Energy and the Environment Environmental Science and Technology Library VOLUME 15 The titles published in this series are listed at the end of this volume. Energyand the Environment Edited by Adrian Bejan Duke University, Durham, Ne, U. Peter Vadâsz University of Durban-Westville, South Africa and Detlev G. Kroger University of Stellenbosch, South Africa SPRINGER-SCIENCE+BUSINESS MEDIA, B.
Catalogue record for this book is available from the Library of Congress. ISBN 978-94-010-5943-5 ISBN 978-94-011-4593-0 (eBook) DOI 10.1007/978-94-011-4593-0 Cover design: River basin dendrites generated by the constructal principle ofthermodynamic optimization subject to constraints (see pp. 21-22 in this book; also M. Bejan, Fractals, VoI.
Printed an acid-free paper AII Rights Reserved © 1999 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1999 Softcover reprint of the hardcover 1st edition 1999 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, includ ing photocopying, record ing or by any information storage and retrieval system, without written permission from the copyright owner. Table of Contents fuf~ Vll M. MORAN Exergy analysis, costing, and assessment of environmental impact 1 ABEJAN The method of entropy generation minimization 11 AE. BERGLES Advanced enhancement for heat exchangers 23 AD.
KRAUS Optimization of finned arrays 37 RK. BENFORADO Opportunities for heat exchanger applications in environmental systems 49 F.R HOWELL Inverse design of energy and environmental systems 65 B.WEBB Advances in modeling radiative transport in high temperature gases 75 T. TONG and A TARAFDAR Heat transfer in porous radiant burners 89 R VISKANTA Radiation heat transfer in materials processing and manufacturing 101 D.A ZUMBRUNNEN The production of improved plastic materials by chaotic mixing of polymer melts recovered from environmental waste 113 D. WEINER Perspectives and directions of the electric power industry in the next millennium 125 P.
VADAsz The impact of energy storage technologies on the environment 135 S.OLEK Potential impact of pumped energy storage on the lower reservoir aquatic ecology 149 D. KROGER Development of industrial cooling systems and their impact on the environment 163 v vi G. STIEGER Advances in the measurement of convective heat transfer coefficient in gas turbine applications 175 J. YOU Thermally affected flows in power plants 185 A.
VOSLOO Advances in the technology of liquid synfuel production from coal 199 D. NIELD Some geophysical problems involving convection in porous media with application to energy and the environment 209 J. LAGE Convection of hazardous substances through rock fractures and faults 217 C. BRAESTER Radioactive waste repositories in fractured rocks formations: hydrodynamic aspects 229 J.
MEYER Evaluation of energy efficient and environmentally acceptable pure and zeotropic refrigerants in air-conditioning and refrigeration 239 G. ROUSSEAU Application of heat pumps in the South African commercial seCtor 247 Index 261 Preface This book brings together the work of some of the world leaders on energy research and the environmental impact of energy technologies. "Energy" and "environment" are keywords for two of the most important directions in contemporary thermal sciences. Many new advances and reassessments of old results have been made in the 1980s and 1990s.
This book provides a bird's-eye view of the current state of the art, and in what directions the field is expanding. Most representative of these new developments is the field of engineering thermodynamics and energy engineering. This field has experienced a real revolution in the two decades since the energy crisis. The renewed emphasis on higher efficiencies, energy-resources conservation and environmental impact of energy systems has transformed the discipline and practice of thermodynamics.
The methods of exergy analysis, entropy generation minimization, and thermoeconomics are the most visible results of this revolution. In exergy or availability analysis the engineer uses the second law of thermodynamics (in addition to the first law) to establish theoretical limits to the design of proposed energy systems and measures of the departure of real systems ,from their theoretical limits. Losses-their size and distribution through a complex system-are determined on a rigorous scientific basis. The minimization of these losses is the objective of thermodynamic optimization (entropy generation minimization).
Losses are measured in terms of exergy destruction or entropy generation, and are expressed as functions of the physical parameters (geometry, size, materials) of the device. Their minimization is carried out subject to the constraints that account for the size of the device and its time of operation. In thermoeconomics the thermodynamic losses are combined with other costs into a comprehensive cost function that is subjected to constrained minimization. The three methods are now the standard in modern thermal engineering education and practice, and are ideally suited for computer-aided analysis, design and optimization.
This book is timely for two reasons. First, these new methodologies have been developed through individual papers at annual conferences, mainly in the 1980s and 1990s. This book puts these methodologies in perspective, through a team of highly qualified authors and a comprehensive list of contributed chapters. Another direction that defines what is modern in thermal sciences is the area of heat transfer augmentation (enhancement, intensification).
This is an extremely important science and art. Its objective is to improve thermal contact between heat-exchanging entities, for example, between a fluid and a solid wall. The augmentation methods that have been devised over the years are extremely diverse: special wall structures (roughness, fins, dimples), wall or fluid motion (vibrations, pressure-wave forcing), fluid additives, wall coatings, and mechanical accessories such as wall scrapers and vortex generators. vii viii Although the heat transfer augmentation field is young, it is developed enough so that it can be reviewed systematically.
