Vortex control for motive flow rate modulation of transcritical R744 ejector systems.

This paper presents results of a novel expansion device refrigerant flow control mechanism called vortex control. The key advantage of this control mechanism is being far less vulnerable to clogging than conventional expansion devices since the flow control is achieved without having to adjust the cross-sectional flow area in order to achieve the desired modulation effect. Vortex flow control is seen as particularly promising when applied to transcritical R744 ejectors, where flow control of the motive nozzle is known to substantially impact ejector and cycle efficiencies. Vortex control can potentially offer the advantage that overall ejector efficiency is less impacted than designs where a needle is used to modulate the motive nozzle flow. The effects of operating conditions were investigated experimentally. It is shown that vortex flow control appears to be feasible for two-phase ejectors using R744 and similar flow modulation ranges as with needle control were achieved.