Hyperspace Pirate - 2022-12-27
Part 1: https://www.youtube.com/watch?v=GjRoThMyNGA This is the second part of my video series on attempting to build a Pulse Tube cryocooler. I managed to make significant progress by removing the linear motor and using a conventional rotary motor with a large gear reduction ratio and a flywheel to produce the larger forces needed for higher compression ratios. For pistons, I used pneumatic actuators. I evaluated a 25mm bore and a 40mm bore piston, both with a 50mm stroke. Pneumatic actuators have more friction than conventional pistons due to their rubber lip seals, but theoretically have zero blowby, so they hold pressure, which makes them more effective for low frequency applications. Here are some specifications for the cooler: Pipe diameter: 18mm Regenerator Length: 30mm Regenerator Material: Fine steel wool Pulse Tube Length: 100mm Flow resistance source: 1/8 NPT needle valve Inertance Tube Length: 10' (~3m) Inertance Tube Diameter: 4.4mm Buffer Tank Volume: 2L Piston Swept volume (25mm): 23CC Piston Swept volume (40mm): 57CC Compression Ratio (25mm): 1.4 Compression Ratio (40mm): 2.0 Maximum Frequency: 15 Hz Motor KV: 750 Motor Voltage: 16V Motor reduction ratio: 5:1 Flywheel moment of Inertia: 0.012 kgm^2 Maximum recorded temperature drop below ambient: -91C Lowest recorded temperature: -75C I think with some more optimization, this system can probably reach -100C, although without helium or hydrogen as a working fluid, I think it's unlikely that I'll reach cold enough temperatures to liquefy oxygen/nitrogen. In part 3 of this video, I'll do more investigation into hot-end heat exchanger design, regenerator design, and the effect of increasing the power density of the system by pressurizing it. I'll also be comparing the pulse tube performance to a similar spec alpha stirling cooler. Links for parts: Motor: https://www.amazon.com/dp/B084QCLTM1?psc=1&ref=ppx_yo2ov_dt_b_product_details 25: and 40mm pistons: https://www.amazon.com/gp/product/B082FW5XKS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1 https://www.amazon.com/dp/B08YYQZ5CQ?ref=ppx_yo2ov_dt_b_product_details&th=1 Music Used: Kevin MacLeod - Lobby Time Kevin MacLeod - Groove Groove
This is by far, the most interesting video project recommended by YouTube in a long time. Great explanation and accurate presentation. Amazing work, keep up the good work. Hope to see -200C in a while :)
I second that. Looking forward to some liquid nitrogen in the near future :)
So True otherwise youtube only promotes garbage and clickbait
Gotta agree with ya!
I agree this is highly relevant to my interests.
I've been wanting to test out instead of using heat to evaporate water from my 3D printer filament, sublimate it with cold instead.
Freeze drying machines are ridiculously expensive.
I could do so much science with this!
In case You don't know: watch the "star in a jar" project by the plasma channel. Just a recommendation
This is fascinating. The first DIY cryocooler that works sufficiently This is the first DIY project reaching really low temperatures without complicated multistage refrigerant stages.
:) Not the first that works well, but with a really cool presentation!
That's some seriously impressive data analysis and scientific method for a simple prototype! Great work - subscribed!
Yeah, couldn't agree more. Often that sort of info is missed during YT content which I assume is to make it palatable to a wider audience who just want to see stuff built, tested, and completed. (Or blow up; intentionally or otherwise).
When cleaning wire wool up wrap the magnet in a rag so you can separate the captured steel wool from the magnet to dispose.
Great to see an explanation of why gas-gas heat exchangers are hard to design!
Gas-to-gas heat exchangers are much harder than the other because overall heat transfer coefficient is substantially low that you need very large equipment for that. Because of that, the diameter and length of the heat exchanger gets larger and larger. If you intend to do gas to liquid heat exchanger, it is far worse than it seems, because the liquid will have higher conductivity while gas will have very low conductivity which makes a lot of problems on the design process. Other than this, the pressure drop across the heat exchanger will be very high for gas effluent (because of high velocities) depending on what type of heat exchanger and which side you intend to have liquid flowing (if it is shell and tube heat exchanger of course)
In my process design course, I had a lot of problems with superheated vapor stream and it was a nightmare to get the correct design values.
Great suggestion. Could use a vacuum cleaner or a small brush.
Instead of a rag you can also use a sandwich bag but the rag works well too.
The clarity & detail in your explanations is absolutely amazing, the collected data and visualizations really help to make this more intuitive. You're a great teacher!
