Ejector flow in an ejector air conditioning system using R245fa is analysed for entrainment ratio and potential refrigeration effect, at varying temperature and heat input conditions in the generator ranging from 60 °C to 100 °C and 2 kW to 5 kW respectively. The effect of varying generator temperature in cooling capacity of the system when the vapour ejector is operating at design evaporator and condenser temperatures of 10 °C and 35 °C respectively is investigated. The mathematical model of the vapour ejector with optimum area ratio is developed and validated. A critical entrainment ratio of 0.385 is obtained corresponding to generator temperature of 100 °C. When the generator temperature is varied from 60 °C to 100 °C, the cooling capacity ranges from 0.3 kW at generator heat input of 2 kW to 1.78 kW at 5 kW heat input. Further, the operation of the system is analysed for off design operating condition corresponding to reduced heat input rate in the generator. In that case the state of primary refrigerant flow in ejector inlet will be two phase and a mathematical model for two-phase ejector flow is developed and validated. Ejector flow analysis revealed the minimum quality of flow at ejector inlet to maintain adequate backpressure for condensation to occur ranges from 0.72 at 60 °C to 0.22 at 100 °C. The corresponding refrigeration effect produced is less than the respective designed operation value by 12.2% to 8%. Further, analysis of the system shows that at least 7 kW heat input at 100 °C is required to produce 1 ton of cooling effect.