Hyperspace Pirate - 2023-04-11
In this video i'll show how to put together a single-stage vapor compression refrigeration system and explain the theory behind it. This machine uses propane (R290) as a refrigerant, because it has properties very similar to standard Hydrofluorocarbon (HFC) refrigerants, but is extremely cheap and readily available, and has almost no negative environmental effects. The obvious disadvantage is its flammability. If you're careful, though, propane or butane are perfect substances for a DIY vapor compression system. This is still part of my long term project to build a DIY cryocooler to make my own liquid nitrogen, but I've pivoted away from gas-phase systems like stirling/GM and decided to focus more on phase change systems due to the greater availability and low cost of parts. In upcoming videos, i'll be staging multiple vapor compression loops together to get temperatures below -100C. After that, i'll use a joule-thompson cycle to make the final push down to liquid nitrogen temperatures, but will do so with a mixture of hydrocarbons rather than nitrogen. Here's some performance specs of the device in this video: Condenser Pressure: 10-15 bar Condenser Temperature: 27-44 C Evaporator Pressure: 1.2 bar Evaporator Temperature: -37 C Capillary tube ID: 1mm Capillary tube length: 2m Compressor nominal rating: 5,000 BTU Compressor locked rotor amps: 27A Compressor operating limit (estimated): 5.4A Input power: 667W (529W from compressor, 138W from fans) Refrigerant charge: ~50 grams of propane Maximum recorded cooling power: 116W (COP 0.173) *Note that this power was recorded by testing the temperature drop of water reservoir at room temperature with lots of heat leaks, which was a far from optimal condition. Also, recording cooling power by multiplying the water flowrate of 13.5 grams/sec by water's heat capacity times the temperature differential across the coil of 3.3C yielded a higher cooling power of 186W. In upcoming videos, this system will be used to cool the condensor of a second refrigeration circuit, which will then evaporate to a far colder temperature close to -100C. This requires ethylene as a refrigerant (R1150). It's pretty hard to find and expensive to buy commercially, so in the next video, i'll be showing how to make it. Other useful tidbits: Propane bottle NPT thread adapter: https://www.amazon.com/Hooshing-Propane-Adapter-Throwaway-Cylinder/dp/B082MBGVXN/ Condenser fan: https://www.amazon.com/BLACKHORSE-RACING-Universal-Electric-Radiator-Thermostat/dp/B07DLSPDN1/ -Window AC unit that was stripped for condenser coil was rated at 5,000 BTU. The manufacturer/model number you use is not important as long as its sized right. Music Used: Kevin MacLeod - Lobby Time
All us fellow nerds are living vicariously through you, sir. We commend you.
I don't commend him. He exterminated all of my monkeys. In facts as soon as I get my last moon sapphire I will...yes we commend you yess
I am an engineer and he is even stranger than I am.
“…pressure gage had a leak”
Crying laughing at the subtle flex.
This video is so full of wisdom I’m going to be rewatching it repeatedly over the next two years.
You are so kind to share.
Frost is actually pretty effective insulation, so while an HVAC guy (me) doesn't generally like to see it, you can see how it serves your purpose, preventing unnecessary heat loads migrating into the system once the layer forms.
Bruuuh! Also an HVAC guy here, were you about to explode right up until he said? Oh yeah by the way I did vacuum the system down😅😂 ....
The way he did it it looked like he was like. Oh yeah, I just built this compressor and evap soft soldered it and then dumped a bunch of propane in there @atmospheric pressure. I was dying for a second but also I was like there's no way he doesn't know this
@@smn368 I just assumed Pirate did it. He mentions having a vac pump just laying around so while he didn't spell it out in the moment and I admit, I had a little nagging doubt, he's also pretty comprehensive about everything else so I figured he'd covered that step in its time.
I threw a solder patch on a pinhole once and then forgot about it for the next five years. Don't disregard solder too quickly.
Nope... All of it... nope.
plus you can easily tell it is working
@@ShainAndrews how so?
You probably already know this, however you didn't mention your flow configuration in the video. Make sure you're running all your tube-in-shell heat exchangers in countercurrent flow for best heat transfer. This series is fantastic and extremely high quality, I look forward to seeing the end result.
Lol I work on tube in shell heat exchangers and I didn't know that.
