Pulse Tube Cryocooler - Part 2 (-75C)

Part 1:
• Pulse Tube Cryocooler ...
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:
www.amazon.com...
25: and 40mm pistons:
www.amazon.com...
www.amazon.com...
Music Used:
Kevin MacLeod - Lobby Time
Kevin MacLeod - Groove Groove

[@HyperspacePirate]

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]

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]

- 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]

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]

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]

is the volume really really low or what?

[@Aeogenia]

This is by far, the most interesting video project recommended by KZbin in a long time. Great explanation and accurate presentation. Amazing work, keep up the good work. Hope to see -200C in a while :)

[@drezster]

I second that. Looking forward to some liquid nitrogen in the near future :)

[@pradipda3171]

So True otherwise youtube only promotes garbage and clickbait

[@xmysef4920]

Gotta agree with ya!

[@jtjames79]

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!

[@fickgooglefickthem6884]

In case You don't know: watch the "star in a jar" project by the plasma channel. Just a recommendation

[@odw32]

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!

[@kellenfoore5182]

This is the best thing that KZbin 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!

[@krystianstolarczyk4544]

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.

[@lidamullendore6166]

Fantastic progress!!! I admire your bravery to take on such a challenging problem. Can't wait for part 3. Thank you so much! 😘

[@AttilaBlade]

It was a great presentation again! Congratulation! DELTA EC program from Penn State University could help a lot to you in the next steps. There is possible variations of heat engines and heat pumps from simple alpha Stirling to pulse tube via thermoacoustics. The resonant frequency of the system is one of the main thing to increase the performance with a better performance of HX & regenerator also with changed basic parameters. Try to abstract from the pressure ratio a bit, because ThermoAcoustic systems could rich this temperature range easily with low compression ratio, typically under 10%. These materials that you used are enough good for a trial run where you can see the effect basically, but with this density, wire diameter and thermal properties of the regenerator just with a bit poor performance. The Achilles-heel the HX parts in every "homemade" heat pump. (I think it again, because maybe just we've made this type of unit in public...) I know you've learnt a lot about this unit, I'm impressed!, so I just suggest to you look around the thermal penetration depth for better performance of heat exchangers. The regenerator density is not a big problem here, that will create a phase shift too, when it will dense enough so try to not worry about it too much. The moisture is a real problem, because the ice could block the gaps. Alpha Stirling has a high compression ratio but if you can hit the -100 degrees Celsius you will experience strange things with sealing, or around the solid material when you want to going under. BLADE SPS: Sorry for the essay!

[@Al5052H32]

Would a phasor diagram be of help here? I have been led to assume that mass flow is king. Edit: also that the goal of a phasor diagram is to balance the diagram on the middle of the regenerator. Would this be correct?

[@mikeconnery4652]

Thank you for the essay

[@amannarwal7032]

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

[@drfoop]

That I could understand this using memories of high school physics from the distant past speaks volumes for your presentation skills. The KZbin recommendation engine has a success for once. Excellent video.

[@thonkingintensifies9510]

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

[@GautamSharmaCA]

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.

[@brandonwyffels8002]

Really excited to see such great results! I definitely plan on building one for myself in the future

[@vincentli9106]

if you do it, for the love of God tell me how you did it. I can't build crap!

[@b-beluga4510]

@@vincentli9106 sit in toilet bruh

[@crusiethmaximuss]

Just found this channel via KZbin recommendations, and I must say, I am thoroughly enjoying it. Subscribed.

[@udovan]

Great video. One bonus for your tip for the cleanup of steel wool with a magnet, is to put the magnet into a plastic bag first. Then when you're done you can just fold over the bag and remove the clean magnet :)

[@NiphanosTheLost]

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

[@LexYeen]

This is the kind of garage science everyone should know is possible.

[@nolanmods7172]

I really think adding the second piston will yield better results! Can't wait to see the next video on this!!

[@ivprojects8143]

Very impressive! It's clear you put a ton of effort into both the project itself and the video. Thanks for sharing!

[@vernonzehr]

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".

[@Vinzmannn]

Man, refrigeration is such a cool topic. Thank you for this video.

[@williamogletree4153]

PV=NRT WITH THERMAL CONDUCTANCE AND DISSIPATION... EXCELLENT VIDEO

[@williamogletree4153]

however you're not fully accounting for thermal conductance in the shotgun dissipators

[@williamogletree4153]

if you spread your thermal dissipators over the XYZ axis instead of stacking them, in other words, in a spherical configuration it should achieve much greater thermal dissipation. goes in it from the core goes out it from the outside of the sphere to rejoin to a central manifold should boost efficiency exponentially. then consider cooling the outside of the sphere with the secondary cooling system you may get within liquid nitrogen range at low energy input just a suggestion keep up the good work brother

[@corey736]

This is amazingly thorough and well thought out. Congrats on the Hackaday link too.

