CryoBUG is Back

[mytekcontrols]

Hey, who's that good lookin' guy in the pics?

My wife for some odd reason which I can not fathom agrees with you

Stack looks great btw. I like your use of the brazed captube for subcooling. I started using that myself on most systems so I could get a nicer tuning charge.

For this I think it's crucial, and it should take less HP charge to get effective condensing which could hopefully keep lowering the head pressure and CT.

Well it was my only option, since I haven't quite mastered the knack of stuffing another piece of tubing inside an already coiled HX. It's rather tricky as you probably well know, to keep the cap tube tight against the tubing you want to braze it to. And as can be seen in the pic below, even more difficult to keep it going in a straight line. But assuming this works, in a future build I would simple stick it inside with the other one before I coil the HX, or change the ID of the existing one to suit the flow requirements.



And yes I use Windex as a truly "clean" refrigerant to power this thing

Pics work from here too though, not sure what's up at Kang's end

Yep working here on all my devices, OS's, and Browsers
My only thought would be that I am hosting on Blogger which is now owned by Google, and I know China has been censoring some of Google's content. Perhaps they think it's some strange version of :banana::banana::banana::banana: (Bondage or Sadomasochism)

[mytekcontrols]

Hopefully this one will be easier to follow.

[ultralo1]

Brazing the cap tube is a PITA. I have ended up brazing one end onto the suction line, then puling it tight like I want. Then i use soft solder and flux for the rest of the connection.

On the cascade HX/SLHX, is that an accurate representation of the placement of LP refrigerant cap tube? Approx half way?

[mytekcontrols]

On the cascade HX/SLHX, is that an accurate representation of the placement of LP refrigerant cap tube? Approx half way?

Yes that is correct. So the first half of the HX is the Cascade Condenser, and after the cap tube disappears you have the SLHX section which is essentially a sub cooler. And obviously since the cap tube that feeds the cascade condenser is inside it, it too gets useful sub cooling by the returning gases.

BTW, do you like this diagram better?

[Gray Mole]

Definitely like the new drawing. Easier to follow, though the original Fuderer wasn't really that bad. His pics representing the components were a bit weird tho

Seems like he actually got TEV's to work on an auto too. That's pretty cool. The first Auto I made was exactly like that, only with captube as well.

Complete hideous failure though

I've finally gotten most of the stuff together to start mine too.

I'll make up a thread for it, don't want to hijack this one.

[mytekcontrols]

Definitely like the new drawing. Easier to follow, though the original Fuderer wasn't really that bad. His pics representing the components were a bit weird tho

Seems like he actually got TEV's to work on an auto too. That's pretty cool. The first Auto I made was exactly like that, only with captube as well.

The first diagram I posted is actually done more in a schematic format for what is called a P&ID drawing (Process and Identification). It isn't suppose to be very detailed, but more importantly it is to map out all the main components in a simple form.

Yeah I've never seen a successful AutoC based on TEV's. Although if you had to do it, I'd say the Fuderer system would be the best candidate due to only having two throttling devices.

Hey I got my "BUG" recharged, and I fired it up for a quick run (no Argon at this point). It got down to -100C in about 20 minutes, and it looked to be leveling off at a good solid -111C within an hour. Pressures were only 16.5/176 psig. Prestart static balance pressure was 210 psig. And the start-up peak was 295 psig.

My initial charge was: 100 Grams of R-134a, 50 Grams each of R-23 and R-14, no Argon

So far I like what I am seeing, next will be playing with Argon additions.

EDIT: I took a better look at my notes, and saw that it took 30 minutes, not 20 minutes to hit -100C from a warm start.

[Gray Mole]

Really nice pressures so far

Sounds like a pretty ideal mix. Cooldown is faster than I usually see on Auto's. Hope you get to see that magic -150c on this round

[kang-China]

Hey I got my "BUG" recharged, and I fired it up for a quick run (no Argon at this point). It got down to -100 C in about 20 minutes, and it looked to be leveling off at a good solid -111 C within an hour. Pressures were only 16.5/176 psig. Prestart static balance pressure was 210 psig. And the start-up peak was 295 psig.

My initial charge was: 100 Grams of R-134a, 50 Grams each of R-23 and R-14, no Argon

So far I like what I am seeing, next will be playing with Argon additions.[/QUOTE]

[sdumper]

Great thread thanks for sharing your knowledge guys!!

[kang-China]

yes -100 I do it already,with R14 and R22

but i think -150 is not very easy ,use your 3+sub-cooler ,

[mytekcontrols]

Great thread thanks for sharing your knowledge guys!!

