Pulse Tube Cryocooler (Part 3)
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- čas přidán 20. 01. 2023
- This is the third video in my series on building/testing a Pulse Tube cryocooler with the eventual goal of liquifying nitrogen/oxygen.
Part I:
• Pulse Tube Cryocooler ...
Part II:
• Pulse Tube Cryocooler ...
In this video I investigated the effects of different pulse tube materials, regenerator materials, heat sink designs, inertance tube geometry, and pressurization of the working fluid. While I didn't manage to exceed my record from the previous video of -75C drop (corresponding to a drop below ambient of about 100C), I did gather a lot of information about design factors.
My initial design in this video used a stainless steel pulse tube/regenerator housing, but i found that the temperature difference generated for a given power input was dramatically lower than with PVC parts due to conduction losses.
One of the biggest takeaways from the tests i ran was that performance is almost directly proportional to the pressurization of the working fluid, and having a large average pressure is much more important than having a high compression ratio. This is consistent with how real cryocoolers are built, which are typically pressurized anywhere from 10 to 30 atmospheres, but have pressure oscillations of under 10% of average pressure.
I also experimented with different regenerator materials, such as ceramic beads, glass beads, plastic pellets, and glass fibers, but found that compacted stainless steel wool (which i started with) still performed best.
For configurations both with the 25mm diameter piston and the 40mm diameter, i found that the cooler seemed to hit a wall at around ~100 degrees of temperature drop below ambient, where application of additional power only marginally improved performance. I suspected this was related to limitations imposed by the inertance tube and compared my 1/4" copper tubing against 3/8" flexible silicone tubing of a greater length, but I found that this change reduced performance, most likely due to increased surface roughness and flexibility in the line dissipating energy. In a future video I'll probably try to use rigid copper/aluminum tubing with a 3/8" or 1/2" inner diameter.
I also reconfigured the entire device into an alpha-type stirling cooler, but found that performance was actually dramatically reduced despite the ability to mechanically set the phase angle between compression and expansion. I think this is because the cold expander piston was causing large conduction losses through its thin aluminum walls.
I ran the device with loads disconnected, and with pistons disconnected to determine the amount of power being consumed by mechanical action as opposed to pneumatic power, and found that less than 30% of the input electrical power was actually going into the system.
Finally, I examined the effect of a double-inlet valve, which has the effect of improving phase shift and removing some of the load on the regenerator. While this didn't make a tremendous difference, the difference is very obviously apparent and repeatable.
In my next video, I'm going to build an entirely different test setup using a valve-based (or "Gifford-McMahon") configuration and a standard air compressor as a high pressure source. While this configuration is less efficient, because the input power would be so much larger, it should be an overall net positive. In addition, control over valves allows me to achieve consistent timing via digital control and fine tune it for best performance.
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I love the systematic scientific evaluation of this DIY project.
It's probably the only way to make some progress here - who would have guessed that the far more professional looking stainless steel construction underperformed the PVC construction so significantly...
@Alexander Gräf I was... mostly because of heat transfer through the hardware. With the last video I was thinking about adding a heat break I. Between the hot and cold sides, a small section that is ceramic... keep the hot side hot and the cold side cold.
@@kayakMike1000 That sounds like a good idea.
I personally was not able to decide whether steel would have a negative impact, seeing how heat transfer is actually wanted in certain parts. Like there's a literal heat exchange. But you're right, you want the hot and cold side not to be able to conduct to each other.
This is an excellent project. Thanks for sharing your work and making it easy on those who will recreate it in the future.
Love your vids, would like to see you try this
You've consistently been one of the most fascinating channels I've seen. Good job!
Amennnn
Yeah! There are very few "maker" channels that also have a high-level engineering/physics approach like this. Love it!
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What would happen if you placed the whole system into a vacuum chamber?
