This video was kind of crazy, both with how badly the original goal failed (save money on a pre-built system) but also on just how unsafe much of it seemed.
This video was kind of crazy, both with how badly the original goal failed (save money on a pre-built system) but also on just how unsafe much of it seemed.
Huh? In the video (at 50m25s) he said that it cost $500 less and outperforms the pre-built systems he was originally looking at on Alibaba. Earlier in the video he said his produces ~30L/d of...
how badly the original goal failed (save money on a pre-built system)
Huh? In the video (at 50m25s) he said that it cost $500 less and outperforms the pre-built systems he was originally looking at on Alibaba. Earlier in the video he said his produces ~30L/d of liquid nitrogen, vs 20L/d the prebuilts advertise. And his also has the added benefit of potentially being able to make liquid helium too, since his cryocooler is significantly more powerful than any the pre-builts use due to it being originally designed for an MRI machine.
The only mistake he made in terms of cost was with the compressor, since he later discovered that a new one could probably have been bought for significantly less than he spent on that older model. And if he had known that and hunted for good deal, it would have made his setup significantly cheaper than any of the pre-builts.
I 100% agree about the safety concerns though. At the very least he should definitely upgrade his dewar to something that doesn't have a leak, was not made 3 decades ago, and can actually handle being pressurized so his siphon technique doesn't risk causing it to explode.
Edit: Found a good comment about other potential safety issues that he probably needs to address as well:
So cryogenics engineer here. Couple of notes:
Safety: The danger in handeling cryogenic fluids lies among others in the chance for frostbite, but particular in its capability to explode or suffocate living beings. If for any reason, the "thermal integrity" is broken (i.e., loss of vacuum seal), it results in rapid vaporization of your cryogenic fluid. If it is a closed vessel, you're waiting for an explosion to happen. For this reason, it is extremely important to place pressure relieve valves/burst disks on every closed volume. Besides the explosion, suffocation is also no joke. If 100L of LN2 evaporates. it fills a room of about 5x5m with a height of 2.4m. While a O2 sensor won't help you in case of an explosion, it will warn you in case of a leak.
Construction: That gasket between your flange and the "dewar" is made out of TPU which is unlikely to hold cryogenic temperature. Switch that out for something like a conflat.
Dewar: so I'm quite certain that dewar you have is more a cryostat used for experimental physics. I.e., you load it with an experiment which you would like to perform at temperatures of your cryogenic bath (i.e., LHe or LN2 temperatures), you fill it with said cryogen and run the experiments. This I think because its a top loaded tube and its a tube. Tubes are not great at handling high pressures due to the sharp corners at the top and bottom. Dewars should be able to handle high pressures because you usually extract some cryogen by evaporating a bit of liquid which increases the pressure. This pressure increase then pushes out the cryogen through the extraction tube as seen in this video. I would very much advise against pressurizing this vessel because it is not meant for this application.
Liquid Helium: So you mention that you want to make LHe with this setup in the future. Be cautious that this requires significantly more energy (read up on Carnot on wiki). Furthermore it requires much better heat management because of this reduced efficiency and poses some additional risks. Besides He3 and He4, all other substances are in the solid state at 4.2K. This means that any foreign substances can clog your system, causing an enclosed volume which in turn is a safety risk.
So there's probably much more to talk about, but be aware that because your setup performed safely once, it might not indefinetely. Structural failures can happen over time, i.e., metal fatigue, embrittlement, etc.
I got the vibe that he ended up with a super high end system for about the price of a low end one, rather than the original plan of an equivalent low end one for cheap, and he was probably playing...
I got the vibe that he ended up with a super high end system for about the price of a low end one, rather than the original plan of an equivalent low end one for cheap, and he was probably playing it up the a bit for the narrative (it’s been 15 years since I was last in an actual lab, but I remember liquid helium stuff being on a whole different level to liquid nitrogen so I’m guessing that hasn’t drastically changed).
But yeah, there were definitely a few places the sketchiness made me wince a bit, and I’m just hoping that was better managed off camera too.
