CryoBUG is Back

[Patrickclouds]

i think it's better to move posts that have nothing to do with the cryobug in a new topic or you cascade topic.

i would go with captube in an autocascade because they are self regulating.
especially when you get temps at your valve of around -140°C because if you do not have a perfect oil seperation your valve will freeze and is not adjustable anymore. so there is no difference between cpev, txv or eev.

the problem with eev is also that you need a controller with the p/t chart of your chosen refrigerant. i did not find a controller with charts of r170, r1150, r14, .....
i only saw controller that where able to deal with r23. so blends like you'll have to use in an autocascade are not available on the market either. maybe you can use an eev to adjust it by manually steps.

i also think that -150°C chamber temp is nearly not possible with r14 and r50. maybe with the need of argon, but high pressure will be too high in my opinion, when using these gases.

[mytekcontrols]

Is anyone tried ethylene and R14 in AutoC ? Maybe it's a key to get low pressure ratio isn't it ?

...what do you recommend ? Cap tube, CPEV, custom TXV ?

Side note : in my actual two-stages cascade, R23 TXV makes clicky sound when closing down, like " tic...tic...tic " ( T° around -90°C ), don't know if it could gets any worse @ lower T°, since you're kind of expert, maybe you have an advice ?

Although this is getting a bit as Patrickclouds pointed out, I still feel compelled to answer your questions.

I have tried ethylene and R14 with good results in an AutoC. When compared to using either ethane or R23 with R14, I saw less of a temperature gradient across the evaporator, which is to be expected. All in all, it worked quite well.

I agree with Patrickclouds, go with cap tubes.

I'm no expert on the use of TXV's since in my industry they are seldom if ever used. So unfortunately I can offer no help in that area.

And now back to CryoBUG ramblings...

[Sk_rmouche]

Hello,

Thanks to both of you ! And sorry if I'm disturbing about the first point of your topic, I'm just not quite used to that forum, It won't happen anymore, sorry again

[mytekcontrols]

Thanks to both of you ! And sorry if I'm disturbing about the first point of your topic, I'm just not quite used to that forum, It won't happen anymore, sorry again

No problem, and no apologies necessary. I would certainly hope that this thread can veer off course every now and then

Often times this is how we learn even more.

[n00b 0f l337]

Rambling rambling rambling...
You used the 340 correct? Did you try the 304?
From what I can see, it's got a bit less volume up to the oil line. My pour from a shot glass with oil showed almost zero trapment if tilted only 15-20 degrees towards the oil port.


And although I'm done with break, I dug this sucker up and pressure tested it..

[mytekcontrols]

Hi Adam

Actually I used the 340S which looks identical to what you are holding in your hand. The only difference from the 340 to 340S that I see, is the port sizing. Standard 340 has 3/8" ports and 340S has 1/4" ones. Yes I did mess around with tilting it towards the oil port side. But this is kind of a compromise, because it also means there is a slightly higher chance that the coalesced droplets of oil and/or refrigerant will possibly fall towards the gas outlet port which is unfortunately on the same side.

Here is an image based on what I am talking about...
340.png
Temprite 340 is shown with a tilt of 20 degrees

I don't know if my concern is valid. But I thought I'd toss it out there.

Hey cool looking AutoC stack

I bet that wasn't easy to bend. So how soon before we see some test results? What kind of charge, HC's?

[n00b 0f l337]

I used a water barrel and tie down straps to hold the coils in place piece by piece. Next time ill use some steel tube and braze the end of the tube in tube to it (possibly crimping it heavily first) and get a tight spiral. The top two were much easier as 3/16 in 3/8 and a normal pipe bender interact nicely.
Interesting thought on the tilting but I was under the impression that the top of the filter has a solid swag of tube around it to force the coalescing to begin. Maybe ill chuck one in the bandsaw and see the carnage.

Sadly this stick is going to sit for quite some time... Again.. I have my gases and all the parts I could ever want but none of the time. My spring break just ended and all I managed to do was rebuild the entire shop dynamic and outfit the milling machine. Didn't even get around to a new bandsaw table or building the last table for metal bending and such.

Alas there is always time in the future. But I will have about a week for my last summer break.

And if your strainer phase sep is working and cheap/diy why change!

[mytekcontrols]

Interesting thought on the tilting but I was under the impression that the top of the filter has a solid swag of tube around it to force the coalescing to begin. Maybe ill chuck one in the bandsaw and see the carnage.