@@michaelnonamehere9003 I have often thought about this and came to that conclusion myself, it makes sense. The exchange is more efficient as the input is closer to the output in temperature. As the fluid, or gas goes through the exchanger the difference in temperature remains close and, as such, retains the efficiency.
Yes, noticed that the diagram had arrows going in the same direction, but counter-current is optimal in linear exchangers. Props for Adrian, and yes, props for HypPir. Good job.
I was going to mention the same. Countercurrent flow maximizes the temperature difference between the two fluids, enhancing heat transfer.
i paused to comment this too. the same flow direction will have both fluids exiting at (almost) the same temperature. opposite flow direction will much more effectively transfer (nearly) all of the temperature of one to the other, for example the hot side will exit right at the coldest part of the cold side, therefore the hot input will exit (almost) that cold.
Like half this stuff is well beyond me, but it's so interesting to watch you methodically go through, explain everything, not dumb it down, and then actually put it in practice. Can't wait to see the next vid!
Don`t underestimate your knowledge Sir, It`s a great time to be living in, with all the information anyone could need just a button push away! Anything you don`t immediately understand can be put right with a few clicks, all you need is a desire to learn. The internet has made it possible for anyone to have access to all this wonderful technology. I am involved in R&D, but before the internet was available, it used to take me ages to do the necessary research, but now it`s all right in front of us! (Scientific papers etc). Channels like this are great because they get people asking `how` and `why` things work.
it's not actually as complicated as it looks. it's intimidating, but if you take the time to learn pieces of it, break it down into smaller chunks, you can learn it.
This is basically a thermodynamics class, which is not actually as hard as people claim. Probably some free courses online somewhere if you were interested enough in learning more.
But even if you're not that interested, doesn't mean you're not capable of learning and understanding it.
@@SoloRenegade do you have any recommendations of where one could learn this?
@@xXx-yv7vg Search the internet, YouTube videos/lectures, and find books on topics such as;
Thermodynamics (refrigeration cycle)
Heat Transfer (Conduction, Convection, heat sinks)
HVAC, Refrigeration and Air Conditioning
Pumps, valves, plumbing
Tons of good books, lectures, and such on these various topics.
@@TheTemporalAnomalyevery single day I say this too myself at some point. I was pretty smart back in the day, now I am like the new guy every single day and I can accomplish so much more. Even if I don't fully understand it it is just like baking a cake. Which I can also do now. 😊
The quality and humour in something that could be presented so blandly is very much appreciated
Dude, as a refrigeration mechanic myself, I gotta say, your content and understanding of the refrigeration theory is fantastic. Keep doing what you do! I’m very impressed
I’m taking thermodynamics right now in college. I really love the class and the math that comes with it so watching this and seeing someone design a refrigeration cycle is awesome. It really helps show how what I’m currently doing in school applies to real world design challenges. This was really cool to watch. Phenomenal job sir!
While it's easier to just buy an A/C unit, seeing a system built from the ground up was really cool (ha ha). Vapor phase refrigeration systems were always a little mysterious to me, the many unstated details necessary to make one work, so seeing one built from scratch was really appreciated.
I finally realized that the structure of your videos is a near-perfect example of an experiment report. Actually seeing one in video format like this has already helped me figure out how to make my reports for work so much better. Thank you.
This is the first video iv found of someone actually making a phase-change system from scratch like this.
Iv been fascinated with heat-pumps for a while now so this channael is a blessing.
13:55 - Copper work-hardens, so your straightening of the coil to thread the other one through would have already hardened it, made it more difficult to re-coil (in addition to the added internal pipe). Annealing (heating and quenching) isn't really an option here either with 18ft of straight pipe, so you often need to be frugal with your manipulations, lest you end up with some really stiff pipe.
Yeah that's very true. I've noticed my pipe also getting stiff when I manipulate it. 😅🤣
You can anneal it, it will be just fine with no quench .
Sigh.... Ever heard of induction heating? He could literally just run the line over a cheap induction cooker on high with one hand and use the other to drizzle a water hose.
@@custos3249 Wow, that's brilliant - it doesn't sound difficult and subject to having specialist equipment on hand because induction cooktops are of insufficent power and design at all. You should comment more, your input is well considered and valuable.
Good luck induction heating copper.
This is the best video I've seen on the subject, and I've watched many. I had to make a coaxial tube heat exchanger a number of year ago...
