Engineering Design and Optimization of Thermofluid Systems
Description
Engineering Design and Optimization of Thermofluid Systems is designed to help students and professionals alike understand the design and optimization techniques used to create complex engineering systems that incorporate heat transfer, thermodynamics, fluid dynamics, and mass transfer. Designed for thermal systems design courses, this comprehensive textbook covers thermofluid theory, practical applications, and established techniques for improved performance, efficiency, and economy of thermofluid systems. Students gain a solid understanding of best practices for the design of pumps, compressors, heat exchangers, HVAC systems, power generation systems, and more.
Covering the material using a pragmatic, student-friendly approach, the text begins by introducing design, optimization, and engineering economics--with emphasis on the importance of engineering optimization in maximizing efficiency and minimizing cost. Subsequent chapters review representative thermofluid systems and devices and discuss basic mathematical models for describing thermofluid systems. Moving on to system simulation, students work with the classical calculus method, the Lagrange multiplier, canonical search methods, and geometric programming. Throughout the text, examples and practice problems integrate emerging industry technologies to show students how key concepts are applied in the real world. This well-balanced textbook:
* Integrates underlying thermofluid principles, the fundamentals of engineering design, and a variety of optimization methods
* Covers optimization techniques alongside thermofluid system theory
* Provides readers best practices to follow on-the-job when designing thermofluid systems Contains numerous tables, figures, examples, and problem sets
Emphasizing optimization techniques more than any other thermofluid system textbook available, Engineering Design and Optimization of Thermofluid Systems is the ideal textbook for upper-level undergraduate and graduate students and instructors in thermal systems design courses, and a valuable reference for professional mechanical engineers and researchers in the field.
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Person
David S.K. Ting is a Professor of Mechanical, Automotive, and Materials Engineering at the University of Windsor, Ontario, Canada. He has taught over a dozen courses at UWindsor and is the founder of its Turbulence and Energy Laboratory. He has co-authored over 140 journal papers, authored 3 textbooks and co-edited 10 volumes, is affiliated with ASHRAE, ASME, and SAE, and was named the 2018 Best Reviewer of the Year by ASME's Heat Transfer Division.
Content
Preface xi
Acknowledgments xiii
1 Introduction 1
1.1 What Are Design and Optimization of Thermofluid Systems? 1
1.2 Differentiating Engineering from Science 3
1.3 Development, Design, and Analysis 5
1.4 The Design Process 6
1.5 Existing Books on Thermofluid System Design and/or Optimization 9
1.6 Organization of the Book 10
Problems 10
References 12
2 Engineering Economics 14
2.1 Introduction 15
2.2 Worth of Money with Respect to Time 15
2.2.1 Compound Interest and Effective Interest 17
2.2.2 PresentWorth Factor 19
2.3 Money Flow Series 20
2.3.1 Cash Flow Diagram 20
2.3.2 Rate of Return, Benefit-Cost Ratio, and Capital Recovery Factor 25
2.4 Thermo-economics 29
Problems 29
References 30
3 Common Thermofluid Devices 32
3.1 Common Components of Thermofluid Systems 33
3.2 Valves 34
3.2.1 Ball Valves 34
3.2.2 Butterfly Valves 35
3.2.3 Gate Valves 35
3.2.4 Globe Valves 35
3.2.5 Needle Valves 37
3.2.6 Pinch Valves 38
3.2.7 Plug Valves 38
3.2.8 Poppet Valves 39
3.2.9 Saddle Valves 39
3.2.10 Some Comments on Valves 40
3.3 Ducts, Pipes, and Fittings 40
3.3.1 Laminar and Turbulent Flow 40
3.3.2 Entrance to Fully Developed Pipe Flow 42
3.3.3 Friction of Fully-Developed Pipe Flow 44
3.3.4 Head Loss along a Pipe Section 47
3.3.5 Minor Head Loss 50
3.4 Piping Network 52
Problems 54
References 55
4 Heat Exchangers 56
4.1 Effective Exchange of Thermal Energy 57
4.2 Types of Heat Exchangers 59
4.3 Indirect-Contact Heat Exchangers 60
4.3.1 A Single Fluid in a Conduit of Constant Temperature 60
4.3.2 Heat Transfer from a Hot Stream to a Cold Stream 64
4.3.3 Log Mean Temperature Difference 66
4.3.4 Correction Factor 69
4.4 Comments on Heat Exchanger Selection 71
Problems 73
References 74
5 Equations 75
5.1 Introduction 76
5.1.1 Model Versus Simulation 77
5.1.2 Simulation 79
5.2 Types of Models 80
5.2.1 Analog Models 81
5.2.2 Mathematical Models 84
5.2.3 Numerical Models 84
5.2.4 Physical Models 85
5.3 Forms of Mathematical Models 85
5.4 Curve Fitting 86
5.4.1 Least Error Linear Fits 86
5.4.2 Least Error Polynomial Fits 89
5.4.3 Non-Polynomial into Polynomial Functions 92
5.4.4 Multiple Independent Variables 93
