Abstract:

In this paper, a numerical study has been carried to simulate a two-phase flow with evaporation in a vertical tube. The VOF multiphase flow method and a phase-change model have been used. For an accurate modeling, the effect of axial conduction has been also taken into account, using a conjugate heat transfer model. Our numerical simulation procedure has been validated by comparing our results with those obtained by other authors. Temperature and void fraction fields have been calculated for various conditions. Since thermal oscillations are undesirable, as they can lead to a tube failure, flow instabilities have also been analyzed, using FFT (Fast Fourier transforms), in order to comprehend their behavior. A control study of the flow instabilities in the tube has also been carried out. For that purpose, an annular control element with a rectangular cross section, acting as a vortex generator, has been attached to the tube wall.

Publisher's Version