The Evaporating Falling Film On Horizontal Tubes

A model of combined boiling and evaporation of liquid films on horizontal tubes was developed. Specifically, this work was directed toward developing a heat transfer model applicable to the design of horizontal tube falling film evaportors for OTEC. The heat transfer process is modelled as combined boiling and evaporation of the liquid film. In modelling the behavior of single tubes special account is taken of heat transfer in the initial thermal developing region of the film. Predictions were found to agree favorably with the published experimental data for boiling and evaporation of thin water films on single horizontal tubes. The predicted upper and lower limits of heat transfer for ammonia on a vertical bank of plain horizontal tubes are 5.4 kW/m2-K and 3.1 kW/m2-K, respectively. The upper limit will be approached when the influence of between-tube evaporation and turbulence created by the liquid falling from one tube to the next are important. For an OTEC evaporator with plain tubes, the upper and lower limits of the overall U are 2.33 kW/m2-K and 1.82 kW/m2-K, respectively. With ammonia-side boiling enhancement, the overall U can be increased to about 3.8 kW/m2-K.

Heat and mass transfer is the core science for many industrial processes as well as technical and scientific devices. Automotive, aerospace, power generation (both by conventional and renewable energies), industrial equipment and rotating machinery, materials and chemical processing, and many other industries are requiring heat and mass transfer processes. Since the early studies in the seventeenth and eighteenth centuries, there has been tremendous technical progress and scientific advances in the knowledge of heat and mass transfer, where modeling and simulation developments are increasingly contributing to the current state of the art. Heat and Mass Transfer - Advances in Science and Technology Applications aims at providing researchers and practitioners with a valuable compendium of significant advances in the field.

This long awaited second edition of a popular textbook has a simple and direct approach to the diversity and complexity of food processing. It explains the principles of operations and illustrates them by individual processes. The new edition has been enlarged to include sections on freezing, drying, psychrometry, and a completely new section on mechanical refrigeration. All the units have been converted to SI measure. Each chapter contains unworked examples to help the student gain a grasp of the subject, and although primarily intended for the student food technologist or process engineer, this book will also be useful to technical workers in the food industry

Falling Liquid Films gives a detailed review of state-of-the-art theoretical, analytical and numerical methodologies, for the analysis of dissipative wave dynamics and pattern formation on the surface of a film falling down a planar inclined substrate. This prototype is an open-flow hydrodynamic instability, that represents an excellent paradigm for the study of complexity in active nonlinear media with energy supply, dissipation and dispersion. It will also be of use for a more general understanding of specific events characterizing the transition to spatio-temporal chaos and weak/dissipative turbulence. Particular emphasis is given to low-dimensional approximations for such flows through a hierarchy of modeling approaches, including equations of the boundary-layer type, averaged formulations based on weighted residuals approaches and long-wave expansions. Whenever possible the link between theory and experiment is illustrated, and, as a further bridge between the two, the development of order-of-magnitude estimates and scaling arguments is used to facilitate the understanding of basic, underlying physics. This monograph will appeal to advanced graduate students in applied mathematics, science or engineering undertaking research on interfacial fluid mechanics or studying fluid mechanics as part of their program. It will also be of use to researchers working on both applied, fundamental theoretical and experimental aspects of thin film flows, as well as engineers and technologists dealing with processes involving isothermal or heated films. This monograph is largely self-contained and no background on interfacial fluid mechanics is assumed.

This excellent volume combines a great deal of data only previously available from many different sources into a single, informative volume. It presents evaporation technology as it exists today. Although evaporation is one of the oldest unit operations, it is also an area with dramatic changes in the last quarter century. Although other methods of separation are available, evaporation remains the best process for many applications. All factors must be evaluated in order to select the best evaporator type. This book will be extremely useful in evaluating and deciding which evaporation technology will meet a particular set of requirements.