Experimental and numerical simulation of non-equilibrium phase change flow in converging-diverging nozzle based on H2O/LiBr

In H2O/LiBr absorption refrigeration cycles, an ejector is commonly used to circulate the solution and enhance absorber efficiency. However, within the ejector nozzle, the H2O/LiBr solution undergoes a non-equilibrium phase change accompanied by spontaneous nucleation, where bubbles generated by high-speed fluid disrupt traditional modeling and significantly impact ejector performance and equipment stability. This paper establishes a one-dimensional model of the delayed phase change in a two-phase ejector based on the absorption-working-fluid and uses high-speed camera experiments to verify the model's accuracy. The model is refined using the homogeneous nucleation model and desorption/absorption mass conservation equations to predict the delayed phase change process in the nozzle. The research results show that under two experimental conditions, the average root mean square errors of the proposed model is 3.23 × 10−6, outperforming the equilibrium phase change model, and improving the accuracy of predicting the vaporization rate by 25.8 %. Compared to the isentropic model, the outlet flow velocity predicted by the proposed model increases by 52.86 %. This model successfully reveals the complex relationship among mass transfer rate, nucleation rate, and superheat in the H2O/LiBr binary solution-based converging-diverging nozzle.