Contribución a la modelización del crecimiento de una burbuja de vapor sobre una placa sobrecalentada: Acto elemental de ebullición

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] The objective of this thesis is to set a model for the growth of a vapor bubble superheated solid substrate, also referred to as an elementary boiling act. It falls in the European Spatial Agency RUBI experiment framework, in which TIPs department takes part. Those experiments will be carried out on the International Spatial Station, and thus under microgravity conditions. First, we review the existing literature about boiling for a good understanding of the phenomenon and also in order to decide along which lines the present should be carried out. Further, we introduce the governing equations and we discuss the relevant physical effects through a simplified problem in the absence of the solid substrate (`free bubble¿). Next, we include the substrate and follow the implications. We use a multiscale approach, consisting in the subdivision of the liquid domain around the bubble into several zones mainly the interface subdivision in several zones: the macroregion and the supplementary region, the latter subdivided into the bubble foot and the microregion. We set forth a model for the macroregion, a previously developed one is used for the supplementary region. We carry out coupling between the different zones to get the global model. After that, we implement it using the numerical software COMSOL Multiphysics ©. In doing so, we carefully construct the geometry and mesh coherent with the physics of the problem, verifying the correspondence between the mathematical expressions figuring in the problem formulation and their COMSOL language counterparts, and using an adequate solving method as far as the sequence, solver and time step are concerned. The results, computed for four different case studies, are treated using various graphs plotted in COMSOL. The evolution of the temperature field, bubble radius growth versus the time or the superheat, the importance of the substrate and of the advective effects and the validity of the hypothesis made at the stage of model construction are analyzed. Finally, we summarize this thesis contribution to the boiling study. Furthermore, we set a list of elements that could be added to the model in order to improve it in prospective studies.