This is the best thing that YouTube has sent my way in a LONG time. Thank you so much for the amazingly well made video, and I can't wait for the next part!
this is incredible
you are the only youtuber that shows how to make a cryocooler
keep this up
The use of the scaling exponents to predict the behaviour, along with the brute force empirical parameter sweep was beautiful ❤️
I wanted to click like so many times in this video but sadly I am limited to just one.
This is so beautiful.
I love how far diy projects have come since the early days of YouTube a decade ago which were 90% LED projects keep up the good work
Love this series, seriously. I feel like I understand now how “real” engineering is done. Keep the videos coming!
I was kind of getting board of all the math then... "my homemade CNC Mill"! I was instantly paying 100% attention.
Great Video Man!
I more or less stumbled by accident over your videos, but the subject is very fascinating and they are one of the best youtube videos I ever saw up to now that combine practical use with scientific background. Wish my scool lessons in physics or thermodynamic would have been so interesting! As already said by others, you would be a very good teacher! Many greetings from Germany and all the best for upcoming 2023! 😃
Once you can turn air to liquid i know this channel is gonna blow up. Great editing, the graphs are sweet. I'm getting ready to follow along.
I just want to say that in terms of video produciton, you've done an excellent job in the treatment of the calculations and design considerations. You've somehow kept your explanations concise without glossing over anything big, and made it accessible without dumbing it down.
Your channel is the best one Youtube has recommended me in a long time.
I think you just gave me an idea to rescue my old GM-Cryo system...
Great video, excited to see where your journey will continue to go!
You could try to improve regenerator performance by using several "sub-regenerators" to prevent heat conduction axially. In practice, instead of making one blob of steel wool, make several and stack them inside the tube.
I wonder if adding an insulator material or air gap between them would help as well
@@mitchellstrobbe7779 What I've read, having an air gap or insulator material between sub-regenerators does not improve the perfomance much at all. Axial discontinuity in the regenerator should be enough to prevent axial conduction.
Try a stack of stainless steel filter mesh. Not only does stainless steel have a much lower thermal conductivity than the steel in steel wool, but heat has to flow laterally along the before reaching a contact point where it can flow axially to the next screen. The second part contrast with the random orientations allowing comparitivly faster axial heat conduction with steel wool.
I recently signed up for Paramount+ and was watching "The Love Boat" before I clicked on this video. My GOD, the vast difference in the intelligent content between these two programs is astounding. I believe they are fighting for control of my brain (it didn't matter so much back in the 70s and 80s). I'm not sure if this could cause some sort of brain damage. Like a kind of "content intelligence quotient whiplash".
This is excellent! Having scratch-built several high temperature Stirling engines, I very much appreciate your approach to this.
Were you thinking of using the waste heat. Also, would a sterling engine make a good power source on the moon?
I love the intelligent and thoughtful community you've fostered, I scroll down and all I see is intelligent and thoughtful comments instead of my first instinct which was laughing at the robo pubes at 8:45
Your channel is a goldmine for us mechanical engineering students. Thank you for the detailed content!
This id one of the best documented experiment with best scientific illustration, salutes
Man, refrigeration is such a cool topic. Thank you for this video.
Fantastic progress!!! I admire your bravery to take on such a challenging problem. Can't wait for part 3. Thank you so much! 😘
Awesome video. I have been intrigued by pulse tube coolers since I heard about it on JWST, so to see a functional DIY build is astounding. Great work, looking forward to part 3!
This is super cool, I went down a rabbit hole of research into cryocoolers about 6 months ago but never found anyone else doing it DIY. I'm glad you took it to the next step and built it!
What a magnificent video. I love how well you are keeping track of all the variables and then plotting them on a graph, it's a very nice tool to have when trying to optimize such a system. Well done.
So, I don't comment often, but you are fantastic. This is such a great example of scientific and data driven innovation. Finding ways to isolate, measure and iterate individual components is the name of the game, and you have done it wonderfully.
The explanations, calculations, and even concept presentation in this video is top notch. I’m learning and enjoying it
This is the kind of garage science everyone should know is possible.
Simplest way to give these 3D printed parts better performance and tolerances is to press in some bushings, typically made from brass. It works similar to putting in inserts, heating them up and then just pushing. Bushings are very often the better solution compared to roller or ball bearings anyway.
Bushings are only really significantly better if you're worried about contaminant intrusions into the race or concentricity. For a continuous low speed, ambient temperature, high torque system in an open and dry environment, ball bearings are pretty much perfect. A bushing would need much more careful tolerances for the shafts and alignment. If he were working with hydrogen gas you might have an argument though.
