Hello
Just got my PWM speed control. Hooked up to the Eurotherm 818s ( double PID regulator 0-10V 4-20 mA ), it works perfectly, I'm in love with its self-tuning abilities, now you can set HP with two buttons
Hello
Just got my PWM speed control. Hooked up to the Eurotherm 818s ( double PID regulator 0-10V 4-20 mA ), it works perfectly, I'm in love with its self-tuning abilities, now you can set HP with two buttons
Made a little video to show how it performs
http://www.youtube.com/watch?v=3LQ8iO21xzM
And some pictures :
Last edited by Sk_rmouche; 04-18-2012 at 06:26 AM.
The cooling chamber is almost done, the door with PS insulation is drying from the glue. On the picture the chamber will be ~15 cm above the cascade.
Now, I have to continue insulation with some armaflex, and install the evaporator and all electrical stuff ( infrared lamp to heat up whatever you put into, and some light and temp regulator ).
I'm also collecting parts for the third stage. I'm thinking about a Danfoss GS34CLX.
Some news, that's where I am currently :
I was thinking about what many of you said about CPEV, I finally decided to braze it directly to the evaporator, into the cooling chamber, no need to insulate, no losses due to the ambiant room, theorically maximum efficiency. I'm wiring the front panel, where I hooked up two PID's regulator, the upper one for cooling process', the other to heating process.
For that matter I want to try something unexpected : a PIC-based dimmer to get a smooth regulation with 0-10v output of that PID reg', I'm even able to put some profiles ( PID ramp, maximum glowing of IR lamp, ... ) according to whatever I put in that chamber.
Last time I also wanted to run the third stage with a GS34CLX, I've changed my mind for a strong rotary, mostly for space issue.
Stay tuned !
Last edited by Sk_rmouche; 06-16-2012 at 04:25 AM.
You also don't want to overwhelm stages 1 and 2 with an overly monsterous compressor.
But your project looks amazing. Keep going and I'll start posting mine up in July again so we can bounce or try some new ideas. I've moved away from CPEV, but I have an evaporator that looks like a cannon shell for my project and am considering a TXV again.
Originally Posted by Movieman
Hello NoL !
Yeah... But with CPEV it's easy to set the aimed temp, low evap T° means low duty too, so I'm not afraid about overwhelming anything, I'm much concerned to not get overheat with the third compressor just because of huge superheat, I think I got to balance that stuff, to get the better running T° @ all points.
I'm aiming -120°C evap' temp with R14, and -110°C with ethylene, if I'm not able to get that damn CF4 :o
Oh I meant compressor size, not the CPEV itself.
I'm away from CPEV's because they can leak (as mine have started to show even with a super low temp rated CPEV from Sporlan (rated for -90C was as low as they'd go, and started leaking at -110C)) and because when cold they're bastards to work with. Capillary adjusts itself better, and TXV's are "hard" to adapt but NOT impossible I'm finding (and I believe Bazx found too).
You should be able to manage lower than -120C with R14, we'll see though.
As for temp control, we could just go to the EEV like the germans, but the price can be nutty. I'm taking the approach of, build a machine that can do 500W @ -125C, and if I need warmer use a "cold gas bypass" instead of a hot gas bypass, to avoid burning out the compressor.
Interesting ... However, I'm not giving up with my CPEV, I brazed the inlet ( one potential issue away ) and can't wait to see that beast in action. I don't think EEV it's the solution, because if CPEV leaks, why EEV wouldn't ? About modding TXV, I'm not a huge fan, mostly because it's fairly dangerous ( too much gas and kaboom !, not enough and it doesn't work properly ), I leave that stuff to Danfoss ( or others ) engineers.
If my CPEV leaks, I will certainly go for captube, unless I was wrong about EEV and leaks, after all it could fits pretty well with my PID controller, without a doubt.
Haha almost no risk of "kaboom". I've been tinkering and they're actually very easy to work with. Once you pierce the bulb, and have managed to weld or braze on an access stem. Well, hookup to the N2 tank and turn on the regulator, and just tweak away. You see the pressures drop way off as the bulb gets cold, and if it has "no pressure" in it, then it sees a super low temp and just closes the valve to its minimum. So you can just adjust the regulator until you see it clearly start to open up.
As for EEV, they're commonly used in these super low temp applications. There just solenoid valves of sorts, and the electronics can be easily separated from the temperature issue. Like you see on the "5 stage monster".
I said that if you fill the entire bulb with the cap with liquid, little expansion with higher temp, and kaboom ! Already seen that on transferring bottle ( not sure of the word, then again, I'm french
Long story short, I'm not a huge fan as said earlier.
About EEV, I'm more interested, do you have any advice, or model in mind ? I'm just concerned by the fact of putting the EEV into the chamber, what about the solenoid and so with low T° ? If it's in 230VAC, maybe I'll insulate with grease, you know, just to prevent some shorts and sparks @ defrost
Thanks for helping me with that kind of details !
http://www.extremecooling.de/forum/forum.php
Gotta point you in their direction! They seem to have them working.
