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Pump Air Bubble

Pump Air Bubble

Pump Air Bubble

I hope someone out there is able to help me on this question:
This is in regard to a cooling loop configuration. I have 1" ID vertical pipes with 180 deg bends on top/bottom. The top ones will most likely accumulate entrapped air after initial filling. The pipe is filled with water-glycol.
After the initial filling I need to get the air out of the system but I can not pump high rates. What would be a sufficient flow rate for the fluid to carry the air out of the system.
Much Thanks.

RE: Pump Air Bubble

Can you turn the coils sideways so that instead of the bends being top/bottom, they are left/right?


RE: Pump Air Bubble

thanks for asking this questions. I should have noted in my initial question that I am restricted by the design to choose this very unfavourable layout.
I did some further calculations - with a 5 gpm flow rate I end up with turbolent flow with a velocity of around 2 ft/s. My gut feeling says that with the centrifugal effect and turbolent flow this will be sufficient to get the air out.
Any ideas.

RE: Pump Air Bubble

Where is the pump in relation to your bends?

RE: Pump Air Bubble

I will have an outside pump that I can elevate above the bends if necessary. I guess this is were you were heading...?
When pumping with the mentioned 2 ft/s there will be the fluid flow in the downwards direction after the 180 bends but the taken air bubbles will tend to rise again. Some slippage occurs and a resultant velocity will be establish. Any ideas what the rise velocity of air bubbles will be in this situation?

RE: Pump Air Bubble

If this is a closed loop system just make sure you have a Rolairtrol or some other type of air removal device in the system.  This will remove the air in the system gradually.

If it is an open system, you may never be able to eliminate air out of that bend without an auto air vent at the top of the 180 return.  An auto vent would remove air after a large amount accumulates.  Not ideal, but it would work.  If this fluid can't be released to atmosphere, I think the vent can be discharged to a drain.  

A manual vent can also be used (1/2" ball valve) in this situation.

RE: Pump Air Bubble

Thrusterman, I am curious whether you found a solution to your air bubble problem, as I am currently having a similar event happening in a heating/cooling line. Do you have any luck? -Druck

RE: Pump Air Bubble

Can you get a pig in the line?  (and recover it) depends on pressure and the radius of your bends.  If it's possible it would certainly eliminate the air

RE: Pump Air Bubble

currently thinking in using several 'tap-in' points with various valves to be able to circulate in multiple flow paths one at the time. That should be feasible but probably not the best solution.   

nope - can not use a pig because there are filters in the system. I have thought about that as well because I used sponge pigs for cleaning beer pipes back in the days when I used to work in a pub.


RE: Pump Air Bubble

Air is more soluble in cold water than it is in hot water.  This is the principle behind the boiler deaerator.  Heating the water drives off the air.  Your pipe is a cooler.  Hot water with entrained air enters the cooling loop and collects at the first 180 degree bend.  After that, the water/glycol mixture starts to cool off, so any remaining air would go back into solution.  Every time you heat the water/glycol, more air will come out, until all the air is gone.  I suggest an automatic air vent at the top of the first loop.  (Armstrong, Spirax/Sarco, etc)

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