[@theGraphicAutist]

very cool... I'm after the same thing but ur way smarter than I! I'm routing for u... and waiting impatiently for ur next video!

[@BrilliantDesignOnline]

As a random passerby, with science knowledge, I had no idea this was possible..Great video. Fly Wheel doesn't hurt either :-)

[@clive4500]

Very impressive and a joy to watch journey of Discovery💯 ps high-quality glass syringes. Would be a good possibility for the pistons. Easy way to get hold of Close tolerance. Displacement could be increased by using more than one of these syringes

[@namaefumei]

data analysis and scientific method is unbeliavable. Thanks a lot for sharing!

[@qownson4410]

You need a patreon or something. Some people might wanna throw money at you? What you're doing is refreshing. Happy New Year.

[@poprawa]

This project is as mental, as impressive. I love it

[@camfocus8888]

From both you and me have same nail, I believe we think the same way too! I like your idea and work as well!

[@alexscarbro796]

A tip I like for cleaning up ferrous metal swarf. Put the magnet in a bag. Swipe it over the swarf, then turn the bag inside out. The magnet remains clean and the swarf stays inside the bag.

[@poldiderbus3330]

This is kind of a project I would have expected to see from Ben / Applied Science! Really cool, great job!

[@danjohnstone8196]

Nice progress. A couple of suggestions, for what they are worth: measure the impedance of the components and match, rework the regenerator for lower axial conduction. May be able to measure impedance by comparing current draw at the driving motor with load and subtract no-load. Capacitance would be decreasing in impedance with f, resistance would be flat, and inductance would increase in impedance with f. Your dogged determination is inspirational. Also makes you admire Stirling et al, and wonder how they did it.

[@nitromeano]

I love your content, it is a beautiful example for everything engineering stands for, thank you for producing it.

[@Tristoo]

god damn I wish I could subscribe twice man. absolutely sick. and this video I actually understood like 95% of it. Lmao the scenario of being your roommate just came to mind and it's absolutely hilarious- +"hey man" "hey" +>looks at contraption of 3d printed stuff with bolts on it, some piston, steel wool, PVC piping, some copper tubing and some tank-like thing. can't for the life of self figure out what it could possibly be +"so you making like a kart or something?" "nope" +"steam engine?" "closer kinda" +"what is it?" "cryo cooler" +>doesn't believe random assortment of random could possibly be the type of thing used mostly in incredibly expensive industrial equipment +"no way" "way" +"so you like freezing water or something?" "that was last prototype, this is now freezing co2 " +>looks up freezing point of CO2 and realizes that's cold af +>further looks at assortment of random things bolted onto the board +"... okay now that's cool" "quite.. but still only half as much as it will be" I've had that happen before where I do something insane and people are like "no way you made that.. you made that?" - but this is on another level. Anyway, thank you for the video once more. And as always looking forward to the next one.

[@Hclann1]

Your knowledge and understanding of thermodynamics is impressive.

[@giovanni4151]

amazing video thanks. i study engineering and watching this video was way more clear then many labs experiences in my uni

[@JCGver]

Tips for cleaning up after steelwool: put something around the magnet, like a it of paper. After you got all the fibers on the magnet, you can remove the paper with the fibers and not have the hassle of cleaning the magnet of fibers.

[@irkedoff]

I see a new PC cooler. Great work. I can't wait to see more.

[@NourMuhammad]

I came here because I saw 3d printed parts and thought this should be easy since I have 3d printer, but after 5 min of watching I changed my mind! :LOL Subscribed!

[@fr3zer677]

Can't wait for the next video! Very nice job!

[@SmiteBostil]

your videos are some pretty unique content here, hope you stay here.

[@zidbits1528]

Just subscribed (I rarely subscribe to channels, I'm only subscribed to 3 channels not including yours). I've worked in HVAC most of my life so I find this stuff absolutely fascinating and super interesting, keep it up! If you're looking to dump off a lot of heat quickly, have you considered vapor chambers (i.e, heat pipes)? It's what they use to dump huge amounts of heat from CPUs and they're shockingly good at doing so. Some of them can dump off 120+ watts of heat almost instantly. They use these copper tubes with a liquid inside of them but the inner walls have a mesh, grooved or sintered lining. There's a picture of the inside of one on the wikipedia article for heat pipes. They're *incredibly* efficient and since you can machine some of your own parts, it shouldn't be too hard to create some sort of base to attach them. Either way, keep it up man. Loving your channel.