What, 100L of liquid nitrogen in an unsecured dewar couldn't do that much damage if someone climbing a loose stepladder accidentally slipped and tipped it over, could it?
What, 100L of liquid nitrogen in an unsecured dewar couldn't do that much damage if someone climbing a loose stepladder accidentally slipped and tipped it over, could it?
I'm not qualified to discuss any of the safety parts, of which there are apparently a variety of issues, but the siphon was hilarious to me. A nearly-level siphon trying to operate on a vessel...
I'm not qualified to discuss any of the safety parts, of which there are apparently a variety of issues, but the siphon was hilarious to me. A nearly-level siphon trying to operate on a vessel that can't safely be pressurized. Either get gravity to help by increasing the height difference of the siphon ends or, better yet, use suction!
I use an auto siphon when bottling home brew and his dribbling hose looked basically just like when I don't use a big enough height difference on my siphon.
I mean, he was slightly pressurizing the Dewar to pump the liquid through the siphon, though to your point it's really just a hose and not really working like a gravity siphon. It looks like about...
I mean, he was slightly pressurizing the Dewar to pump the liquid through the siphon, though to your point it's really just a hose and not really working like a gravity siphon. It looks like about 4 psi gauge pressure was just enough to overcome gravity up the siphon tube. I don't think suction is really an option is this setup as it would require pulling a vacuum on the Dewar instead (which at that point positive pressure is probably just as dangerous and doesn't require an extra piece of equipment), or submersing a pump that could handle the cryogen pressure at the bottom. I think for the setup he has, his only option is to use a different Dewar that can handle higher pressurization which would give him a higher flow rate out of the hose.
It isn't clear to me why suction wouldn't work. Fundamentally it is just using the same principal of trying to get it to flow from high pressure to low pressure, but your high pressure doesn't...
It isn't clear to me why suction wouldn't work. Fundamentally it is just using the same principal of trying to get it to flow from high pressure to low pressure, but your high pressure doesn't need to be so dangerously high anymore.
If suction isn't the answer then how is the dewar designed to have the liquid removed? It only has top openings, isn't designed to be pressurized, and doesn't seem like it's meant to be tipped. The only option left I can think of is to suck it out.
4 seemed both dangerously high and barely enough.
Edit: another comment from YouTube suggests that it doesn't have an obvious way to remove the liquid because this model isn't intended to have the liquid removed.
Suction doesn’t work in a vacuum. When you drink through a straw, you lower the pressure in the straw, but that lower pressure doesn’t “pull” the liquid up at all. The atmospheric air pressure on...
Suction doesn’t work in a vacuum. When you drink through a straw, you lower the pressure in the straw, but that lower pressure doesn’t “pull” the liquid up at all. The atmospheric air pressure on the rest of the liquid, which is now higher than the pressure in the straw, pushes the liquid up the straw. If you had the drink in a vacuum container with the straw exiting the vacuum (the same scenario as the dewer), and lowered the pressure in that straw, the liquid levels would happily stay the same. You need some pressure on the liquid to move it up the straw.
That being said, I am also confused about how the dewer is supposed to be used.
To be clearer my suggestion of suction does still require that the dewar is pressurized, at least for some definition of pressurized. It just doesn't need to be so highly pressurized when the...
To be clearer my suggestion of suction does still require that the dewar is pressurized, at least for some definition of pressurized. It just doesn't need to be so highly pressurized when the pressure on the other end has been lowered. With a vacuum on the other end of the tube it may be possible to achieve flow at the regular operating pressure.
That's a pretty good point, it's not super obvious how it was designed to have its contents removed. And I'm not disagreeing that a suction pump could work. Surely there are pumps designed to...
That's a pretty good point, it's not super obvious how it was designed to have its contents removed. And I'm not disagreeing that a suction pump could work. Surely there are pumps designed to handle pumping cryogenic liquid, though probably also expensive. But the way I'm thinking it through I see it introducing a new logistical challenge, at least for the high nitrogen purity he seems to be prioritizing. If you're going to suck liquid out you'll need to still balance pressure in the tank. The Dewar must have been designed with some kind of system in mind to balance the pressure (maybe from a similar gas air separation system to the one he's using), or it wasn't designed with maintaining such a high purity in mind in which case you could balance pressure with ambient air as you pump the liquid out.
