Experimental study of the performance of an ejector system using Freon 134a

Abstract This paper presents experimental data of the entrainment ratio as a function of the outlet mixture pressure of an ejector. A single ejector geometry, manufactured from brass bore rods, is installed into a closed-circuit loop that uses Freon 134a as primary and secondary working fluids. Different inlet flow pressure conditions are applied for both the primary and secondary flows while the outlet mixture flow pressure is varied from 500 to up to 975 kPa. This range of the outlet pressure permitted on-design (i.e. formation of a first plateau on the diagram of the entrainment ratio as function of the pressure) and off-design operation conditions to be largely covered. It is thus, systematically observed that within the off-design zone there is formation of a secondary plateau which seems to indicate that the flow undergoes an unusual choking flow condition. A preliminary analysis of the data indicates that the off-design behavior is mainly controlled by the interaction between two currents of fluid without mixing, and the effect of the entropy on the speed of sound. The presence of a second plateau triggers a flow transition which can affect the on-design performance. The collected data were also compared with similar ones obtained by other research groups. Hence, these comparisons reinforce the trends of the actual experiments.