Experimental Investigation of Inline De-Aeration in Automotive Coolant Using an Outer-Ring Helical Swirl Vane

Air entrained in automotive coolant reduces heat transfer and may cause pump cavitation, but traditional passive de-aeration and expansion tanks depend on gravity to cause bubbles to rise and on sufficient residence time, which makes them unsuitable for the high flow rates and limited space found in modern engines. This paper describes the design, mathematical modeling, and experimental verification of a compact, inline active de-aeration device consisting of an outer-ring helical swirl vane with a 2 mm central stabilizing hub, and is designed for use with a standard 10 mm automotive coolant hose. The vane gives the 50/50 ethylene glycol–water coolant a controlled swirl, using centrifugal separation to push the denser liquid towards the outer side and to gather the entrained air into a stable central air core, which is then removed by a downstream coaxial air collector. The device was tested at vane exit angles ranging from 20° to 70° and at flow rates between 3 and 9 LPM; the stable operating range was found to be between 30° and 56°, with peak performance occurring at 45°. At an angle of 45° and a flow rate of 6 LPM, the active system cut the de-aeration time by 76.6%, reducing it from 13:14 min (the passive baseline) to 3:07 min, while keeping a local hydraulic blockage of 17.00%. The results demonstrate that outer-ring helical swirl vanes provide a practical, low-blockage solution for inline de-aeration of coolant in space-limited automotive and powertrain cooling systems.