Energy and the Environment PDF
Preview Energy and the Environment
Energy and the Environment Environmental Science and Technology Library VOLUME 15 Thetitlespublishedinthisseriesarelistedattheendofthisvolume. Energyand the Environment Edited by Adrian Bejan Duke University, Durham, Ne, U.S.A. Peter Vadâsz University of Durban-Westville, South Africa and Detlev G. Kroger University of Stellenbosch, South Africa SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. A C.I.P. 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.R. Errera & A. Bejan, Fractals, VoI. 6, No. 3, pp. 245-261, 1998). 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.J. MORAN Exergy analysis,costing,and assessmentofenvironmentalimpact 1 ABEJAN The methodofentropygenerationminimization 11 AE. BERGLES Advancedenhancementforheatexchangers 23 AD. KRAUS Optimizationoffinned arrays 37 RK. SHAH, B. THONON, D.M. BENFORADO Opportunitiesforheatexchangerapplicationsinenvironmentalsystems 49 F. FRAN<;A,C. LAN, J.R HOWELL Inversedesignofenergyandenvironmentalsystems 65 B.W.WEBB Advancesinmodelingradiativetransportinhightemperaturegases 75 T.W. TONGandA TARAFDAR Heattransferinporousradiantburners 89 R VISKANTA Radiationheattransferinmaterialsprocessingandmanufacturing 101 D.AZUMBRUNNEN Theproductionofimprovedplasticmaterials bychaoticmixingof polymermeltsrecoveredfromenvironmentalwaste 113 D.WEINER Perspectivesanddirectionsoftheelectricpowerindustryinthe next millennium 125 P. VADAsz Theimpactofenergystoragetechnologiesontheenvironment 135 S.OLEK Potentialimpactofpumpedenergy storageonthelowerreservoir aquaticecology 149 D.G. KROGER Developmentofindustrial coolingsystemsandtheirimpactonthe environment 163 v vi G.DJ. SMITH, G.C. SNEDDEN, R.D. STIEGER Advancesinthemeasurementofconvectiveheattransfercoefficient ingas turbineapplications 175 J.H. KIMand K.-W. YOU Thermallyaffectedflows inpowerplants 185 A.C. VOSLOO Advancesinthetechnologyofliquidsynfuelproductionfrom coal 199 D.A. NIELD Somegeophysicalproblems involvingconvection in porousmedia withapplicationtoenergyandtheenvironment 209 J.L. LAGE Convectionofhazardoussubstancesthroughrockfractures andfaults 217 C. BRAESTER Radioactivewasterepositoriesinfracturedrocksformations: hydrodynamicaspects 229 J.P. MEYER Evaluationofenergyefficientand environmentallyacceptablepure andzeotropicrefrigerantsinair-conditioningandrefrigeration 239 G.P. GREYVENSTEIN and P.G. ROUSSEAU Applicationofheatpumps in theSouthAfricancommercial seCtor 247 Index 261 Preface Thisbookbringstogethertheworkofsomeoftheworldleadersonenergy researchand the environmental impact of energy technologies. "Energy" and "environment" are keywords for two ofthe most important directions in contemporary thermal sciences. Many new advances and reassessments ofoldresults have been madein the 1980sand 1990s. This bookprovides a bird's-eye viewofthe currentstateofthe art, and in what directionsthefield isexpanding. Most representative of these new developments is the field of engineering thermodynamicsandenergyengineering. Thisfield hasexperiencedarealrevolution in the two decades since the energy crisis. The renewed emphasis on higherefficiencies, energy-resources conservation and environmental impact of energy systems has transformed the discipline and practice ofthermodynamics. The methods of exergy analysis, entropy generation minimization, and thermoeconomics are the most visible results ofthis revolution. In exergy or availability analysis the engineer uses the second law of thermodynamics (inaddition to thefirst law) to establishtheoretical limitsto thedesign ofproposed energy systems and measures ofthe departure ofreal 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 ofthermodynamic optimization (entropy generation minimization). Losses aremeasured interms ofexergydestructionorentropy generation, and areexpressedas functions ofthe physical parameters (geometry, size, materials) ofthe device. Their minimization is carried out subject to the constraints that account for the size ofthe device and its time ofoperation. 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 engineeringeducation and practice, and are ideally suited for computer-aided analysis, designandoptimization. 