On straightening tubing: Grab one end with a vise, grab the other end tightly in a drill chuck, pull HARD and turn the drill a few revolutions until the tubing is straight. Don't overtwist the tube. Cut off the mangled ends. Annealing the tubing should not be necessary. Putting one tube inside another is quite easy when both are straightened. I learned this method from an electrician who used it to straighten solid copper wire. 🙂
Segmented capillary tubes in series and parallel with bypass valves at convenient intervals would allow you to have a digital adjustment without much more complexity. Great project, your insights are helping with the ship repairs, thank you.
You’ve probably already thought of this, but it’s really important to make sure no liquid refrigerant gets into the suction line of the pump; that’s called “slugging” and will ruin a pump in short order.
Absolutely fantastic series!
First, I think your channel is probably the best on YouTube for inventing/engineering discussions that show the actual process of trial/evaluation/retrial of ideas. Keep up the excellent work.
However, a few points that are likely also being made by other commenters:
Soldering propane connections is unsafe and prohibited by the gas code (at least where I'm from).
The connections at the end of your evaporator/heat exchanger are very sketchy. The wetted surface area of your soldered joint is very small, and will be subjected to substantial thermal stress. Don't be surprised if it starts to leak. If you rebuild it, I would strongly reccomend you use a reducing tee instead of a 90. You can find models that are AxBxB sized where you can have a sidearm and one through connection at the smaller tubing size, with the second through connection larger. You then file/grind/drill out the stop inside the smaller through connection and can run your smaller tubing right through the tee. This allows a full sized brazed or soldered joint on all three pipe connections. The home distilling community has lots of examples of condensers made this way.
You might also want to consider using a small brazed plate exchanger instead of a tube-in-tube. You can get these quite cheaply in the usual spots online, and they're often rated for refrigerants and their working pressures.
For filling large soldering gaps Sil-Fos brazing rods work awesome. For pipe threads rector seal tru-blue works great for refrigeration.
Its 3am, yea i got 28 minutes to spare, suree
“10 minutes till class starts”
Yea I got time
Real
My life summed up!!
Well its 2:30 for me, so ill just have this in the background till i can find a good 3am Vid
Watch at 2x Speed with Closed Captions and you have even more time to spare!
A little while back, I repaired a -50c cryocooler. It uses a 1/3hp pump similar to the first one you showed and a custom blended refrigerant I couldn't find any details on. One major mistake was that measuring the evaporator pressure at the compressor gave inaccurate pt chart results for the minimum temperature observed. After a lot of trial and error, it was discovered that measuring the pressure at the meters' entrance to the evaporator more accurately predicted the observations.
A pressure gradient is formed inside the tubing. In normal hvac applications, this gradient is not an issue as the goal is higher efficiency, and the 'exact' boiling point is almost irrelevant. But for your application of mathematics, I believe it should be accounted for.
There is a post on sciencemadness about it. I hope your success continues, and I really enjoy the videos you're making. Stay safe
To get the centre pipe through the heat exchanger, you might want to send a flexible piece of plastic through first, then attach the copper. That way you can `pull` the copper through and it will be much easier. To clean the `fuel` type propane up, I have a tank that contains a few pounds of activated charcoal, I transfer a quantity of of propane and let it sit for a day or so. This will absorb most of the stenching agent. This is needed for a long term unit as the stencher is rather corrosive to some materials. Lastly, the soft solder is not suited to long term operation in a unit like this. Some people think it`s not suitable for the pressure, this is incorrect though. The real reason that it is not suitable is that after many cycles of hot, cold, it begins to crack. You will most likely see this effect where the layer of solder is thickest, like in the connection to the capillary tube. Great video series, watching with interest!
I'm so excited for the next part, this is easily becoming my favorite series
In your diagram of the coaxial heat exchanger, it shows a concurrent flow. Usually countercurrent heat exchangers are better, as they allow for more efficient heat transfer. There's other engineering reasons for concurrent flow but I don't think any apply here.
You are correct, very good point!
Never heard "concurrent" before, I only knew it as cocurrent or co-current. Are your sure that the n is supposed to be there?
@@leocurious9919 Concurrent means at the same time or in this case it means in the same direction, so his choice of word is correct. Incidentally, I don`t approve of this `nit picking` I does nothing to encourage conversation or understanding.
Correct
@@TheTemporalAnomaly It does help to "nit pick" something like that. It could be wrong or it could be a new term to learn for people like me. Either case is a win for me.
