Process Heat Transfer Principles and Applications By Robert W Serth

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Process Heat Transfer Principles and Applications By Robert W Serth

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Contents

Preface viii
Conversion Factors x
Physical Constants xi
Acknowledgements xii
1 Heat Conduction 1
1.1 Introduction 2
1.2 Fourier’s Law of Heat Conduction 2
1.3 The Heat Conduction Equation 6
1.4 Thermal Resistance 15
1.5 The Conduction Shape Factor 19
1.6 Unsteady-State Conduction 24
1.7 Mechanisms of Heat Conduction 31
2 Convective Heat Transfer 43
2.1 Introduction 44
2.2 Combined Conduction and Convection 44
2.3 Extended Surfaces 47
2.4 Forced Convection in Pipes and Ducts 53
2.5 Forced Convection in External Flow 62
2.6 Free Convection 65
3 Heat Exchangers 85
3.1 Introduction 86
3.2 Double-Pipe Equipment 86
3.3 Shell-and-Tube Equipment 87
3.4 The Overall Heat-Transfer Coefficient 93
3.5 The LMTD Correction Factor 98
3.6 Analysis of Double-Pipe Exchangers 102
3.7 Preliminary Design of Shell-and-Tube Exchangers 106
3.8 Rating a Shell-and-Tube Exchanger 109
3.9 Heat-Exchanger Effectiveness 114
4 Design of Double-Pipe Heat Exchangers 127
4.1 Introduction 128
4.2 Heat-Transfer Coefficients for Exchangers without Fins 128
4.3 Hydraulic Calculations for Exchangers without Fins 128
4.4 Series/Parallel Configurations of Hairpins 131
4.5 Multi-tube Exchangers 132
4.6 Over-Surface and Over-Design 133
4.7 Finned-Pipe Exchangers 141
4.8 Heat-Transfer Coefficients and Friction Factors for Finned Annuli 143
4.9 Wall Temperature for Finned Pipes 145
4.10 Computer Software 152
5 Design of Shell-and-Tube Heat Exchangers 187
5.1 Introduction 188
5.2 Heat-Transfer Coefficients 188
5.3 Hydraulic Calculations 189
5.4 Finned Tubing 192
5.5 Tube-Count Tables 194
5.6 Factors Affecting Pressure Drop 195
5.7 Design Guidelines 197
5.8 Design Strategy 201
5.9 Computer software 218
6 The Delaware Method 245
6.1 Introduction 246
6.2 Ideal Tube Bank Correlations 246
6.3 Shell-Side Heat-Transfer Coefficient 248
6.4 Shell-Side Pressure Drop 250
6.5 The Flow Areas 254
6.6 Correlations for the Correction Factors 259
6.7 Estimation of Clearances 260
7 The Stream Analysis Method 277
7.1 Introduction 278
7.2 The Equivalent Hydraulic Network 278
7.3 The Hydraulic Equations 279
7.4 Shell-Side Pressure Drop 281
7.5 Shell-Side Heat-Transfer Coefficient 281
7.6 Temperature Profile Distortion 282
7.7 The Wills–Johnston Method 284
7.8 Computer Software 295
8 Heat-Exchanger Networks 327
8.1 Introduction 328
8.2 An Example: TC3 328
8.3 Design Targets 329
8.4 The Problem Table 329
8.5 Composite Curves 331
8.6 The Grand Composite Curve 334
8.7 Significance of the Pinch 335
8.8 Threshold Problems and Utility Pinches 337
8.9 Feasibility Criteria at the Pinch 337
8.10 Design Strategy 339
8.11 Minimum-Utility Design for TC3 340
8.12 Network Simplification 344
8.13 Number of Shells 347
8.14 Targeting for Number of Shells 348
8.15 Area Targets 353
8.16 The Driving Force Plot 356
8.17 Super Targeting 358
8.18 Targeting by Linear Programming 359
8.19 Computer Software 361
9 Boiling Heat Transfer 385
9.1 Introduction 386
9.2 Pool Boiling 386
9.3 Correlations for Nucleate Boiling on Horizontal Tubes 387
9.4 Two-Phase Flow 402
9.5 Convective Boiling in Tubes 416
9.6 Film Boiling 428
10 Reboilers 443
10.1 Introduction 444
10.2 Types of Reboilers 444
10.3 Design of Kettle Reboilers 449
10.4 Design of Horizontal Thermosyphon Reboilers 467
10.5 Design of Vertical Thermosyphon Reboilers 473
10.6 Computer Software 488
11 Condensers 539
11.1 Introduction 540
11.2 Types of Condensers 540
11.3 Condensation on a Vertical Surface: Nusselt Theory 545
11.4 Condensation on Horizontal Tubes 549
11.5 Modifications of Nusselt Theory 552
11.6 Condensation Inside Horizontal Tubes 562
11.7 Condensation on Finned Tubes 568
11.8 Pressure Drop 569
11.9 Mean Temperature Difference 571
11.10 Multi-component Condensation 590
11.11 Computer Software 595
12 Air-Cooled Heat Exchangers 629
12.1 Introduction 630
12.2 Equipment Description 630
12.3 Air-Side Heat-Transfer Coefficient 637
12.4 Air-Side Pressure Drop 638
12.5 Overall Heat-Transfer Coefficient 640
12.6 Fan and Motor Sizing 640
12.7 Mean Temperature Difference 643
12.8 Design Guidelines 643
12.9 Design Strategy 644
12.10 Computer Software 653
Appendix 681
Appendix A Thermophysical Properties of Materials 682
Appendix B Dimensions of Pipe and Tubing 717
Appendix C Tube-Count Tables 729
Appendix D Equivalent Lengths of Pipe Fittings 737
Appendix E Properties of Petroleum Streams 740
Index 743