Hold off on cutting one open

I already did this about 2 weeks ago, and did not see anything like what you are describing. I've also cut open many other Temprite's (various model series), and have found them all to be very similar, only having different lengths and diameters in filters. When I get a chance later today I'll post some photos of what I found when I cut open the 340 I used on the early CryoBUG.

And if your strainer phase sep is working and cheap/diy why change!

Yep that's the way I look at it too

[n00b 0f l337]

Here's a Henry. Figured the temprite would be similar in having the input run to the very bottom then helical separation applied. But that is a better more expensive product.

[mytekcontrols]

Helical is an entirely different setup compared to a coalescing separator. Check out the pics of my cut open Temprite 340...

Temprite340(1).jpg

Temprite340(2).jpg

Temprite340(3).jpg

Temprite340(4).jpg

Temprite340(5).jpg

It's built more like a filter, and in essence that is precisely what it is (filters down to 3 microns). But it also coalesces oil mist into oil drops that drop down to the bottom for separation and return to the compressor.

This particular oil sep, served as the phase separator on my initial Fuderer style CryoBUG AutoC. It was the only 340 series I had, with all my other stock being the 340S (1/4" ID ports -- I don't think this is currently offered). After cutting it open I filled the bottom section with water just up to where it was starting to feed out the oil return port. I then transferred it to a measuring cup and discovered it represented 1 ounce (by volume). For my very tiny system, this really is too much liquid hang-up for use as a refrigerant phase separator.

Probably a better choice would have been the Temprite 320...

product_320_322_s.jpg

Which has the oil return port coming out of the bottom.


Of course like you said Adam, you really can't beat this DIY alternative for cost...

CryoBUG_V5_PhaseSep.jpg

[n00b 0f l337]

Doh. Thought it was a helical.
Duh!

[mytekcontrols]

This will be a quick post (I plan on going into much more detail in my blog a bit later today).

Anyway I have what looks to be a stable -152 C charge based on R600, R170, R14, and Argon with a good cool-down rate (see below).

-100 C @33 minutes
-110 C @36 minutes
-120 C @41 minutes
-130 C @64 minutes
-135 C @70 minutes
-140 C @77 minutes
-145 C @85 minutes
-150 C @98 minutes
-152 C @just under 2 hours (flat line)

That's 2.36 Amps on the Amp Probe (this is the total for the compressor & two fans)...
CryoBUG_Running_4-11-12.jpg

Good running pressures...
CryoBUG_Pressures_4-11-12.jpg

A bit of wobble on CC SUCT (where the phase separator's cap tube feeds)...
DAQ_CryoBUG_4-11-12.png

As can be seen in the Temperature Chart Viewer above, the evaporator circuit is rock steady, with only minor fluctuations in the Cascade Condensers suction out temperature.

Edit: To be clear CC SUCT is a temperature point between the Cascade Condenser and the Sub Cooler that follows it.

After running many tests with both R290 and R600, I came to the conclusion that I needed to reduce the flow in my evaporator cap tube. And I also saw that the freeze-out problem was only associated with the R600 getting into the evaporator circuit (it freezes at -138 C). So although this latest test result is with R600, I would like to switch over to R600a which has a freezing point of -160 C. This will give me some assurance that the refrigerants will never freeze-out at my targeted temperature range (-150 to -155 C).

[n00b 0f l337]

Interesting so it wasn't oil necessarily.
And good power with the HC's. It'd be interesting to see your talents applied to R50.

[mytekcontrols]

Interesting so it wasn't oil necessarily.

Nope doesn't appear to be. And I am amazed out how well the oil has bound itself to the hydrocarbons. Because I strongly suspect if it had not, then it would have either frozen in the phase separator which is running at -78 C or probably in the region where the #1 cap tube feeds which was close to -100 C.

And good power with the HC's.

Yep that cool-down is quite impressive for such a small AutoC.

It'd be interesting to see your talents applied to R50.

Hmm... perhaps someday, although I really like how R14 and Argon compliment each other. Keep in mind that it's not just about boiling points, but also about the partial pressure effect of evaporating into an Argon atmosphere which unless I'm mistaken should look like a lower pressure than a Methane atmosphere.

[mytekcontrols]

Here's the chart...
DAQ_CryoBUG_4-11-12_4hours_plus.png

Very slight warm-up of evaporator which coincides with increase in ambient temperature.

Still looking good

[Sk_rmouche]

Hey Mytek

I'm still kinda speechless about results with such tiny compressor !
What's about the rotary's heat ?
I know you're not friend with valves, but I'm still thinking how amazing it could be to set expansions at each stage, aren't you ?

