Design and Optimization of Thermal Systems Episode 1 Part 2 pptx

A wide range of examples from many different applied areas, such asenergy, environment, heating, cooling, manufacturing, aerospace, and transpor-tation systems, are employed to explain t

The second edition of this book follows the basic principles, approaches, andtreatment presented in the first edition The focus is clearly on systems in whichthermodynamics, fluid flow, and thermal transport form the main considerations.However, the ideas, methodology, and pedagogy are applicable to a wide variety

of engineering systems The main thrust is to design and optimize systems based

on inputs from simulation and experimental data on materials and on componentsthat constitute the system A systematic approach is followed to finally obtain anoptimal design, starting with conceptual design and proceeding through mod-eling, simulation, and design evaluation to choose a feasible design Additionalaspects, such as system control, communicating the design, financial consider-ations, safety, and material selection, that arise in practical systems are also pre-sented A wide range of examples from many different applied areas, such asenergy, environment, heating, cooling, manufacturing, aerospace, and transpor-tation systems, are employed to explain the various elements involved in model-ing, simulation, and design Even though there are many significant differencesbetween such a diversity of systems, the basic approach is still very similar andcan be used for relatively simple systems with few components to large, com-plex systems with many components and subsystems A large number of solvedexamples and exercises are included to supplement the discussion and to illustratethe ideas presented in the text

The book is appropriate as a textbook for engineering senior undergraduate orfirst-year graduate level courses in design, as well as for capstone design coursestaught in most engineering curricula It is also appropriate as a reference book incourses at this level in heat transfer, fluid mechanics, thermodynamics, and otherrelated basic and applied areas in mechanical engineering and other engineeringdisciplines The book would also be useful as a reference for engineers working

on a wide range of problems in industry, national labs, and other organizations.Among the major differences from the first edition is a greater emphasis onthe use of MATLAB®instead of high-level programming languages like Fortran

or C, for numerical modeling and simulation of components and systems This is

in keeping with the current trend in engineering education where MATLAB hasemerged as the dominant environment for numerical solution of basic mathemati-cal equations Several Fortran programs in the first edition have been replaced bycorresponding MATLAB programs or commands The resulting simplification innumerical simulation is demonstrated through exercises and examples in MAT-LAB, which are included to strengthen the presentation Additional solved exam-ples and exercises on thermodynamic systems like heating, cooling, and powersystems have been included because of the relative ease of simulating the compo-nents as lumped and steady Other simple systems are included in the discussion,

examples are included in all the chapters, as well as additional projects at theend of the book Extra information is added at various places, as appropriate; forinstance, in materials and in optimization Much of the presentation has beenrevised and, in several cases, simplified and clarified to make it easier to follow.The presentation has also been updated to include recent advances in designand optimization Among the additional topics included are artificial-intelligence-based techniques like genetic algorithms, fuzzy logic, and artificial neural net-works Response surfaces and other optimization techniques are included in thediscussion, along with effective use of concurrent experimental and numericalinputs for design and optimization Multi-objective optimization is particularlyimportant for thermal systems, since more than one objective function is typicallyimportant in realistic systems, and a detailed treatment is included Other strate-gies to optimize the system are presented Additional references have been added

on these topics, as well as on the others that were covered in the first edition ous references have been updated The application of these ideas to the optimiza-tion of thermal systems is reiterated with examples of actual, practical systems.The material presented in this textbook is the outcome of many years ofteaching design of thermal systems, in elective courses and in capstone designcourses The inputs from many colleagues and former graduate and undergradu-ate students have been valuable in selecting the topics and the depth and breadth

Previ-of coverage Discussions with colleagues outside Rutgers University, particularly

at the conferences of the American Society of Mechanical Engineers, have beenimportant in understanding the instruction and concerns at other universities.Inputs from reviewers of the first edition were also useful in fine-tuning some

of the presentation The support and assistance provided by the editorial staff ofTaylor & Francis, particularly by Jessica Vakili, have been valuable in the devel-opment of the second edition Finally, I would like to acknowledge the encour-agement and support of my wife, Anuradha, and of our children, Ankur, Aseem,and Pratik, as well as Pratik’s wife, Leslie, and son, Vyan, for this effort It didtake me away from them for many hours and distracted me at other times Theirpatience and understanding is thus greatly appreciated

