Considering the interfacial shear force

a mathematical model to the condensation of turbulent vapor flowing downward in an inclined flat tube is proposed and implemented in computational fluid dynamics (CFD). The predicted results from the CFD model are compared with the experimental results from the literature for the vapor condensation in a prototype tube (2600 mm length

3 mm width and 50 mm altitude in 60° inclination to vertical). It is found that the condensate rate and mean condensation heat transfer coefficient (HTC) from CFD simulation agree very well with the experimental quantities. Using CFD model to calculate the interfacial shear stress by varying vapour velocity

the results demonstrate that the value of shear force depends on the vapor velocity at the tube inlet

and shear force decreases continuously with the vapor flow and condensation. Simulating the interfacial shear effect on the condensation

it shows that the interfacial shear increases the local condensation HTC

and meanwhile

reduces the local condensate rate. The simulation results also shows that the interfacial shear weakens the gravitational effect on the film accumulation and obviously decreases film thickness from 0 to 0.8 m in the tube axial length. However

from 1.0 m to the tube outlet

the gravitational force dominates over the shear force

and thus the shear effects can be completely neglected. It is also found that the condensate film is speeded up particularly from 0 to 0.2 m in axial length thanking for the interfacial shear.