M.Sc Thesis


M.Sc StudentAvni Or
SubjectA Theoretical Study of Flash-Boiling under Intense Radiation
Constraints
DepartmentDepartment of Mechanical Engineering
Supervisor PROF. Eran Sher
Full Thesis textFull thesis text - English Version


Abstract

The limits for the onset of sudden homogeneous nucleation in liquids containing heterogeneous impurities were investigated. The relevant processes, which include the constant isobaric heating, nuclei formation, heat absorption by the liquid, and heat consumed for evaporation have been analyzed using classical nucleation theory, hydrodynamic conservation equations, and simple thermodynamic relations. Numeric solution for bubble growth in a uniformly heated metastable liquid was derived and used for the prediction of vapor generation around the heterogeneous sites. Special attention is drawn to the transition between two boiling regimes, and a clear distinction between them was derived when accounting for the vapor formation around the heterogeneous centers. An analytic criterion for the onset of homogeneous nucleation in water is proposed for any given system of real liquid, based upon the measurable heterogeneous ready centers.  Numerous results are presented for water at atmospheric pressure, demonstrating the effect of variable heating rates and the heterogeneity of the system on the boiling process. Correlations for the critical heating rates were developed, quantifying the influence of the heterogeneity of the system on the maximum attainable superheats before the inception of massive nucleation. The present work thus proposes a grounded and simple-to-use model for the prediction of homogeneous nucleation in non-ideal real liquid.