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-   -   Best coolant for -40c ? (https://www.overclock.net/forum/134-cooling-experiments/1719864-best-coolant-40c.html)

Hydroplane 02-04-2019 05:37 PM

Best coolant for -40c ?
 
Hey all,

I've reverse engineered an R22 dehumidifier for chiller use. Since R22 boils at -41c I am looking for a coolant that can handle that. Not sure if the whole evaporator would get down to -41c but it certainly gets below 0c, since when I run it the water just freezes into an ice block around it.

The ideal fluid would have the following properties:
1. Freezing point of -45 or so
2. Does not get too viscous or slushy at low temps (i.e. doesn't destroy pumps)
3. Decent heat transfer (specific heat of ~2.5)
4. Does not fill house with toxic fumes
5. Non-flammable

I'm looking at the following fluids, all of them in roughly a 50/50 mix with distilled water:

1. Propylene Glycol: Non-toxic and easy to dispose of. However, I've heard it turns into slush and would basically destroy pumps due to very high viscosity at low temps. Easy to buy as RV Coolant. Not sure on the mix ratio with water they sell though. Non-flammable.
2. Ethylene Glycol: Non-fuming at least, no pets or kids in house that would drink the stuff (toxic). Is this any easier to pump at low temps? Any less viscous/slushy? Very easy/cheap to buy as antifreeze concentrate and can control ratio when mixing with water. Non-flammable.
3. Methanol: Available as windshield washer fluid i.e. Rain-X de-icer. Most of these are only available as max 35% methanol which would go down to -30c or so. However, I've read that it fumes quite badly and is obviously very toxic. I don't think I could seal my reservoir well enough that I could limit the fumes so I've more or less ruled this one out. Flows nicely at low temps, but might damage rubber & plastics. Also flammable.
4. Ethanol: Not sure where to buy this, denatured alcohol looks pricey by the gallon. E85 maybe? Nowhere near as toxic as methanol, I mean, it's basically the booze we drink lol. Probably still evaporates too easily? Also flows well at low temps but could damage plastic/seals, and is flammable.

Anyone experienced with using any of these at subzero temps? Leaning towards either ethylene glycol or ethanol. Other suggestions would be welcome too.

The Pook 02-04-2019 05:46 PM

I can't imagine ethanol being a good idea. E85 eating rubber gaskets and seals in older cars not designed for it is apparently an issue (though I've ran E85 in my old non-flex fuel Silverado for months just fine without ill effect, just going off what the mob mentality seems to suggest) and I can't imagine it being any better in a loop.

Propylene/ethylene glycol would be my bet. Most of the temp ranges are off specific mixtures, usually 30/70 or 50/50. Get the non-premix and mix it yourself to the temp range you need and no slush.

http://i471.photobucket.com/albums/r...-PeakChart.jpg

speed_demon 02-04-2019 06:21 PM

I recall a similar technical problem dealing with cooling at sub-zero temps and part of the solution was an additive like water-wetter (IIRC) in ethylene glycol. https://www.redlineoil.com/waterwetter

There are a variety of additives available for coolant. Maybe consider a two component solution to your problem? Just be certain it won't corrode or degrade anything in the loop. Ethanol is nasty nasty stuff notorious for degrading containers and will turn some plastics to mush in short order. Of course everclear is quite good in fruit punch. Haha.

___

Oh pook no... friends don't let friends drive modern GM products.. :o

J7SC 02-04-2019 06:35 PM

Quote:

Originally Posted by Hydroplane (Post 27839138)
Hey all,

I've reverse engineered an R22 dehumidifier for chiller use. Since R22 boils at -41c I am looking for a coolant that can handle that. Not sure if the whole evaporator would get down to -41c but it certainly gets below 0c, since when I run it the water just freezes into an ice block around it.

The ideal fluid would have the following properties:
1. Freezing point of -45 or so
2. Does not get too viscous or slushy at low temps (i.e. doesn't destroy pumps)
3. Decent heat transfer (specific heat of ~2.5)
4. Does not fill house with toxic fumes
5. Non-flammable

I'm looking at the following fluids, all of them in roughly a 50/50 mix with distilled water:

1. Propylene Glycol: Non-toxic and easy to dispose of. However, I've heard it turns into slush and would basically destroy pumps due to very high viscosity at low temps. Easy to buy as RV Coolant. Not sure on the mix ratio with water they sell though. Non-flammable.
2. Ethylene Glycol: Non-fuming at least, no pets or kids in house that would drink the stuff (toxic). Is this any easier to pump at low temps? Any less viscous/slushy? Very easy/cheap to buy as antifreeze concentrate and can control ratio when mixing with water. Non-flammable.
3. Methanol: Available as windshield washer fluid i.e. Rain-X de-icer. Most of these are only available as max 35% methanol which would go down to -30c or so. However, I've read that it fumes quite badly and is obviously very toxic. I don't think I could seal my reservoir well enough that I could limit the fumes so I've more or less ruled this one out. Flows nicely at low temps, but might damage rubber & plastics. Also flammable.
4. Ethanol: Not sure where to buy this, denatured alcohol looks pricey by the gallon. E85 maybe? Nowhere near as toxic as methanol, I mean, it's basically the booze we drink lol. Probably still evaporates too easily? Also flows well at low temps but could damage plastic/seals, and is flammable.