TXV bulb only has liquid in it for warmer temperature bulbs. The low temperature ones are all gas though, haven't had an issue with a real pressure rise past an area I felt comfy with. Most of my bulbs have about a bar of pressure in them in the functional range, and warmed up only ~2.5 bars or so.
Thanks for the link, got into my signet !
2.5 bars @ room temp ? No problem indeed, I didn't know it was such low pressurized
It's really a good option, those EEV's ( don't even need to buy the special Danfoss controller though ) if they don't leak, because it's really efficient, CPEV is for hand tuning, funny but need to warm up to become manageable. By the way, where did you find leaks on it ? Inlet ? Outlet ? Is it for flaring or brazing ?
Neither! The damn things started leaking from the back seal at the knob, and one even cracked at the diaphragm.
They were cheap $10 suckers. The low temp one started leaking at the back seal after I attempted to see if it was even adjustable (didn't move it more than 10 degrees) @ -80C.
As for TXV's, I was surprised too. But the TXV @ 1 bar in the bulb, that is, brought up to 1 bar once the bulb and 2nd stage had reached -8xC, was enough to start changing the flow. Below that the pressure was too low, and the TXV assumed the temperature at the evaporator was too low. So it closed as much as it can (basically the pressure in the bulb acts in reverse to push UP the diaphragm and open it!). So more pressure makes it think the temperature is higher, and thus open up to give more refrigerant, and thus deal with the increased load. Fairly simple.
But even if I put in 1 bar of pressure into the bulb at -80C (or 193 kelvin), and it warms back up to room temp at 25C (298 K), it's only 50% more pressure.
I remember Bazx was using more like 6-8 bars of pressure. So I guess its per TXV, these are just Danfoss ones rated for R502 I popped into.
Next one I'll make a guide and step by step. Still not entirely skilled at dealing with tiny tiny tiny thin steel and puncturing. For the first one I just used an Awl and tapped a hole in one shot through the opposite side of the bulb of the captube. Inserted a 4ft piece of .028" captube I had laying about, and just brazed a 3/16" to that, and a 1/4" schrader valve and stem to that. Let's me still hook the bulb to the suction, and drag the adjuster out.
So far though I have no load results with this, as I was just makeshifting an evaporator of some coiled 1/4" tube. Still waiting on the mega-vap (I need to come up with a name with it because I keep forgetting what I've called it before). Oh and good news! Megavap can be built without a mill or lathe if your willing to elbow grease in with a hacksaw, or have access to a bandsaw or realllyyyyy good miter saw!
Interesting
About EEV, when you said earlier, I quoteIs there some piece by Danfoss ? I already worked with one of those things on a negative cooling chamber filled with R404a. Tiny Danfoss controller and a pressure sensor to connect, then you tell what kind of refrigerant you're using to the controller,, setting desired values, cycle rate, and it goes on/off on a defined cycle rate. I prefer the option of PID regulation, more universal and fun to play with, even if there isn't any liquid bottle to cut some slack to EEV ( I can't with liquid R14 @ ~ -80°C, too hard to manage ).As for EEV, they're commonly used in these super low temp applications
I was wondering about brazing some 2/4mm tubing ( just between 1.2 mm captube and 1/4" ) to limit the vapour flow and make sure to feed ~ 100% liquid to EEV, I don't know yet I've no experience ....
Well last one first.
If you want a liquid feed, add a receiver, that's why we use them, right? Yep! So they even work in cascade operations, but you won't want as much volume, and you are going to need to reflect the extra liquid volume in a larger expansion tank most likely. At least that's the common practice. Referencing back to the 5 stager by the Germans (on here and on that link), they used EEV's for everything, and made there own miny receivers of sorts between stages. Just really an increased volume for a moment, I don't believe it had anything fancy, just basically helped gravity do it's shindig.
As for models, again never gotten to use one in this application. That's they're department (UnRockstar and Patrick Clouds), but they cover them rather extensively.
Oh and if you don't have this already, knab it!
http://www.ipu.dk/English/IPU-Manufa.../CoolPack.aspx
Really a must have on hand chart. I generally print out the charts for each refrigerant I have and have them pinned on the board or laminated and taped to the bottle. Just nice to have.
Do you mean you can't manage to liquify R14 @ -80C? That's only 12 bars of pressure. 12 absolute, so 11 bars on the gauges! Seems very reasonable. When I built the 3 stager for Sdumper I found that colder than -90C and I just couldn't hold a solid load on the third stage. I ended up "detuning" stage 2 to nearly an overcharge just to warm it up enough. That kept the pressure reasonable to keep a good differential, and thus a good delivery.even if there isn't any liquid bottle to cut some slack to EEV ( I can't with liquid R14 @ ~ -80°C, too hard to manage ).
