Air-bleeding Guidelines

Discussion in 'Extreme and Water Cooling' started by Cathar, Oct 8, 2004.

  1. Cathar

    Cathar Storm Father

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    Been thinking about the air-bleeding thing and playing with it a bit with 1/2" ID tubing.

    It seems to me that rapid (less than a few minutes) bleeding of air occurs at >1m/s tubing velocities, and once we get below about 0.75m/s tubing velocities air-bleeding becomes problematic and slow.

    I decided to draw up a little chart comparing tubing sizes and bleeding ease based on the flow rate.

    1/2" ID <5.70 LPM (poor bleeding) >7.25 LPM (easy bleeding)
    7/16" ID <4.35 LPM (poor bleeding) >5.80 LPM (easy bleeding)
    3/8" ID <3.20 LPM (poor bleeding) >4.25 LPM (easy bleeding)
    5/16" ID <2.25 LPM (poor bleeding) >3.00 LPM (easy bleeding)
    1/4" ID <1.40 LPM (poor bleeding) >1.90 LPM (easy bleeding)
    5/32" ID <0.55 LPM (poor bleeding) >0.75 LPM (easy bleeding)

    This is just a rough and dumb assessment. If anyone has a more scientific assessment, perhaps based on turbulence patterns at various flow rates, then please share it.
     
  2. malonem

    malonem Member

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    Easy bleeding or poor bleeding.... Eventually all the air will be bled out of a system, and a small top up will be needed

    I spose its just a matter of time?
     
  3. thod898

    thod898 Member

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    I have found that with my system, the pump just chops the bubbles into what people call "micro bubbles" and they take too long to float to the top. They tend to just flow around in the water until they collect in the rad. To prevent this I attempt to fill as much of the tubing and rad before I turn on the pump and all seems to be good.

    Are the little bubbles common because if they were not there the tubing would be easy to bleed.
     
  4. arasta

    arasta Member

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    cathar - curious results :)

    i hope you still have the test loop setup - im curious what happens to the 'minimum LPM for easy bleed' if you use the ole jungle trick of dropping some handwash soap into the loop (the lower surface tension thingy).

    ive intended to use the trick for myself and wondering if it REALLY does work and theres a noticable drop in the lpm to dislodge bubbles n crap - or not. if youve already stripped the test down thats ok but i AM definitely curious to know.

    Cheers
     
  5. Cluey

    Cluey Member

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    Since I have added corrosion inhibitor to my setup I have noticed the little bubbles are much worse, you could almost describe them as froth!
    I got the guys who built my radiator for me to put a bleed plug in the tank connected to the pumps outlet.
    Since redoing this the plug hole is big enough to be a fill point too.
    I have found while bleeding my system that it seems to be air free but when you stop the pump bubbles will come out of it. I guess while spinning the impeller traps the air.
    After getting this sorted out and repositioning the bleed point I found filling and bleeding the system was a lot easier but the last few little bubbles are still persistent :(
     
  6. minushuman

    minushuman Member

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    edit: Hehehe, hope no-one saw that. God i'm dumb.
     
    Last edited: Oct 11, 2004
  7. phextwin

    phextwin Member

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    schwass? :confused:

    Edit: Hahahah i did :p
     
    Last edited: Oct 11, 2004
  8. MrMagoo2

    MrMagoo2 Member

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    Why not fill up and air bleed in a large reservoir (like bath tub) to avoid the bubles cycling through system. Then after a few minutes/hours hehe close the loop. In case of limited volume coolants do as above and when air free transfer inlet hose carefully (while not running plug it tightly with your finger ) to coolant reservoir and pump till coolant cycled through system than close system. This i guess still doesnt solve the problem of disolved gases that take a week or two to be released (especially when system is stopped), anyone that has ever owned a water bed would understand this :) The best way i know of degasing water is actually to pass it through a micro filter under a decent vacuum (around 10mm Hg,thats what i have to do with some solvents in order for them to be usable for analysis) but thats a bit hard to do at home for the average water cooling buff. So i guess youre stuck with reservoirs and inline air traps.
    Cheers
     
  9. banshee

    banshee Member

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    In the end I purchased a small res. Due to space requirements it is now fitted on the front of my comp. :/

    I first tried the coolant into res at top & out at bottom, but found that the velocity of the coolant coming into the res stirred all the air back in as micro bubbles as above. :(

    What I then did, was disassemble the system partly & remove the res. I glued on a baffle @ ~45degrees over the bottom res port, (now inlet), and reconnected the outlet at the top.

    This had the effect of turning my cylindrical res into a 'whirlpool' separator for the air. I now have better clarity in my coolant than ever before & a nifty little maelstrom in the top of my res so I can see that the coolant is circulating properly. :)
     
  10. Cluey

    Cluey Member

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    @ MrMagoo2
    A nice plan with a couple of holes in it.
    What if you don't have a bath?
    I live in a small flat and the biggest sink we have is the kitchen sink, I have had my loop leak testing in there for a couple of nights and I have to get it out as the dishes are piling up!
    Also I am not sure if you were suggesting submersing the radiator, if you were you have obviously never tried drying a radiator out without an air gun!

    @ banshee
    Sounds cool with the vortex :)
    I know what you mean about the velocity of the fluid just sending the bubbles back in.
    Its looking like patience is working though as I am almost bubble free, pity I will have to do it all again in a few weeks after the dissolved gases crop up :(
     
    Last edited: Oct 11, 2004
  11. MrMagoo2

    MrMagoo2 Member

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    hey cluey you can use a large bucket or container etc just direct the flow onto a baffle like mentioned before and make the intake at bottom and outlet at top in such a way as not to cause new bubbles (a spoon is good if you can affix it somehow). if you have really short hoses that dont permit this, use some hoses as extensions until air free, then remove extensions under water and voila.

    And no there is no need to wet the radiator.
     
  12. ir0nhide

    ir0nhide Member

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    I just bleed in a bucket then close the loop.
     
  13. Cluey

    Cluey Member

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    Here is a pic of my system being leak tested, in it you can see a red funnel with a short bit of hose on the end of it.
    I put that over the plug you can see on the radiator, this is a better picture of the plug.
     

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