Problems 94
References 95
6 Thermofluid System Simulation 96
6.1 What is System Simulation? 97
6.2 Information-Flow Diagram 98
6.3 Solving a Set of Equations via the Matrix Approach 100
6.4 Sequential versus Simultaneous Calculations 106
6.5 Successive Substitution 106
6.6 Taylor Series Expansion and the Newton-Raphson Method 113
6.6.1 Taylor Series Expansion 113
6.6.2 The Newton-Raphson Method 116
Problems 122
References 124
7 Formulating the Problem for Optimization 125
7.1 Introduction 126
7.2 Objective Function and Constraints 127
7.3 Formulating a Problem to Optimize 128
Problems 139
References 142
8 Calculus Approach 144
8.1 Introduction 145
8.2 Lagrange Multiplier 146
8.3 Unconstrained, Multi-Variable, Objective Function 148
8.4 Multi-Variable Objective Function with Equality Constraints 151
8.5 Significance of the Lagrange Multiplier Operation 155
8.6 The Lagrange Multiplier as a Sensitivity Coefficient 161
8.7 Dealing with Inequality Constraints 163
Problems 164
References 166
9 Search Methods 167
9.1 Introduction 168
9.2 Elimination Methods 169
9.2.1 Exhaustive Search 169
9.2.2 Dichotomous Search 172
9.2.3 Fibonacci Search 175
9.2.4 Golden Section Search 178
9.2.5 Comparison of Elimination Methods 181
9.3 Multi-variable, Unconstrained Optimization 181
9.3.1 Exhaustive Search 181
9.3.2 Lattice Search 183
9.3.3 Univariate Search 185
9.3.4 Steepest Ascent/Descent Method 187
9.4 Multi-variable, Constrained Optimization 193
9.4.1 Penalty Function Method 193
9.4.2 Search-Along-a-Constraint (Hemstitching) Method 196
Problems 205
References 207
10 Geometric Programming 208
10.1 Common Types of Programming 209
10.2 What is Geometric Programming? 210
10.3 Single-Variable, Unconstrained Geometric Programming 210
10.4 Multi-Variable, Unconstrained Geometric Programming 215
10.5 Constrained Multi-Variable Geometric Programming 218
10.6 Conclusion 225
Problems 226
References 227
Appendix: Sample Design and Optimization Projects 228
A.1 Introduction 229
A.2 Cavern-based Compressed Air Energy Storage 229
A.3 Underwater Compressed Air Energy Storage 233
A.4 Compressed Air Energy Storage Underground 235
A.5 Geothermal Heat Exchanger 235
A.6 Passive Cooling of a Photovoltaic Panel for Efficiency 237
A.7 Desert Expedition 238
A.8 Fire- and Heat-Resilient Designs 240
References 241
Index 243
1
Introduction
To develop a complete mind: Study the science of art; Study the art of science.
- Leonardo da Vinci
Chapter Objectives
- Understand what design and optimization of thermofluid systems mean.
- Differentiate engineering from science.
- Discern development, design, and analysis.
- Become familiar with the design process.
- Be aware of the existing books on thermofluid system design and/or optimization.
- Appreciate the organization and contents of the book.
Nomenclature
HVAC heating, ventilation, and air conditioning Idir direct radiation on a horizontal surface KISS keep it simple, stupid LED light-emitting diode PV photovoltaic UWCAES underwater compressed air energy storage X, x (design) variables or influencing parameters Y a variable, the objective function
1.1 What Are Design and Optimization of Thermofluid Systems?
Design and optimization of thermofluid systems are
the design and, subsequently, optimization of the design of engineering systems involving significant fluid flow, thermodynamics, and/or heat transfer.
To more fully understand Design and Optimization of Thermofluid Systems, we need to clearly comprehend the four main terms:
Within this context,
- design is the creation of an engineering system which will provide the desired result, and
- optimization is taking the workable design one step further, attaining not just a better but the best design.
There usually exist a few unavoidable constraints, putting practical limits within which the optimal design is bounded. The optimal car may be the one performing the best in terms of mileage. For a typical middle-class engineer with four mouths to feed, however, the price of the car may be the deciding factor, limiting the selection to within a low-budget ceiling.
Example 1.1 Design a residential solar thermal energy storage system
Given
An engineering student living in a temperate climate region wishes to store the thermal energy harnessed from the sun when it shines during the day, for residential use during the night.
Find
An appropriate storage system.
Solution
A workable design is running a glycol-water line from the solar thermal collector into an adequately large insulated water tank. Glycol-water is appropriately employed to prevent freezing. The temperature of the stored fluid has to be sufficiently high for the intended usage. Reasonable drops in the temperature from the solar collector to the storage tank and to the delivery end use must be accounted for, as some losses are inevitable.