@@dustinbrueggemann1875 Yes yes, high torque like here lol. It's low-torque, low-load, low-speed, and very limited operating hours, so the main argument for bushings is the fact that they're low profile. Which I guess is the reason he didn't install ball bearings in the first iteration of the rod, as there wasn't enough space.
Just found this channel via YouTube recommendations, and I must say, I am thoroughly enjoying it. Subscribed.
One of the most underrated channels on YouTube
Very impressive! It's clear you put a ton of effort into both the project itself and the video. Thanks for sharing!
4:00 this is a very well done explaination for a really complex system that throws numbers and formula symbols at you like a gatling.
Bravo! Looking at your channel - all the videos you have made - you should have at least a few million followers! You indeed, are one of the few.
Man, I loved the last video and this one didn't disappoint. Great job I'll be watching for updates.
Well I must say, this is my new favorite channel. I love the inclusion of the formulas. Thanks!
That I could understand this using memories of high school physics from the distant past speaks volumes for your presentation skills. The YouTube recommendation engine has a success for once. Excellent video.
That was one of the most interesting videos I have seen in a long time. I semi-learnt a ton of things from it. I say "semi" because there was stuff in it that I didn't know I didn't know. So I didn't exactly "learn" but now I know where to start in truly understanding some of the science and engineering behind the fluid and thermo dynamics of this. Thank you, I've subscribed and look forward to the next part.
And he's using the correct units! +10 points!
This is the best fluid dynamics lesson I've ever had
You're perseverance is the spirit of the scientific method and it gets you results. As a result This is SOOO damn inspiring
I have a ton of these types of components laying around, I have doubts I will ever get around to actually doing this but this is extremely cool. You have my respect and you have my subscription.
Truly remarkable in my whole life as an engineer to this date it's the first time I realised how difficult it is to build something when you are dealing with multiple variables
I really think adding the second piston will yield better results! Can't wait to see the next video on this!!
This project is as mental, as impressive. I love it
This stuff is fantastic and explained so well. I feel like I'm watching advanced Bill Nye the Science Guy.
This is a super fun project to follow, thanks for the thorough presentation!
Brother what the hell did you study to all know all this, not only physics but your grasp on electricity is also astonishing, keep making videos love this stuff
@HyperspacePirate - 2022-12-27
I've read through the comments and thought I'd address a few of them:
-The 40mm piston is probably not optimally matched to the pulse tube geometry,
since i optimized it for higher frequencies on the 25mm piston
-For part 3 or 4 i'll probably try using Hydrogen as a working gas. It has a lower
specific heat ratio than helium, but the highest thermal conductivity of any
gas, so I should see an increase in performance as long as all the components are
sealed well enough to avoid leakage
-For part 3 I'll be looking at heat exchangers with multiple heat pipes and
water cooling, as well as single tubes packed with copper wool.
-I do intend to evaluate a segmented regenerator with polymer "heat breaks"
to slow down axial conduction losses by breaking the continuity of the metal
mesh
-For higher pressures and lower temperatures, I'll be replacing the PVC
with stainless steel to avoid explosion hazards.
-The ESC has flyback diodes across the H-bridge MOSFETs, so any back-current
from the flywheel after motor shutoff should be dissipated through those.
-Multiple stages might be neccesary to reach LN2 temperatures with a DIY setup.
Pulse tubes can be staged by connecting a much smaller pulse tube to the output
of the compressor's aftercooler and thermally anchoring the second heat exchanger
to the cold end of the first stage. Pulse tubes used for liquefying helium/hydrogen
typically have 3 or 4 of these stages and can reach single-digit kelvin temperatures
@Axman6 - 2022-12-28
I’d be really interested to see more tests with increasing the regenerator diameter so the gas flowing over the steel wool is moving at a slower velocity; if your idea about the velocity of the air getting too high is right this should help… maybe 🙃
@BirdbrainEngineer - 2022-12-28
- Hydrogen is incredibly difficult to keep sealed; just look at the troubles and delays with SLS
- I wouldn't be so sure that you can use water cooling... wouldn't the heat exchanger itself not get cold enough at one point to freeze water inside the heat exchanger? Then you have an insulator in the pipes instead!
@marttileppanen - 2022-12-28
Could you add a new stage just by eg. adding a Peltier element (with a heat sink) to forcibly cool down the hot end and thus increasing the temperature difference? They're not terribly efficient, but can move tens of watts of heat without using moving parts?
@vladovrhovsek - 2022-12-28
You should ISOLATE ALL around the precision valve and after on the right, all the way to coper pipe and reservoar. When air from the resevoar expands through valve, it cools off, and it is good, that it is cool as posible, before expands.
@WetDoggo - 2022-12-28
is the volume really really low or what?