The -150c 'Cryo Challenge'

[Gray Mole]

Well it's not an official competition, just a couple guys trying to do what some guy already did 50 years ago

Mytekcontrols is making one based on a Fuderer Autocascade with his own experience and design, and I'm working with my own 'Flash chamber graduated captube' Single stage.

Both have elements of an autocascade, both are just different enough to 'maybe' work. His much more likely than mine

So really, Mytek's huge advantage is...

1. His vast experience in this kind of project.
2. His system does have elements of a real autocascade which is more likely to work well without safety issues.

My advantages...

1. Hydrocarbons. Lighter, condense more easily, lower headpressures, blend nicely.
2. Not using autocascade forumae means more direct, more efficient use of capacity.

Mytek's thread is here if you wanted to see his (impressive) and I posted some pics of my V1 attempt.

http://www.xtremesystems.org/forums/...ryoBUG-is-Back

So I'll start my thread here, hope I can keep up.

I'd abandoned this for a while since it has no real application for high load. Without the use of autocascade principles, load simply isn't something that this will do at any advantageous level compared to upsizing compressor SS or just going to Cascade. As a Low temp cryo freezer however, this will hopefully work extremely well, and be more compact than current designs, as well as be a fast cooling fridge where small loads are concerned. Ideal for biomedical sample storage where -150c (I hope) is needed.

Hydrocarbons aren't yet US/Canada approved for commercial applications but that's changing I hear. Hopefully in future this might be something that could be used to reduce size/power consumption. Might also create a more portable design, so the fridge itself (with a matching 12v/120v transformer) could be powered in a vehicle in transport instead of just an insulated box, or LN2 injection fridge.

My Layout...



I made a couple of small errors in that drawing but for the most part that's the idea.

I'm shooting for a low load low temp fridge setup. Basically, you open the fridge, put your cryo samples in, close the door, and it will maintain 'hopefully' -150c.

So I only need 5-15w of actual load handling and I think that in the way I'm going to build it, I should have something like that with just an exposed evaporator.

Right, so materials...

1 x 'Highly' Rotary compressor - 4000btu manufacturer's rating (though they put this POS in 5200btu window AC)
1 x 375psi cutoff switch
1 x 10k btu condensor/fan
3 x captube - 30" x .042" / 45" X .031" / 60" x .028"
1 x Temprite 340 oilsep
1 x 'Horseshoe' 5/8" evap x 12" long (Rollbond replacement, flattened for plate mount in fridge)
2 x SLHX 'manifold' parts.
1 x Discharge Muffler (refrigeration research)
Gasses - All Hydrocarbon gas charge

R290 / R1150 / R50 (Propane/Ethylene/Methane)

My theory is that while these gasses are a fairly aggressive stepping, being Hydrocarbons they have a great tendency to blend in use. I'm hoping to acheive an unstable blend within the captube to promote a very aggressive 'glide', but to (hopefully) fractionate almost fully when they hit the evaporator. I want to see the R50 boil off within the evap, and the rest remain in mostly liquid form until they get to the SLHX system and boil, condensing the gas mixture in a 'staged' approach. My system relies on the theory that the gas that enters the captube is NOT a full liquid head, but a mixture of gas and liquid phase. Only closer to the end do you see a liquid head, and the amount of liquid head dictate temperature and capacity alongside the tuning itself.

I'm also hoping that with the discharge muffler (for the pressure spiking and general volume concern) as well as the amount of suction volume with the SLHX/HX setup, that pressure from the R50 won't be a serious issue, considering how compact this approach is. I like that part, but I do find in my compact cascade system that volume is my only real battle. Though I like to think I'm getting closer to mastery over the use of HX/vapor control by tech, there really is NO replacement for space when it comes to refrigerant return.

This system is hopefully fast in cooldown. My last project (simplified version of this) was 10-15min max to -100c and I'm hoping to still be close to that. This layout doesn't need much gas to do the job. However it is extremely sensitive to pressure spiking more so than 'real' autocascade setups. So I have the pressure switch since I can't move as fast as a pressure wave from sudden condensing and liquid head development. I had that happen on the last one, and I expect to see it pronounced with R50, we'll see.

Pics of What I have...









Update...

