Hydrodynamics And Heat Transfer During Boiling In High Pressure Boilers

Over the past two decades, two-phase flow and heat transfer problems associated with two-phase phenomena have been a challenge to many investigators. Two-phase flow applications are found in a wide range of engineering systems, such as nuclear and conventional power plants, evaporators of refrigeration systems and a wide vari ety of evaporative and condensive heat exchangers in the chemical industry. This publication is based on the invited lectures presented at the NATO Advanced Research Workshop on the Advances in Two-Phase Flow and Heat Transfer. The Horkshop was attended by more than 50 leading scientists and practicing engineers who work actively on two-phase flow and heat transfer research and applications in dif ferent sectors (academia, government, industry) of member countries of NATO. Some scientific leaders and experts on the subject matter from the non-NATO countries were also invited. They convened to discuss the state-of-the-art in two-phase flow and heat transfer and formulated recommendations for future research directions. To achieve these goals, invited key papers and a limited number of contributions were presented and discussed. The specific aspects of the subject were treated in depth in the panel sessions, and the unresolved problems identified. Suitable as a practical reference, these volumes incorporate a systematic approach to two-phase flow analysis.

Stable boiling in a rotating cylindrical annulus with continuous through-flow of water was obtained at heat fluxes as high as 818 000 Btu/(hr)(ft^2) (2. 58 MW/m^2) at atmospheric pressure. Incipient- and nucleate -boiling heat -transfer coefficients were obtained at accelerations up to 400 g's. Measurements were made of void fractions, radial temperature profiles, and wall pressures in the boiling fluid. Convective secondary-flow cells and fluid temperature inversions were revealed. Increased fluid thicknesses increased heat-transfer coefficients, but inlet liquid subcooling had no effect. Coefficients increased with acceleration at low heat fluxes, but at high fluxes varied less than the usual data scatter.

Annular Two-Phase Flow presents the wide range of industrial applications of annular two-phase flow regimes. This book discusses the fluid dynamics and heat transfer aspects of the flow pattern. Organized into 12 chapters, this book begins with an overview of the classification of the various types of interface distribution observed in practice. This text then examines the various regimes of two-phase flow with emphasis on the regions of occurrence of the annular flow regime. Other chapters consider the single momentum and energy balances, which illustrate the differences and analogies between single- and two-phase flows. This book discusses as well the simple modes for annular flow with consideration to the calculation of the profile of shear stress in the liquid film. The final chapter deals with the techniques that are developed for the measurement of flow pattern, entrainment, and film thickness. This book is a valuable resource for chemical engineers.

The collection consists of articles expounding the results of a significant number of investigations in the region of heat exchange during boiling and condensation and on the hydraulics of liquidgas mixtures.