As small as ur collection pot is u could easily make tub denatured alcohol that u cool w $25 a/c outfitted to run through the bucket of alchohol w the coils…takes some customizing
Or just cool alcohol w dry ice and pump it through
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To get good cooling you will need compression and decompression (otherwise your refrigerant is just another heat transfer fluid). This would basically mean building a chiller with the collection base serving as the evaporator. The main issue with this (other than it seems a bit more involved than what you are looking for) is that the jacket probably isn’t rated for the standstill pressure of the chiller when it is off, so you’d need a fade out tank or other mechanism to keep it from popping when the system isn’t running.
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What about prvs and gauges? Jw. And by “fade out tank” do you mean a separate refrigerant tank?
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Hi,
what your referring to is called direct expansion refrigeration, you would need a cascade refrigeration system to go that low.
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You need an expansion tank on the low side of the cascade system, when the second stage isn’t being cooled it has a very high pressure.
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So, short answer is yes, you would need at least one PRV and probably want gauges. What you’re asking about is pretty much just a chiller, so here’s the basics (I’m sure you’re probably aware how they work but it can’t hurt to go over it, at least for some other mystery reader’s sake):
You take gaseous refrigerant and compress it, raising the pressure and temperature substantially. This makes the refrigerant easier to condense, and allows it to condense at a higher temperature than before it was compressed.
You use a heat exchanger to cool the hot, high pressure refrigerant, causing it to condense to a liquid. The basic version of this is just a radiator. It leaves you with room temperature but high pressure liquid refrigerant. This section is called the condenser.
Then you force it through some sort of valve/orifice/small hole that allows the pressure to be maintained in the condenser and causes a large pressure drop. A TXV is the thing to use here unless we’re still in the 1950s. When the pressure drops, the refrigerant will want to boil because the boiling point is a lower temperature than room temp (substantially) at the new lower pressure.
Then you end up with low temperature low pressure liquid refrigerant that is boiling in your evaporator (your base in this example), turning into gas by stealing heat from your system.
The fade out issue I mentioned is this: let’s say you run r404a as your refrigerant (probably a pretty good choice). To run -40 at your base you have an evaporator pressure around 16 psia. To condense that refrigerant at room temp, you’re running a condenser pressure of around 220 psia. This is not an issue if you never turn the system off because the jacket can handle 1.5 psi above atmospheric pressure. However, if you lose power or just don’t want to run the thing forever, it will turn off and the pressure of all that refrigerant will equalize in the system. This will likely leave a standstill pressure of close to your condenser pressure (180 psi is a decent guess depending on the low-side and high-side volumes). That is obviously a problem if the base jacket is only rated for 60psi. Mind you, venting that refrigerant is a big no no
The “basic” solution to this is to make your evaporator volume (between the expansion valve and compressor) much much larger than the condenser volume so that the total mass of refrigerant is such that the standstill doesn’t exceed your working pressure. Basically, if the evaporator was of infinite size, you’d still be able to make some small condenser run at 220 psia because you wouldn’t be stealing that much mass, but when you equalize the system it wouldn’t cause the evaporator pressure to rise at all because it’s just a drop in the bucket.
Edit: @Soxhlet knows how to say it in the right number of words lol
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short answer is it’s safer to not.
your base is probably not rated for this.
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that is so useful, it’s perfect those that want to hack apart ac units to make a chiller cough cough me
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Now I’m just thinking it would be safer to use nitrogen for cooling the base at a regulated pressure.
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You don’t need to chill your collection if you are using n2
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Why is this so controversial to my brain.
I started doing this. Then tried a run without it. Works fine without it…
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Any gas or liquified gas will cool when it expands/boils. Some are better than others because the phase change takes more energy (CO2 is actually very good as far as cooling per mass). Refrigerants are generally better. But, you aren’t allowed to/supposed to just dump pressurized refrigerant through your jacket, and it will be very expensive if you do. So if you want to use a refrigerant, you’ll need all the other parts of a refrigerant system.
FYI buying and modifying an existing chiller is probably the easier and bestest option, but certainly more involved than dumping dry ice in a party cooler.
So wait what if you have the refrigerant moving thru the jacket at a regulated pressure say 55 and have two prvs one high one low. What if I evacuate the refrigerant via vacuum pump the moment I shut off the flow of refrigerant by having the vacuum pump powered on before I shut off the flow.
Fuck you’re right I should just look into building a chiller.
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Ding ding ding! My job here is done
I mean it’s kind of a glass half full/half empty thing: the mechanically inclined might look at it and say it’s too complicated, it’s almost a complete chiller to essentially vent and recapture refrigerant. On the other side of that coin, an optimist might look at it and say that when you list it out, all a chiller is is a system that vents and recaptures refrigerant except you don’t turn the pump off.
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I built a chiller from and AC unit. I spent about $50 besides AC. It works great!
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This is who I was referring to…extended the coils so they set in a tub right. Fill tub w alcohol. Turn ac on the lines running through the alcohol chills the alchohol
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soooo…using @Soxhlet’s 1k word substitute, and @SidViscous’s well worded suppliement, you should be able to warp your head around using a craigslist CLS and r600 to solve this…
bonus question: does this count as a cascade refrigeration system?
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You can make a much cleaner looking one with a window ac. These portable ac’s have a lot of extra bells and whistles you don’t need. It’s even got a remote lol
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only if the first stage shares an inter cooler with the second. 