For a Vortex Air Separator (VA or VAS), how does one determine the minimum flow rate?
The VAS relies on centrifugal acceleration to remove entrained air from a system. A Vortex (a conical swirl) is created and the entrained air migrates from the high-pressure area to the lowest pressure center of the Vortex. At this point, the air bubbles break-up and the free air moves to the top of the unit where it is removed. As a general rule, the higher the fluid entrance velocity, the deeper the Vortex. This depth (height) of the swirl is directly proportional to the amount of entrained-air removed. At the upper end of the flow rate range for each size VAS, these forces are highest so air removal effectiveness is best. However, the unit is still effective even at the lower end of the flow rate range. The minimum pressure drop through the unit determines the minimum flow rate. A minimum 1/2 ft. pressure drop is required for proper air removal.