So I've got the bulky discharge section together.

Hard to see where it's going but I held the one manifold section against the discharge line so you could tell why the line to the condensor is there. That's the SLHX effect for the discharge part of it.

Idea is to heat the outside of each SLHX. Mostly the one closer to the compressor return, and a little on the one close to the evap.

I'm trying to focus subcooling on the captubes, while enhancing vaporization on the return. In a virtual 'no load' freezer (like a basic chest freezer) this is the entire method, using parasitic heat for condensing. That's why you don't see condensors on chest freezers for the most part, it's just cooled discharge pipe and captube soldered along the return pipe path.

So some pics...







OK, so I've got the handvalve, and I'll get that brazed in right away.

On a note, I was mentioning how expensive Canada can be for parts. I paid $46 canadian for one handvalve.

Ron's Under The Ice shop in $22 or $35 for a braze-on depending on the brand. I bought the 'sweat' version, since it was 'only' $5 more than the flare version. I got lucky on a couple cheap ones off the 'Bay for about $20 each incl. shipping but they're not here yet I really need to put an order together from Ron again.

Right, some pics of it now, valve isn't there but it's pretty obvious where it'll go.











In the pics of the evap and HX's I've labelled them to show where the captube bunches are. Basically the 28 chamber should be working the R290, the 31 chamber the Ethylene, and in the evap I've put the captube through it and it's spraying just at the end. So subcooing shouldn't be an issue.

The pics are hard to see, but the discharge line, just after the oilsep, is brazed to the HX's. Path makes the 28 chamber the 'warmer' of the SLHX's, and the colder is the 31.

Not a huge amount to report. Xmas eats up time like crazy, and I'm tired as hell.But a good vac and a quick charge is getting me started. I'm light on something but I haven't spent any real time. So far I'm just starting to use the ethylene in actual condensing but it's not quite the mix I want. I'm going to have to watch though. I may add a bit of R50 before I go further with the R1150 just in case the response totally changes.

I was interrupted by dinner, but I did get the starter mix in. Running around 15psi low and 260psi high.

Was down to -65ish so far, and was creeping down but I had to stop. I let it run a bit with the pipework exposed to see the layout.

I may have gone too far in the third captube 'upsize' though. I could see the second flash tube frosting with just the R290. I may be evaporating too much in that section to accomplish what I need but we'll see.

If the stepped tubes are an issue, I may go back to identical sizing with different lengths.

Here's a few pics...








More to come, I'm hoping to see -100c today but I don't want to go too far with the Ethylene before I get at least a taste of the R50 in there. Better to see what a small amout will do overall to the HX's and pressures in general. Don't know if I'll get hooked up for the R50 today or not.



Gray

[Sk_rmouche]

Hi, ( sorry for bad english, I'm french )

Interesting, but what dou you mean by hydrocarbons forming "blends" ? In a classic pattern, gasses must not have affinity, right ?

Beside that, I've always wondered if adding a little of R50 to R1150 would evaporate lower than ethylene alone, @ given pressure...

[Gray Mole]

Hey

Well almost any time you mix gasses you end up with a blend. Companies do it on purpose to give different results.

I'm hoping that I get what you're talking about, but in reverse to a certain extent. Alongside the 'higher evaporating temperature' should come a 'lower condensing temperature'.

I'm going the opposite direction from the autocascade. I don't want full separation in phase separators. I need them to mix going through, then separate at the end. Ideally they will as the temp drops but we'll see.

I'm looking to get the condensing temp/pressure lower, and as the temperature drops, seeing the R50 boil on it's own. This should make it faster to cool down, and ultimately end up at the natural BP (or close).

That is also something else I'll be taking away from this little experiment. I would like to put together a 3 stage without the grief of R14.

If I can see a change in R50 using R1150 in the mix, I can likely use it in 3 stages with correctly sized compressors. I'm nervous about using it pure, but I'm not sure if the blend of Ethylene and Methane would make it useful in a 3rd stage.