As a refrigeration technician for a hospital who has worked on ultra low temp freezers. These videos where fun to watch. I wouldn't braze with plumbing solider. However it does work. I just prefer 15% silver solider. Keep up with the entertainmenting videos. ^.^
I really can't find words to express how amazing you are in so many aspects
Since my childhood, I have been working in the refrigeration and air conditioning departments for nearly thirty years. I know very well and appreciate the enormous amount of effort that you have made in these experiments.
Much more than wonderful
I would like us to meet, but there are many obstacles, but I will write to you by mail, and this is my pleasure and happiness
I was impressed, enjoyed and honored to see you
My sincere wishes for all success and I would like if I can help you
Sorry for the inaccuracy of the expression, I use a translator👍👍👍
I love the humor and production in this video. I've wanted to build a cryocooler for the longest time. Have no background in engineering, and no use for one other than I've always wanted one.
Being EPA certified in this stuff, I say keep up the good work!
I made my own wonky system to run in my computer for super cooling before.
And I've got a project or 2 for the books for problems that aren't really problems. But this is awesome! 😊
Nice video, I really like when a people make their own equipment for refrigeration/hvac, several years ago I read that the rule of thumb for max compression ratio is 1:10, out of that your efficiency is out of range, that's why cascade systems are used for deep freezing, as side note: deep freezing use R23.
I was doing this 15 years ago for cooling CPUs, I still have a mostly full D sized cylinder of ethylene. Pro tip, get your hands on a plate heat exchanger for the interstage, they have incredible performance for their tiny size and are easier to insulate.
When I did this 25 years ago.
People said I was insane for putting propane in a cooling system.
I repaired an old Pepsi cool box.
Whit just propane that was for the bbq.
It is still working.
Now all fridges are filled whit propane
@@jantrammelant I thought it was just the small ones that were filled with propane and/or isobutane?
I saw the title and instantly remembered a PC case I had back in the day with a vapor chiller. It was a special edition ThermalTake and had a proper multistage fridge compressor for extreme overclocking. I used it to push a Phenom <3ghz quad core to almost 5ghz in 1999.
this kind of videos is public education and will start a revolution.
🤫
Pass the capillary tube around the suction line, it will increase your compressor life and COP by overheating the gas exiting the evaporator and undercooling the liquid exiting the condenser.
Bro, these vids are like CRACK to me, every time I see you've posted a new video I instantly binge and rewatch it a couple times for good measure ☺️
Aside from your epic and super interesting project, all the refrigeration knowledge you're pumping directly into my eyeballs is seriously informative, and I'm now finally starting to understand why my first air conditioner unit failed with the entire thing feeling 80 deg C on the outside with the lack of noise waking me up deep in the night when I panicked from the external plastic casing temperature and immediately turned the thing off. I haven't dated turn it back on ever since, and I was fiddling with the starter capacitor because I though that was the cause of the issue, but now I'm starting to doubt that. Thanks to your videos I really feel like I'm finally learning enough about this topic to be able to fix the thing myself in the future (I hope!!).
thanks for your epic vids, AWRRRRRR MATEY! I really appreciate all the effort and hard work you out into these super educational videos of yours! ♥️
I needed these videos to learn how to work on Thermotron environmental chambers. The old guys(massive respect for them) spoke in frost patterns and qualitative methods, and I became great tech with numbers and quantitative measurements. And thanks to your videos, I'm finally getting the numbers and science I need.
Idea for the capillary tube: You could put a few taps in it like you would for a transformer. That'll give you a couple of "gears" to switch through.
ie: Every couple of turns you could attach a valve and then depending on the length you want, open that valve. it'd be a bit of work but it would give you some variability.
Just gotta say your videos gave me the confidence to install and charge air conditioning on my classic truck with mostly junkyard parts
Very impressive results! I absolutely love this series on compressor-based cooling systems, would you mind creating a playlist of these videos on your channel? As always, great stuff. Cheers
Many years ago my 87 Grand Marquis developed a refrigeration leak ( R-12 ). After three expensive trips to three different A.C. "Specialists" it still required Monthly recharges of (Then Very Expensive) R-12.
I built my own set of recharge lines and began using very cheap Propane. The car NEVER was parked inside a closed space and it never leaked inside the car. Worked like a charm. The leak was somewhere under the hood and so small that there was no danger of explosion.
The cool video series continues!
