Solar ejector cooling system: Optimal performance of the ejector under off-design conditions

The stable operation of solar-driven ejector cooling systems depends critically on the performance of the ejector under varying (off-design) conditions. This study presents a detailed analysis of ejector performance across a wide range of operating parameters. A universal 1-D model is proposed for predicting the performance of ejectors with both cylindrical and conical-cylindrical mixing chambers. The model incorporates key geometric dimensions of the ejector and accounts for changes in the parameters of the primary, secondary, and mixed flows. The model was validated against published experimental data for different ejector geometries and operating conditions. The predicted entrainment ratio showed an error within ±10 %. The prediction error for the condensing temperature at the critical and breakdown points is ±1.5 % and ±3 % for the ejector with a cylindrical mixing chamber, and ±2.5 % and ±2 % for the ejector with a conical-cylindrical mixing chamber, respectively. Additionally, the analysis of ejector operation enabled the identification of conditions that maintain the double-choking mode, which ensures stable system performance. The results provide practical insights for optimizing the performance of solar ejector cooling systems and can serve as a basis for developing adaptive control strategies that respond to varying environmental and operating conditions.