The initial workable design, however, is probably not the best design as it may occupy the entire basement. The use of phase-change material will probably keep the size in check. Molten salt is also worth exploring, especially when dealing with larger utilization, such as a multiple-housing residence. Comparing different existing options, such as off-the-shelf tank sizes and storage media to achieve the best option is called optimization. Since the budget, as well as the available space for the storage tank, are likely limited, the optimization of the residential solar thermal energy storage system is thus subjected to budget, space, and other constraints.
Example 1.1 hints that a workable design does not necessarily need to be the best design. In fact, it typically is not. When the project is adequately large and there are (financial) backings for it, optimization is invoked to deduce the best design. Furthermore, for a company to compete in mass-selling of such systems, progressively better designs which are cheaper to manufacture are necessary. By and large, there will be budgetary, space, and other constraints. Other constraints for a thermal storage tank can be a maximum workable storage temperature, particular charging and discharging rates, etc. In some sense, moving from a feasible design to an optimum design is like progressing from an "ad hoc art and/or experience" to a "systematic scientific artistic endeavor."
Figure 1.1 Workable versus optimal design of electricity-driven household light bulbs. Source: Photos taken by X. Wang and Y. Yang.
A familiar design versus optimization exemplification is the three types of light bulb for everyday usage, see Figure 1.1. The incandescent light bulb is a workable design, and it has been satisfying our need since Thomas Edison invented it in 1879. Much later, the fluorescent light bulb is optimized in terms of energy usage and cost. For this reason, the compact fluorescent light bulb has finally squeezed out its archetype after being in the market for a couple of decades, the duration for the price to drop to a competitive level. Over the long run, the LED (light-emitting diode) light bulb is the best, because the money saved due to its low wattage and very long life span far exceed the high initial cost. In short, the incandescent light bulb, with a typical life span of 1,000-2,000 hours, is a workable design. The compact fluorescent light bulb, which lasts on the ballpark of 10,000 hours and uses around 75% less energy, is currently the optimum design. The LED light bulb, which outlasts the fluorescent by up to 50,000 hours while using 90% less energy, is the fruit of the latest design and optimization endeavor, and it is expected to be the new optimum design in a few years, as its manufacturing cost drops.
1.2 Differentiating Engineering from Science
The challenging tasks associated with thermofluid systems' design and optimization are only to be executed by individuals well educated and trained in engineering, i.e. competent engineers. But what is engineering? How does it differ from science? Science may be defined as the systematic knowledge of the physical world that is testable, repeatable, and predictable. Concisely,
Science is the systematic knowledge of the physical world.
Simply put,
Engineering is putting science into practice.
Figure 1.2 The millennia-old spoked wheel for horse chariots (created by S. Akhand). Shown are four-spoke chariot wheels resembling those found in the Red Sea, which are attributed to the powerful Egyptian army, as recorded in Exodus, Chapter 14.
By and large, engineering was initiated for, and still is, the exploitation of science to create practical systems to make life easier for society. In relation to the context of the material covered in this book,
Engineering is the science and art of efficient dealing with materials and forces . it involves the most economic design and execution . assuring, when properly performed, the most advantageous combination of accuracy, safety, durability, speed, simplicity, efficiency, and economy possible for the conditions of design and service.
J.A.L. Waddell
Let us look briefly at the millennia-old wheels, sketched in Figure 1.2. Horse chariots date further back than the Old Testament, where the Pharaohs were largely feared because of their vast number of powerful horse chariots. Durable wood was the material adopted, and the forces at play included the load on the chariot and the required torque. As per "economic design and execution," the wood has to be readily available locally, or relatively accessible and affordable to acquire from a not-too-distant land, or from subject nations as tributes under one's dominance. Accuracy may be viewed as the wood that does not expand or contract excessively with moisture and/or changes in the weather. Safety and durability may be perceived as keeping the soldiers from falling off as they charge the chariots forward into partially-rocky or muddy fields3 at great speeds. Note that speed, to a large extent, decides the fate of the riding warriors. Simplicity and efficiency can easily be inferred from the spoke design, including the number of spokes. This becomes particularly obvious when contrasted with the predecessor of the spoked wheels, the clumsy, spoke-less, solid wood wheels; see Figure 1.3. For war chariots, securing sharp weapons on the outer side the (spoked) wheel further illustrates ingenious, effective design for the intention.
Further to the differentiation between science and engineering, a scientist is an expert in science, whereas an engineer creatively converts the scientific findings into useful applications. A good scientist indiscriminately strives to improve all kinds of knowledge, irrespective of any potential usage, of the physical world. An applied scientist undertakes only applications-oriented scientific endeavors. This includes an engineering researcher who develops ideas that advance the frontiers of knowledge but may not be applied for a number of years....