Usually r600a(isobutane) not r600(n butane) is used in residential/small commercial fridges.
MO and I think AB oil dissolved in r290 along with POE.
R134a sometimes has PAG in automotive.
Different refrigerants are compatible with different oils.
Just make sure if you are getting to super cold temperatures that you aren’t flooding the compressor with liquid refrigerant otherwise it can damage the compressor since liquid is generally incompressible and it will remove the oil from the compressor
Great video!
About the ethylene side: since your cooling efficiency is bad, keep in mind that the cold (ethylene) stage compressor is going to be dumping its entire heat budget into the hot (butane) stage if you use a sealed compressor unit. So your hot stage cooling power needs to be at least as much as the cold stage total power.
And good luck finding a liquid lubricant that doesn't freeze at -100C (in the cold stage evaporator) or boil at room temperature. An oil separator doesn't really matter here if your lubricant has turned into a gas anyway and is spread through the whole line.
Oh, also, maybe just stick the whole hot stage evaporator in a cheap styrofoam cooler for now? Its way easier than having to foam and tape everything. Also also, you might find that those $2 mylar emergency blankets are a lot more manageable than aluminum foil. I used those two things to make a passive sky freezer that gets down to -40C at night when it isn't too humid.
My understanding is that other refrigerants are used as lubrication on cryogenic systems - like propane or butane for example.
@@brianwelch1579 Let me explain myself a little more clearly. Almost without exception, "refrigerants" are just alkanes or alkenes or halogenated (fluoro, chloro, bromo) alkanes and alkenes.
When you're dealing with a normal compressor being used normally, it gets really hot and it never gets super cold, so you could use something like decane which boils at 170C and freezes at -30C. The compressor will never not be in that range. It stays solidly at 50C-80C (ish).
For cryocooling, you're not just dealing with -40C for boiling and -100C for freezing. You're dealing with 30C for not boiling (if you don't want it to get into the evaporator coil) and -100C (more actually, if you don't want it to freeze in the evaporator coil).
The problem is that these refrigerants almost always form azeotropes so if you're using a higher boiling point refrigerant as a lubricant, some of it will end up in the evaporator, even if its only when everything is brought up to room temperature. Frozen oil in your evaporator can be terminal for your whole cooling system.
When you're talking about industrial cryocooling, you're usually talking about one of two mechanisms: stirling cycle coolers and turboexpanders. I don't know what lubricant is used in either one, but I think its "none" in the cold end of a stirling cooler and in a turboexpander it could literally be a gas bearing.
They're so expensive and/or slow that the few university things I've had experience with have either been LN2 based or dry ice based.
Anyway, he might want to look at 1-butene, which goes from -180C to -6C as lubricant? At least it won't freeze in the evaporator and at a few bar it might stay a liquid at room temperature too.
Worth shot I guess.
I'll try to read through the list of hundreds of coolants that might work as a lubricant for what he's trying to do later. 1-butene was just a shot in the dark that looks kinda ok.
@@htomerif All of these systems just use an oil separator after the compressor to return the oil to the crankcase or suction line since the only purpose the oil serves is lubricating the compressor. If you needed very low temperature refrigeration oil for some reason such as poor oil separation then there are oils such as zerol 150 with a floc point below -100. Apparently propane also greatly increases the oil carrying capacity which helps oil return to the compressor when in the refrigerant blend.
@@Blaxkor Don't try to BS me. I noticed you didn't put a unit on that "-100". I know why.
You wanna edit that comment again?
I mean I'll be fair. That could just be a mistake on your part but it looks like intentional misinformation.
this series has been so much fun to watch so far. really looking forward to seeing how everything eventually pans out.
I was using a roofing torch while wearing shorts the 20lb tank was rubbing against my leg as I was carrying it around it caused a patch of frostbite that took about a month to heal so yeah it gets cold.
This series just keeps getting better and better!
My only complaint about this video series is that the videos have to end
Congrats its not often that a youtubers content and delivery pulls me in enough to subscribe in under 4 minutes.
14:17 Take a look at this arrangement of tubing for a VCC system in a modern regenerative VCC refrigerator, linked below. In this design, the capillary tube itself is used in the heat exchanger, and the heat exchanger is in a counter-flow arrangement, which should yield higher efficiency. I linked straight to the timestamp where the coaxial capillary tube and gas return tube (which is effectively a heat exchanger) is explained.