Honestly it's weirder to me that it wasn't designed to be used with some moderate level of pressurization. Pressurizing it (positively or negatively) seems to make it much easier to use.
As for the output stream, I think part of the issue is a lot of his liquid is probably vaporizing once it's in contact with the hose walls. I think if he ran it long enough the liquid flow rate will probably go way up as the hose chills down. For being a remarkably clever accidental mechanical engineer, he seems overly ignorant of the heat transfer at play (such as most of his initial liquid vaporizing at the bottom the Dewar for the first hour until the Dewar walls cooled down to match the temperature). Like, surely he realizes things need to cool down and it's going to take a while because he's going to such low temperatures, right? O.o Maybe he's just doing a bit.
My guess about removal is that you aren't meant to just spray it out but instead transfer it to more manageable vessels. To fully simplify the mental model I'm thinking, imagine a bottle with 2...
My guess about removal is that you aren't meant to just spray it out but instead transfer it to more manageable vessels. To fully simplify the mental model I'm thinking, imagine a bottle with 2 hoses going into the top where one is vacuum and the other is going to the bottom of the liquid. That bottle could then be designed to be tipped, have a bottom spout, etc. Now that I think about it I basically just wrote out of a design for a wet vac.
The impression I get is that he's aware of those things, but just didn't put much thought into it. Like he seemed aware that it was normal for it to immediately evaporate when hitting the bottom, but was just surprised how long it took to stop. My guess is that if he'd purchased something that he knew worked, or at least expected to based on the product description, he would have been more patient before panicking that his newest money pit wouldn't work.
My best guess is it would probably introduce a significant thermal bridge at the part of the tank you would want to stay the coldest. Heat would be able to conduct along that out let's pipe wall...
My best guess is it would probably introduce a significant thermal bridge at the part of the tank you would want to stay the coldest. Heat would be able to conduct along that out let's pipe wall straight to the bottom of the liquid and significantly reduce its insulating characteristics.
Ah, this takes me back… my senior design project was to deliver very pure (99.99% or something like that) liquid nitrogen with a $10k budget. Telling the academic panel how much liquid nitrogen...
Ah, this takes me back… my senior design project was to deliver very pure (99.99% or something like that) liquid nitrogen with a $10k budget. Telling the academic panel how much liquid nitrogen they could buy with that budget was unfortunately not an acceptable answer if we wanted to graduate (it was a lot of LN2). I never thought I’d hear that compressor click again…
A cryocooler is the probably the most practical small-scale approach and there is an even more dangerous way to do this. McGraw Hill put out a monograph that was out of print and somewhat hard to find when we did this project. It looks readily available now, but along with these helium loop cryocoolers for things like MRIs and xray crystallography, the text describes some high pressure expansion cycles that could also reach cryogenic temperatures. So, in theory, it seemed like a scuba compressor was another potentially low budget, but again, dangerous, way to reach the required pressures without contaminating the purity of the filtered nitrogen.
At scale this gas liquefaction is done on large distillation columns, and really I can’t imagine why anyone would want to produce liquified gases at home instead of just procuring them from an industrial supplier.
I mean, the reasons he's doing this is to make air into alcohol, gasoline, and a bomb. Not exactly, uh, practical solutions. This is very much a journey-over-destination kind of thing. The actual...
and really I can’t imagine why anyone would want to produce liquified gases at home instead of just procuring them from an industrial supplier.
I mean, the reasons he's doing this is to make air into alcohol, gasoline, and a bomb. Not exactly, uh, practical solutions.
This is very much a journey-over-destination kind of thing. The actual product NileRed makes is interesting youtube videos, not any of the chemicals that are the final results. In that aspect, this video alone made thousands of dollars.
A number of NileRed's videos are for the cachet, not because it's the most practical way to do the thing. Near the end of the video he says that he wants to recreate a supercooled electromagnet...
