Simulation of nucleate boiling flow using a multiphase mixture modelling approach

Effective prediction of nucleate boiling flows in many engineering application has become very important in order to avoid overheating of materials that could ultimately result in failure. In the present study, nucleate boiling is modelled using a multi-phase mixture modelling approach within the framework of a general computational fluid dynamics code VECTIS-MAX, where the mixture equations for the momentum, energy and turbulence along with the liquid and vapour volume fraction equations are solved. The nucleate boiling model builds on the mechanistic model of Kurul and Podowskis Rensselaer Polytechnic Institute and is used to predict the wall heat flux as well as its partitioning into three essential components, namely the single-phase forced convection, the wall quenching (transient conduction) and the evaporation heat flux. The evaporation heat flux then determines the vapour mass rate generated at the wall. The mass transfer due to evaporation or condensation in the bulk flow is calculated with mass transfer model. Due to large density variations associated with phase change, the problem of pressure, velocity and density coupling is also addressed. The nucleate boiling model is validated against experimental data as well as in a real engine case.