Ammonia-based solar ejector cooling systems are greener cooling systems than conventional ones, however, the coefficient of performance (COP) of the conventional systems is higher than the Solar-driven ejector ones. This paper aims to evaluate the performance of ammonia-based solar ejector cooling by considering several ejector geometries. The effect of ejector inlet operating conditions (generator and evaporator temperatures) on the entrainment ratio is investigated at several condenser temperatures. The computational fluid dynamic model (CFD model) proposed in this study is validated with experimental and numerical data. The Realizable k–ε model enabled simulating turbulence characteristics with the compressible flow nature across the entire ejector, and the near-wall treatment is employed as a scalable wall function. The results showed that at an evaporator temperature of 15 °C and generator temperature of 90 °C, the highest coefficient of performance of 0.547 was obtained at an area ratio of 6.44. The maximum cooling capacity of 34.93 kW is reached at an area ratio of 6.77. The present findings complement experimental works by guiding the pre-experimental design and providing a better understanding of flow phenomena to improve the efficiency of ammonia-based solar ejector cooling systems and mitigate the environmental effect of cooling operations.