Abstract: 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%.

摘要： 采用气液两相湍流k-ε模型，通过引入局部冷凝推动力实现两相传热传质的耦合，对冷表面作用下高湿气流的冷凝过程进行了模型研究，并应用CFD方法对模型进行了数值模拟.对恒壁温冷凝管外混合气体在环形空间湍流冷却冷凝的温度分布、湿度分布及其凝雾区间分布的模拟结果显示，凝雾的产生受蒸汽过饱和度控制，而其分布受过程传热推动力影响.基于体系整体不饱和、局部过饱和的热力学非平衡状态，冷凝区间前端主要发生雾状冷凝，在x*＝0.7附近，随着凝雾在冷表面上逐渐积聚成膜，凝雾过程过渡为膜状-雾状冷凝协同作用.相同工况下，由本模型计算得到的冷凝量与高湿气流冷却冷凝现场实验数据的相对误差为±9%，验证了本文的模型与数值模拟.