Preface

This book is based on a course in process heat transfer that I have taught for many years. The course
has been taken by seniors and first-year graduate students who have completed an introductory
course in engineering heat transfer. Although this background is assumed, nearly all students need
some review before proceeding to more advanced material. For this reason, and also to make the
book self-contained, the first three chapters provide a review of essential material normally covered
in an introductory heat transfer course. Furthermore, the book is intended for use by practicing
engineers as well as university students, and it has been written with the aim of facilitating self-study.
Unlike some books in this field, no attempt is made herein to cover the entire panoply of heat transfer
equipment. Instead, the book focuses on the types of equipment most widely used in the chemical
process industries, namely, shell-and-tube heat exchangers (including condensers and reboilers),
air-cooled heat exchangers and double-pipe (hairpin) heat exchangers.Within the confines of a single
volume, this approach allows an in-depth treatment of the material that is most relevant from an
industrial perspective, and provides students with the detailed knowledge needed for engineering
practice. This approach is also consistent with the time available in a one-semester course.
Design of double-pipe exchangers is presented in Chapter 4. Chapters 5–7 comprise a unit dealing
with shell-and-tube exchangers in operations involving single-phase fluids. Design of shell-and-tube
exchangers is covered in Chapter 5 using the Simplified Delaware method for shell-side calculations.
For pedagogical reasons, more sophisticated methods for performing shell-side heat-transfer
and pressure-drop calculations are presented separately in Chapter 6 (full Delaware method) and
Chapter 7 (Stream Analysis method). Heat exchanger networks are covered in Chapter 8. I normally
present this topic at this point in the course to provide a change of pace. However, Chapter
8 is essentially self-contained and can, therefore, be covered at any time. Phase-change operations
are covered in Chapters 9–11. Chapter 9 presents the basics of boiling heat transfer and two-phase
flow. The latter is encountered in both Chapter 10, which deals with the design of reboilers, and
Chapter 11, which covers condensation and condenser design. Design of air-cooled heat exchangers
is presented in Chapter 12. The material in this chapter is essentially self-contained and, hence,
it can be covered at any time.
Since the primary goal of both the book and the course is to provide students with the knowledge
and skills needed for modern industrial practice, computer applications play an integral role,
and the book is intended for use with one or more commercial software packages. HEXTRAN
(SimSci-Esscor), HTRI Xchanger Suite (Heat Transfer Research, Inc.) and the HTFS Suite (Aspen
Technology, Inc.) are used in the book, along with HX-Net (Aspen Technology, Inc.) for pinch
calculations. HEXTRAN affords the most complete coverage of topics, as it handles all types of heat
exchangers and also performs pinch calculations for design of heat exchanger networks. It does
not perform mechanical design calculations for shell-and-tube exchangers, however, nor does it
generate detailed tube layouts or setting plans. Furthermore, the methodology used by HEXTRAN
is based on publicly available technology and is generally less refined than that of the other software
packages. The HTRI and HTFS packages use proprietary methods developed by their respective
research organizations, and are similar in their level of refinement. HTFS Suite handles all types
of heat exchangers; it also performs mechanical design calculations and develops detailed tube
layouts and setting plans for shell-and-tube exchangers. HTRI Xchanger Suite lacks a mechanical
design feature, and the module for hairpin exchangers is not included with an academic license.
Neither HTRI nor HTFS has the capability to perform pinch calculations.
As of this writing, Aspen Technology is not providing the TASC and ACOL modules of the HTFS
Suite under its university program. Instead, it is offering the HTFS-plus design package. This
package basically consists of the TASC and ACOL computational engines combined with slightly
modified GUI’s fromthe correspondingBJACprograms(HETRANandAEROTRAN),and packaged
with the BJAC TEAMS mechanical design program. This package differs greatly in appearance and
to some extent in available features from HTFS Suite. However, most of the results presented in the
text using TASC and ACOL can be generated using the HTFS-plus package.
Software companies are continually modifying their products, making differences between the
text and current versions of the software packages unavoidable. However, many modifications
involve only superficial changes in format that have little, if any, effect on results. More substantive
changes occur less frequently, and even then the effects tend to be relatively minor. Nevertheless,
readers should expect some divergence of the software from the versions used herein, and they
should not be unduly concerned if their results differ somewhat from those presented in the text.
Indeed, even the same version of a code, when run on different machines, can produce slightly
different results due to differences in round-off errors. With these caveats, it is hoped that the
detailed computer examples will prove helpful in learning to use the software packages, as well as
in understanding their idiosyncrasies and limitations.
I have made a concerted effort to introduce the complexities of the subject matter gradually
throughout the book in order to avoid overwhelming the reader with a massive amount of detail
at any one time. As a result, information on shell-and-tube exchangers is spread over a number of
chapters, and some of the finer details are introduced in the context of example problems, including
computer examples. Although there is an obvious downside to this strategy, I nevertheless believe
that it represents good pedagogy.
Both English units, which are still widely used by American industry, and SI units are used in this
book. Students in the United States need to be proficient in both sets of units, and the same is true
of students in countries that do a large amount of business with U.S. firms. In order to minimize
the need for unit conversion, however, working equations are either given in dimensionless form
or, when this is not practical, they are given in both sets of units.
I would like to take this opportunity to thank the many students who have contributed to this
effort over the years, both directly and indirectly through their participation in my course. I would
also like to express my deep appreciation to my colleagues in the Department of Chemical and
Natural Gas Engineering at TAMUK, Dr. Ali Pilehvari and Mrs.Wanda Pounds.Without their help,
encouragement and friendship, this book would not have been written.