I noticed that the copper tubing you are using was cut with a standard tubing cutter but the ends were not de-burred. The burr formed on each tube is effectively turning your tubes into double orifices causing expansion losses at each end. And while the "orifices" are deep into the open end of the fitting they can behave like venturi tubes and waste valuable gas expansion. If you can get your hands on a 2mm swage tool so that the tube itself is the venturi instead of the ends I estimate 5 to 8% increase in capacity with the double inlet setup. Having about 1m^3/min airflow over the hot end per watt total input power will help dissipate friction loss heating significantly.
My background is only phase change refrigeration and air conditioning so do with that what you will. Use of a common refrigerant like pure CO2 or 134a are my choice for hobby projects but I don't remember if you were trying to use pure air at which point I would like to point out the obvious that any moisture in the air makes all the above moot since it has a massive effect due to it's specific heat capacity. Cheers!
You are absolutely correct 9:17 all of those need to be deburred and chamfered. That will increase flow rate a bit. Should upvote this its a easy thing to forget.
@@fajile5109 You could place the fitting in a lathe and machine the tube ends flush with the fitting and perhaps even countersink then a bit with a drill bit.
Great project and I hope you succeed. A potential source of Nitrogen would be the exhaust vent of a small consumer Oxygen concentrator. Having liquid nitrogen always available opens up a lot of possibilities. You can make multiple cold traps at N2(l), CO2(s), H2O(s) and perhaps a couple more phase change temperatures. Let you gain better solvent separation and freeze drying performance.
I was thinking the same thing. Also he could put a larger copper pipe over the hot side and phase change cool it
It is an absolute delight to watch a such a disciplined and thorough design process performed by somebody who is willing to go into the thermodynamics. As an engineer in a different field (comp/elec), it’s a privilege to get an inside view of a design process and issues being grappled with.
Exactly! Dude I don't know jack ish about this but following along with the math presentations, hypotheses, trials, and plot-graphing is soooo fin dope dude
What a radical dude, dude...
Use HELIUM instead of regular air inside your system. I have a pulse tube cryocooler that can reach -196c. I repaired and charged it with helium @265psi and it operates at 60hz. The pistons use gas-bearing tech which keeps loss and wear low. 150 watt input will lift 5 watt load at -196c. Unit was pulled from a Superconductor Technologies band-pass filter for cell tower application.
Might be interesting to try neon, or nitrogen, instead of air. We'll be out of helium pretty soon.
STI Sapphire cooler is not pulse tube, but Stirling type cooler, so different system altogether :).
@@xDevscom_EE Yes, you are correct that the STI is a Stirling type. However, even though the term Pulse Tube refers to a specific type that does not employ a displacer, it is still often loosely used to describe any regenerative system because of the oscillatory movement of the working fluid. I will try to be more accurate.
He said in an earlier video that he knows to use helium but that he plans for that to be the last thing he does. He wants to tinker with all the other stuff as helium gets expensive.
I do hope that once you reach your goal, and you will, that the series can still continue to find efficiency gains. Making something work is always goal number one on any project starting out. Making it work well is an even longer, and just as interesting, road.
So interesting. I hope we get to LN2 temps, and there’s an open source design that anyone can build and iterate with basically just a McMaster order. Great work!
I've always wanted to make my own LN2!
If you need the regenerator to cause less resistance then, like last video, I suggest trying out a different regenerator construction. Take stainless steel strips/foil, press some dimples on it (apparently a sewing machine works fine for this; alternatively I'd imagine just pressing some slight sharp notches with a knife or something would also work), and then roll it up like a rolled cake. It would be like a very dense air-cooler heatsink - air can pass (relatively) unimpeded between the different fins (layers of the roll), while still exposing a large surface area for heat transfer.
While I doubt a better regenerator design alone is a miracle magic bullet for the project, if it gives you another 5C gain, then that's worth it, no?