[@scottneels2628]

Man that's cool! I'm hooked. Can't wait for the next installment.

[@noimagination99]

Really cool project and great video. I like the technical details you show, and your methodical experiments, all very educational. I do think moisture in the air is limiting performance. The easiest way to get really dry gas is to use nitrogen or argon. Helium is expensive, and both He and H2 are really difficult to seal completely, leakproof.

[@sparc5]

this is the COOLEST thing I've ever seen on KZbin.

[@lambdaprog]

This video is a good reference for engineers.

[@defenestrated23]

Awesome job! I tried building a thermoacoustic cryocooler with a jigsaw once. Barely got any temperature drop, but never got around to really tinkering with all the parameters.

[@Somnifluous]

Sub'd 30 seconds in. You speak fluent nerd and present it well. Great video, fun project! Good luck!

[@flomojo2u]

Great work!! Very exciting performance for very modest materials, I'm really looking forward to your next video.

[@cerberes]

This project is very interesting and giving me ideas on how to cool my new AMD 7950 CPU.

[@adrian5895]

Thanks for your videos! I really enjoy them.

[@FriendlyCynic]

All of our Gifford-McMahon Cryocoolers use two stages in which the 2nd stage (lower temp) is always a proportional fraction smaller ID than the 1st stage as to increase compression

[@bentboybbz]

Just a thing that popped into my head when you soldered the copper tubing into the caps is that you could flare the end or cut it and open up the flaps and solder them for extra safety...don't want you getting hurt....I need you to finish this project so I have something actually interesting to watch

[@oddzc]

Cant wait to see part 3, great stuff

[@ItsKyleMang]

From one nerd to another, I thank you.

[@Kadeshy]

This is real engineering! Attaboy Pirate! 👏

[@marktennant7415]

Quick Tip : when cleaning up the Steel Wool with a magnet, if you place the magnet in a plastic bag then turn it inside-out the scrap is bagged and the magnet remains clean.

[@Rukkus333]

I love this pulse cooler series. I'm hoping you continue this until you hit your goal of liquid nitrogen and show us how you collect it.

[@herzogsbuick]

This is great. Can't wait for part 3

[@iforce2d]

Most people would build it and wonder why cooling was so difficult, this guy crunches the numbers and sees it coming a mile away

[@DavoodAnsariOgholBeig]

Amazing piece of work. Really impressed!

[@luismoroco4972]

Very very Nice job, thanks for share.

[@theopendoor3716]

Wow an actual engineer

[@christ2290]

I need to read up more on this concept. I'm all to familiar with traditional phase change refrigeration and work on typical refrigeration systems all the time. The pulse tube concept....I understand part of it, and the other parts seem counterproductive.

[@gakich.]

Nice project，I know what to do next year :D maybe next project is to make pure nitrogen filter?

[@jamescarter9147]

Really interesting, subscribed for the next one!

[@henningklaveness7082]

Great stuff. YT just recommended this, and I'm looking forward to binging your channel. One question though: Why didn't you start out with a large air compressor hooked through a VFD, and optimize the plumbing to suit? That'd spare you the hassle of dealing with mechanical issues, and let you concentrate on the thermodynamic side of things...

[@BestSpatula]

This is very cool!

[@rafaeldiegonavarro]

Finger licking good . Super juicy content. Thanks for uploading and sharing with us. Can't wait for the next part ! very good engineering principles also ! keep at it !

[@bytesandbikes]

Super interesting deep dive. Thank you!

[@PhG1961]

Great ingenuity and an amazing project !

[@sunroad7228]

"No system of energy can deliver sum useful energy in excess of the total energy put into constructing it. This universal truth applies to all systems. Energy, like time, flows from past to future".

[@Gribbo9999]

Wonderful that you are using metric units. Just a point CC is bit of an archaic usage. Millilitre (or milliliter if you prefer) is the usual SI unit abbreviated to "ml" though we Australians prefer "mL" to reduce symbol confusion. Millilitre follows the thousands rule and is consistent. Eg 1 mL is 1 mg of water at standard temperature. Try that with those pesky gallons (and whose gallons anyway?) and pounds (weight not currency).

[@suryakamalnd9888]

Amazing video bro

[@ElizabethGreene]

Regarding helium, you should be able to see a significant performance difference, even with low grade helium "balloon" gas. Get a balloon, "fill" the system as best you can, and you should see a notable difference. The speed of sound is higher in helium so you'll need to retune your buffer length and driver frequency.