I'll update tomorrow with more pics. I've got it assembled other than the oil control valve. Ugly, but it's holding pressure and ready to go soon as I have a handvalve for the oilsep

Gray

[Sk_rmouche]

Yeah, I follow your project with interest. I'm currently trying to make a three-stages cascade with R507A/R23/R14 ( or NF3, or ethylene/methane blend ) and I haven't get any answers about mixing R50/R1150 to try having boiling temp above the ethylene one alone. It's not a problem to condense at lower temperature, since R1150 alone is so easy to condense in the third stage ( R23 or R744a @ second stage ), difficult part is making blend with precision

Another way would be to conduct an auto-cascade @ third stage, with R14/R50 ideally, or R1150/R50 ( hard to set up I think ). But for that, I have to know what the reaction of R1150/R50 mixed together at 50/50 ratio for example.

[Gray Mole]

I must say I'm definitely more interested in lowering both the evap temp and condensing temp/pressure of R50 for a third stage. Bit aggressive on it's own unless you have 1/2 stages that can keep the HX 3rd stage to -110c or so and that's not so easy without some big power. I'd like to have 350 or so watts capacity and that's a strain for the base.

If I could bring down the condensing requirement to more like -100c or even -95c then I'd be happy to use it even if it meant 'only' a -140ish 3 stage.

Oh, and I've update the first post again

[mytekcontrols]

Gray -- You're falling behind

I just hit -140 C today

I sure hope you can keep up

[Gray Mole]

Oh Noez!

Keep up? I can't seem to stay up

Best I got to was -67c and that was at a strange charge. 240psi high/12psi low.

I think I know where I've gone wrong and it may mean a rebuild of the captube.

My low is staying too low and I have a feeling the initial portion is too small for the gas/liquid mix to get through in a way I need it.

I'll likely get to that tomorrow though. I'll have to, with Xmas on the way. No rest for guys like us

I'm ending up on a bit of a timetable too. There's someone bugging me about a 3 stage again, and while I don't do custom orders any more, I will consider 'requests' especially if it's something I'd like to do.

-140c though

You're just about there. I'll have to pop over to your blog and check it out. Please tell me you're showing it off

I won't give up, but I have to bow down to your mad skills and superior design

[mytekcontrols]

Yeah it's tough to juggle the needs of Christmas, the wife, working for a living, and of course the fun part... our projects.

Just curious, on your design I only see one oil sep in use, but your diagram shows two in series. Are you sure one will be enough? You are using HC's so that does have superior oil return as compared to HFC's. But then again you aren't doing any phase separation, so if any oil is present it has to get all way through the refrigerant circuit before it gets back to the compressor. Any fears about the residual oil freezing and plugging things up? just a thought.

You probably already checked out my blog by now, so you know I've provided details on today's test already. I'll tell you I'm pretty happy with what I am seeing. But please don't let my enthusiasm squash your efforts, because I think what you are doing has a lot of value, especially when you consider the simplicity of construction. Also could be made even more compact then what I am doing. BTW have you seen those Aspen compressors? They are unbelievably tiny, and might lend themselves to your system.

[Gray Mole]

Yeah, without the R14 I just used one for this one.

It's fine though. I haven't had any oil issues. Edit: One of the reasons for the oil control working well too is the discharge muffler. Dampening the pressure oscillations before they reach the oil sep is creating a much more stable pressure feed to it. When the compressor is at the higher pressures it was 'bouncing' the guage a bit. It's very stable now, and I know that helps to prevent oil getting by the sep, as well as preventing the oil in the sep from getting agitated enough to cause it to get back out.

I had my Father in the Garage looking at the system and he commented how quiet it was compared to other 'experiments' I'd done. I don't get him over that often so it was nice to hear

But even at high pressures, it's pretty quiet. The combination of muffler and oilsep are a bit like a car's exhaust. With silencer and muffler working together, the pressure wave and resultant noise are lessened greatly. Using mufflers in a system all the time takes up a fair bit of space and get's costly so I usually don't bother.

The issue with mine is my captube layout. I just used what was 'kicking around' and I got too aggressive in the third section as well as being a bit too restrictive in the first.

I'm starting to think that stepping down in cap just at the end, but not as dramatically, will get it back to where I'm viable.

In my cooldown, I could see that just before I was condensing enough to begin cooling, I was flashing heavily in the second chamber.

I could see it frosting there as the end of my Evap was beginning to frost.

