Engineering flow and heat exchange

Octave Levenspiel Engineering Flow and Heat Exchange Third Edition Tai ngay!!! Ban co the xoa dong chu nay!!! Engineering Flow and Heat Exchange Octave Levenspiel Engineering Flow and Heat Exchange Third Edition Octave Levenspiel Department of Chemical Engineering Oregon State University Corvallis, OR, USA ISBN 978-1-4899-7453-2 ISBN 978-1-4899-7454-9 (eBook) DOI 10.1007/978-1-4899-7454-9 Springer New York Heidelberg Dordrecht London Library of Congress Control Number: 2014947869 © Springer Science+Business Media New York 2014 This work is subject to copyright All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher’s location, in its current version, and permission for use must always be obtained from Springer Permissions for use may be obtained through RightsLink at the Copyright Clearance Center Violations are liable to prosecution under the respective Copyright Law The use of general descriptive names, registered names, trademarks, service marks, etc in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made The publisher makes no warranty, express or implied, with respect to the material contained herein Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Preface This volume presents an overview of fluid flow and heat exchange In the broad sense, fluids are materials that are able to flow under the right conditions These include all sorts of things: pipeline gases, coal slurries, toothpaste, gases in high-vacuum systems, metallic gold, soups and paints, and, of course, air and water These materials are very different types of fluids, and so it is important to know the different classifications of fluids, how each is to be analyzed (and these methods can be quite different), and where a particular fluid fits into this broad picture This book treats fluids in this broad sense, including flows in packed beds and fluidized beds Naturally, in so small a volume, we not go deeply into the study of any particular type of flow; however, we show how to make a start with each We avoid supersonic flow and the complex subject of multiphase flow, where each of the phases must be treated separately The approach here differs from most introductory books on fluids, which focus on the Newtonian fluid and treat it thoroughly, to the exclusion of all else I feel that the student engineer or technologist preparing for the real world should be introduced to these other topics Introductory heat transfer books are devoted primarily to the study of the basic rate phenomena of conduction, convection, and radiation, showing how to evaluate “h,” “U,” and “k” for this and that geometry and situation Again, this book’s approach is different We rapidly summarize the basic equations of heat transfer, including the numerous correlations for h Then we go straight to the problem of how to get heat from here to there and from one stream to another The recuperator (or through-the-wall exchanger), the direct contact exchanger, the heat-storing accumulator (or regenerator), and the exchanger, which uses a third go-between stream—these are distinctly different ways of transferring heat from one stream to another, and this is what we concentrate on It is surprising how much creativity may be needed to develop a good design for the transfer of heat from a stream of hot solid particles to a stream of cold solid particles The flavor of this v vi Preface presentation of heat exchange is that of Kern’s unique book; certainly simpler, but at the same time broader in approach Wrestling with problems is the key to