This paper describes a simple computational model for prediction of thermal/hydrodynamic behaviors of a horizontal stream inside multi-stage-flash evaporators. By using the PSI-Cell method, steady, two-dimensional conservation equations with the standard k - epsilon turbulence model were solved in conjunction with the bubble motion/growth equations. Information on the bubble nuclei embedded in the incoming liquid was also given as boundary conditions at the inlet for two-phase calculations. Velocity and temperature distributions and bubble trajectories were obtained; the results were in general agreement with the experiments reported previously, and the performance of flashing may be predictable with the present calculations.