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Peltier chilling system - Page 2

post #11 of 167
Thread Starter 
Here's the latest. Hit -15.4C at one point. Though i think my fluid might be freezing around that point because the cold side rapidly drops off. That or my pump is failing at that temp. It's a cheapy. Or its freezing the pump.










post #12 of 167
Thread Starter 
Happened again. Hit around -15c and then it dropped all the way to 2c, and the pump was hot. So pretty sure the fluid is freezing in the tecs and its just stopping flow. I'll need a heavier glycol mix or even go to something like what you have. Do you have any thermal conductivity data on that stuff lol?
post #13 of 167
yea,

http://imgur.com/TLRh6tE

open the pic in a new tab to read it more easily

I have gotten the dex cool with the anticongelant in it, to -25C at a 60% AF 40% DW without it freezing or thickening up.
Edited by toolmaker03 - 6/29/16 at 10:07pm
post #14 of 167
Quote:
Originally Posted by mrkubanftw View Post

Happened again. Hit around -15c and then it dropped all the way to 2c, and the pump was hot. So pretty sure the fluid is freezing in the tecs and its just stopping flow. I'll need a heavier glycol mix or even go to something like what you have. Do you have any thermal conductivity data on that stuff lol?

Is there no way for you to monitor the pump's RPM? Should help you to determine what exactly is happening in your loop.
post #15 of 167
Thread Starter 
Quote:
Originally Posted by Gilles3000 View Post

Is there no way for you to monitor the pump's RPM? Should help you to determine what exactly is happening in your loop.

PWM control is not being used. My guess is, its just spinning in place. So pump rpm wouldn't really change in this case. It's just not moving any water. A flow meter in-line would be awesome. I'll snag something like that. Should allow me to get some accurate data on how temp affects flow overall as well.

Was going to go with something like this

https://www.adafruit.com/products/828?gclid=CLza98Ldz80CFZCIaQodGXACCA

But it only accommodates up to a 30L/M flow. Pretty slow. Even my little cheapy pump runs ~200



*edit- that flow rate sensor will work fine. I didn't notice it specs the flow rate in L/M rather L/H (typical). Translates to 1800 L/H
Edited by mrkubanftw - 6/30/16 at 8:44am
post #16 of 167
Thread Starter 
OH also! I thought of a very good way to perhaps test a heat load. I'm thinking it could be as simple as using something like a soldering iron. I have a few of them. Just setting (2) 40 watt soldering irons into the chilling fluid should be a good way to test this ? My processor runs a 84watt TDP but that could be a lot higher with a OC. Somewhere around 100 watts of heat load would be a good start i would think.
post #17 of 167
Thread Starter 
Anyone know of any pumps that work well at low temps? Even a MCP655 Swiftech is only rated to "Temperature Range: 32°F to 140°F (0°C to 60°C)"

http://www.xoxide.com/swiftech-mcp655.html


That's scary
post #18 of 167
true, but that is not because of the pumps physical makeup, but rather the seals that are being used to make them water tight, they are a Viton seal, and thus the reason for the temperature rating. if you strengthen the seals by covering them with a RTV sealant that is rated for a lower temperature, you effectively change the temperature rating of the pump. normally when the seals get to a temperature below 0C they become hard and small cracks start to form on the seal this will cause leaks. that is the whole reason that I have spent the time to covered all of my seals in RTV sealant, this is including the seals on the water blocks, the seals in the water pumps, the seals on the fittings, and even the seals on the external reservoir, have all been coated with RTV sealant that has been rated for -65C.
post #19 of 167
Thread Starter 
Quote:
Originally Posted by toolmaker03 View Post

true, but that is not because of the pumps physical makeup, but rather the seals that are being used to make them water tight, they are a Viton seal, and thus the reason for the temperature rating. if you strengthen the seals by covering them with a RTV sealant that is rated for a lower temperature, you effectively change the temperature rating of the pump. normally when the seals get to a temperature below 0C they become hard and small cracks start to form on the seal this will cause leaks. that is the whole reason that I have spent the time to covered all of my seals in RTV sealant, this is including the seals on the water blocks, the seals in the water pumps, the seals on the fittings, and even the seals on the external reservoir, have all been coated with RTV sealant that has been rated for -65C.



