buy that off you in a heart beat.
I think it's more like 1/2hp --- 6500BTU. Probably should have went bigger, but I am curious what I can get out of something this size.Quote:
Also: Still what, 3/4hp rotary?
Yep it sure is. Rated for a working pressure of 500 psig. Not bad for FREE :up:Quote:
And that a true expansion tank?
We were doing warranty work for another company, and they gave us a brand new tank to replace this one with, all because the valve stem leaked on the 3-way valve that I ended up cutting off. Just gotta be in the right place at the right time :)
Yes it is, and I put it to good use.Quote:
Love what looks like a hell of a gas selection in the backgroud.
I sent you back your marked up picture with some added notes (see below).
What gasses are in the back of the picture with the evaporator?
Hi Polizei :) You must have posted at the same time as I. If you look back, you'll see that I marked them on the picture.Quote:
What gasses are in the back of the picture with the evaporator?
On another subject...
Final packaging:
I will be using this service to create my front and rear panels: Front Panel Express
The 2 gauges will be mounted flush in the panel, along with an IEC (computer type) power jack, and 3 access valve ports (suction, discharge, expansion tank) so I don't have to remove the panels for charging.
The original top (as can be seen behind the unit) is perfectly usable as is.
No no no, I mean this picture.
http://www.xtremesystems.org/forums/...1&d=1202082706
The ones on the shelf.
Oh those tanks :confused2
Mainly recovered refrigerant charges that we use to top-up in house units.
Ah. No worries. :)
Nice work on the unit. :up:
I dont think Ive ever seen the quick disconnects on the suction or cap before. Would make different evap testing easier for other phase builders here to test to see which evap is best.
Would those valves be ok with the temps?
No not really. At least not the schrader pin aspect. However I've pulled out the pins, and am only using them as flared connectors (-valve). In this regard they will work just fine.Quote:
Would those valves be ok with the temps?
But of course the charge is lost when disconnected.
Ah, I see.
How would R-124 work instead of R-123? R-124 is 400 dollars for 13.4Kg here where as R-123 only comes in 45Kg and is 900 dollars! excluding the tank/cylinder deposits!!!
Well I hope you nail that goal, very inspiring and masterful work :)
Thats awesome Michael! Kepp working, i am thrilled for more pictures of the progress :clap:
I think what I like the most, its not even the tubing and piping which is nice and neat and compact, its that the compressor and condenser with fan assembly comes together, something I never get here in the USA it seems is those damn fan and condenser assemblies. Plus a nice cheap case! I do like your heat loader coil Michael, could easily be stretched out a bit more and become an immersion chiller coil.
This appears to be very similar to Isobutane (R-600a) with a boiling point of -11C (R-600a = -11.7C). Yes I think it would work, although it would be better suited for a water-cooled unit, since the higher boiling point of R-123 seems to work better at moving heat for the elevated temperatures in air cooling.Quote:
How would R-124 work instead of R-123?
Being so similar to R-600a, it makes me wonder what the price difference would be between this and R-124.
Yes I totally agree. Much of the work is done for you, and it allows you to concentrate on the business end, that being to build the HX Stack. And as you pointed out, the main part of the case is already provided as an additional bonus. Just need to fabricate a front panel. Speaking of which, did you check out Front Panel Express? They offer a very slick service, and provide a free CAD application for doing the design.Quote:
I think what I like the most, its not even the tubing and piping which is nice and neat and compact, its that the compressor and condenser with fan assembly comes together, something I never get here in the USA it seems is those damn fan and condenser assemblies. Plus a nice cheap case!
But at these temperatures, what would you use as the liquid? :eek:Quote:
I do like your heat loader coil Michael, could easily be stretched out a bit more and become an immersion chiller coil.
Thanks godmod :) Don't worry, more will be coming soon.Quote:
Thats awesome Michael! Kepp working, i am thrilled for more pictures of the progress
Well, could your autocascade hold a load of say 400w at -40c?Quote:
Originally Posted by mytekcontrols
read the thread and you will know the aimed temps ;)
i think he is more after some -140 at 200W i think
Hoping for:
-100C @ 200 watts (no argon)
-120C @ 150 watts (maybe a very small amount of Argon)
-130C @ 100 watts (even more Argon)
Reality may step in and shave 25-50 watts off of these estimates.