A number of NileRed's videos are for the cachet, not because it's the most practical way to do the thing. Near the end of the video he says that he wants to recreate a supercooled electromagnet experiment entirely with components he made himself, and so this is a step along that process.
This video was kind of crazy, both with how badly the original goal failed (save money on a pre-built system) but also on just how unsafe much of it seemed.
Huh? In the video (at 50m25s) he said that it cost $500 less and outperforms the pre-built systems he was originally looking at on Alibaba. Earlier in the video he said his produces ~30L/d of liquid nitrogen, vs 20L/d the prebuilts advertise. And his also has the added benefit of potentially being able to make liquid helium too, since his cryocooler is significantly more powerful than any the pre-builts use due to it being originally designed for an MRI machine.
The only mistake he made in terms of cost was with the compressor, since he later discovered that a new one could probably have been bought for significantly less than he spent on that older model. And if he had known that and hunted for good deal, it would have made his setup significantly cheaper than any of the pre-builts.
I 100% agree about the safety concerns though. At the very least he should definitely upgrade his dewar to something that doesn't have a leak, was not made 3 decades ago, and can actually handle being pressurized so his siphon technique doesn't risk causing it to explode.
Edit: Found a good comment about other potential safety issues that he probably needs to address as well:
I got the vibe that he ended up with a super high end system for about the price of a low end one, rather than the original plan of an equivalent low end one for cheap, and he was probably playing it up the a bit for the narrative (it’s been 15 years since I was last in an actual lab, but I remember liquid helium stuff being on a whole different level to liquid nitrogen so I’m guessing that hasn’t drastically changed).
But yeah, there were definitely a few places the sketchiness made me wince a bit, and I’m just hoping that was better managed off camera too.
What, 100L of liquid nitrogen in an unsecured dewar couldn't do that much damage if someone climbing a loose stepladder accidentally slipped and tipped it over, could it?
I'm not qualified to discuss any of the safety parts, of which there are apparently a variety of issues, but the siphon was hilarious to me. A nearly-level siphon trying to operate on a vessel that can't safely be pressurized. Either get gravity to help by increasing the height difference of the siphon ends or, better yet, use suction!
I use an auto siphon when bottling home brew and his dribbling hose looked basically just like when I don't use a big enough height difference on my siphon.
I mean, he was slightly pressurizing the Dewar to pump the liquid through the siphon, though to your point it's really just a hose and not really working like a gravity siphon. It looks like about 4 psi gauge pressure was just enough to overcome gravity up the siphon tube. I don't think suction is really an option is this setup as it would require pulling a vacuum on the Dewar instead (which at that point positive pressure is probably just as dangerous and doesn't require an extra piece of equipment), or submersing a pump that could handle the cryogen pressure at the bottom. I think for the setup he has, his only option is to use a different Dewar that can handle higher pressurization which would give him a higher flow rate out of the hose.
It isn't clear to me why suction wouldn't work. Fundamentally it is just using the same principal of trying to get it to flow from high pressure to low pressure, but your high pressure doesn't need to be so dangerously high anymore.
If suction isn't the answer then how is the dewar designed to have the liquid removed? It only has top openings, isn't designed to be pressurized, and doesn't seem like it's meant to be tipped. The only option left I can think of is to suck it out.
4 seemed both dangerously high and barely enough.
Edit: another comment from YouTube suggests that it doesn't have an obvious way to remove the liquid because this model isn't intended to have the liquid removed.
Suction doesn’t work in a vacuum. When you drink through a straw, you lower the pressure in the straw, but that lower pressure doesn’t “pull” the liquid up at all. The atmospheric air pressure on the rest of the liquid, which is now higher than the pressure in the straw, pushes the liquid up the straw. If you had the drink in a vacuum container with the straw exiting the vacuum (the same scenario as the dewer), and lowered the pressure in that straw, the liquid levels would happily stay the same. You need some pressure on the liquid to move it up the straw.
That being said, I am also confused about how the dewer is supposed to be used.