So I have a feeling that I'm getting more of a residual cooling effect instead of the mild flash/condensing effect I was after in that section.

I'm hoping to get the captube changed, but try it with the opposite pattern.

Next will be .042 / .042 / .031 or something to that effect. Still with the flash tubes, but shorter ones.

Means longer captube, but since I've seen how much it can flash in a small chamber I can see where I'd need to rework it.

Some theories work, some not so much

It's funny you mention the oil freezing though. In a way, I'd be better off if I could get a small restriction near the end to get the flashing to slow down in the second section. I need more restriction in my third captube at the very least.

Almost forgot...

I've seen the Aspen compressors but haven't been able to try them out. They're pretty expensive (400 to 500 bucks I'm told) and not that powerful. So you really need to know your system is something that needs it.

For a computer case install they'd be ideal, maybe a pair of them working a chiller, or a way to run dual chambered evap for a SS.

They're very small though, amazing breakthrough for rotary tech. If I can find out where they've been used and find a cheap chiller or cooling system that's broken on the 'Bay or something to test one out and see if it would work for what we do in here, then I'd love to see if a nice tiny SS would be possible.


Don't worry though, I'm as happy for your results as if they were my own The destination isn't really the target, but the journey to get there

[mytekcontrols]

My thoughts exactly on finding something that someone else builds that uses an Aspen. Find it cheap, and steal the compressor and condenser out of it. Kinda like what we do with window AC units. The really cool thing about the Aspen's besides being incredibly small, is that they run on DC, which means you could speed control them fairly easily, thus having a way to ramp up on start-up and control your head pressure through an active feedback loop. Might allow you to have more of the low boiling hard to condense gases, without the associated problems of going over pressure when things are warm.

Never thought of using a discharge muffler to smooth things down for better oil separation, but it sure makes sense now that you mentioned it.

Speaking of how quite your unit is, I wish you and I both had DB meters, so that we could compare. I'm sure that muffler helps out a bit, but it would be nice to know by how much. Although I gotta say mine is pretty quite when everything has cooled down, but it does whine for awhile after start-up due to the Argon.

[Gray Mole]

Heh I'm sure it does

I was a bit surprised how much it helped. I can only comment on the difference from 1st to 2nd stage on a cascade for instance. The second stage always has a bit more strain on it, just the nature of the gas.

This one's pretty much 'normal to below average' of noise whether high or medium discharge pressure, and even when I'm charging I don't get the 'grind' as much as I expected.

I may look at making a smaller version of the muffler I'm using for install into the 2nd stage of future cascades. I used one on my first Auto and it helped.

I just made one about the size of the oilseps we use, with a very large pipe from the compressor to the muffler, and then the standard smaller pipe carrying on.

It helped but I was using a 2hp compressor on the Auto. Noise was always going to be an issue but it did help smooth out the discharge pressure and temp a bit.

Aspens...

Well I looked up the larger of them, and they're ok for 404a use.

So...I worked out their chart for celcius and it's actually pretty good.

They say that full speed, best condensing temp, the larger model of 48v compressor will do 363w at around -20c with 404a if you have 26c condensing temp.

That's pretty good. If you take 300w max average capacity need for a 4core to mild 6 core OC, You could see an evap temp of -25c or a touch lower (depending how well these will maintain LP under spec) at full load.

Considering how small they are, that's damn good.

What I wonder is if they need fan cooling or if static cooling is enough.

If you can get away with it, you can 'package' the compressor for noise reduction. They're only quiet at lower speed, bit whiney at full. If you can box them in foam you can dampen noise to almost nothing.

Besides, then you could build an enclosed 'package' for case install into a lower chamber and also better control heat flow out of the PC case.

Just the cost of trying it.

I think an external PSU would be better too. The smaller compressor, full load runs just under 10 amps, likely 15 amps (max) on the larger one, little as 12amps I guess.

So you would need a decent 48v psu to get the best out them, 24v minimum on the larger series compressor.

I like the look of them now though performance is better than I remember seeing last time I looked.

[mytekcontrols]

Today it happened. I not only made it to, but past -150 C



It took quite a few modifications to the hardware to pull it off (mainly a redistribution of lengths in the two HXC's), and a tiny bit of tweaking to the refrigerant charge.