Not built for this temperature range. I have too many stages. A design with only 1 phase separator, and 2 HX's would be far more suitable for -40C.Quote:
Well, could your autocascade hold a load of say 400w at -40c?
I bow my head to the master.... looks VERY nice. If it performs even close to the estimates, I am totally stunned.
Regards,
Philipp
Philipp, he just told Polizei his goals. There are nor results yet, you might have misunderstood this as loadtesting results.
godmod:
i think you are the only one misunderstanding ;) he wrote:
If it performs even close to the estimates, I am totally stunned.
and I agree, with 6-7k btu compressor and -90-100 @ 200w load, I would be very happy.
Yes, youre totally right :)
I didnt read that right
He does have access to all the gases, which I've been slowly accumulating for my own projects. Whop is getting trimmed as I have so much extra height, and truly Mytek's window ac approach is novel. Many of us phasers have done window AC chillers and single stages, but always been too bulky though cheaper, he's used all that space. Even my cascade with small compressors in a window ac wasn't as nice and sorta cramped. He's done a hell of a job.
Ok perfect as most the stuff I build is water cooled! Now trying to find a spare 500 bucks for some R-124!
Adam.... I'd love to see some pics of that cascade in a window ac, do you have a build thread on it anywhere?Quote:
Originally Posted by n00b 0f l337
BTW... Awesome work mytek :up:
Sure I'll dig em up :)
I know I got those pics somewhere, and I know Philly Boy also has a window AC chiller I did for him.
Details of that were a 5500 BTUh lg/panasonic/matsu with a 5500 BTUh rechi, 10 plate hx, capillary on both stages.
Thanks again everyone for your encouragement and praise. It is this which drives me to make this project as excellent as I can. Also as I've reviewed many of the other projects on this site, I have seen several examples of the quality that is possible when someone puts their heart into it. It has been truly inspiring!
I also learned about the possibility of using R-600 from some of you guys, and based upon some preliminary tests I've run on another unit, this stuff is totally awesome in an autocascade. If only it wasn't so flammable, I could see this being used in some of the big Polycold's. But it would require some extensive safety procedures, and special equipment to deal with recovering a charge that consists of several lbs of this stuff (not good to have your vacuum pump's exhaust light up with a match and keep burning for quite some time thereafter). On a small unit, where you are only talking a few ounces, it is not a problem.
What's left to do:
- Thermocouple Stack for Temperature Profiling (I have attached a location diagram)
- Route Access ports for suction, discharge, and expansion tank to the front for later panel mounting
- Make up forms for foam insulating stack
- Foam Stack
- Wire up compressor and fan
- Finish Test Load
- Decide on initial charge composition
- Charge unit and test
- Create Front and Rear panels for unit
As always, I'll be posting updates to keep you guys informed along the way.
the diagrams are very nice and easy to read and understand. i like those.
I'd say you'd want an oilless pump setup to remove the charge. But they use ethane already so isn't it not so much a problem? Or just a large amount of liquid or near liquid state butane might prove to be a problem.
Good diagram work, got a few similar projects now too.
Def going to be doing a much smaller setup as well :)
wow very slick unit! love it
It's the large amount of liquid, plus the fact that it's boiling point is rather high as compared to the other refrigerants being used. Basically the ethane in the charge tends to have it's flammability squelched by the R-14 and Argon that stay mixed with it. Also these 3 gases come out fairly quickly during the recovery process, leaving the R-600 liquid behind. With the other refrigerants gone, the R-600 that is left, is in a nearly pure state (think liquid butane). Being a liquid, it tends to say in all the low spots, and is mingled with the oil. Getting it out by pumping takes considerable time. Also unless you have the pump exhaust vented outside, it is spewing lots of butane gas into the enclosed environment :explode2:Quote:
I'd say you'd want an oilless pump setup to remove the charge. But they use ethane already so isn't it not so much a problem? Or just a large amount of liquid or near liquid state butane might prove to be a problem.