Modern refrigerators explained (timestamp links to introduction of the coaxial capillary tube + evaporator vapor return tube, which acts as a recuperator. Hot condensate is used to warm up cold vapor/cold vapor is used to cool down hot condensate, making the whole system more efficient, as less refrigerant needs to be evaporated to cool the remaining refrigerant to your target temperature. )
https://youtu.be/7NwxMyqUyJw?t=301
This arrangement would save you a good bit of flow friction losses, and would perhaps perform better than the design you showed in this video.
This indeed increases efficiency but it impacts absolute temperature IME. I did this on some "early models" of my freeze dryer.
In a former career I was an industrial / petrochemical refrigeration technician and have worked on many weird and wonderful simple, compound and cascade refrigeration systems utilising various Freon, Ammonia, Propane and Polypropylene.
Just a couple of suggestions, first you really need to understand and carefully select your compressor oil as the propane is a solvent and the oil if not selected correctly will be miscible in the propane, now on a small system it may be something you get away with but it’s something you need to consider when you using hydrocarbons as refrigerant.
Also with regard to your propane from a torch bottle like what you used it’s very likely going to contain other gases that will effect your pressure temperature relationships in both your evaporator and condenser, these will likely include butane, Ethane, pentane, some can be purged from the high side (this should reduce your condenser pressure as some will be non condensible at your system pressure & temperature)
If you are going to use a capillary you should be measuring the amount of superheat at the end of the evaporator and adjust your capillary to achieve maybe 5 - 10 Kelvin of superheat above your evaporator saturation temperature otherwise your compressor has very little cooling, too little superheat and you could slug liquids into the compressor. Alternatively if the evaporator operating temperature is similar to R22 saturation conditions then you could possibly get a way with using an R22 TX valve.
Also I’d suggest using 15% silver solder on copper joints and 45% on anything dissimilar ie copper to steel or stainless
12:37 shouldn't the flows be going in opposite directions? The on-screen graphic shows the flow going in the same direction. Counter-flow heat exchange is what enables you to get the most heat exchange. Parallel flow heat exchange will only ever approach meeting in the weighted average temperatjre of the two (with heat capacity considered), but counter-flow heat exchangers have the possibility of heating the target fluid hotter than the outlet of the heating fluid.
I was reading trough the comments not to post this same concern. I also think this will make a huge difference.
I really appreciate this whole deep dive into esoteric cooling technologies and seeing how you're going about modifying stuff. I'm a big proponent of DIYing glycol chillers for homebrewing and I usually just take a whole AC unit and bend it for my purposes. I've been thinking about ways to get creative with using liquid cooling to eliminate the fan noise, or... oh shit I just realized that fridge hot coils are passive! That's a huge benefit for doing some DIYing on what I'm planning...
@carbontetlabs8606 - 2023-04-11
A few notes, from someone currently going to school for this:
- Install your filter dryer last and change it as close to every time the system is opened as possible. Installing a filter dryer should be a very quick hot potato sort of operation, you get the pipes lined up, swaged or flared and ready, and right after popping the filter dryer caps off you stick it into the pipes and start brazing or tightening. There should also be zero temperature drop across the filter dryer (within your measurement margin of error), a temperature drop indicates the filter dryer is clogged or otherwise producing a resistance to flow. That dryer spent way too much time open to atmosphere and is unlikely to have much dry dessicant left, especially if you blew air through it testing the cap tube in that one clip
- Solder, no no no. Solder can't be trusted with the sort of pressures you're working with. You should be using brazing rod, and learning to make flare fittings will do wonders for the ease of disassembly and modification of your system
- Awesome work on the calculations for your capillary tube! All that homework you did is the only reason this is working at all.
