dept. of mechanical engineering - uevora.pt · dept. of mechanical engineering and materiais...
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..Adrian BejanDuke UniversityDept. of Mechanical Engineering
and MateriaIs ScienceDurham, NC [email protected]
Ibrahim Dincer
University of Ontario Instituteof Technology
School of Manufacturing EngineeringOshawa, Ontario LIH [email protected]
Sylvie LorenteLaboratoire Matériaux et
Durabilité des ConstructionsInstitut National des Sciences AppliquéesDépartement de Génie Civil31077 [email protected]
Antonio MiguelUniversidade de ÉvoraDepartamento de FisicaColegio Luis Verney7000-671 ÉvoraPORTUGAL
Heitor ReisUniversidade de ÉvoraDepartamento de FisicaColegio Luis Verney7000-671 É[email protected]
Library of Congress Cataloging-in-Publication DataPorous and complex flow structures in modern technologies / Adrian Bejan . .. [et al.].
p. cm.Includes bibliographical references and index.ISBN 0-387-20225-0 (alk. paper)1. Fluid dynamics. 2. Porous materials--Fluid dynamics. I. Bejan, Adrian, 1948-
TA357.P6952004620.1'06--dc22 2003060456
ISBN 0-387-20225-0 Printed on acid-free paper.
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Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 Porous Media FundamentaIs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.1 Structure..............................................
1.1.1 Microporous Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.1.2 Mesoporous Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.1.3 Macroporous Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Mass Conservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.3 Darcy Flow and More Advanced Models . . . . . . . . . . . . . . . . . . .1.4 Energy Conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.5 Heat and Mass Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.1 Fluid Flow ......................................1.5.2 Heat Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 FIows in Porous Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1 Use Simple Methods First . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2 Scale Analysis of Forced Convection Boundary Layers . . . . . . .2.3 Sphere and Cylinder with Forced Convection. . . . . . . . . . . . . . .2.4 Channels with Porous Media and Forced Convection . . . . . . . .2.5 Scale Analysis of Natural Convection Boundary Layers . . . . . .2.6 Thermal Stratification and Vertical Partitions . . . . . . . . . . . . . .2.7 Horizontal Walls with Natural ConvectioIÍ . . . . . . . . . . . . . . . . .2.8 Sphere and Horizontal Cylinder with Natural Convection . . . .2.9 Enclosures Heated from the Side .........................2.10 Enclosures Heated from Below ... . . . . . . . . . . . . . . . . . . . . . . . .2.11 The Method of Intersecting the Asymptotes ...............
2.11.1 The Many Counterflows Regime. . . . . . . . . . . . . . . . . . . .2.11.2 The Few Plumes Regime. . . . . . . . . . . . . . . . . . . . . . . . . .2.11.3 The Intersection of Asymptotes . . . . . . . . . . . . . . . . . . . .
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3 Energy Engineering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 673.1 Thermodynamics Fundamentais: Entropy Generation or
Exergy Destruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.2 Exergy Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3 Thermal Energy Storage ................................3.4 Sensible Heat Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.5 Aquifer Thermal Energy Storage . . . . . . . . . . . . . . . . . . .3.6 Latent Heat Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.7 Cold Thermal Energy Storage . . . . . . . . . . . . . . . . . .. . . . . . . . . .3.8 Porous Medium Model of a Storage System with
Phase-Change Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1003.9 Fuel Cell Principies and Operation. . . . . . . . . . . . . . . . . . . . . . .. 1053.10 Fuel Cell Structure and Performance . . . . . . . . . . . . . . . . . . . . .. 109
3.11 The Concept of Exergy-Cost-Energy-Mass (EXCEM)Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 119
3.12 Exergy, Environment, and Sustainable Development 120
67717680878996
4 Environmental and Civil Engineering . . . . . . . . . . . . . . . . . . . .. 1254.1 The Energy-Environment lnterface . . . . . . . . . . . . . . . . . . . . . .. 1254.2 Wakes: Concentrated Heat Sources in
Forced Convection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1264.3 Plumes: Concentrated Heat Sources in
Natural Convection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1274.4 Penetrative Convection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 130