learning, and each of the chapters has illustrative examples and a number of practice problems Teaching and learning should be interesting, so I have included a wide variety of problems, some whimsical, others directly from industrial applications Usually the information given in these practice problems has been designed so as to fall on unique points on the design charts, making it easy for the student and also for the instructor who is checking the details of a student’s solution I think that this book will interest the practicing engineer or technologist who wants a broad picture of the subject or, on having a particular problem to solve, wants to know what approach to take In the university it could well form the basis for an undergraduate course in engineering or applied fluids and heat transfer, after the principles have been introduced in a basic engineering course such as transport phenomena At present, such a course is rarely taught; however, I feel it should be an integral part of the curriculum, at least for the chemical engineer and the food technologist My thanks to Richard Turton, who coaxed our idiot computer into drawing charts for this book, and to Eric Swenson, who so kindly consented to put his skilled hand to the creation of drawing and sketch to enliven and complement the text Finally, many thanks to Bekki and Keith Levien, who without their help this new revision would never have made it to print Corvallis, OR, USA Octave Levenspiel Contents Part I Flow of Fluids and Mixtures Basic Equations for Flowing Streams 1.1 Total Energy Balance 1.2 Mechanical Energy Balance 1.3 Pumping Energy and Power: Ideal Case 1.4 Pumping Energy and Power: Real Case Compression 1.4.1 Expansion 3 Flow of Incompressible Newtonian Fluids in Pipes 2.1 Comments References and Recommended Readings 21 26 43 Compressible Flow of Gases 3.1 Adiabatic Flow in a Pipe with Friction 3.2 Isothermal Flow in a Pipe with Friction 3.3 Working Equations for Flow in Pipes (No Reservoir or Tank Upstream) 3.4 Flow Through an Orifice or Nozzle 3.4.1 Comments 3.5 Pipe Leading from a Storage Vessel References 45 46 49 51 52 54 54 70 Molecular Flow 4.1 Equations for Flow, Conductance, and Pumping Speed 4.1.1 Notation 4.1.2 Laminar Flow in Pipes 4.1.3 Molecular Flow in Pipes 4.1.4 Intermediate or Slip Flow Regime 71 73 73 74 75 76 vii viii Contents 4.1.5 Orifice, Contraction, or Entrance Effect in the Molecular Flow Regime 4.1.6 Contraction in the Laminar Flow Regime 4.1.7 Critical Flow Through a Contraction 4.1.8 Small Leak in a Vacuum System 4.1.9 Elbows and Valves 4.1.10 Pumps 4.2 Calculation Method for Piping Systems 4.3 Pumping Down a Vacuum System 4.4 More Complete Vacuum Systems 4.5 Comments References and Further Readings Non-Newtonian Fluids 5.1 Classification of Fluids 5.1.1 Newtonian Fluids 5.1.2 Non-Newtonian Fluids 5.2 Shear Stress and Viscosity of a Flowing Fluid 5.3 Flow in Pipes 5.3.1 Bingham Plastics 5.3.2 Power Law Fluids 5.3.3 General Plastics 5.3.4 Comments on Flow in Pipes 5.4 Determining Flow Properties of Fluids 5.4.1 Narrow Gap Viscometer 5.4.2 Cylinder in an Infinite Medium 5.4.3 Tube Viscometer 5.5 Discussion on Non-Newtonians 5.5.1 Materials Having a Yield Stress, Such as Bingham Plastics 5.5.2 Power Law Fluids 5.5.3 Thoughts on the Classification of Materials References and Related Readings 77 79 79 80 81 81 82 84 87 87 97 99 99 99 100 102 104 104 107 109 110 111 112 112 113 115 115 117 117 131 Flow Through Packed Beds 6.1 Characterization of a Packed Bed 6.1.1 Sphericity ϕ of a Particle 6.1.2 Particle Size, dp 6.1.3 