Numerical study of steam condensation inside a long, inclined, smooth tube at different saturation temperatures

In this study, the effects of the inclination angle on the heat transfer coefficients and on pressure drops were investigated numerically, during the process of development of heat condensation inside a long smooth tube, at different saturation temperatures. The simulation model included a smooth tube with a diameter of 18 mm and a length of 7.2 m. The imposed inclinations varied between −60° (downward flow) to +60° (upward flow). Moreover, the saturation temperatures varied between 40 °C and 70 °C. The flow field was assumed to be three-dimensional, unsteady, and turbulent. The Volume of Fluid (VOF) multiphase flow method was utilised to solve the governing equations comprising mass, momentum, energy, and turbulence equations, along with phase change rates. The simulation results were in good agreement with the experimental data. The results showed that the condensation heat transfer coefficient first increased and then decreased along the length of the tube. Furthermore, it was noted that the condensation heat transfer coefficient and pressure drop decreased when the steam saturation temperature increased.