The results of the application of a general mathematical model to simulate two-phase annular gas-liquid flow in both horizontal and vertical pipes are presented. The method is based on the transient one-dimensional two-fluid model wherein the two phases are considered as (i) liquid layer and (ii) a mixture of the gas and liquid droplets in which the droplet concentration in the mixture is treated as a flow variable. The model entails the introduction of a scalar transport equation for the conservation of mass of liquid droplets accounting for liquid transfer to and from the film liquid layer. The rates of the entrainment and deposition of droplets are supplied as closure relations derived from modifications of models existing in the literature. Using the new model, the droplet entrained fraction (E), which is defined as the ratio of the droplet to the total liquid mass flow rate, can be computed. The purpose of the present paper is to validate the entrainment and deposition closure models used through comparisons of the computed entrained fraction against different experimental data found in the literature for steady, fully developed flow. The present comparisons show satisfactory agreement with most of the data with discrepancies of around±30%. What is significant is that both horizontal and vertical annular flows can be predicted to this degree of accuracy using the same model.