4.5 .Aerosol Transport and Collection in Filters . . . . . . . . . . . . . . .. 1344.6 Filter Efficiency and Filtration Theories . . . . . . . . . . . . . . . . . .. 1394.7 Pressure Drop, Permeability, and Filter Performance . . . . . . .. 1464.8 lonic Transport 1524.9 Reactive Porous Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1564.10 Electrodiffusion 1624.11 Tree-Shaped Flow Networks 1664.12 Optimal Size of Flow Element. . . . . . . . . . . . . . . . . . . . . . . . . . .. 1734.13 Hot Water Distribution Networks. . . . . . . . . . . . . . . . . . . . . . . .. 177
4.14 Minimal Resistance Versus Minimal Flow Length . . . . . . . . . .. 183
5 Compact Heat Transfer Flow Structures . . . . . . . . . . . . . . . . .. 193
5.1 Heat Exchangers as Porous Media. . . . . . . . . . . . . . :. . . . . . . .. 1945.2 Optimal Spacings in Natural Convection 2015.3 Optimal Spacings in Forced Convection 2075.4 Pulsating Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2125.5 Optimal Packing of Fibrous lnsulation 2165.6 Optimal Maldistribution: Tree-Shaped Flows. . . . . . . . . . . . . .. 2185.7 Dendritic Heat Exchangers : 224
5.7.1 Elemental Volume. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 224
--~ _..-
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Contents VIl
5.7.2 First Construct 2295.7.3 Second Construct 230
5.8 Constructal Multiscale Structure for Maximal Heatilansfer Density 2385.8.1 Heat ilansfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2415.8.2 Fluid Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2425.8.3 Heat ilansfer Rate Density: The Smallest Scale . . . . .. 243
5.9 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 245
6 Living Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 247
6.1 Respiratory System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2476.1.1 Airflow Within the Bronchialilee. . . . . . . . . . . . . . . . .. 2496.1.2 Alveolar Gas Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . .. 250
6.1.3 Particle Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 251
6.2 Blood and the Circulatory System . . . . . . . . . . . . . . . . . . . . . . .. 253
6.3 Biomembranes: Structure and ilansport Mechanisms 2546.3.1 Cell Membrane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 254
6.3.2 Capillary Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2636.4 ilansport of Neutral Solutes Across Membranes . . . . . . . . . . .. 266
6.5 Transport of Charged Solutes Across Membranes . . . . . . . . . .. 2756.5.1 Membrane Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 276
6.5.2 Electrical Equivalent Circuit . . . . . . . . . . . . . . . . . . . . . .. 278
6.6 The Kidney and the Regulation of Blood Composition 2796.6.1 Kidney Failure and Dialysis. . . . . . . . . . . . . . . . . . . . . . .. 280
6.6.2 Pumping Blood Through SemipermeableMembranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 281
7 Drying of Porous MateriaIs. . . . , . . . . . . . . . . . . . . . . . . . . . . . . .. 2837.1 Introduction 2837.2 Drying Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2847.3 Drying Periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2847.4 Basic Heat and Moisture Transfer Analysis 2857.5 Wet Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2887.6 Types of Moisture Diffusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2947.7 Shrinkage 2957.8 Modeling of Packed-Bed Drying . . . . . . . . . . . . . . . . . . . . . . . . .. 2987.9 Diffusion in Porous Media with Low Moisture
Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3027.10 Modeling of Heterogeneous Diffusion
in Wet Solids 3037.10.1 Mass Transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3047.10.2 Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3057.10.3 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . .. 306
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7.10.4 Numerical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3067.10.5 Heat and Mass Transfer Coefficients . . . . . . . . . . . . . . .. 308
7.11 Correlation for the Drying of Solids . . . . . . . . . . . . . . . . . . . . . .. 310
8 Multidisciplinary Applications . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3158.1 Walls with Cavities: lnsulation and Strength Combined 3158.2 Fibers Coated with Phase-Change Material. . . . . . . . . . . . . . .. 3268.3 Methane Hydrate Sediments: Gas Formation and
Convection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 337
Nomenclature 349
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 359
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 389