Anyone experienced with using any of these at subzero temps? Leaning towards either ethylene glycol or ethanol. Other suggestions would be welcome too.


XOCers like DerBauer seem to like 3M Novec (non conductive)...no idea about it's exact temp qualities (pls see link in spoiler), but it has a pour point of up to -100c


Hydroplane 02-04-2019 06:53 PM

Quote:

Originally Posted by speed_demon (Post 27839180)
I recall a similar technical problem dealing with cooling at sub-zero temps and part of the solution was an additive like water-wetter (IIRC) in ethylene glycol. https://www.redlineoil.com/waterwetter

There are a variety of additives available for coolant. Maybe consider a two component solution to your problem? Just be certain it won't corrode or degrade anything in the loop. Ethanol is nasty nasty stuff notorious for degrading containers and will turn some plastics to mush in short order. Of course everclear is quite good in fruit punch. Haha.

___

Oh pook no... friends don't let friends drive modern GM products.. :o

What about Dex-Cool? Turn my blocks into peanut butter lol.

As far as the ethanol, I think plastic in the loop would be limited to tubing (could find an ethanol-compatible type) and the pump itself. I'm not sure if a pump with plastic internals (D5?) could even handle these temps without cracking. The rubber seals on the pump could be an issue. I would probably need a stronger pump for either of the glycols.

The 3M Novec I've heard it's hundreds of dollars :o So far I've got $0 into this, the dehumidifier was a "gift" from the previous owner of my home lol.

This is for test bench setup only, will not be used on my sig rig, so not too worried about killing stuff

JackCY 02-04-2019 07:41 PM

Probably industrial fluids that only companies can buy and don't get sold to private individuals. Such as the mentioned 3M fluids. There is tons of stuff from companies but they don't want to (by law often) sell it to people, they will only sell it to companies, weird I know as if companies use only robots for work.
Yes fluids ain't cheap if you want the good stuff.

Try asking XOCers.

CJMitsuki 02-04-2019 08:22 PM

Once you drop to temps that low then arent glycols starting to get really thick? That would take a very strong pump and possibly a custom made block as the orifices may be too small for the thickening glycols. A car doesnt have a problem because 1. The water pump is belt drive by the engone and 2. The tubing is much bigger than you will find in a computer setup so the thicker fluid would pump much easier. I think the Antifreeze at -40 would burn the pump up. As far as Ethanol mixtures, you can find seals and gaskets that are compatible with Ethanol such as Neoprene, Teflon, Polypropylene, Nitrile, Viton, etc. HERE is a page showing some chemical resistances of certain materials.

Edit: What about Acetone? Isnt that used as a Dry Ice medium when DICE OCing?

Hydroplane 02-05-2019 04:50 PM

Quote:

Originally Posted by CJMitsuki (Post 27839270)
Once you drop to temps that low then arent glycols starting to get really thick? That would take a very strong pump and possibly a custom made block as the orifices may be too small for the thickening glycols. A car doesnt have a problem because 1. The water pump is belt drive by the engone and 2. The tubing is much bigger than you will find in a computer setup so the thicker fluid would pump much easier. I think the Antifreeze at -40 would burn the pump up. As far as Ethanol mixtures, you can find seals and gaskets that are compatible with Ethanol such as Neoprene, Teflon, Polypropylene, Nitrile, Viton, etc. HERE is a page showing some chemical resistances of certain materials.

Edit: What about Acetone? Isnt that used as a Dry Ice medium when DICE OCing?

That is what I am concerned with on either of the glycols. Maybe a stronger pump like an Iwaki RD-20 or RD-30 could handle it? I will have to do some more research on the ethanol. Should be okay with copper/nickel waterblocks and the right tubing. Just would need a "safe" pump.

Nice OC on that 2700X!

Hydroplane 02-09-2019 11:14 AM

1 Attachment(s)
Picked up some FLUIDS today at wally world lol

The Rain-X contains 35% methanol. I marked a line on it where the top of the fluid is, then took the cap off and let it sit outside. I'm gonna see how badly it evaporates. The RV fluid (unknown percentage of propylene glycol, apparently with a touch of ethanol added) I put in the freezer at 14F to see if it becomes slushy/thick.

I looked for a temperature laser thingy but alas, Walmart failed me. Harbor Fright or Home Cheapo may have one in stock. I'd like to check how cold the e-vap actually gets. -41C in theory, but no idea if the entire thing could get 4 gallons of fluid down to that temp.

Hydroplane 02-10-2019 05:16 AM

UPDATE:

The Rain-X sitting outside with the top off appears to have evaporated a little. Not much, but more than I want to breathe in my home lol. And that's through the top of a bottle which is a pretty small hole. In a cooler with pipes and tubing going in/out it would be tougher to seal properly. No big deal, just pour it into my car instead. With the weather, I'm probably due for a refill anyway :)

The RV coolant in the freezer at 5F-15F did not get slushy or syrupy at all. So that appears to be the way to go for now at $3 a gallon. Just need an igloo cooler and a temp laser thing to test it on the evap.

As a side note, I know the evaporator gets colder than 5F. I pulled the glycol out of the freezer and the bottle frosted much more slowly than the evaporator.


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