Yogesh Jaluria

Yogesh Jaluria, M.S., Ph.D., is currently Board of Governors Professor at

Rutgers, the State University of New Jersey, New Brunswick, and the chairman

of the Department of Mechanical and Aerospace Engineering He received hisB.S degree from the Indian Institute of Technology, Delhi, India, in 1970 Heobtained his M.S and Ph.D degrees in mechanical engineering from CornellUniversity

Jaluria has contributed more than 400 technical articles, including over 160 inarchival journals and 16 chapters in books He has two patents in materials pro-cessing and is the author/co-author of six books Jaluria received the 2003 RobertHenry Thurston Lecture Award from the American Society of MechanicalEngineers (ASME), and the 2002 Max Jakob Memorial Award for eminentachievement in the field of heat transfer from ASME and the American Institute

of Chemical Engineers (AIChE) In 2002, he was named Board of GovernorsProfessor of Mechanical and Aerospace Engineering at Rutgers University Hewas selected as the 2000 Freeman Scholar by the Fluids Engineering Division,ASME He received the 1999 Worcester Reed Warner Medal and the 1995 HeatTransfer Memorial Award for significant research contributions to the science ofheat transfer, both from ASME He also received the 1994 Distinguished AlumniAward from the Indian Institute of Technology, Delhi

Jaluria is a Fellow of ASME and a member of several other professionalsocieties He served as the chair of the Heat Transfer Division of ASME during

2002–2003 He is presently the editor of the ASME Journal of Heat Transfer.

Design is generally regarded as a creative process by which new methods, devices, and techniques are developed to solve new or existing problems Though many professions are concerned with creativity leading to new arrangements, struc-tures, or artifacts, design is an essential element in engineering education and practice Due to increasing worldwide competition and the need to develop new, improved, and more efficient processes and techniques, a growing emphasis is being placed on design Interest lies in producing new and higher quality products

at minimal cost, while satisfying increasing concerns regarding the tal impact and safety It is no longer adequate just to develop a system that per-forms the desired task to satisfy a recognized need of the society It is crucial to optimize the process so that a chosen quantity, known as the objective function,

environmen-is maximized or minimized Thus, for a given system, the output, profit, tivity, product quality, etc., may be maximized, or the cost per item, investment, energy input, etc., may be minimized

produc-The survival and growth of most industries today are strongly dependent on the design and optimization of the relevant systems With the advent of many new materials, such as composites and ceramics, and new manufacturing processes, several classical industries, such as the steel industry, have diminished in impor-tance in the recent years, while many new fields have emerged It is important

to keep abreast of changing trends in these areas and to use new techniques for product improvement and cost reduction Even in an expanding engineering area, such as consumer electronics, the prosperity of a given company is closely linked with the design and optimization of new processes and systems and optimiza-tion of existing ones Consequently, the subject of design, which had always been important, has become increasingly critical in today’s world and has also become closely coupled with optimization

In recent years, we have also seen a tremendous growth in the development and use of thermal systems in which fluid flow and transport of energy play a dominant role These systems arise in many diverse engineering fields such as those related to manufacturing, power generation, pollution, air conditioning, and aerospace and automobile engineering Therefore, it has become important to apply design and optimization methods that traditionally have been applied to mechanical systems, such as those involved with transmission, vibrations, con-trols, and robotics, to thermal systems and processes In this book, we shall focus

on thermal systems, considering examples from many important areas, ranging from classical and traditional fields like engines and heating/cooling to new and emerging fields like nanomaterials and fuel cells However, many of the basic concepts presented here are also applicable to other types of systems such as

those arising in different fields of engineering, for example, civil, chemical, trical, and industrial engineering.

elec-In this chapter, we shall first consider the main features of engineering design, its importance in the overall context of an engineering enterprise, and the need to optimize We will also examine design in relation to analysis, synthesis, selection

of equipment, and other important activities that support design This discussion will be followed by a consideration of systems, components, and subsystems The basic nature of thermal systems will be outlined, and examples of different types

of systems will be presented from many diverse and important areas

in terms of a new and different approach to the solution of an existing engineering problem that has been solved by other methods or a solution to a problem not solved before The process by which such new, different, or improved solutions are derived

and applied to engineering problems is termed design.