As to Coolpack above ^
To find refrigerant info easily, at the top you have three major buttons, a snowflake for "Refrigeration Utilities", R22 button for "Refrigerant Calculator", and NaCl for "Secondary fluids for heat transfer".
Click the Snowflake "Refrigeration Utilities" and a second window will open.
Then at the top you'll notice a few odd shaped lines, if you mouse-over you see one is labelled Log(p)-h diagram, click that and select your refrigerant.
From there you can get any info at any temp or pressure, but remember the pressures are in absolutes! So generally subtract 1 bar from the listed amount to see your on gauge
Hope that helps and wasn't redundant or ranting. I've been up for almost three days now, crazy tests coming up! Back to studying!
No I meant : avoid feeding the EEV with some liquid/vapor refrigerant. I want to try a tiny drier filter ( you know, full copper one, we found them on refrigerator for instance ) as a receiver. No problem to liquify R14 @ -80°C obviously, and I already have Coolpack, thanks. I although made some simulations to see if I can use this incredible tool :
I totally agree with you for the rest !
By the way, what do you think of that EEV :
http://www.danfoss.com/France/Produc...1d2d20930.html
Danfoss say -60°C, what's your opinion about -120 to -130°C ?
There's one like this on sale, on eBay, around 100$ ( 80 euros )
I've never had issues with a Danfoss, but I've also never brought one down that cold.
The r502 Danfoss TXV's I'm messing with though have been holding up. And one's run at least 36 hours now at -8xC. So that says a good bit for there "solid" products. That's a different story though!
Maybe go CPEV first? See what happens? If your not using r14 yet, then no harm no foul really.
Yeah I don't have any gas for replacement, I'm just waiting to get some money for R14 ( ~ 1k euros for a good bottle + gasoline to bring that baby @ home ), it's complicated let's say. I remember how much pain I got through to buy that stupid R23 bottle, good price though ( 200 euros for 6 kilos + bottle and some extra for gasoline ). Did you try R14 by your side ?
I think I'll buy that EEV, still.
Last edited by Sk_rmouche; 06-17-2012 at 07:12 AM.
I bought 5 lbs a long time ago. At $140 a lb + costs for cylinder ($250 deposit) + rental fee ($14.95 a month for years... and then finally.... mwahaha that company got bought out and new company said I now owned the cylinder) it was pricey.
Luckily I've scored two separate 20 lb R23 jugs lately, both for under $90 each.
Awesome price !
R14 is such a pain in the ass, I wanted to try some Krypton instead, but price definitely turn me off, unless I get a big bag of money from nowhere... It's also tacky to use in three-stager, we're close to sat. pressures of methane ( -153 vs -162°C @ 1 bar ). I had a hope with NF3 ( close to R14, but more expensive and need special oil ) finally gone. And I still have no answers about mixing ethylene and methane.
Awesome? Insane.
Ow, 90$ each lb, sorry misunderstanding
Oh you meant for the R23. Nope! $90 for the 20 lbs, 99.95% purity, no cylinder cost, etc. Gotta love ebay.
The ~$225 a pound for r14 was brutal though.
For $195 though these 40 lbs of R23 could do me quite well on resale. Had one tested by Air-gas for purity and such since the cylinder had no info on it except a Deltron R23 label. $15 well spent. Apparently this craps going for $80-120/lb on RECOVERED gas prices lately. Price just keeps going up. There isn't exactly a replacement for R23 in the low temp market. Especially since the USA is vehemently against hydrocarbons it would appear. Well except Arizona.
Understood, and yes I wildly keep my 10 lb of R23, even if I'm not against some ethane. We're such in trouble to get a nice replacement in the -130°C zone. I mean, warmer refrigerants are rather available, and colder refrigerants too, what do you have as choice to achieve around -130°C evap temp ? I really wanted to try some krypton ( $$$$$$ ) and NF3 ( $$$ ) instead of R14, seems to be at least as hard as R14 to get.
Did you ever try HC's as a blend ( C2H4 and CH4 for instance ) ?
I have sadly only once gotten to play with methane. When I first started I got about 3 hours of Q&A with Pc ice, a builder of some "infamy" back in the early Chilly1 phase days. And it wasn't happy running it that was for sure. But things were very ghetto back then.
It shouldn't be overly hard to work r1150 and r50 together, Before has done it a few times to great results. And the HC spectrum just squishes together so well it's almost magical.
I need a tank of methane. But I also need a new tank of ethane. And some r123. And more things.
But again, med school means I'm lucky if I get 2 weeks in my workshop a year now.
So spending money on the shop has become very back burner. Last spring break I put a $1000 into my milling machine, and $500 into new tables and shelving. So I'm just trying to keep my shop, well, a "shop" at this point. So that when I do get time there, it's as massively efficient at possible. And as fun as possible!
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