This project is insane! Keep it coming man, I am staying updated! :)
Yes!!! This is one of the two CZcams projects I’ve been so excited for. This and Callum Long’s mini liquid rocket engine. Keep killing it!!
lol same here
Cylos garage has a pretty tight ultra precision lathe he's building, and I mean, like, machine an optical grade mirror using a chip making machine precision lathe.
Another excellent video, with great experimental planning and detailed data and discussion! As a point of reference, FYI, I have a system at work with a 2-stage Gifford-McMahon Cryocooler for condensing Helium. It has 40 W cooling capacity for stage 1 and < 1 W for stage 2. This requires a 10 HP (about 8 KW) compressor, with some serious cooling for the compressor itself. You may be running up against a compressor power constraint now. Great work, very impressive progress so far though! I can't wait to see more. Best wishes!
Taking us through the hypothesis then proving or better yet, when you prove yourself wrong, is really gratifying and unique. Good work!
Been waiting for so much anticipation for part 3. I hope we get a part 4. You're amazing.
I can't wait to see where this journey is going! Great video!
Ahh, this series has got to be one the the ones Im most hyped about, not just on CZcams, but anywhere.
Love the quick turnaround on uploads. If you have a fulltime job I have no idea how you are cranking out updates on the project so fast but I love to see it.
Fascinating..... Your willingness to try out different techniques to see how they affect your results AND document the failures as well as the successes is really refreshing! THAT is the core of science! You WONDER what this will do and what that will do.. and I WONDER right along with you.. it is exciting... and makes me want to watch more to see the outcome. I dare to say that MOST other channels likely do the same type of work that you do.. but merely issue a "This is how you do it" video.. and that's fine... But it's not entertaining.. I'm not interested in ever building a Pulse Tube Cryocooler... But i am incredibly interested in watching you go through the process of building one!
A couple of others have noted, and I'll add as a reminder. You are pushing into air liquification temperatures, and that will eat up a lot more power. At one atmosphere you are already hitting CO2 liquification, and at higher pressure you could be getting close to O2 liquification. And since your thermocouple is averaging the temperature over a second or two, the per cycle temperature may be oscillating above and below liquid temperatures. These rapid phase changes, many times per second, will eat up power until the bulk temperature is below the liquid temps.
Probably best to switch to at least pure N2, to help mitigate the potential of phase changing. And N2 is cheaper and easier to get at welding shops then He.
Great videos, and have fun exploring.
Yea i was just about to comment that that flatline he keeps hitting close to -80C makes me feel like he's coming up against a phase change or something. I'd love to see him address this concern with one of his neato charts!
Thank you for using metric.
I have no idea how this works even after watching all the videos, but it's very interesting.
I'm glad that I found this channel, awesome content
Great work, sound experimental findings leading to incremental discovery and improvements!
You hit the nail on the head with your A/C circuit analogy. I would suggest you pay mind to your pump's resonant frequency, its effect on performance and efficiency, and how you could tune that. Using the analogy again, your flywheel is like an inductor, and compressing air in the total system acts like a capacitor. This forms a resonant tank in and of itself. Adding and removing "counter springs" to your air cylinder has the analogous effect to adding and removing capacitors in parallel to the tank. You may, alternatively, wish to add or remove weight to your flywheel, and see what this does. It may not bring the system the direction you want, but it will provide useful information to be sure. 👍
Looking good! I can't wait to follow you down this rabbit hole
Just leaving a thumbs up seems inadequate for the quality of this series, so I just wanted to add my thanks for the amazing information and your excellent presentation!
I didn't know I liked watching thermo acoustic videos. But you did. Thank you for letting me know.
I’m drooling over this series omg
This is my favourite series on youtube.
can i just say thankyou for using °C much love from the rest of the world ❤❤
This series is why i'm hitting the bell notification button.
One of the Best CZcams channels ever! Im learning real stuff!
Superb presentation of the data and experimental data collection.Extreemly thorough. Its lovely to see real numbers. The high static pressure with lower ripple would favour a linear electric motor where a sprung offset can be applied. Not sure how that could be done on a crank. . Fascinating. A real adventure.