1.1.1 D ESIGN V ERSUS A NALYSIS

We are all quite familiar with the analysis of engineering problems using mation derived from basic areas such as statics, dynamics, thermodynamics, fluid mechanics, and heat transfer The problems considered are often relevant to these disciplines and little interaction between different disciplines is brought into play In addition, all the appropriate inputs needed for the problem are usually given and the results are generally unique and well defined, so that the solution to a given problem may be carried out to completion, yielding the final result that satisfies the various

infor-inputs and conditions provided Such problems may be termed as closed-ended.

The calculation of the velocity profile for developed, laminar fluid flow in a circular pipe to yield the well-known parabolic distribution shown in Figure 1.1(a)

is an example of analysis Similarly, the analysis of steady, one-dimensional heat conduction in a flat plate results in the linear temperature distribution shown in Figure 1.1(b) Textbooks on fluid mechanics and heat transfer, such as Fox and McDonald (2003) and Incropera and Dewitt (2001), respectively, present many

such analyses for a variety of physical circumstances Many courses are directed

at engineering analysis and students are taught various techniques to solve simple

as well as complicated problems in fundamental and applied areas Most students thus acquire the skills and expertise to analyze well-defined and well-posed prob-lems in different engineering disciplines

The design process, on the other hand, is open-ended, that is, the results are

not well known or well defined at the onset The inputs may also be vague or incomplete, making it necessary to seek additional information or to employ approximations and assumptions There is also usually considerable interaction between various disciplines, particularly between technical areas and those con-cerned with cost, safety, and the environment A unique solution is generally not obtained and one may have to choose from a range of acceptable solutions In addition, a solution that satisfies all the requirements may not be obtained and

it may be necessary to relax some of the requirements to obtain an acceptable

solution Therefore, trade-offs generally form a necessary part of design because

certain characteristics of the system may have to be given up in order to achieve some other goals such as greater cost effectiveness or smaller environmental

impact Individual or group judgment based on available information is needed to

decide on the final design

FIGURE 1.1 Analytical results for (a) developed fluid flow in a circular pipe and

(b) steady-state one-dimensional heat conduction in a flat plate.

x

– )

A Few Examples

Consider the example of an electronic component located on a board and being cooled by the flow of air driven by a fan, as shown in Figure 1.2 The energy dissipated by the component is given If the temperature distributions in the com-ponent, the board, and other parts of the system are to be determined, analysis or numerical calculations may be used for the purpose Even though the numerical procedure for obtaining this information may be quite involved, the solution is unique for the given geometry, material properties, and dimensions Different methods of solution may be employed but the problem itself is well defined, with all the input quantities specified and with no variables left to be chosen arbitrarily There are no trade-offs or additional considerations to be included

Let us now consider the corresponding design problem of finding the

appro-priate materials, geometry, and dimensions so that the temperature T c in the

component remains below a certain value, Tmax, in order to ensure satisfactory performance of the electronic circuit This is clearly a much more involved problem There is no unique answer because many combinations of materials, dimensions, geometry, fan capacity, etc., may be chosen to satisfy the given

requirement T c < Tmax There is considerable freedom and flexibility in ing the different variables that characterize the system Such a problem is, thus, open-ended and many solutions may be obtained to satisfy the given need and constraints, if any, on cost, size, dimensions, etc It is also possible that a sat-isfactory solution cannot be found for the given conditions and an additional cooling method such as a heat pipe, which conveys the heat dissipated at a much higher rate by means of a phase change process, may have to be included, as shown by the dotted lines in Figure 1.2 Then the design process must consider the two cooling arrangements and determine the relevant characteristic param-eters for these cases Thus, different approaches, often known as conceptual designs, may be considered for satisfying the given requirements

choos-Fan

Forced air flow

Electronic component

Circuit board

Heat pipe

FIGURE 1.2 An electronic component being cooled by forced convection and by a heat

pipe.