Determination of the Effective Sphericity ϕeff from Experiment 6.1.4 Bed Voidage, ε 6.2 Frictional Loss for Packed Beds 6.3 Mechanical Energy Balance for Packed Beds References 133 133 133 134 137 137 139 140 151 Contents Flow in Fluidized Beds 7.1 The Fluidized State 7.2 Frictional Loss and Pumping Requirement Needed to Fluidize a Bed of Solids 7.3 Minimum Fluidizing Velocity, umf References 153 153 Solid Particles Falling Through Fluids 8.1 Drag Coefficient of Falling Particles 8.1.1 The Small Sphere 8.1.2 Nonspherical Particles 8.1.3 Terminal Velocity of Any Shape of Irregular Particles References Part II ix 155 156 166 167 167 167 168 169 176 Heat Exchange The Three Mechanisms of Heat Transfer: Conduction, Convection, and Radiation 9.1 Heat Transfer by Conduction 9.1.1 Flat Plate, Constant k 9.1.2 Flat Plate, k ¼ k0 (1 + βT) 9.1.3 Hollow Cylinders, Constant k 9.1.4 Hollow Sphere, Constant k 9.1.5 Series of Plane Walls 9.1.6 Concentric Cylinders 9.1.7 Concentric Spheres 9.1.8 Other Shapes 9.1.9 Contact Resistance 9.2 Heat Transfer by Convection 9.2.1 Turbulent Flow in Pipes 9.2.2 Turbulent Flow in Noncircular Conduits 9.2.3 Transition Regime in Flow in Pipes 9.2.4 Laminar Flow in Pipes (Perry and Chilton, pg 168 (1984)) 9.2.5 Laminar Flow in Pipes, Constant Heat Input Rate at the Wall (Kays and Crawford 1980) 9.2.6 Laminar Flow in Pipes, Constant Wall Temperature (Kays and Crawford 1980) 9.2.7 Flow of Gases Normal to a Single Cylinder 9.2.8 Flow of Liquids Normal to a Single Cylinder 9.2.9 Flow of Gases Past a Sphere 9.2.10 Flow of Liquids Past a Sphere 9.2.11 Other Geometries 179 179 181 181 181 181 182 182 182 182 182 183 184 185 186 186 186 187 188 189 189 189 190 376 Appendix For liquid water Temperature,  C μ, kg/ms 10 15 20 25 30 40 50 60 70 80 90 100 1.79  10
3 1.52  10
3 1.31  10
3 1.14  10
3 1.00  10
3 0.894  10
3 0.801  10
3 0.656  10
3 0.549  10
3 0.469  10
3 0.406  10
3 0.357  10
3 0.317  10
3 0.284  10
3 The following listing shows the wide range of viscosities of familiar Newtonian fluid Fluid Gases H2 (20  C) Steam (100  C) CO2 (20  C) Air (0  C) (20  C) (100  C) Liquids Gasoline (20  C) H2O (20  C) C2H5OH (20  C) Kerosene (20  C) Whole milk (0  C) Sucrose solutions (20  C) 20 wt% 40 wt% 60 wt% 70 wt% SAE 10W-30 motor oil (
18  C) (99  C) Olive oil (20  C) SAE 30W motor oil (20  C) μ, kg/ms 0.876  10
5 1.25  10
5 1.48  10
5 1.71  10
5 1.83  10
5 2.17  10
5 0.6  10
3 1.0  10
3 1.2  10
3 2.0  10
3 4.3  10
3 2.0  10
3 6.2  10
3 58  10
3 486  10
3 1.2–2.4  10
3–12  10
3 84  10
3 100  10
3 (continued) Appendix 377 (continued) Fluid Heavy machine oil (20  C) Glycerin (20  C) Molasses, very heavy (20  C) Clover honey (20  C) Pitch (0  C) μ, kg/ms 660  10
3 860  10
3 6.6 10–50 5.1–1010 The viscosity of liquids is practically independent of pressure; that of gases increases slowly with a rise in pressure, not even doubling at the critical pressure With an increase in temperature liquids become less viscous, gases become more viscous For the viscous characteristics of non-Newtonians see Chap A.14 Kinematic Viscosity ν¼ A.15 m2 cm2 ¼ 104 ¼ 104 stoke ¼ 106 centistoke s s Thermal Conductivity
k¼ 10−3
2 μ m ¼ ρ s  
W W ¼ mK ðm2 c:s:ÞðK=m lengthÞ 10−2 10−1 Gases Liquids 10 100 Metals Building insulation Nonmetallic structures: silica, alumina, activated carbon, etc W cal Btu ¼ 0:00239 ¼ 0:578  mK s cm C h ft  F k ffi independent of pressure 1000 378 Appendix For water (20  C): k ¼ 0.597 W/m K For air (20  C): k ¼ 0.0257 W/m K For steam (100  C): k ¼ 0.0251 W/m K See Appendix A.21 for more k values A.16 Specific Heat