By pressurizing the crank case
This video tingles my engineering bone. Can't wait for the next video.
I like that you aren't dumbing down or simplifying the content and theory it makes it so much more enjoyable that way
This is really great and the graphs are very helpful to understand where there's a away from a linear response.
The pragmatic and sincere methodology keeps inspiring me. Thank you for great content!
I appreciate you being so open and sharing your journey. You are becoming one of my favorite creators. Keep going my friend. 🙏
Wow, this is very impressive! It’s amazing to see the methodical and detailed approach to solving this problem. Can’t wait to see the next video.
I am truly baffled by the quality of your work, it's a pleasure to follow your project. thank you !
I really cant wait for the next instalment of this series! Was very happy this morning when I spotted you uploaded this video. Albeit I’m somewhat versed in the technical field, this is beyond me and extremely interesting. Thank you for this contribution!
This here is definately my new favorite channel
This is really impressive engineering, with exceptional attention to detail.
Damn! Impressed again. Had to share this video with some people thats probably interested.
I mean this in the best way possible, but these are the best videos to fall asleep to. Also very educational.
It's fascinating to see the inner workings of a genius's brain! Your technical analysis capabilities are unsurpassed... 👍
This is a great series, thanks very much. I suggest you try operating with the unit vertical in gravity, with the cold end of the pulse tube down, to avoid gravitationally-driven convection in the pulse tube, which will be present even despite the oscillating flow.
It's not often that the first attempt is so effective. But you still managed to learn from it and improve design. Impressive
'Finally found 'SmartTube" THANK YOU !!! SUBBED
Great depth, data-driven analysis and optimization. Math meets Mechanics !!
I'm sure there are Fluid Dynamics factoring into the resonance such as turbulence, Reflection, standing waves etc
Bring in Mr. Viktor Schauberger techniques !
Fascinating! Thank you for all the effort you put into these projects and videos.
Your videos are very cool, and the things you make are always very unique
Can’t wait for updates on this project every time a new video drops. You’re doing great!
Amazing video as always! You can definitely get better performance and lower temps with helium or argon especially under pressure. It would also be very interesting to see a dry vs humid air performance chart. You could start playing with these once you've honed down the parameters you're already tracking. Also the regenerator may be packed too tightly and the 8g vs 2g is not very conclusive since 2g is too little material and would underperform anyway. You could try 4g or 6g steel wool in the same space or even 8g but in more space. Can't wait for the next part in the series!
Great data set. It makes clear explanation why commercial PTR and GM coolers have very thin stainless steel outer housings.
Can't tell you how much I enjoy seeing real engineering presented with clarity and precision. Thank you so much for this series! I can't wait for the next installment. Incidentally, the "t" in Carnot is silent (it's French).
That's what I was going to say.
It's "Car-no", not "Car-not."
Nifty AF ! This series is fantastic.
Well, you mentioned everything I was going to suggest.
Lookin forward to the external cooling on the hotend test results.
Brilliant to watch! Love your videos.
oh yeah, I love a youtube channel with graphs and unanswered questions. can't wait for part 4
Wow, that is everything i could hope for regarding cryocoolers, thanks for you great work, looking forward for next video!
Good progress, looking forward to see part 4
I've worked with pulses tubes few month ago, I'm not an expert but I may have some idea to improve your system!
You can use silica aerogel as insulator. It's way better than glass wool. You can increase the surface area of your heat exchanger with heat pipe(cuts both ends and use it like a copper pipe).
I've heard that regenerator is often made of stainless steel or small lead balls which have a high thermal capacity and doesn't reduce the flow too much!
Commercial pulses tubes use helium mostly because it liquidized at 4K but I'll recommend you to use at least really dry air, any water vapor can drop the efficiency!
