The influence of primary nozzle geometry on the ejector refrigeration system has been investigated numerically, and the variations of pressure and velocity have been analyzed and discussed for various geometries. Various bell-shaped primary nozzle geometries are numerically analyzed and compared to the existing conical nozzle in an ejector. The results show that the bell-shaped nozzle has a higher entrainment ratio and that the optimal design of the bell-shaped nozzle has been determined. It has also been observed that oblique shock waves generated in the bell-shaped nozzle result in a low-pressure region downstream, causing an increase in mass flow rate and the entertainment ratio raised by 3.13%. This indicates that the ejector modified with the bell-shaped primary nozzle can perform higher than the conical nozzle.