NUMERICAL SIMULATION AND EXPERIMENTAL ANALYSIS FOR THE BUBBLE GROWTH RADIUS BY CONSIDERING THE FLUID-SURFACE INTERACTION

Resumo

The advance of new technologies, associated with the minimization of manufacturing and
installation costs, presents a great challenge for the refrigeration area since the heat generation has
increased in recent years. Several studies have shown the influence of surface topography on the heat
transfer performance, a strategic subject for the development of techniques for cooling of miniaturized
electronic components, thermal control of satellites, cooling of high concentration photovoltaic cells
and others. The objective of this work is to develop a theoretical and numerical study of the heat
transfer phenomenon with phase change involving pool boiling, taking into account the influence of
the heating surface characteristics and the use of different fluids (e.g., water or refrigerants) by the
numerical simulation of a vapor bubble dynamic onto the heating surface. A computational code is
developed in Fortran 90 language to solve the continuity, momentum, energy and interface capture
equations in three-dimensional spherical coordinates. Moreover, it is implemented a method to
capture the interface based on the coupled algorithm of Volume of Fluid Method and Level Set
Method (CVOFLS). The effects of microlayer, contact angle and surface tension on the vapor bubble
dynamic are also considered. The CVOFLS algorithm also allows the simulation in Eulerian fixed
mesh. The finite element method is applied for space discretization and the Characteristic Based Split
scheme (CBS) is applied for time discretization. The comparison with experimental data obtained by
the research group and by other researchers is used to validate the numerical model. Thus, the rate of
bubble growth and the bubble shape could be predicted until its departure time taking into account the
effects of microlayer and surface/fluid interaction.