Theoretical modeling and numerical solution of stratified condensation in inclined tubes

Abstract

The heat transfer phenomenon occurring during stratified condensation inside an inclined tube is investigated theoretically and numerically. Differential equations governing the kinematic, dynamic, and thermal aspects for vapor condensation inside inclined tubes, which are derived from a thin film flow modeling, are solved simultaneously. These solutions are achieved by applying an explicit finite difference numerical method to predict the condensation heat transfer coefficient variations along the tangential and axial coordinates. The inclination angle is found to have a significant effect on condensation heat transfer coefficient inside inclined tubes. In addition, in accordance with the given physical and thermal condition of working fluids, there is a specific optimum inclination angle. In this study, the 30°-50° range from the horizontal position is found to be the range of the optimum inclination angle for achieving the maximum condensation heat transfer coefficient, with R134a, R141b, and R11 as the working fluids. The results of the present study are compared with experimental data, and a good agreement is observed between them.

Condensation heat transfer in smooth inclined tubes for R134a at different saturation temperatures

“…Theoretical investigations of the heat transfer coefficient in R134a, R141b and R11 were carried out by Saffari and Naziri [12]. The governing differential equations of kinematics, dynamics and thermal aspects of two-phase flow were derived from a thin film flow model and solved simultaneously while numerical solutions were obtained.…”

Stratified flow model for convective condensation in an inclined tube

“…Some improvements, mainly in the calculation of the shear stresses, were proposed by different authors. Spedding et al (1998) summarised some of these models and compared their results with an experimental database of air-water flow in slightly inclined tubes. However, Ullmann et al (2003) showed theoretically and experimentally that several liquid hold-ups can occur during certain conditions, which makes the study of this kind of flow more complex.…”

“…Fiedler and Auracher (2004) proposed a model for condensation inside inclined thermosyphons. Recently, Saffari and Naziri (2010) published a numerical falling film and liquid pool model for condensation. Their model was able to predict the maximum heat transfer coefficient in an inclined tube from 30° to 50°.…”

Theoretical modelling of stratified condensation of two-phase co-current flow including pressure drop in inclined tubes

“…Regression analysis was used for developing the correlation. Hamid Saffari et al [4] developed theoretical model for condensation inside inclined tube. C. E. Rufer et al [5] analyzed stratified flow considering effect of different tube inclination angles.…”