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 ofhighly qualifiedauthorsandacomprehensivelistofcontributedchapters. Anotherdirection thatdefines whatis moderninthermalsciencesis theareaofheat 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 afluid and asolid 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 vortexgenerators. vii viii Although the heat transfer augmentation field is young, it is developed enough so that itcan bereviewed systematically. This book is an ideal vehicle for providing this view, especially since alarge segmentofthe world powergeneration industry is based on burningcoal in powerplants thatrequire highly efficientand reliable heat-exchange equipment. Augmentationtechniquesaregenerallyapplicablein heatexchangerdesign, 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. Thefirst 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 ofthe environment is one ofthe important costs that must be included in thermoeconomic optimization. The environment-its properties, andhow theyvary intime-plays alsoacentralroleinexergyanalysis. The very concept of exergy requires an unambiguous understanding of the state of the environment, and whether this state will be altered by the operationofthe powerplant thatisbeingdesigned. Thesecondenvironmental areacovered in this bookisconvection inporousmedia. This field experienced an astonishinggrowth during thepastdecade, and now isoneof the most active in thermal sciences. Its developmment is comparable with that of classicalconvection (transportby theflow ofapureflluid): governingprinciples are in place, experimental data continue to stimulate improvements in the governing principles, and there is an abundanceofpractical applications. From an environmental standpoint, the fundamental aspects that are covered in this book are relevant to understanding the spreading of contaminatedfluids through the ground, the leakage of heat through the walls of buildings, and the flow of geothermal fluids through the earth's porouscrust. The research material selectedin this bookhas been used in aweek-long workshop format, infront ofan audienceofresearchers and practicingengineers. The venue was the USA-RSA Energy and Environment Workshop, held on June 8-12, 1998, at the University ofDurban-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 ofDurban Westville and Duke University. They also acknowledge the substantial assistance providedbyDr.G.Govenderin theorganizationoftheworkshop. ThisbookwaspreparedbyDeborahAlfordatDukeUniversity. August 1998 Durham AdrianBejan Durban Peter Vadasz Stellenbosch DetlevG. 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. Ms. Hannekie Botha, Science Liaison Centre, Foundation for Research Development, South Africa. Ms. Jill Sawers, Manager: Competitive Industry, Foundation for Research Development, South Africa. Dr. Ganasagren Govender, Workshop Secretary, University ofDurban Westville, South Africa Ms. Patricia J. Tsuchitani, Division ofInternational 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 ofMechanical Engineering and Materials Science, Duke University, USA A.B.,P.V. &D.G.K. EXERGYANALYSIS, COSTING, AND ASSESSMENT OF ENVIRONMENTAL IMPACT M.J. MORAN TheOhioState University DepartmentofMechanicalEngineering Columbus, OH43210, USA 1. Introduction The method ofexergy analysis enables the location, cause, and true magnitude of energyresourcewasteandlosstobe 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 atthe componentlevelto be identified: capital investmentcosts, 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 ofexergyanalysis and thermoeconomics are provided in (1-4). 2. DefiningExergy An opportunityfor doingworkexistswhenevertwo systems at different states are placedincommunicationbecause, in principle, work can be developed as the two are allowed to come into equilibrium. When one ofthe 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 ofmatter from substances present in the environment and to bring the mattertoa specifiedstate.) Exergyisa measure ofthe departure ofthe state ofthe systemfrom that ofthe environment, and is therefore an attribute ofthe system and environment together. Once the environment is specified, however, a value canbeassignedto exergyinterms ofpropertyvaluesfor thesystemonly, so exergy can be regardedasan extensive propertyofthesystem. 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. Bejanetal. (eds.), EnergyandtheEnvironment, 1-10. © 1999KluwerAcademicPublishers.
The list of books you might like
