CFD model of wall boiling including a population balance model

In this work the present capabilities of CFD for wall boiling are investigated. The computational model is based on the Euler / Euler two-phase flow description with heat flux partitioning. In the framework of interpenetrating continua the exchange of momentum, mass and energy between the phases are essential. The description of the interfacial morphology plays an important role. In the actual work a population balance model for the description of the gaseous phase considering bubble coalescence, bubble fragmentation and bubble size changes caused by condensation of evaporation is applied. The wall boiling model is coupled with the population balance model.
For the demonstration, DEBORA tests (Garnier, 2001) were used. In the DEBORA tests in a vertical tube Dichlorodi¬fluoromethane (R12) was heated from the side walls. Radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size were measured.
The results show the potential of this model approach which is able to describe the observed bubble size increase after leaving the wall as well as the change of gas volume fraction profile from wall to core peaking with increasing inlet temperature.