A QUASI-2D MODEL FOR PREDICTING ENTRAINMENT CHARACTERISTICS OF EJECTORS UNDER VARIOUS OPERATING CONDITIONS

Abstract

The ejector is a key component in low-grade thermal refrigeration systems thanks to its simple construction and its potential to boost cycle efficiency. This paper presents a quasi-2D mathematical model that accurately predicts entrainment ratio of ejector in both critical and sub-critical regimes. Unlike conventional one-dimensional methods, the quasi-2D approach captures the radial velocity distribution, boundary-layer effects, and shock-wave region. The model is validated against a wide experimental database covering several refrigerants and operating conditions; the maximum deviation is below 7%, while pressure trends and entrainment ratios—especially in the sub-critical zone—are reproduced faithfully. These results highlight the necessity of simultaneously accounting for axial and radial flow directions and provide a reliable basis for ejector geometry optimisation, ultimately improving the COP of ejector-based refrigeration systems.