Dr. Adriano Milazzo is Associate Professor of Thermodynamics and Heat Transfer at the University of Florence. He has published multiple papers in international scientific journals on ejectors, and coordinated the design of the ejector chiller prototype at Frigel Firenze, a leader in advanced process cooling technology.
Despite the good performance of ejectors in the studies, most of the research on the performance of ejectors has assumed that the ejector works under the designed condition. However, due to the instability of solar energy, it is difficult to ensure that the concentrated photothermal MED desalination systems operate under fixed conditions. Inevitably, the departure from the design condition will result in the deterioration of the ejector performance. While researchers have investigated some structured ejectors that can meet the requirements of off-design conditions to a certain extent, the operating conditions are still limited and the ejector performance is not suited for concentrated photothermal MED desalination. Thus, it is challenging to adapt to the operating environment and the situation where the steam parameters fluctuate greatly.
As for the optimization of ejector thermodynamic models with conventional working fluids in the ERS, Keenan  made two assumptions about the fluid mixing mode in the mixing chamber: constant-area and constant-pressure mixing. The latter theory is widely used in subsequent research, providing a theoretical basis for ejector mixing modeling. Huang et al.  presented a one-dimensional model to predict the ejector performance with R141b under the double-choking state and obtained the coupling relationship between the loss coefficient and the structural parameters. Zhu et al.  pointed out that there was a shock circle at the inlet of the constant-area mixing chamber. This theory simplifies the traditional one-dimensional model and can predict the ejector performance under the critical mode more accurately, making the theoretical model more consistent with the actual fluid flow characteristics inside the ejector. Ma et al.  innovatively put forward a one-dimensional modeling method to estimate the ejector performance with steam under the critical state by using steam sound velocity at the throat, and they analyzed the influence of ejector structural parameters and loss coefficients of different parts on ejector performance. To further analyze the non-equilibrium condensation phenomenon, Zhang et al.  proposed a modified model to predict the condensation phenomenon in a Moses and Stein nozzle and found that the modified model was more accurate than the original model in predicting the Wilson point position and its thermal parameters. Piotr et al.  thoroughly investigated the effects of four often-used condensation models on the condensation characteristics in moist air flows and recommended the most suitable model for moist air transonic flow. Zhang et al.  also studied the influence of impurities in steam ejectors on the non-equilibrium condensation phenomenon and pointed out that the process of steam condensation on salt particles had a significant impact on two-phase variables and flow parameters. The thermodynamic model of the ejector has been gradually improved with the efforts of scholars, but the influence of the ejector structural parameters on the ejector performance has not been considered. Expasito et al.  used a multi-objective optimization algorithm to optimize the ejector structural parameters with air based on CFD numerical simulation and pointed out that the nozzle throat and the diameter of the mixing chamber have the greatest impact on the ejector performance. Wang et al.  investigated the influence of nozzle structure on ejector performance with R134a and pointed out that the roughness of the nozzle diffuser and throat should be given more attention when designing ejectors. Wang et al.  put forward a mathematical model for designing the steam nozzle structure and pointed out that the change in the entrained fluid pressure can lead to the axial movement of the shock wave. Liu et al.  explored the influence of the steam ejector area ratio on the ejector efficiency of various components. They pointed out that the mixing chamber efficiency had the greatest impact on the ejector performance with the change in the area ratio. 2b1af7f3a8