Shadowgraph visualization of condensing R134a flow through ejectors

• Demonstrates shadowgraph visualization of two-phase jet emanating from ejector motive nozzle.
• Presents first undistorted visualization images of refrigerant flow at conditions for ejector-based chiller.
• Analytical and CFD models validated with experimental flow images.
• Condensate exiting motive nozzle can be found from flow quality at equilibrium.
• Increasing degrees of condensation at nozzle exit correspond to drop in MER.

Accurate simulation of ejector flows has been challenging due to the difficulties in modeling two-phase supersonic flows of fluids other than air or steam at high temperature and pressure conditions. Such modeling is necessary for ejector optimization, but the models currently available have yet to be validated. A transparent ejector test section is designed, fabricated, and operated in an ejector-based chiller loop using R134a as the working fluid. Undistorted visual access allows for detailed shadowgraph visualization of the motive jet in the mixing section at various degrees of condensation. High-speed imaging is used with measured temperatures and pressures at the ejector inlets to validate available analytical and CFD models. It is found that the best modeling techniques assume that the motive flow exits the motive nozzle at full thermodynamic equilibrium, and that the k-ε RNG turbulence model in ANSYS FLUENT captures these equilibrium conditions sufficiently.