This book is an ideal vehicle for providing this view, especially since a large segment of the world power generation industry is based on burning coal in power plants that require highly efficient and reliable heat-exchange equipment. Augmentation techniques are generally applicable in heat exchanger design, in fact, they form the backbone-the limiting technology-in the development of compact heat exchangers. Another extremely important application of heat transfer augmentation is in the efficient cooling of electronic packages, where, again, the miniaturization evolution is ruled by the progress made on heat transfer augmentation methods. There are at least two major environmental areas that are covered in this book, because they go hand-in-hand with the energy issues described until now.
The first is the environmental impact of energy systems. To bring this issue and make it an integral part of the optimization of the enregy system is one of the contributions of thermoeconomics. The local degradation of the environment is one of the important costs that must be included in thermoeconomic optimization. The environment-its properties, and how they vary in time-plays also a central role in exergy analysis.
The very concept of exergy requires an unambiguous understanding of the state of the environment, and whether this state will be altered by the operation of the power plant that is being designed. The second environmental area covered in this book is convection in porous media. This field experienced an astonishing growth during the past decade, and now is one of the most active in thermal sciences. Its developmment is comparable with that of classical convection (transport by the flow of a pure flluid): governing principles are in place, experimental data continue to stimulate improvements in the governing principles, and there is an abundance of practical applications.
From an environmental standpoint, the fundamental aspects that are covered in this book are relevant to understanding the spreading of contaminated fluids through the ground, the leakage of heat through the walls of buildings, and the flow of geothermal fluids through the earth's porous crust. The research material selected in this book has been used in a week-long workshop format, in front of an audience of researchers and practicing engineers. The venue was the USA-RSA Energy and Environment Workshop, held on June 8-12, 1998, at the University of Durban-Westville, South Africa. The authors and the participants in this workshop greatfully acknowledge the support received from the National Foundation (USA), the Foundation for Research Development (RSA), the University of Durban- Westville and Duke University.
They also acknowledge the substantial assistance provided by Dr. Govender in the organization of the workshop. This book was prepared by Deborah Alford at Duke University. August 1998 Durham Adrian Bejan Durban Peter Vadasz Stellenbosch Detlev G.
Kroger ix Acknowledgement The editors acknowledge with gratitude the support received from the following colleagues in organizing the Energy and the Environment workshop: Professor Mapule F. Ramashala, Vice-Chancellor and Principal, University of Durban-Westville, South Africa. Hannekie Botha, Science Liaison Centre, Foundation for Research Development, South Africa. Jill Sawers, Manager: Competitive Industry, Foundation for Research Development, South Africa.
Ganasagren Govender, Workshop Secretary, University of Durban- Westville, South Africa Ms. Tsuchitani, Division of International Programs, National Science Foundation, USA Professor Ashley F. Emery, Thermal Transport and Thermal Processing Program, National Science Foundation, USA Professor F. Hadley Cocks,' Chairman, Department of Mechanical Engineering and Materials Science, Duke University, USA Professor Devendra P.
Garg, Department of Mechanical Engineering and Materials Science, Duke University, USA A. EXERGY ANALYSIS, COSTING, AND ASSESSMENT OF ENVIRONMENTAL IMPACT M. MORAN The Ohio State University Department of Mechanical Engineering Columbus, OH 43210, USA 1. Introduction The method of exergy analysis enables the location, cause, and true magnitude of energy resource waste and loss to be determined.
Such information can be used in the design of new energy-efficient systems and for improving the performance of existing systems. Exergy analysis also provides insights that elude a purely first-law approach. For example, on the basis of first-law reasoning alone, the condenser of a power plant may be mistakenly identified as the component primarily responsible for the plant's seemingly low overall performance. An exergy analysis correctly reveals not only that the condenser loss is relatively unimportant, but also that the steam generator is the principal site of thermodynamic inefficiency owing to combustion and heat transfer irreversibilities within it.
When exergy concepts are combined with principles of engineering economy, the result is known as thermoeconomics. Thermoeconomics allows the real cost sources at the component level to be identified: capital investment costs, operating and maintenance costs, and the costs associated with the destruction and loss of exergy. Optimization of thermal systems can be achieved by a careful consideration of such cost sources. From this perspective thermoeconomics is exergy-aided cost minimization.
Discussions of exergy analysis and thermoeconomics are provided in (1-4). Defining Exergy An opportunity for doing work exists whenever two systems at different states are placed in communication because, in principle, work can be developed as the two are allowed to come into equilibrium. When one of the two systems is a SUitably idealized system called an exergy reference environment or simply, an enVironment, and the other is some system of interest, exergy is the maximum theoretical useful work (shaft work or electrical work) obtainable as the systems interact to equilibrium, heat transfer occurring with the environment only. (Alternatively, exergy is the minimum theoretical useful work reqUired to form a quantity of matter from substances present in the environment and to bring the matter to a specified state.) Exergy is a measure of the departure of the state of the system from that of the environment, and is therefore an attribute of the system and environment together.
Once the environment is specified, however, a value can be assigned to exergy in terms of property values for the system only, so exergy can be regarded as an extensive property of the system. Exergy can be destroyed and generally is not conserved. A limiting case is when exergy would be completely destroyed, as would occur if a system were to come into equilibrium with the environment spontaneously with no provision to obtain work. The capability to develop work that existed initially would be I A.
Bejan et al.), Energy and the Environment, 1-10. © 1999 Kluwer Academic Publishers.MORAN completely wasted in the spontaneous process. Moreover, since no work needs to be done to effect such a spontaneous change, the value of exergy can never be negative.