Thank you Scott, and as always we all learn something in the process

yes -100 I do it already,with R14 and R22

but i think -150 is not very easy ,use your 3+sub-cooler ,

Agreed -150C will be very difficult, but not impossible. I've already got this unit to do -134C before I made my cap tube modifications (see earlier post). Now I'm just creeping up on it once again with the new hardware configuration, taking it slow, so my first test yesterday was without any Argon.

[mytekcontrols]

5:05PM About 25 minutes ago I started her up after adding about 35 psi of Argon to the 210 psig BP (new BP = 245 psig).

She's already at -105C Evap, 22.5/338 psig running pressures (and dropping).

More to come...

Well It's now about 11:20PM and although I got done running my tests about 4 hours ago, I just now was able to get back on the computer to tell you all how things went. To keep it short and sweet a photo or two is better than words...


Evap-Out (left), Evap-IN (right)


Compressor Running Pressures



Pretty friggin cool

[Gray Mole]

That's amazing

I wasn't sure if you'd get to pulling it off, auto or no. There's limits to his design, and you're currently surpassing them

Not far now though. Your initial discharge pressures aren't over the limit, and you've got a bit more room there if needed. The running pressures are phenomenal. At that level you shouldn't be seeing serious compressor strain, and by the time your compressor warms to running levels your pressure is low enough that it shouldn't be overheating.

On your next runs, could you map out the compressor temp/time and gas pressure/time?

I bet it feels great to see it so close to target. Seeing something in your head that 'should' work isn't quite as satisfying as seeing it come to life

[mytekcontrols]

Yep it was such an amazing feeling yesterday, because in my head I just knew that I'd make it to -140. And to see it actually happen was everything I could have wished for. Maybe there's something to this positive visualization stuff that I keep hearing about

Yeah I'll do a chart for compressor pressures and temperature next time. I would do it now, but I wasn't plotting the discharge temperature in my readings. After the first couple of tests, I kinda got a good feel for where it's probably at based on current draw, so I didn't bother to hook the TC up to the meter (also ran out of switch positions because of all the other TC's I have attached across the stack). Speaking of which, I need to get a TC positioned where CT #1 ends (expansion point for the cascade part of the HXC). Very curious to see what this is running at, and it'll also tell me how good the sub cooler end is doing as well.

Opps almost forgot, using an infrared thermometer, I was seeing about +55C on the top of the compressor body towards the end of the test. Since the discharge is common to the body in these rotaries, that gives you a pretty good idea of how the compressor is doing (within a couple degrees of actual discharge temperature).

[Gray Mole]

Wow.

Your mass flow/temp is ideal then.

In the cascade I just made with this size rotary I was seeing around 70c load temp on the 2nd stage compressor, 65c on the first stage. bit lower unloaded.

55c is a great running temp. Far lower than spec to be honest.

I start to worry around 80c. 55c and burnout should never be any issue at all. That's cooler running that almost anything I've seen in a running cooler with a rotary

Nice work. I was expecting to see a much higher temp.

My test system is running around 60c on average. Even at 240psi I'm not getting any overheat issues, but the combination of discharge muffler and high mass flow I'm doing ok.

[mytekcontrols]

Me bad. I kinda got confused in my excitement and accidentally posted some of the latest CryoBUG news in Gray's -150C Cryo-Challenge thread. Anyway so as not to double post, I'll just briefly say that CryoBug passed -150C today.

[Gray Mole]

Hehe

Maybe they'll think it was me

A huge congrats to you sir!

your pressures at that -150c mark aren't high at all, which is great. It would be really interesting now to make a small enclosure and put something in to cool down and see what the time to temp is.

I'm thinking some kind of fuel, maybe 100% ethynol or something. Would be interesting to see an ice cube of alchohol but the time to freeze would be interesting in a small chamber.

Nice! What's the next step for the 'Bug?

[mytekcontrols]

A huge congrats to you sir!

Thank you, it's been very enlightening. I had always thought that to reach these kinds of temperatures in an AutoC, it would take at least 2 cascade HX's. In fact Dale Missimer founder of Polycold Systems always preached that it would take 3 stages. And he even went on to patent such a system, and insisted upon the utilization of what he called distributed phase separators, which incorporated a metered feed system as well as a liquid overflow bypass. It was as he called it "to prevent system refrigerant imbalance". Well that theory was the first one to have holes shot in it, when a successful -170C 2-stage AutoC was developed by a fellow engineer Scott Forrest and myself that incorporated nothing more then basic spun copper phase separators very similar to Refrigeration Research's accumulators. The funny thing is, that Dale had studied the works of Andrija Fuderer before he ever developed his 3-stage AutoC system. Kinda makes me wonder if he also missed the simplicity of what Fuderer was saying, just like I have for so many years.

