Characterization of choking flow behaviors inside steam ejectors based on the ejector refrigeration system

Abstract

Abstract In order to maximize the working potential of a steam ejector, aside from experiment testing of various design parameters, it is also important to understand the involved thermal fluid mixing behaviors. In this study, an ejector refrigeration experimental system was established, and a numerical model was developed to comprehend the complex and non-linear flow characteristic using an ideal gas model which is more consistent with the experimental data compared with the wet steam model. Herein, it was discovered that the choking flow and the occurrence locations of this phenomenon played an essential role in the system efficiency. For the first time, three choke behaviors modes were characterized by means of numerical investigations: “fit-choked flow mode”, “sub-choked flow mode” and “super-choked flow mode”. The relationship between the choke and the normal shock wave was revealed to analyze the two mixing fluids flow conditions. The influence of primary fluid pressure and the back pressure on the ejector performance under three choke flow modes were comprehensively discussed. The simulation results indicated that the choking flow was a critical factor in affecting the performance of the steam ejector, and the performance optimizes at “fit-choked flow mode” when the primary fluid pressure was 0.36 MPa with a remarkable entrainment ratio of 0.525.