Tangential or coalescing air separator for hydronic system?

[mrev23]

I hear that coalescing air separators are much quicker about removing air from a system. They are also supposed to be better at removing "dissolved" air.

They are also filled with media that seems subject to clogging (hence, higher maintenance cost), and I think their purchase price and pressure drop (hence, operating cost) are higher.

Won't a tangential separator eventually remove air that is problematic?

Page 14 (in the link below) says a tangential separator removes 40% of the free air --- 60% of the free air would remain. But that is after one pass.

After the second pass, the remaining air would be (1 - 0.4) * (1 - 0.4) = 36% of what it was when the system was started.

After the 10th pass, the remaining air would be (1 - 0.4) ^ 10 = 0.6% of what it was when the system was started.

Is it worthwhile to endure higher first cost, operating cost, and maintenance costs that may be associated with a coalescing air separator to recover (perhaps only sooner rather than later) from a small amount of air that may be admitted into the system when repairing a control valve?

There is a payback analysis here:

https://www.whea.com/media/108195/neutral-slide-show-whea.pdf

But I am not sure it accounts for added operating cost due to pressure drop.

Page 31 mentions "low pressure drop," but that seems to be relative to other kinds of dirt-removal devices, not air separators.

There is no direct comparison in this file between pressure drops through tangential and coalescing air separators.

Any thoughts on whether to prefer a coalescing air separator over a tangential type?

 

[Drazen]

quick air removal could have been feasible requirement only for old system with lot of suspected air entry spots, to improve daily operation of system.

for new systems, all entrapped air should be removed during filling process! later, release of air from the water is usually slow process, so slow air separators should not be a problem.