Analysis Of Heat Transfer In Horizontal Tube Falling Film Evaporators

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 book collects current scientific information on advanced technologies and management practices associated with the desalination industry in the Middle East and elsewhere around the world. The book opens with introductory chapter which briefly recounts the history of desalination, and describes the current state of development in the field. Part I: Desalination Systems includes ten chapters which describe a variety of techniques and designs intended not only to minimize the impact of desalination, but also to save energy and use natural resources to maximize the output of integrated desalination systems. Among the highlights are a chapter on the use of ceramic membrane technology for sustainable oil water production; a case study on the use of solar heating systems in desalination technology in Oman; discussion of fouling and its effect on design and performance of desalination systems; a review of shore approaches and sea-lines with case studies from Australia and Germany; and a discussion of the integration of desalination technology with renewable energy for climate change abatement in the Middle East and North Africa region. Part II: Environmental Systems includes among others a chapter on regulating the use of water resources and desalination technology on a regional scale reducing the carbon footprint of desalination, with examples from Australia; a description of desalination for irrigation in the Souss Massa region in the south of Morocco; a study of the impact of the coastal intake environment on operating conditions of thermal desalination plants in the United Arab Emirates; a discussion of hydrodynamic and thermal dispersion modeling of the effluent in a coastal channel, with a case study from Oman; and a mathematical model study of effluent disposal from a desalination plant in the marine environment at Tuticorin in India. The book aims to inspire developments in desalination technologies which are specifically aimed at reducing energy consumption and cost, and minimizing environmental impact.

This unique and comprehensive text considers all aspects of heat exchanger fouling from the basic science of how surfaces become fouled to very practical ways of mitigating the problem and from mathematical modelling of different fouling mechanisms to practical methods of heat exchanger cleaning. The problems that restrict the efficient operation of equipment are described and the costs, some of them hidden costs, that are associated with the fouling of heat exchangers are discussed. Some simple concepts and models of the fouling processes are presented as part of the introduction to the subject. Advice on the selection, design, installation and commissioning of heat exchangers to minimise fouling is given. A large part of the text is devoted to the use of chemical and other additives to reduce or eliminate the problem of fouling. Another large section is designed to give information on both on-line and off-line cleaning of heat exchangers. One of the difficulties faced by designers and operators of heat exchangers is anticipating the likely extent of fouling problems to be encountered with different flow streams. Another large section addresses the question and describes methods that have been used in attempting to define fouling potential. The book concludes with a chapter on how fouling information can be obtained using plant data, field tests and laboratory studies.

This broad-based book covers the three major areas of Chemical Engineering. Most of the books in the market involve one of the individual areas, namely, Fluid Mechanics, Heat Transfer or Mass Transfer, rather than all the three. This book presents this material in a single source. This avoids the user having to refer to a number of books to obtain information. Most published books covering all the three areas in a single source emphasize theory rather than practical issues. This book is written with emphasis on practice with brief theoretical concepts in the form of questions and answers, not adopting stereo-typed question-answer approach practiced in certain books in the market, bridging the two areas of theory and practice with respect to the core areas of chemical engineering. Most parts of the book are easily understandable by those who are not experts in the field. Fluid Mechanics chapters include basics on non-Newtonian systems which, for instance find importance in polymer and food processing, flow through piping, flow measurement, pumps, mixing technology and fluidization and two phase flow. For example it covers types of pumps and valves, membranes and areas of their use, different equipment commonly used in chemical industry and their merits and drawbacks. Heat Transfer chapters cover the basics involved in conduction, convection and radiation, with emphasis on insulation, heat exchangers, evaporators, condensers, reboilers and fired heaters. Design methods, performance, operational issues and maintenance problems are highlighted. Topics such as heat pipes, heat pumps, heat tracing, steam traps, refrigeration, cooling of electronic devices, NOx control find place in the book. Mass transfer chapters cover basics such as diffusion, theories, analogies, mass transfer coefficients and mass transfer with chemical reaction, equipment such as tray and packed columns, column internals including structural packings, design, operational and installation issues, drums and separators are discussed in good detail. Absorption, distillation, extraction and leaching with applications and design methods, including emerging practices involving Divided Wall and Petluk column arrangements, multicomponent separations, supercritical solvent extraction find place in the book.