Keep in mind that a 10HP autocascade will use somewhere between 3-5 lbs of R-600. That's a lot of butane!
What is needed is a cold trap between the vacuum pump, and the unit (something like my original AC project). Although this cold trap will need to run down to around -70 to -80C, in order to 100% trap out the butane (remember as we go into a vacuum, the condensing temperature also drops).
Gives me a few ideas ;)
Sent ya another email.
Too secret or too offtopic to post it here?
Hehe, will stay tuned
^^NoL, why did you delete the post? Or was it a Mod?
Hahaha yep deleted em, useless posts and don't add to mytek's thread.Quote:
^^NoL, why did you delete the post? Or was it a Mod?
mytek:
i've reading the thread and I see 3 cascade hxes and one aux, but i havn't really figured out what gases you will use.
r123-r22-r23-r14, argon.. as far as i understand, r123 and r22 will be separarted together with oil in the first separator, right?
then we have 3 gases left.
r23, r14 and argon
r23 will be separated after firsta cascade hx in second phase sep, right?
then we have r14 and argon left.. as well as 2 hxes..
argon is an absorber and you normally use a subcooler to get it work proper, right?
r14 will be condensed by the suction gas together with r23 in second cascade hx,
but whats the last hx (cascade hx 3) ment for?
cheers
Tim
Hi Tim :)
I will probably test with at least 2 different blends initially.
Freon Blend: R123-R22-R23-R14
HC/Freon Blend: R600-R170-R14
And then later try adding a small amount of Argon into the mix.
Your observation about there seeming to be one too many HX's would at first appear to be correct, but remember the ability for the system to completely fractionate the individual refrigerants at each stage is far from perfect.
So for example, if we use the HC/Freon charge which has only 3 components. In a perfect world, or should I say a perfect autocascade, you would expect the following:
1st phase sep = condensed R600 (later evaporated in cascade HX 1)
2nd phase sep = condensed R170 (later evaporated in cascade HX 2)
Final Feed = condensed R14 (later evaporated in cold head)
Notice I left out phase sep #3 and cascade HX #3. A system built like this will work. However to achieve the purest form of R14 at the end, it will require excellent heat exchange, and phase separation design. Many times it is simply easier to add another stage, of a less than precise nature, to achieve a final feed composition that is more purified. Of course the more stages that are added, means you will also proportionally lose out on the ultimate heat load that the evaporator can take on for a given system mass flow. So if you want to move lots of heat, minimize the number of stages, or look at boosting the mass flow (bigger compressor).
Also having another stage, will better enable the system to utilize either another condensible refrigerant with a lower boiling point then R14, or one that can work by absorption like argon.
Just remember too, that a subcooler isn't always required in an autocascade when argon is to be employed. This is especially true when the evaporator heat load will be moderate. A subcooler does it's best work when the heat load is comparatively large, since it is isolated from the returning heat of the evaporator.
I hope that answers your question ;)
sounds good michael :)
I'm currently playing a little with my autocascade and I can't use the hcfc's since I'm in europe.
goal:
~-70 -75*C @250w load
gases I have in stock:
r134a, r23, r290, r404a, r410, r507, r600, r600a, argon, co2
gases I aim to use:
r600, r290 and r23,
parts:
14k btu rotary, 2kw condenser
one phase sep (10" height and 1"3/4 diameter, filled with steel wool),
hxes:
12plate hx as cascade hx
and for slhx/aux condenser I have 13ft 1/4" in ½" as slhx/aux condenser due to the lack of 3/16" in stock (purged during brazing ofcourse).
what do you think about that configuration?
what I havn't figured out is captubes I have 0,026", 0,028", 0,031" and 0,042" avaiable at the moment but other diameters is no problems to get.