Edit: typo and french
I searched calloducs but no results, plus "lead bids" please explain? All I get in the search is auction like results,
@@seeker1015 sorry calloducs is the french name you should search "heat pipe"
Sorry I meant balls don't know why it wrote bids
@@oneilgoisot9615 Ah, yes, I can see that now. Callo=heat, ducs=ducts/pipes. Thank you.
Loved the RCL comparison!
I can see how this would be frustrating, but you keep pushing ahead!, keep up the great work!
I'm about to finish my single stage precooled joule thompson cryocooler tomorrow. Wish me luck. Will soon share the details about it. It's using a mix of ethylene and nitrogen 60:40 as working fluid.
good luck!
This is the best content on CZcams. Looking forward to every and any video in this series. I hope that when you reach -196 C you will continue the development so that I one day can have a flashlight sized HPGe-detector in my pocket.
Great scientific procedure. Congrats!
Loving these videos, cant wait to see the next one.
Great to see this much progress
ive been waiting for part 3 thank you
This is very cool! I'm already excited about the next part.
Love it! Science and engineering is amazing in practice like this!
Thank you for all the work on this!
Very well documented progress! Another thing I'd look at is whether the water vapor in your gas causes a significant decrease in performance. It should be relatively easy to compare the performance with regular compressed air and some form of drying(even a pipe full of baked silica gel will do).
Awesome stuff! Grab bag of ideas:
* You tried alternate regenerator materials but none of the ones shown were fibrous like your steel, so I think surface area : volume ratios were ruining them all. Have you tried plain old cotton balls, or the various types of fibrous insulation?
* Have you thought about using insulative liners inside of metal components to get the pressure rating of metal but avoid contacting your working fluid with metal exposed to ambient?
* You can DIY a super dense heat exchanger with 3D printed stamping molds and thin 1000 series aluminum (it's super soft and easy). Print a pair of dies wavy in one axis to make a tiny version of corrugated roof panels, then alternate a stack of corrugated, flat, corrugated, flat. Clamp the edges of your stack so they get good thermal contact with the outside of your housing.
This is great, awaiting part 4 :)
Love this series!
Can't wait for part 4!
I'm green red colorblind i wouldnt have even noticed :D
I found your Channel via this project and i'm instantly hooked , great videos :)
excellent job! Thanks for sharing your project with us. I can't wait until you cool the hot end! Hopefully you can calculate the total cooling capacity for this beast! Amazing work!
Incredible work!
Try to get a beefy subwoofer speaker and convert it into a membrane piston.
Theoretically if you pressurize both sides of the membrane you should be able to run at higher pressures too.
With a smart driver you should be able to precisely control the pressure wave.
Maybe it is even possible to autodetect the best resonances with it.
Thank you Sir! 😊👍👍
Wonderful Video!
Nice weekend 🌞🌨❄
Great work, thank you for sharing it with us!
Finally, I was waiting for this...
If i may make a suggestion for heat extraction, LED lamps are often cooled with an extruded tubular heat sink with a significant number of fins on the outside. If you arrange this heat sink within another pipe and run coolant through the middle with your gas in the space between the two pipes you would have an incredible amount of surface area in play.
Excellent videos as always!
Nice, can't wait to try doing it!
Two years ago I was playing with different mixtures of propane and butane to see how well heat pipes worked.
We think very much alike. But you make videos about it.
Okay - I will focus...
i just rewatched part 1 & 2 haha , love the project man!
Can’t wait fot part 4! Keep it up!
Can't wait for part 4
Top content! Good luck man!
Love this project
Very neat demonstration and analysis. Will recommend this for a physics instructor to demonstrate to the class good experimental method. 🤓
really interesting, keep up the good work
Thank you for these videos!
That flatline looks like you didn’t have the torque. Great job on these videos, you’re a genius. I love learning this stuff. Keep up the great work
simply outstanding video (s)
This is excellent thank you for sharing this!
Looks great, keep it up!