In this study, the performance of five ejectors has been investigated with working fluids of water and water vapor. The diameters of nozzle and mixing tube of five ejectors were 1 and 1.5(ejector A), 1 and 2(ejector B), 1 and 2.5(ejector C), 1 and 3(ejector D), 2 and 4(ejector E) in millimeters. The length of the mixing tube was 8-10 times of its diameter. For each ejector, the ratio of mass flow rate of ejected water to that of entrained water vapor, $mu$, was evaluated in terms of evaporator pressure, mass flow rate of ejected water, and water temperature. It was found that the performance of an ejector was not stable when the ratio of diameters was too small or too large(ejector A and D) and $mu$ was almost the same for two ejectors with the same diameter ratio(ejector B and E). It was also found that $mu$ increased almost linearly with an increase of evaporator pressure and the ratio $mu$ increased as water temperature decreased. As expected, $mu$ converged to zero as the water temperature approached the evaporator temperature. Finally, a non-dimensional correlation has been developed to predict$mu$ terms of evaporator pressure and saturation pressure of ejected water