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post #1 of (permalink) Old 02-04-2019, 05:37 PM - Thread Starter
Hydroplane
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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.

CHILLER DESTRUCTION
Build Log - White Voodoo
Z390 Station
(10 items)
White Voodoo
(14 items)
CPU
9900K @ 5.5 1.46v
Motherboard
EVGA Z390 Dark
GPU
Titan RTX 2085/8500
RAM
Trident Z 3200c14 @ 4133c16 1.5v
Hard Drive
Samsung 970 Evo Plus 250gb
Power Supply
EVGA 1300 G2
Cooling
Dehumidifier
Case
Dimastech Test Bench
Monitor
AOC Agon AG251FZ 240Hz
Audio
Built-in Monitor Speakers (3 watt)
CPU
Intel Core i9-7980XE @ 4.3 GHz 1.10v
Motherboard
Asus Rampage VI Apex
GPU
Gigabyte Aorus Waterforce WB 1080 Ti SLI 2037/6318 1.09V
RAM
Trident Z 32GB (4x8GB) 3200C14 @ 3800C16 1.50V
Hard Drive
Samsung 960 Evo 1TB
Power Supply
EVGA 1600 T2
Cooling
HWLabs Nemesis GTR 420+280 Rads
Cooling
(7) Noctua NF-A14 iPPC-3000 PWM Fans
Cooling
EK-XRES 140 Revo D5 RGB PWM
Case
LD Cooling PC-V7 280/420
Operating System
Windows 10 LTSB
Operating System
Linux Mint 19.1
Monitor
NEC PA271W 2560x1440
Keyboard
Razer Blackwidow Chroma V2
CPU
Dual Intel Xeon L5520 2.26 GHz
RAM
48 GB Samsung DDR3-1066
Hard Drive
120 GB Samsung 750 Evo SSD
Hard Drive
2 TB Western Digital Green
Hard Drive
2 TB Hitachi 7200 RPM
Power Supply
650W Delta PSU
Case
1U Rackmount
Operating System
Ubuntu Server 16.04
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