[mytekcontrols]

What's about the rotary's heat ?

51 C, pretty comfortable

I know you're not friend with valves, but I'm still thinking how amazing it could be to set expansions at each stage, aren't you ?

Yes it would be nice, but they'd have to be very small, otherwise they would add considerably to the package size.

[Sk_rmouche]

Well, okay

How much do you evaluate the refrigeration power at ~ -150°C ? Is krypton could do a better job than R14 in your circuit ?

[mytekcontrols]

How much do you evaluate the refrigeration power at ~ -150°C ? Is krypton could do a better job than R14 in your circuit ?

Krypton, I forgot all about that gas

Well at least from a boiling point (-153 C) it looks good. Can't really say much more then that without doing some research, although I suspect that it would be extremely expensive.

Anyone else care to chime in with an opinion on this?

[Sk_rmouche]

I made some invoices to Air Liquide and Linde, you may get it for about 4000 to 5000 $ ( 3500 euros ) for a cubic meter, it's clearly a killer for price, R14 seems almost cheap compared to

[mytekcontrols]

Well since I'm still waiting for my R600a to arrive, I thought I'd begin development on the control system for CryoBUG. So since I run Linux on almost all of my computers, I thought I'd see if the latest version of ExpressPCB would work under Wine. Well that would be a big giant YES!

Here's a look at the schematic...

CryoBUG-Controller.png

(Edit: Rev 1.1 added missing resistor, changed functionality and pin-out of remote interface. Also re-ordered component ID numbering.)

J3 is a remote connector that allows monitoring of 3 status conditions via contact closure ("Unit Running", "Unit Ready -- @Set Point", "Fault -- Safety Cut-Out"), and a universal 6-24 Volt AC/DC input to toggle the unit ON or OFF.

If it is desirable to disable the manual On/Off switch via the remote, then holding the remote in an active high state will do so. With this inverted logic, it would be necessary to momentarily remove the remote On/Off signal (bring it Low) in order to toggle power remotely, and then immediately restore the signal (bring it High). However If simultaneous manual and remote operation is desired, then use normal logic for remote power control (momentary High to toggle power).

J2 is a terminal block for connecting the safeties (LLCO, LPCO, HPCO), the relay output of a temperature display/controller, and the ON/OFF momentary push button switch w/integral Bi-Color LED (Red = Fault, Green = GO).

J1 is for connection of either 115 or 230 VAC power and the switched power connection for the compressor.


Basically the system is designed to be turned ON or OFF by pushing the unit's momentary push button switch. When ON, the switch will glow green. If a safety trips, then the condition is latched and the switch's RED led indicator will be seen flashing (as well as the fault relay being activated for the remote status). The only way to clear the fault and resume operation is to once again push the ON/OFF switch (or toggle the remote control input). This will allow the unit to resume running, assuming that the actual condition that caused the fault has cleared (over temperature, low suction pressure, high discharge pressure), it will also reset the fault latch.

There is some redundancy built into the system in case the electronic logic fails. With the safety loop providing power directly to the compressor relay opto circuit, the compressor simply can not run when a safety is open, even if the logic told it to do so.

Temperature readout and set point are to be provided by an inexpensive temperature process controller...



Automation Direct: Solo SL4824-RR

The controller's output relay will be available as the "Ready" status indicator on the remote connector. Basically the idea is to be able to set the Solo to give a relay closure at or below a user desired temperature. This will let a customer's coating system know that the CryoBUG is down at cryo-pumping temperature, and that they can begin their coating run.

Next I'll be laying out the PCB. I've already selected a short circuit protected control transformer and a sealed relay. All other switching is low voltage and very low current. These precautions are for use with hydrocarbon refrigerants, and should meet all the new rules as set out by the EPA and Europe.

History: Rev 1.0 Schematic Attached

[n00b 0f l337]

That PID seems overpriced compared to China on ebay? Have you checked lately? $30-40 for one of those.

[mytekcontrols]

That PID seems overpriced compared to China on ebay? Have you checked lately? $30-40 for one of those.

Thanks for the heads up, I'll definitely check it out

[mytekcontrols]

Well the circuit checks out, and here is a short video showing it's basic functionality in action...



Next step: Lay out the printed circuit board and have a few fabricated.

[Sk_rmouche]

Quiet a nice pattern, simple and functional

It reminds me my wiring, series of normally-closed switch embedded into a loop with relay's coil