Closed loop water systems are commonly used in industrial and commercial environments for heating and cooling purposes.
Like in the radiator system of your vehicle (also closed loop), air in the system will cause poor or no flow in the system.
In order to remove the air from systems, one can do it as simple as a manual bleed nipple, to automatic air bleeders.
On very large systems, one requires large bleeders and the mechanical versions becomes rather expensive.
I had just this problem once I started to work on large chilled water systems where pipe diameters from 200mm to 600mm is common.
From long observation, it was noted that the most effective way to remove air from these pipes, is to insert a T-piece in the pipe with a riser the same size of the pipe. This way a chamber is created from which almost no air bubble can escape.
The electronic bleeder has two level sensors and a very fast acting solenoid valve on top. It works by simply looking at the level sensors. If the bottom sensor is dry, bleeding starts until the top sensor is wet - and so it will continue until all the air is out.
Tested in the field, we were amazed by the stellar performance of this device and how few we needed on the system to once and for all solve the bleeding problem we had before.
This system offers excellent value for money for pipe sizes 100mm and up and since the price of the device is independent of the pipe size, it only gets better value as the size increase.