Sebastien TANGUY - IMFT - Numerical simulation of nucleate boiling: From nanoscale models in the micro-region to integrated models for large scale systems

Nucleate Boiling is a critical phenomenon in many applications for which accurate numerical predictions are required to improve the efficiency and the reliability of the process. For example, the global heat transfer coefficient of a heated wall immersed in a liquid can be significantly enhanced by increasing the number of bubbles nucleated on the wall. This can benefit to heat exchangers compactness which is crucial in many applications, as micro-electronics cooling devices. Nucleate Boiling is also of utmost importance in space applications for which the management of liquid propellant in micro-gravity is critical for the design of space launchers able to restart in flight conditions. However, in spite of these major applications, many issues are still to be addressed to perform effective numerical simulations of Nucleate Boiling at the industrial scale. Indeed, the numerical simulations of nucleate boiling is made difficult by the multiscale coupling between different phenomena. The range of spatial scales involved in the whole process extends from ~ 10-100 nm, which is the typical size of the so-called micro-region, to several meters or even more for large industrial devices. Between these two extreme scales, several other typical scales can be introduced as the thickness of a micro-layer, which is approximately 1-10 μm or the bubble diameter which usually ranges from 1~mm to 10~mm in most cases. As a result, despite the continuous and huge progress in scientific computing during the last decades a complete description based on first principle equations of all these phenomena remains unpractical for large scale applications. Therefore, different subgrid modelling strategies have to be developed in order to integrate the effect of the smallest scales in achievable large scale computations. The purpose of this presentation is to present different modelling strategy for nucleate boiling numerical simulations going from integrated micro-region model coupled to Direct Numerical Simulation until large scale models that should be relevant in the future for numerical simulations in industrial configurations.