To be clearer my suggestion of suction does still require that the dewar is pressurized, at least for some definition of pressurized. It just doesn't need to be so highly pressurized when the pressure on the other end has been lowered. With a vacuum on the other end of the tube it may be possible to achieve flow at the regular operating pressure.
That's a pretty good point, it's not super obvious how it was designed to have its contents removed. And I'm not disagreeing that a suction pump could work. Surely there are pumps designed to handle pumping cryogenic liquid, though probably also expensive. But the way I'm thinking it through I see it introducing a new logistical challenge, at least for the high nitrogen purity he seems to be prioritizing. If you're going to suck liquid out you'll need to still balance pressure in the tank. The Dewar must have been designed with some kind of system in mind to balance the pressure (maybe from a similar gas air separation system to the one he's using), or it wasn't designed with maintaining such a high purity in mind in which case you could balance pressure with ambient air as you pump the liquid out.
Honestly it's weirder to me that it wasn't designed to be used with some moderate level of pressurization. Pressurizing it (positively or negatively) seems to make it much easier to use.
As for the output stream, I think part of the issue is a lot of his liquid is probably vaporizing once it's in contact with the hose walls. I think if he ran it long enough the liquid flow rate will probably go way up as the hose chills down. For being a remarkably clever accidental mechanical engineer, he seems overly ignorant of the heat transfer at play (such as most of his initial liquid vaporizing at the bottom the Dewar for the first hour until the Dewar walls cooled down to match the temperature). Like, surely he realizes things need to cool down and it's going to take a while because he's going to such low temperatures, right? O.o Maybe he's just doing a bit.
My guess about removal is that you aren't meant to just spray it out but instead transfer it to more manageable vessels. To fully simplify the mental model I'm thinking, imagine a bottle with 2 hoses going into the top where one is vacuum and the other is going to the bottom of the liquid. That bottle could then be designed to be tipped, have a bottom spout, etc. Now that I think about it I basically just wrote out of a design for a wet vac.
The impression I get is that he's aware of those things, but just didn't put much thought into it. Like he seemed aware that it was normal for it to immediately evaporate when hitting the bottom, but was just surprised how long it took to stop. My guess is that if he'd purchased something that he knew worked, or at least expected to based on the product description, he would have been more patient before panicking that his newest money pit wouldn't work.
Why wouldn't it simply have a drain at the bottom? A little tap like on a water cask.
My best guess is it would probably introduce a significant thermal bridge at the part of the tank you would want to stay the coldest. Heat would be able to conduct along that out let's pipe wall straight to the bottom of the liquid and significantly reduce its insulating characteristics.
Ah, this takes me back… my senior design project was to deliver very pure (99.99% or something like that) liquid nitrogen with a $10k budget. Telling the academic panel how much liquid nitrogen they could buy with that budget was unfortunately not an acceptable answer if we wanted to graduate (it was a lot of LN2). I never thought I’d hear that compressor click again…
A cryocooler is the probably the most practical small-scale approach and there is an even more dangerous way to do this. McGraw Hill put out a monograph that was out of print and somewhat hard to find when we did this project. It looks readily available now, but along with these helium loop cryocoolers for things like MRIs and xray crystallography, the text describes some high pressure expansion cycles that could also reach cryogenic temperatures. So, in theory, it seemed like a scuba compressor was another potentially low budget, but again, dangerous, way to reach the required pressures without contaminating the purity of the filtered nitrogen.
At scale this gas liquefaction is done on large distillation columns, and really I can’t imagine why anyone would want to produce liquified gases at home instead of just procuring them from an industrial supplier.
I mean, the reasons he's doing this is to make air into alcohol, gasoline, and a bomb. Not exactly, uh, practical solutions.
This is very much a journey-over-destination kind of thing. The actual product NileRed makes is interesting youtube videos, not any of the chemicals that are the final results. In that aspect, this video alone made thousands of dollars.
A number of NileRed's videos are for the cachet, not because it's the most practical way to do the thing. Near the end of the video he says that he wants to recreate a supercooled electromagnet experiment entirely with components he made himself, and so this is a step along that process.