With the k-ε method for gas-liquid two-phase flow

a model was developed to describe the processes of condensation happening in high humidity gas flow widely existing in process industries.A local driving force for condensation was introduced in the model to couple mass and heat transfer between the gas and liquid phases.Numerical simulation based on the model was carried out by using the CFD method.The profiles of temperature

steam fraction and liquid phase fraction were obtained numerically for turbulent flow of gas mixture in the annular space with an inner cooling pipe with constant wall temperature.It was shown that the generation of fog was controlled by the degree of local super-saturation

while the distribution of density of fog phase is affected mainly by the local driving force for heat transfer.Under the thermodynamic non-equilibrium and highly heterogeneous state

fogging was the dominant mechanism of the transportation between the two phases at the entrance section of the annular flow.As the development of fogging flow

a liquid film was formed along the cooling surface beginning near the position of x*=0.7.Consequently

the condensation was controlled by the mechanism of both fogging and filming.The simulation results were compared with the data obtained from the pilot experiment of cooling and condensation of high humidity gas exhausted from a granulator in an ammonium phosphate plant.Under the comparable conditions

the errors between the experimental data and the simulation results remained within ±9%.