J Cp ¼ kg K 100  1000 10000 Solid metals Nonmetallic solids and organic liquids Gases Liquefied H2, CH4, NH3 J cal Btu ¼ 239  10
6  ¼ 239  10
6  kg K gC lb F For water (20  C): Cp ¼ 4,184 J/kg K ¼ cal/g  C ¼ Btu/lb  F For air (20  C): Cp ¼ 1,013 J/kg K ¼ 29.29 J/mol K ¼ 0.24 cal/g  C ¼ cal/mol C  For steam (100 C): Cp ¼ 2,063 J/kg K ¼ 37.13 J/mol K See Appendix A.21 for more Cp values A.17 Thermal Diffusivity
2 k m α¼ ¼ ρCp s Appendix 379 10−9 10−8 10−7 10−6 10−4 Liquid metals Liquids Cryogenic liquids 10−5 Gases Solid nonmetals Solid metals m2 ft2 ft2 ¼ 10:76 ¼ 38, 750 s s h For air (20  C): α ¼ 2.12  10
5 m2/s  For steam (100 C): α ¼ 2.05  10
5 m2/s For water (20  C): α ¼ 1.43  10
7 m2/s α values for other substances can be found from k/ρCp values in Appendix A.21 A.18 Thermal Radiative Properties , ẳ ẵdimensionless and α for room temperature radiation 0.2 0.4 Metallic paints Polished metal surfaces 0.6 0.8 1.0 Oxidized surfaces of metals Metals Paints and most materials σ ¼ 5.67  10
8 W/m2 K4 ¼ 0.1713  10
8 Btu/h ft2  F4, the radiation constant See Chap 12 for a short table of emissivities and absorptivities 380 Appendix A.19 Heat Transfer Coefficient
 W h¼ m2 K 102 10 103 104 105 Film Condensing organics Forced convection, air Free convection Bed-wall, fluidized bed Dropwise Condensing steam Boiling water Forced convection, water A.20 W cal Btu ¼ 2:39  10
5 ¼ 0:1761 ∘ m2 K s cm2 ∘ C h ft F Dimensionless Groups Archimedes number:    3 d3p ρg ρs
ρg  g Ar ¼ dp ¼ μ2 Biot number:   interior resistance to heat transfer in a particle hL  ¼ Bi ¼ k resistance to heat transfer at surface of a particle Drag coefficient for falling particles: CD ¼  drag force, Fd    ρg u2 =2  πd2p =4 Appendix 381 Darcy friction factor for flow in pipes: f D ¼ 4f f Friction factor for packed beds: ff ¼ ε3  1
ε X  Fd p u20 L ¼  = kgfluidof   kinetic kg of = energy loss fluid frictional energy loss Fanning friction factor for flow in pipes:     frictional area of frictional loss drag pipe wall during flow τw  fF ¼ ¼   ¼ ρu0 =2 kinetic energy kinetic m3 of fluid of fluid energy = = Fourier number: Fo ¼ αt kt ¼ L2 ρCp L2 Graetz number: Gz ¼ Re  Pr    d used in forced convection L Grashof number: Hedstrom number: He ¼ τ0 d ρ η2 382 Appendix Knudsen number:   Kn ¼ πCp 2Cυ 1=2  mean free path of molecules Ma  ¼   Re diameter of flow channel Mach number: Ma ¼ u velocity of gas ¼ c speed of sound Nusselt number:     total heat conduction and transfer convection hd ¼   Nu ¼ ¼ k molecular conduction heat transfer alone Prandtl number:     molecular viscous dissipation momentum transfer of energy Cp μ   Pr ẳ ẳ ẳ heat conductionị k molecular heat tranfer ¼ 0:66
0:75 for air, A, CO2 , CH4 , CO, H2 , He, N2 and other common gases ffi 1:06 for steam ¼ 10
1,000 for most liquids ¼ 0:006
0:03 for most liquid metals Reynolds number: Re ¼ A.21 duρ inertial force ¼ μ viscous force Tables of Physical Properties of Materials Solids: Metals and Alloys Aluminum Copper T  C k W/m K 20 20 204.2 384 ρ kg/m3 2,707 8,954 Cp J/kg K 896 385 α  106 m2/s 84.2 112 (continued) Appendix 383 (continued) Iron Lead Silver Stainless steel T  C 20 20 20 20 ρ kg/m3 7,897 11,393 10,524 7,820 k W/m K 72.7 34.7 406.8 16.3 α  106 m2/s 20.4 23.4 164.5 4.53 Cp J/kg K 452 130 235 460 Solids: Nonmetals Brick (building) Cardboard, corrugated Chalk Coal Concrete Corkboard Glass Ice Leather Rubber Sand (bulk properties, ε ¼ 0.42) Snow, dry packed Wood: Oak across grain Oak with grain Pine across grain Pine with grain T  C k W/m K ρ kg/m3 Cp J/kg K α  106 m2/s 20 20 50 20 20 20 20 30 20