- Pulling a vacuum before charging is, like super duper important, not just necessary. For best results, pull a vacuum below 500 microns of mercury (about .67 mBar), break the vacuum (let <1 bar of pressure in) with an inert gas (ideally nitrogen), pull another vacuum to below the same level, break it with refrigerant, then pull a third vacuum before charging. That's what's done in industry to reliably eliminate all moisture that can reasonably be removed
- That tube-in-tube HX for the cascade system is sketchy, to say the least. I'm very curious what sort of ridiculous pressure drop you have across it, the uneveness in space between the tubes is going to make all sorts of weird constrictions and pressure drops. An evaporator should have the same pressure throughout the whole thing, maybe a couple pounds' pressure drop at the very most, you'd do well to stick a pressure gauge on either side of that evap
- In the industry when we hook up to a system we measure what we call superheat and subcooling. Superheat is how many degrees above its boiling point vapor warms up in the evaporator after boiling, subcooling is how many degrees below its boiling point liquid cools to in the condenser. For instance, at 21:03, you just described 15 degrees C of subcooling, which is really quite a lot of subcooling, I'm taught to generally look for about 10 F/5 C of subcooling, so your condenser was performing quite well. Your evaporator got as cold as it was going to, without knowing the outlet temperature I can't tell the superheat but it was probably also quite high, I'm taught to look for 10-20 F based on application. Looking at a cap tube system, high subcooling and high superheat is generally a massive red flag for undercharged, that setup might have just needed more gas to perform better. With cap tubes, charge until the desired superheat is reached, for your application that's probably 3-4 C under load.
- The compressor is cooled by the cold vapor refrigerant coming back through the suction line. Your compressor didn't overheat because the condensor didn't reject enough heat, the condensor rejected tons of heat, the compressor overheated because at such low pressures it barely got any refrigerant to cool itself with and what vapor did come back was likely highly superheated. Issues with mixing and matching compressors and refrigerant aside, also a sign that the system could have taken more charge
- I don't even want to know what became of what charge was in that AC unit when you bought it to harvest its organs. Whatever happened to it, that was probably all illegal, if you live in the U.S. and aren't EPA 608 certified it was definitely illegal. Not judging, just a heads up
- Second setup: I see 15ish F subcooling and 5ish superheat, high-ish and somewhat low respectively. Condenser is very slightly starved and the evap is bordering on flooded. A flooded evap is fine to see in no-load conditions without the second stage built yet, especially with a few degrees left to protect from sending liquid back to the compressor. Once it gets a load on it and your superheat starts going up your compressor might stop getting cooled as effectively and overheat, though.
- I think you've done this whole video charging passively, but I'm not sure. Just in case you've been opening up your propane bottle with the system off, weighing in a charge and stopping at that, you can charge with the system running by hooking the low side up to your container and metering it in. Should ideally be done with the system having reached its thermal equilibrium so you can charge based off good measurements.
- The cooling power calculations are gonna be off by more than you expect, just that little bit of condensation on the beaker is actually a ton of heat leaking into it. Good news! Your calculation is definitely an underestimate.
Very cool! Also kind of concerningly dangerous but you're definitely doing your research. Interested to see where this goes.
Edit after sleeping on it: Lost in trying to transfer knowledge, was, holy shit! This is really impressive, you've really done your homework. I'm almost only squawking about danger because of the solder rather than brazing, God only know I've done stupider. Keep at it!
@TheTemporalAnomaly - 2023-04-11
You nearly got a like from me when you talked about the compressor being cooled by the refrigerant return stream and you made some good points, then you started beating on the guy! As a refrigerant engineer, have you never done anything a little naughty? The answer will be yes, we all have! This is one of the best You-tube channels, encouraging people to ask the question `how does it work` and how to modify things for other purposes. As for any perceived risks, they are very, very minimal and they are personal risks, and as such are of no concern to us. I don`t mean this to offend, I am just aware that negative comments on You-Tube (and in real life) have the potential to stop people pursuing their hobbies and vocations. In the very least, it might put someone off the idea of publishing and sharing with us.
@JH-tc3yu - 2023-04-11
You're massively overthinking this. SH and SC are refrigeration and application specific. One application might have 5° of superheat and another might have 30. It depends on the application. There's no rule of thumb.
@tomoliver8498 - 2023-04-11
@Carbon good analysis of his efforts and shortcomings. About the only thing I would add is not to use soft solder on discharge lines and original compressor is probably designed for high temp application your low superheat concerns are warranted and you are right adequate mass flo cooling capability at operating temperature is also important. You have to keep the compressor happy. (I have worked in the trade over 40 years)
@jayfowler4747 - 2023-04-11
Agree with everything you say until your actually doing it in a time crunch especially the vacuum stuff.?😅
@Redtooth75 - 2023-04-11
@@jayfowler4747 breaking and redoing the vacuum is really only necessary with very large systems. For light commercial and residential systems a vacuum of 500 microns is fine and no nitrogen purge is required, the manufactures don't say its necessary.