Hyperspace Pirate - 2023-01-21
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: https://www.youtube.com/watch?v=GjRoThMyNGA Part II: https://www.youtube.com/watch?v=WOmjJFk8rl0 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.
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
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!
This project is insane! Keep it coming man, I am staying updated! :)
Yes!!! This is one of the two YouTube 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!
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?
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.
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.
I mean this in the best way possible, but these are the best videos to fall asleep to. Also very educational.
Ahh, this series has got to be one the the ones Im most hyped about, not just on YouTube, but anywhere.
oh yeah, I love a youtube channel with graphs and unanswered questions. can't wait for part 4
I didn't know I liked watching thermo acoustic videos. But you did. Thank you for letting me know.
I'm glad that I found this channel, awesome content
I can't wait to see where this journey is going! Great video!
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!
Great work, sound experimental findings leading to incremental discovery and improvements!
This is my favourite series on youtube.
Thank you for using metric.
I have no idea how this works even after watching all the videos, but it's very interesting.
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!
Looking good! I can't wait to follow you down this rabbit hole
Good progress, looking forward to see part 4
This series is why i'm hitting the bell notification button.
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.
Fascinating! Thank you for all the effort you put into these projects and videos.
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. 👍
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!
I appreciate you being so open and sharing your journey. You are becoming one of my favorite creators. Keep going my friend. 🙏
I am truly baffled by the quality of your work, it's a pleasure to follow your project. thank you !
The pragmatic and sincere methodology keeps inspiring me. Thank you for great content!
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!
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 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.
This is really impressive engineering, with exceptional attention to detail.
Your videos are very cool, and the things you make are always very unique
This video tingles my engineering bone. Can't wait for the next video.
This is really great and the graphs are very helpful to understand where there's a away from a linear response.
Wow, that is everything i could hope for regarding cryocoolers, thanks for you great work, looking forward for next video!
Can’t wait for updates on this project every time a new video drops. You’re doing great!
Great data set. It makes clear explanation why commercial PTR and GM coolers have very thin stainless steel outer housings.
I like that you aren't dumbing down or simplifying the content and theory it makes it so much more enjoyable that way
I’m drooling over this series omg
It's fascinating to see the inner workings of a genius's brain! Your technical analysis capabilities are unsurpassed... 👍
It's not often that the first attempt is so effective. But you still managed to learn from it and improve design. Impressive
@frogstronaut1220 - 2023-01-21
You've consistently been one of the most fascinating channels I've seen. Good job!
@rodjownsu - 2023-01-21
Amennnn
@SamCooler - 2023-01-21
Yeah! There are very few "maker" channels that also have a high-level engineering/physics approach like this. Love it!
@1islam1 - 2023-01-21
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🔴 Islam is not just another religion.
🔵 It is the same message preached by Moses, Jesus and Abraham.
🔴 Islam literally means ‘submission to God’ and it teaches us to have a direct relationship with God.
🔵 It reminds us that since God created us, no one should be worshipped except God alone.
🔴 It also teaches that God is nothing like a human being or like anything that we can imagine.
🌍 The concept of God is summarized in the Quran as:
📖 { “Say, He is God, the One. God, the Absolute. He does not give birth, nor was He born, and there is nothing like Him.”} (Quran 112:1-4) 📚
🔴 Becoming a Muslim is not turning your back to Jesus.
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More ...
@NGPCO. - 2023-01-30
What would happen if you placed the whole system into a vacuum chamber?