A one-dimensional model has been developed to predict liquid phase velocities in bubble columns. The closures of liquid phase material balance, gas phase material balance and energy balance are provided to give predictive capability to the model. A solution procedure has been developed to predict the hold-up profile and liquid phase velocity profile in the bubble columns. The model has been used to compare the experimental data over a wide range of column diameter and gas-liquid systems. An excellent agreement has been shown between predicted and experimental data of all the above cases. The model is extended to predict the velocity profiles in 0.15 m diameter column for a range of superficial gas velocity of 0.06 < V-G < 0.29 m s(-1) and 0.05 < V-L < 0.14 m s(-1). The present model overcomes the limitations of all the previous models that the knowledge of hold-up profile is needed for the prediction of flow pattern. The present model uses the easily available, measurable information of the drift flux constants. The model predictions have been extended to predict the two-phase friction multiplier and wall to bed heat transfer coefficient.