Numerical investigation of vapor bubble condensation characteristics of subcooled flow boiling in vertical rectangular channel

In this study, the behavior of condensing single vapor bubble in subcooled boiling flow within two different vertical rectangular channels has been numerically investigated by using the VOF (Volume Of Fluid) multiphase flow model. The mass and energy transfer model of bubble condensing process induced by the interfacial heat transfer was proposed to describe the interfacial transportation between the two phases. The results of VOF simulations show a good agreements with previous experimental data in the bubble size variation and lifetime. The bubble lifetime is almost proportional to bubble initial size and be prolonged at increasing system pressure. With the increasing of the subcooling, the bubble lifetime reduces significantly, and the effect of mass flux could be negligible. When the bubble size increased, the bubble shape tends to be changed in a large channel. The VOF simulation results of deformation have good agreement with those of Kamei' experiment and the results of MPS (Moving Particle Semi-implicit) simulation in a larger channel. Furthermore, the initial bubble size, subcooling of liquid and system pressure play an important role to influence the bubble deformation behaviors significantly. The bubble could be deformed sharper with the increasing subcooling and initial diameter, or could breakup when the subcooling and the initial diameter reach a certain value at the last bubble stage. Nevertheless, the trends of bubble deformation will be weakening with the increasing system pressure. (C) 2012 Elsevier B.V. All rights reserved.