The present study describes a computer simulation model for steam jet ejectors. The model was developed by application of the equations of continuity, momentum and energy to individual operation of nozzle, mixing chamber and diffuser. Two different approaches used to develop two models are presented. The effect of motive steam pressure, evaporator temperature, and pressure rise across the ejector on the steam to vapour flow ratio were investigated, and the results presented. To test the adequacy of the models, these results were compared with empirical graphs of Power [1] and are found to be in good agreement.