Forced convective boiling of binary mixtures in annular flow. I: Liquid phase mass transport. II: Heat and mass transfer (Q5931881)

The authors give a description of forced convective boiling of binary mixtures in annular vertical pipes. The model accounts for high mass qualities, where the nucleate boiling is expected to be greatly suppressed by forced convection. In part I, a model for droplet interchange, based on a set of correlation equations for pure fluids, is presented and embedded into a model for solving the hydrodynamics of annular flow. Part II deals with heat and mass transfer, and uses the Colburn-Drew model.NEWLINENEWLINENEWLINEThe authors show that, in the annular flow regime, the mechanism of droplet entrainment and deposition coupled with the preferential evaporation of the more volatile component from the liquid film causes that the local concentration in the liquid film is different from that in the entrained droplets. It is also found that the combined effect of mass transfer resistance and droplet interchange gives rise to interfacial temperatures higher than a mean temperature obtained via the calculation of local flow enthalpy (mean equilibrium temperature). Thus, one observes increased wall temperatures.