andre Galligo - UCA, UNS, CNRS, LJAD - Keywords: Boiling

andre Galligo - UCA, UNS, CNRS, LJAD - Keywords: Boiling

Contribution title: Modeling and Computation of a liquid-vapor bubble formation.




Boiling is a complex phase transitioning process in which a new liquid-vapor interface (bubbles) is created.
It is an effective mechanism widely used in energy conversion industrial facilities. However, a precise descriptive/predictive model of bubble formations is needed to better understand its heat transfer characteristics. As an important first step, the question can be addressed from a quasi-static viewpoint. Indeed, at the interface, a classical conservative law governs the surface curvature of the generated bubble. This non-linear law links the difference of pressure and the surface tension effect. After normalization, it can be expressed at each point of the surface by the following equation: K_1 + K_2 - B z = constant; where B is a Bond number, summarizing the context, z is the elevation and K1 + K2 is twice the Gaussian mean curvature.
Therefore, the study of a growing bubble is amenable to solving geometric computations and non-linear differentiable equation. The main difficulty is to design criteria to detect when the growing bubble will detach from the substrate’s nucleation site. Inspired by experimental observations, the second author was able to develop (and publish) a successful computational strategy.
The computational model implemented for the axis-symmetric case (which relies on 2D geometric computations), provides useful information, fully confirmed by experimental observations.
Moving forward, we were able to speed up the computations and introduce the use of splines for representing the plane section of the surfaces.
Moreover, we were able to treat with similar tools the case for which the nucleation site is on an inclined plane; this geometry better models the one effectively used in industrial plants. Our next target is to better formalize our detachment criteria, in collaboration with an experimental team in Dublin, Ireland; then develop and implement a 3D model for a more general situation. Future studies will also include external stress terms such as cross flows and electrical fields in an effort to move towards realistic and accurate boiling models.