I was thinking of something like 10ft of 0,042" for first stage (r600/r290 liquid) and about 15ft on cold head. i talked to adam and he mentioned 7ft first and 12ft second, but I've tried this 0,042" and it's really hard to keep discharge up with a decent suction pressure on SS with 0,042" captube and 18cc compressor.. kinda worried if the rotary will be, or not be able to keep it down.
what do you think about this? I have ball valves which I intend to install captube between for easy access to change captubes... a temporary use ofcourse.. when finding the final tune a recovery will be done and ballvalves be removed and then charging pack the refrigerant.. a good idea?
regards
Tim
Hey Tim :)Quote:
Originally Posted by tim-
If they are able to deal with the cold, there is of course no problem.
Greets
I think right after cap tube maybe a bad idea, however post the flexible line, like Bazx has done will cause less problems.
3 grand for some R-14, don't think I'll be getting any!
Ya for what, like 10 lbs? I payed a crapload for my cylinder of vapor :(
$500 for R-507 and 480 for 13.6Kg R-124
Mr. Pony; using HC's R1150 (ethylene -104C) with a small amount of R50 (methane -161C) might be just the ticket to substitute for the R14 (-128C). I don't know if this would be cheaper, and/or easier for you to get in your area, but it would probably work just fine. The amount of R50 needed would be very small (5%-10%), and it would definitely require at least 3 Cascade Condensers with 3 Phase Separators.Quote:
3 grand for some R-14, don't think I'll be getting any!
Yep thats something I want to try once I get a bit more cash on hand.
Michael, sorry for high jacking the thread, but do you think that you could use the mix of ethene and methane you metioned for the third stage of a conventional cascade? That would be awesome since R50 is cheap, and ethene is anyways needed for the second stage.
This means that ethene and methane go into solution like R14 and argon?
No hydrocarbons don't necesarily work as solute and solution. They can actually make mixes in between that fully condense. Look up non-polar solutions for more.
Wait for Kayl's project. Two stage cascade with twists.
Thanks Michael I was rather disapointed upon hearing that price! R-124 thankfully is within reach albeit pricy. and I all ready have a SGHX ready and waiting ;) Now it is just saving up and geting the gases and prefabed HXs
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Originally Posted by n00b 0f l337
;) Just have to collect some more parts before i start :up:
I suspect that it would, but maybe not to the extent that it would in an autocascade, since we effectively have 2 HX's and a phase separator working with the R1150 and the R50 part of the mix (Cascade Condenser 2 and 3, and Phase Sep 3). This gives us a thermodynamic advantage over the basic 3rd stage of a conventional Cascade. Of course you could always make the final stage of your Cascade into a simple autocascade (Aux and Cascade Condenser with a single Phase Sep). Now wouldn't that be a sweet solution :up:Quote:
Michael, sorry for high jacking the thread, but do you think that you could use the mix of ethene and methane you mentioned for the third stage of a conventional cascade?
This still allows you to make a fairly easy to tune system, since the first 2 stages use only one refrigerant, and the 3rd stage utilizes a binary mix, which is a lot easier to tweak, than a full blown autocascade with 3 or more refrigerants.
Yes it should, and a combination of R14, R50 (methane), and Argon has been used in one of Polycold's smaller units to help bridge the gap, and yield even better load handling at low temps.Quote:
This means that ethene and methane go into solution like R14 and argon?
No problem :) , but don't you mean R-123 instead of R-124?Quote:
Thanks Michael I was rather disapointed upon hearing that price! R-124 thankfully is within reach albeit pricy.
No, I meant R-124 as you stated it would work best with water cooled units, and it is the only one that is reasonably affordable in the quantity range that is of use for me.
Any and all units I make will be water cooled any way so it will work nicely.
Yes that would be a good choice for your application, almost the same as R-600a. The only downside is that it will require POE oil.Quote:
No, I meant R-124 as you stated it would work best with water cooled units, and it is the only one that is reasonably affordable in the quantity range that is of use for me.
It seems to be the only oil around now days in these parts any way! Speaking of which need to pick up another can of the stuff.
Mytec, may I add my thanks and also admiration to the collection of thanks that youve been offered here. Damn nice work in a field thats clearly black magic. Ive read this whole thread over the last few days and the fact that youre prepared to share your hard won experience with the board is very generous.
