Experimental investigation of a novel expansion device control mechanism: Vortex control of initially subcooled flashing R134a flow expanded through convergent-divergent nozzles

A novel expansion device refrigerant flow control mechanism called vortex control has been studied in this paper. This control mechanism is less vulnerable to clogging than conventional expansion device types since the flow control is achieved without having to adjust the cross-sectional flow area in order to achieve the desired modulation effect. Big potential is seen in applying vortex control to modulate the flow through ejector motive nozzles, because it can potentially provide flow control without sacrificing nozzle efficiency. Investigated in this paper were different nozzles flows with initially subcooled R134a. The effects of geometry variations and operating conditions were investigated experimentally. Flow visualizations were performed to gain further understanding of the complex two-phase flow in the vicinity of the nozzle throat. Maximum vortex control range of 42% has been obtained in the current study, which appears to be large enough to be suitable for numerous technical applications.