Ahh that makes sense! I did find one pump that said it was rated down to -35C.

http://www.banggood.com/Mini-DC-12V-Electric-Centrifugal-Water-Pump-Low-Noise-p-87576.html?currency=USD&createTmp=1&utm_source=ebay&utm_medium=cpc&utm_content=saul&utm_campaign=xiao-US&ebay

Tonight i will change over my coolant to a thicker mixture. Purge the hot side system of the air bubbles that gathered. Add two fans to the radiators (one shattered this morning). I'll see where i'm at temp-wise. Knowing what i know now, the freezing is not only stopping coolant flow. Its insulating my sensor from reading true temps, probably much earlier than the point at which it hits -15C. So my assumption is then that this system can hit a much lower temp based on its max delta of 70C. I have not measured the temp of the hot side water coming off the water blocks, but my guess is, i'm floating around 90-100F. (Will add another digital temp sensor as sensor3 on my interface) If you do the math and calculate the cold side off the hot delta, i should be able to hit around -30c. Not saying i will... but iv'e hit almost -20 on one of my more crude setups. The main differences being i was not pumping the coolant, it was just sitting in a bath, on-top of the cold-plate with a sensor sitting in it, AND i know that was for sure a 50/50 mixture. I'm starting to think the mixture i have now is light in concentrate if its freezing at only -15C. Maybe i messed up. Wouldn't be the first time.
post #20 of 167
Keep in mind most of us using those giant TECs are running them at roughly half their rated max for much higher efficiency and less waste heat. Also, chillers work better with multiple smaller TECs while direct-die TECs need to be much larger and more powerful to keep from stalling...just the nature of the beast.

Your build using a shared cold side block for each pair of TECs is a neat idea. Having that much centralized cooling though will need some pretty serious coolant to keep from turning to syrup or freezing - as you have noticed, since it sure sounds like the coolant is just freezing inside the blocks. Easy fix smile.gif.

FWIW a 655/D5 has no seals to mess up with the factory top, only the large body o-ring that does not come in contact with any coolant. The rest is just a heavy impeller with a graphite bushing riding on a single ceramic bearing, with the whole casing magnetized. I ran a pretty nasty Ethanol mix @ 0c through one for over a year and the pump didn't even flinch...until the pump ran dry and the ceramic bearing ate the bushing (the only moving part and wear item in the whole pump, and the 655s only real failure point). Keep in mind the pump was around 7 years old and was ran 24/7 and was still kicking up until that point!

IMO as long as you keep the fluid thin enough to not cause excessive stress on the graphite bushing I do not see any reasonable temps being an issue with a 655. I also trust their reliability a LOT more then any other DC pump because I have had at least 5 of them and they all lived at least 6 years before starting to rattle or vibrate from bushing wear. They usually give tons of warning before dying, and will go from a noticeable vibration to a full on death rattle, giving you plenty of warning to change it vs a pump that just quits one day.

I'm sure if swiftech released a replacement bushing or impeller then we would see plenty of 10yo 655s still running flawlessly.
Edited by Puck - 6/30/16 at 6:35pm
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Intel i7 4790K "Relidded" @ 5ghz <50c Asus Sabertooth Z97 MK1 Custom WC'd 7970 3GB @ 1100/1500 stock volts Custom WC'd 7970 3GB @ 1100/1500 stock volts 
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Two Ported/tapped MCP655 Pumps 2x Black Ice GTX 480 Gen2 Rads DD dual drive bay Res with LCD water temp monit... GPU Loop: Modded Enzotech Sapphire CPU blocks, ... 
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Behemoth
(25 items)
 
  
CPUMotherboardGraphicsGraphics
Intel i7 4790K "Relidded" @ 5ghz <50c Asus Sabertooth Z97 MK1 Custom WC'd 7970 3GB @ 1100/1500 stock volts Custom WC'd 7970 3GB @ 1100/1500 stock volts 
RAMHard DriveCoolingCooling
2X4GB Patriot Viper Extreme 1TB Velociraptor 10k RPM w/ 64MB Cache Two Arqtik TEC Chillers in Series Archimedes TEC block w/TN660 TEC 
CoolingCoolingCoolingCooling
Two Ported/tapped MCP655 Pumps 2x Black Ice GTX 480 Gen2 Rads DD dual drive bay Res with LCD water temp monit... GPU Loop: Modded Enzotech Sapphire CPU blocks, ... 
CoolingOSOSMonitor
36x Globe 120mm 80cfm server fans Win 10 Pro Mint 15(KDE) 4K 28" Samsung U590D 
KeyboardPowerCaseMouse
Logitech G710+ Mechanical CM Silent Power M 1000watt Main, OCZ Z850W Slave Custom Mountain Mods Extended-Extended Ascension Logitech G502 Proteus 
Mouse PadAudioAudioAudio
Homemade 16ga 304 Stainless pad, Neoprene backed Aune T1 DAC Various Tubes: Mostly switching from 60's GE "S... AKG K7XX Headphones 
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