A general expression which can be used either for predicting the average volumetric concentration or for analyzing and interpreting experimental data is derived. The analysis takes into account both the effect of nonuniform flow and concentration profiles as well as the effect of the local relative velocity between the phases. The first effect is taken into account by a distribution parameter, whereas the latter is accounted for by the weighted average drift velocity. Both effects are analyzed and evaluated. The results predicted by the analysis are compared with experimental data obtained for various two-phase flow regimes, with various liquid-gas mixtures in adiabatic, vertical flow over a wide pressure range. Good agreement with experimental data is shown.

Drag coefficient and relative motion correlations for dispersed two-phase flows of bubbles, drops, and particles were developed from simple similarity criteria and a mixture viscosity model. The results are compared with a number of experimental data, and satisfactory agreements are obtained at wide ranges of the particle concentration and Reynolds number. Characteristic differences between fluid particle systems and solid particle systems at higher Reynolds numbers or at higher concentration regimes were successfully predicted by the model. Results showed that the drag law in various dispersed two-phase flows could be put on a general and unified base by the present method. MAMORU ISHIlextensively studied, because of their practical importance. The success of the present correlation at up to the highest concentration range for spherical solid particle systems was accomplished by introducing the maximum packing in the mixture viscosity relation. This was a definite improvement over the existing correlations.It is also noted that the present model is sufficient up to the foam or dense packing regime, with the concentration ranging from 0.5 to 0.95 for both bubbly and droplet flows. These comparisons indicated that the postulated drag similarity law based on the mixture viscosity concept was appropriate. Therefore, the drag law governing the motions of bubbles, drops and particles in various dispersed twophase flows can be explained by a unified and consistent model developed here.

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. UNIVEEISITY OF CALIFOPJfIA, LOS ANGELES .Hydrod-ynamic Aopects ,of Boiling Heat Transfer A dissertation submitted in p a r t i a l satisfaction of the requirements for the degree Doctor of Phflosophy in Engineering

Analytical expressions for bubble radii and growth rates derived by the authors are applied in an analysis of surface boiling at high heat transfer rates. It is shown that the product of bubble radius and radial velocity is a constant, independent of the bubble radius. This circumstance permits the formulation of a Reynolds number for the flow in the thin superheated liquid layer adjacent to the heating surface. The result of the analysis is then applied to maximal heat transfer rates in pool boiling.

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