[@murraymadness4674]

I did a lot of research on making liquid nitrogen, the simple solution is just buy a cryocooler which is what most every video did. I found two that actually made their own, and it was a massive time sink and super inefficient, so very expensive to produce. I also found you can just buy liquid nitrogen pretty cheap if that is all you really want. I bought a big dewar to hold it, but really I need to use excessive solar to create it as energy storage. I thought I could use many stages using different technology, but ultimately ones need the cryocooler as the final stage.

[@HUMBERTOPEREDO-s7u]

Hi Pirate, I would recommend you to find the natural frequency of your PTR. I you match the first mode of the PTR with the frequency of your pump. the diference in the drop temperature may improve!!!

[@amoddev3483]

Love ur vids

[@RT-qd8yl]

Your doggo is awesome.

[@emceebois]

-75°C with no coolant is DEFINITELY nothing to scoff at! How many amps was the motor using at that point? Would be curious how this works out in terms of energy efficiency. My guess would be "not as good as commercial refrigerant-based cooling, but maybe good enough to run off of solar power", which would definitely make it of interest to a large potential audience of off-grid and renewable energy enthusiasts!

[@horrorhotel1999]

You will need to use helium in your final design anyways or you'll get phase changes happening in your refrigerant at the cold end. Pretty sure that is also what actually kept you from going below the freezing point of co2

[@dannysmith8035]

instant subscribed well thought out experimental design

[@carlhelm2402]

You can use hydrogen in the cryocooler. It's easy to make an relatively cheap compared to helium and have similar properties. It is not a fire hazard if the hydrogen is at high concetrations and if it leaks the smaal amount of gas will swiftly dissipate to low enugh concentration as to not be able to ignite.

[@Runoratsu]

When using the magnet to clean up debris, put it into a latex glove or so first-once your done, simply invert the glove and throw it in the trash, no need to clean the magnet.

[@igor12345677]

5:39 Most of the heat is removed when the hot refrigerant gas is cooled and condenses into a liquid. Not very much heat is removed after it becomes a liquid . It is the phase change from a gas to liquid that releases a lot of heat.

[@Jkauppa]

spin casting perfect parabolic mirror lens molds

[@Jkauppa]

epoxy glass metal whatever

[@af0ulwind115]

I have a curiosity, the greater the vacuum drawn on the air medium the cooler it gets yet the greater pressure applied the hotter it gets... thus your need for the heat sink and the flow reducer to restrict the movement of the heat from the compressed medium as the decompression takes place on the other side of the heatsink... I will assume you know how a regular heat pump works, compressing refrigerant into a small confined line then out into a much larger diameter line that has a vacuum pulled on it. the change of density of the refrigerant from the small line to the large line causes a change in state of matter from liquid to gas creating the temperature gradient. I am thinking of maybe using isopropyl Alcohol as a refrigerant in a parallel, secondary line that decompresses, inside the cooling tube either on the cold or hot side of your heatsink. the compressor for this line could easily be a second piston with a much smaller stroke/volume on the same motor. perhaps i am over thinking this.

[@lucaslittmarck2122]

No i need the next video! Good job! :)

[@dtiydr]

Very interesting, thanks for uploading! And you got a new subscriber.

[@landondehart3032]

Just wondering when part two of the kayak will be out! :)

[@user-nu2pj2ch7t]

absolutely love your content! super high quality astuff!! do you have a release date planned for pt 2 pf the submergable kayak series?? I LOVE it!

[@fireprooffox3664]

Can we see more on the submarines, I'm super interested!

[@rashidminhasbhatti9618]

Thanks... your video is very helpful ... understand... Heating system.... thanks again

[@NGPCO.]

I’d be curious to see what would happen if you insulated all the piping you might be struggling with some heat transfer

[@fabianbohnert120]

Did you change the pulse tube for the larger piston? Since that made such a large difference for the smaller piston it might help the larger one as well. Have you measured the heat bildup on the heatsink? That might also be a limiting factor for the large piston

[@LoremIpsum1970]

...I do hope you will pick up the design and optimization of the linear motor as a separate project at some point!

[@dfunited1]

This is so cool! I hear a lot of talk of desalination plants, especially during drought years in California. Wouldn't it be easier to freeze the water out of the air?

[@danielsoderstedt1941]

Hi, love your projects. Heatpumps and thermodynamics is so fascinating. But I have an unrelated question, what's the name of the xylophone jazz you play in the background?

[@shurmurray]

My 5 cents: Before implementing complete stirling with two cylinders, what if split intake and exhaust routes for the air with one-way valves? This may allow to treat gas more efficiently probably w\o the need of regenerator.

[@CooledeYe]

Normal cryo cooler are two cycle cascade cooler and the low temp refrigerant are high pressure refs and liquifies in the high temp evaporator. The problem für cryos is the high wattage you need exponentiell caused of Delta T To the Ambiente.