Numerical investigation of an R744 liquid ejector for supermarket refrigeration systems

This paper presents a numerical investigation of an R744 liquid ejector applied to a supermarket refrigeration system. The use of the liquid ejector enables the operation of the evaporator in a flooded mode and recirculates the R744 liquid phase, which improves the energy efficiency of the refrigeration system. The investigation was performed using two ejectors of different sizes installed in a multi-ejector block. The numerical model was formulated based on the homogenous equilibrium model and validated with the experimental results. The influence of the pre-mixer, mixer and diffuser dimensions on the ejector performance measured using the mass entrainment ratio is presented. The results show that the best liquid ejector performance was obtained for the short lengths of the pre-mixer and mixer compared to the broadly investigated two-phase ejectors connected to the evaporator port. In addition, wide diffuser angles improved the mass entrainment ratio of both liquid ejectors, which may lead to a reduction in the diffuser length.