Numerical study and visualization on flow characteristics of reflux condensation in air-cooled condenser

Highlight• Flow of reflux condensation in air-cooled condenser tube is studied numerically. • A model-based approach to determine the condensation length is proposed. • Effect of varying vapor/air operations on reflux condensation is considered. • Dynamic behavior relating to complete and countercurrent condensation is visualized. A numerical simulation was presented to investigate and visualize the flow characteristics of reflux condensation in core tube related to air-cooled condenser. The simulation had been performed in a flat tube under a saturation pressures of 13 kPa. The sensitivity of condensation length, condensate thickness and interfacial shear was examined with varying the vapor mass flux and cooling air Reynolds number. In addition, the condensate-void and vapor-absence corresponding to complete condensation were visualized in a transient simulation. Interfacial rivulets, film climbing and liquid entrainment corresponding to flow-through condensation were identified by contours of liquid void fraction and further explained by the cross-sectional velocity profiles. Meanwhile, several recommendations to experiment and operation on upflow finned tubes were proposed based on numerical results.