I did have a couple of questions too.
When I first read about autocascades on this board, I got the impression that they only worked properly at one specific load, and that if the load strayed from this (either higher or lower) the performance would drop off rapidley. But some of the things youve written seem to suggest that that is not true. Could you comment on that? For example, if this system you are now creating is tuned to do say 100w at -130C, what sort of temp would you expect at say 75w, 50w, 25w and 0w?
The other thing is that this thread has me wondering how low you can take this technique. Two things come to mind for me when I see this thread and contemplate following your design to make a copy - one is to act as a first stage for a stirling cooler, JT cooler or pulse tube cooler, with the aim of liquifying helium (I would consider this the holy grail of cooling no?), and the other is to make my own liquid nitrogen which would be useful for some of the vacuum work I like to do sometimes (electron tubes and vacuum stuff).
So how about going down to say -180C - I realise that you might not have done this before but in your opinion do you think its possible?
Thanks again for sharing so much information!
Pete
You can get to a methane stage and beyond yes, so liquifing nitrogen could be possible, large amounts is incredibly hard though.
Peterpion let me see if I can answer all your questions...
Yes an autocascade is not limited to a narrow range when it comes to load. Although just like any refrigeration system, there will always be a preferred, or should I say "as-designed sweet spot" load point where it will work at its best.
Many of the Polycold units I have worked on, have quite a diverse range of loads as used in the various customer applications. The biggest unit (PFC-1102HC) will handle as much as 3600 watts of heat load, while still producing an average evaporator temperature just below -100C. But it can just as easily (and comfortably) run at 150 watts forever, with an evaporator temperature of -140C.
However reducing the load even more (10 watts, 50 watts, ect.) wont produce much colder temperatures, since the proportions of the refrigerants in use have pretty much done what they can.
As Nol pointed out, changing the make-up of the charge will allow even colder temperatures, but at ever decreasing efficiency. As an example; the same system with additional Argon, and less R14, can be coaxed into even colder temperatures (-165C @ 100 watts, -145C @800 watts), but it can no longer handle loads much beyond 800 watts.
And yes -180C or colder is possible, and was done in a few prototypes when I worked at Polycold. It took additional stages, and additional refrigerants such as methane, nitrogen, and neon. But in order to get any useful cooling capacity at these temperatures, the system was gigantic with a 25 HP compressor.
The idea of combining an autocascade with other refrigeration methods as you suggested (stirling cooler), might produce some interesting results, but I can't say that I have ever tried such a thing. Although in theory it would seem like a good approach.
Good question, and I'll see what it does when I get to the testing stage. Which if all goes well (unfortunately it never does), I should be conducting the first load tests late next month.Quote:
if this system you are now creating is tuned to do say 100w at -130C, what sort of temp would you expect at say 75w, 50w, 25w and 0w?
Here is the state of the AC-2 Project as of today:
- Heat Exchanger Thermocouples have been installed
- Refrigerant Line has been Insulated
- Heat Exchanger Stack has been Foamed
Next will be trimming off the excess foam insulation. If you are wondering why there is so much extra on the top, it is because #1) I wanted to fill all the voids and required that the foam rise with a lot of pressure, and #2) because it is just plain difficult to judge how much will be required.
I also need to stretch out the line sleeving, glue it down, and cap off the end.
Looks like I am getting pretty close to firing this baby up, just need to do the wiring, and add an access fitting for evacuating the expansion tank. Unfortunately I wont be able to initially chart more than 8 thermocouples due to limitations in our test software. So I think I'll chart out the following which should give a good overview of what is happening:
- Compressor Suction
- Compressor Discharge
- Strainer#1-4
- Eaporator Inlet
- Evaporator Outlet
The last photo shows AC-2's Big Brother in the background. Interestingly enough, AC-2's Heat Exchanger Stack is very similar in geometry. However Big Brother has 2 stacks in parallel.
Impeccable assembly mate!
Looks great! I love the huge autocascade in the background. "Say hello to my little friend". Can't wait to see you fire it up, really interested in it's performance.