Turbulent Boiling Simulations in Vertical Tube and Horizontal-Serpentine Tube Based on the OpenFOAM-VOF Method

The accuracy of turbulent boiling numerical models is essential in CFD studies. This paper performs simulations based on the VOF model under the OpenFOAM environment, coupled with Lee’s phase change model, to study the effect of the mass transfer time parameter (r[s−1]) on the phase change in vertical and horizontal-serpentine ducts. Two different experimental configurations are used: vertical and horizontal-serpentine tubes. Different turbulence models, standard k–ε or k–ω(SST), have been adopted vis-à-vis the shape of the configurations and the related dynamic phenomena. Results show an acceptable consistency for all the treated cases. The first configuration, using the k–ε model, showed reasonably good agreement with experiments compared to other works of literature, with a mean relative error of the void fraction of about 25.7%. At the same time, 0.38% is obtained for the bulk temperature of the mixture at different locations from the inlet. The void fraction distributions for both configurations are coherent, especially for the second one, compared to the experimental visualisations. In this work, the best choice of the mass transfer time parameters for vertical tube and horizontal serpentine were r = 1000 and r = 0.1, respectively. An observed limitation of the OpenFOAM used solver – InterThermalPhaseChangeFoam – leads to the conclusion that conjugated heat transfer must be considered because phase change is problematic at the wall contact.