So now it has been reduced to a single stage, although with some interesting sub cooling aspects. Obviously it'll need more extensive testing to really see what it can do, and how reliable it can be. But so far it is very encouraging.

your pressures at that -150c mark aren't high at all, which is great. It would be really interesting now to make a small enclosure and put something in to cool down and see what the time to temp is.

I'm thinking some kind of fuel, maybe 100% ethynol or something. Would be interesting to see an ice cube of alchohol but the time to freeze would be interesting in a small chamber.

For my first target end application it'll be to cool a copper Cold Head for water vapor cryo-pumping in a very low pressure vacuum coating system. This has always been my intention with creating such a small system capable of -150C. But yea I agree with you, a frozen alcohol ice cube would be quite cool (please excuse the pun).

Nice! What's the next step for the 'Bug?

Next step is to finish my Cold Head design, get a couple machined, braze one up and attach it, then start finalizing the refrigerant charge for both loaded and unloaded parameters.

[n00b 0f l337]

So do you feel you are getting adequate separation? Or just as much as you'd like.
Rereading over your blog online, it's quite an amazing system, the move to a r410a compressor was quite a good idea. Especially with avoiding the expansion tank. But wouldn't the classic buffer system and expansion tank also decrease pull down time significantly?

[mytekcontrols]

So do you feel you are getting adequate separation? Or just as much as you'd like.
Rereading over your blog online, it's quite an amazing system, the move to a r410a compressor was quite a good idea. Especially with avoiding the expansion tank. But wouldn't the classic buffer system and expansion tank also decrease pull down time significantly?

Adam -- let me answer the last question first. From the small temperature spread I'm seeing across the evaporator, and bearing in mind the fact that the evaporating condensate is not composed of a single refrigerant, it would appear that there is plenty of refrigerant circulating in the system (perhaps too much). So adding an expansion tank would only be beneficial in lowering the static balance pressure, and to draw less amps on start-up. It would also increase the pull-down time until said refrigerant was drawn out of the tank and usable within the refrigeration circuit. Since my little R-410a compressor doesn't seem to mind the high static pressure, or the 360 psig head pressure during the first 10-15 minutes, I think I'm better off without the expansion tank.

As for having sufficient phase separation, I really feel that I do. Reason being is that I'm only running it close to zero C phase sep temperature, unlike -30 C on a conventional multi-stage AutoC, and yet where the phase sep's cap tube feeds I'm seeing about -80 C. Considering that R-134a boils at around -10 C at the suction pressure that's present, I'd have to say that there is a good percentage of R-23 mixed in with it and alittle bit of R-14 as well to get those kinds of temperatures. If the phase separation wasn't working very well that would not be the case. Does this seem plausible?

[n00b 0f l337]

Incredibly. Didn't know your phase separator temperature was that warm! That explains quite a bit actually.

As always, nicely done.
I'd be wary on that 360psig personally, but you know this better than I do and the rest is incredible as always.

I would also assume that on any production unit having the option to cycle the cold head on and off, and an expansion tank, couldn't hurt, and certainly wouldn't add too much more to the cost.

[dinos22]

very cool thread guys, keep it up.

[mytekcontrols]

I'd be wary on that 360psig personally, but you know this better than I do and the rest is incredible as always.

From what I gather this should be fine. Check out the following chart...



Compared to R-22, R-410a is definitely a very high pressure refrigerant. So being as how I am using a compressor pulled out of an R-410a Air Conditioning application, I should be OK on this. Also keep in mind that in my application I only subject the compressor to this head pressure for a rather limited time period (10-15 minutes).

very cool thread guys, keep it up.

Thanks

[ultralo1]

Micheal,
EPA has approved some hydrocarbons for residential and commercial use.

http://epa.gov/ozone/snap/download/S...%2012-9-11.pdf

[mytekcontrols]

Micheal,
EPA has approved some hydrocarbons for residential and commercial use.

http://epa.gov/ozone/snap/download/S...%2012-9-11.pdf

That is one very long document, but I was able to scan through it and pick up the main aspects. It appears to be very similar to the rules that govern use of these refrigerants in Europe (specifically the 150 Gram limitation pertaining to retail food storage refrigeration systems, but not sure about the 57 Gram limit for household use). And although it looks enticing, I think I'll be sticking with HFC's in the meantime. Especially since I am seeing good results with them alone.

The problem I still see, is that there would be additional costs associated with HC use due to the stricter regulations. And one thing in particular which I don't see changing, is the extra fees required for hazardous materials shipments of both the unit and replacement charges. Also because of having to label the equipment as having dangerous and explosive risks, this could pose problems in trying to get someone to use your product instead of one that isn't labeled this way. But it is still good to see this country loosening up on this issue, because it does give us some more environmentally friendly alternatives for CFC's and HCFC's.

Thanks for posting this info