Joule-Thompson Cryocooler
217,640
Published 2023-07-03
In this video I'm going to examine the performance of a homemade cryocooler using the joule-thompson effect. A joule-thompson type device was the first method that was used to liquify nitrogen on an industrial scale, but it was very inefficient. Using nitrogen at pressures of 200-300 bar, it would drop the temperature through a regenerative heat exchanger until it reached a low enough temperature that some of the nitrogen would condense to liquid when it expanded through a flow restriction. This process was very inefficient, usually less than 1% of input power went into actually cooling and condensing the nitrogen.
I'm going to be taking a slightly different approach that's a sort of half-way between a joule-thompson device and a vapor compression system. Instead of using air or pure nitrogen as a working fluid, I'm going to use a mixture of hydrocarbon gases (propane, ethylene, and methane), which have dramatically higher joule-thompson coefficients. Unlike a traditional joule-thompson system, this type operates in a closed-loop. Typical low side temperatures get down to -160C to -170C, which is enough to liquify air or pure nitrogen if it's pressurized to 10-20 bar inside the cold end, which is trivial to do.
Higher boiling gases will condense as the temperature of the cold head is reduced and cease to contribute to the joule-thompson cooling, but still make a major contribution to heat transfer when they evaporate in the regenerative heat exchanger.
I built this system using the compressor and condenser coil from a 12K BTU portable AC unit (meaning the compressor pulls around 900W loaded). The oil separator is a temprite 900 series, and the heat exchanger consists of 30 ft (9m) of two 3/16" tubes for the high pressure side and a single 5/8" tube for the low pressure return line.
I only reached -88C in this video, because a defective oil separator was causing oil to overflow into my heat exchanger and freeze at such low temperatures, resulting in clogs in the capillary tube. The heat exchanger also wasn't properly insulated or pre-cooled in this video. With those changes, reaching -150 to -160C should be relatively easy with the correct gas composition.
Music Used
Kevin MacLeod - George Street Shuffle
Kevin MacLeod - Groove Groove
Kevin MacLeod - Lobby Time
Local Forecast - Elevator
All Comments (21)
-
So apparently its "Joule-Thomson", not "ThomPson" with the P, but since William Thomson has been dead for over 100 years, I'm gonna keep spelling his name with a "P" cause he can't call me out.
-
This is easily my favourite series on youtube. The only time I drop everything to watch something
-
Having worked with refrigeration for some twenty years I love this. You are the single most radical mad scientist in this field bar none. Your understanding of the cooling processes and the mechanical and practical equipment design should be taught in schools and we would all be better off. The description of efficiency relating to economy in a few sentences are coming out as an aside but sum up how you make a business case. I love what you do and how you share it. Mad respect!!
-
I get so excited whenever I see an upload from you! This whole cryocooler series has been fascinating from the getgo.
-
"I installed this tap in my natural gas line..." love it
-
Love the R&D in this series, and learning a ton about hobby cryogenics!
-
Fwiw this is probably the most info-dense, engaging series I've ever found outside of Applied Science. I'm normally a mechatronics guy and yet I'm having a really hard time resisting the urge to build one of these myself despite having no need for LN2 and knowing nothing other than what I've learned from you. Love it, keep it up! 🍻
-
Suggestion: add a sight glass plumbed at the correct level in parallel with the oil separator so you can keep an eye on the oil level. Also, why not use an adjustable needle valve for your expansion valve instead of swapping in cap tubes? (Modern refrigeration systems use EXVs which are often needle valve controlled by a stepper motor.)
-
Thanks for explaining how they did this in the 19th century, I find those old compressors fascinating. The Liquid Air car experiment and the whole Paris pneumatic system are such interesting feats of innovation even if it was horribly inefficient. Would a TXV valve help your endeavors? Also when are you going to start playing around with ammonia :P
-
I'm absolutely loving seeing all the ideas and progress you're making... I tried to build a JT liquifier years ago, might I suggest building a small vacuum chamber out of an old lpg tank, I built a large one from a car lpg tank, but your heat exchanger might fit in a regular sized one. Coat the inside of the tank in mylar or flexible mirror to reduce radiation losses, you can then braze the heat exchanger to a decently thick steel sheet for the lid, some soft rubber will work nicely as a seal. I used an adjustable needle valve on the cold tip instead of capillary, you could even put a handle through the side of the vacuum tank so you can adjust the needle valve while the whole system is running in order to increase/ decrease your ratio / remove blockages.... Keep up the awesome work!!
-
Really looking forwards to seeing how those improvements work out. Even if you reach LN2 I think it would be interesting to see you keep trying to improve the efficiency and exploring the different variables.
-
These videos are so cool
-
At this point, I do not even remember what the main goal of this entire endeavor... All I know is that I am buckled in for this cool ride. Such an epic adventure.
-
Happy to see MRJT cryocooler for the first time on youtube
-
This is really cool! By the way, you can usually make gauge screens look clear again with some grease smeared on them. If you want a more permanent solution clearcoat works very well or a thin/runny clear epoxy can work.
-
Thia series is amazing. Im so excited for your eventual success!
-
I've been hyped to watch every video that's been coming out in this series. Learning the ins and outs of a diy cryocooler is pretty awesome.
-
I have been on the edge of my seat this whole series. Love your work ❤
-
Hyped every time I see your uploads. I cant wait to see what happens next!
-
Wondering when we will start seeing college textbooks written by you, as your ability to explain and document with graphs and drawings is stellar!!! Love this series.