For more details check out my blog or just ask me a question here, and I'll do my best to answer it.

[[XC] gomeler]

Well done Michael! Checked out all the photos on your blog and that thing sure is one ugly duckling. It sure does deliver though Any chance of loading the evap at all or is it only capable of dealing with the insulation losses?

[mytekcontrols]

Well done Michael! Checked out all the photos on your blog and that thing sure is one ugly duckling. It sure does deliver though Any chance of loading the evap at all or is it only capable of dealing with the insulation losses?

My biggest mistake the last time I attempted this was trying to build the first prototype as if it were already a production unit, and then failing because I under estimated something without having room to do much about it. This time around I decided to approach it like I do electronics projects, and basically build it on a breadboard, not being concerned about looks, fit, or orientation. So bottom line just worry about making it work correctly and reliably, and then after it's all figured out, build it beautiful.



As for loading the evap, I think I'll hold off until I have a cold head design worked out, and a prototype of it to test with. Speaking of which, any recommendations for someone that can turn around about 3-4 custom copper cold heads? I only need the machining done, and will handle all the brazing and assembly myself.

[kang-China]

hi,Mike ,your blog i looked. but your evaporation i did not see.

happy new year .

A new year is a good begin

[ryba]

My biggest mistake the last time I attempted this was trying to build the first prototype as if it were already a production unit, and then failing because I under estimated something without having room to do much about it. This time around I decided to approach it like I do electronics projects, and basically build it on a breadboard, not being concerned about looks, fit, or orientation. So bottom line just worry about making it work correctly and reliably, and then after it's all figured out, build it beautiful.

As for loading the evap, I think I'll hold off until I have a cold head design worked out, and a prototype of it to test with. Speaking of which, any recommendations for someone that can turn around about 3-4 custom copper cold heads? I only need the machining done, and will handle all the brazing and assembly myself.

Hello there

As a someone who did few SS and Cascades I'm in shock what you did right now -151*C is really ing awesome!

About making evaps, write a PM to me and we can talk about that. I tried to send info to you, but yours PM box is blocked.

[mytekcontrols]

As a someone who did few SS and Cascades I'm in shock what you did right now -151*C is really ing awesome!

Thanks for the kudos, always appreciatted

About making evaps, write a PM to me and we can talk about that. I tried to send info to you, but yours PM box is blocked.

Opps sorry about that, my PM Box should be unblocked now.

[mytekcontrols]

hi,Mike ,your blog i looked. but your evaporation i did not see.

happy new year .

A new year is a good begin

Try the blog again and see if it works for you now. For some reason which nobody knows, you seem to have problems viewing my blog at times.

Happy New Years to you as well Kang

[mytekcontrols]

Gray -- Sorry for hijacking your thread

How's things on your project? I know you have several going in parallel.

If I don't hear from you, have a Happy New Years.

[Gray Mole]

Yeah, I'm kind of on hold with it until I clear up the quad project for sure. When that's done, I'll rework the captube and have another run.

I have a good idea of how to change that now, and it's pretty easy to open it up. I'll just cut the tips of each chamber and remove the cap.

I should get away with that a couple times before it's too short to clamp it shut

I've got the 3 stage ready to build but it's sitting there, and will be there any time I want. It's not an 'order' just a project I've wanted to get to for a while now. I have more parts on the way for it as well, so I can't finish it anyways.

I'm usually not busy at all with the 'hobby' side of the cooling stuff, but I do want the quad done before I start playing again, pretty sure the guy wants it soon as possible.

Happy new year to you, sir hope your setup reaches your goal! I forgot to check your blog, you may already have hit it.

[Gray Mole]

Well it's official (and I should have looked before the last post)

There's a footprint on my butt, about the size of a CryoBug!

Congratulations Michael, you have reached your goal before I got far out of the gates

I certainly owe you a beer, or some kind of sodie pop if you prefer. I hope one day to give you that!

I'd sure like to see where you'll go with yours, whether it's a direct or indirect cooling system that's planned for it, but the Bug is the big winner, and you deserve some huge kudo's for the work and skill that's gone into the project!

My hat's off to you!

[mytekcontrols]

Thanks Gray, I'll take that sodie pop