Another example that illustrates the difference between analysis and design

is that of a casting process, as sketched in Figure 1.3 Molten material is poured into a mold and allowed to solidify If the properties of the material undergoing solidification and of the various parts of the system, such as the mold wall and the insulation, are given along with the relevant dimensions, the initial temperature,

and the convective heat transfer coefficient h at the outer surface of the mold,

the problem may be solved by analysis or numerical computation to determine the temperature distributions in the solid material, liquid, and various parts

of the system, as well as the rate and total time of solidification for the casting (Flemings, 1974) The problem can often be simplified by using approximations such as constant material properties, negligible convective flow in the melt, uni-

form heat transfer coefficient h over the entire surface, etc But once the problem

is posed in terms of the governing equations and appropriate boundary tions, the results are generally well defined and unique

condi-We may now pose a corresponding design problem by allowing a choice of the materials and dimensions for the mold wall and insulation and of the cooling conditions at the outer surface, in order to reduce the solidification time below a desired value Tcast Then, many combinations of wall material and thickness, cool-ing parameters, insulation parameters, etc., are possible Again, there is no unique solution and, indeed, there is no guarantee that a solution will be found All that is given is the requirement regarding the solidification time and quantities that may

be varied to achieve a satisfactory design In other cases, the requirements may

be specified as limitations on the temperature gradients in the casting in order to improve the quality of the product Clearly, we are dealing with an open-ended problem without a unique solution

It is largely because of the open-ended nature of design problems that design

is often much more involved than analysis Consequently, while extensive mation is available in the literature on the analysis of various thermal processes and on the resulting effects of the governing variables, the corresponding design problems have received much less attention However, even though design and analysis are very different in their objectives and goals, analysis usually forms

infor-Insulation Mold Solid Melt Moving solid/melt interface

FIGURE 1.3 The casting process in an enclosed region.

the basis for the design process It is used to study the behavior of a given tem, choose the appropriate variables for the desired effects, and evaluate various designs, leading to satisfactory and optimized systems.

sys-1.1.2 S YNTHESIS FOR D ESIGN

Synthesis is another key element in the design process, since several components and their corresponding analyses are brought together to yield the characteristics

of the overall system Results from different areas have to be linked and sized in order to include all of the important concerns that arise in a practical system (Suh, 1990; Ertas and Jones, 1996; Dieter, 2000) We cannot consider only the heat transfer aspects in the casting problem while ignoring the strength of materials and manufacturing aspects Information from different types of mod-els, including experimental and numerical results, and from existing systems are incorporated into the design process The cost, properties, and characteristics of various materials that may be employed must also form part of the design effort, since material selection is a very important factor in obtaining an acceptable or optimal system Additional aspects, such as safety, legal, regulatory, and envi-ronmental considerations, are also synthesized in order to obtain a satisfactory design Figure 1.4 shows a sketch of a typical design process for a system, involv-ing both analysis and synthesis as part of the overall effort

synthe-Acceptable design obtained Yes

No Acceptable?

Analysis and evaluation Experimental

Inputs

FIGURE 1.4 Schematic of a typical design procedure.

1.1.3 S ELECTION V ERSUS D ESIGN

We are frequently faced with the task of selecting parts in order to assemble a system or a device that will perform a desired duty In several cases, the entire equipment may be selected from what is available on the market, for instance, a heat exchanger, a pump, or a compressor Even though selection is an important ingredient in engineering practice, it is quite different from designing a component

or device and it is important to distinguish between the two Selection largely involves determining the specifications of the item from the requirements for the given task Based on these specifications, a choice is made from the various types

of items available with different ratings or features Design, on the other hand, involves starting with a basic concept, modeling and evaluating different designs, and obtaining a final design that meets the given requirements and constraints The system may then be fabricated and tests carried out on a prototype before going into production Therefore, design is directed at creating a new process or system, whereas selection is concerned with choosing the right item for a given job.Selection and design are frequently employed together in the development of

a system, using selection for components that are easily available over the ranges

of interest Standard items such as valves, control sensors, heaters, flow meters, and storage tanks are usually selected from catalogs of available equipment Sim-ilarly, pumps, compressors, fans, and condensers may be selected, rather than designed, for a given application Obviously, design is involved in the develop-ment of these components as well; however, for a given system, the design of these individual components may be avoided in the interest of time, cost, and conve-nience For instance, a company that develops and manufactures heat exchangers would generally design different types of heat exchangers for different fluids and applications, achieving different ranges in heat transfer rate, area, effectiveness, flow rate, etc Different configurations such as counter-flow and parallel-flow heat exchangers, compact heat exchangers, shell-and-tube heat exchangers, etc., as shown in Figure 1.5, may be considered for a variety of applications These may then be designed to obtain desired parametric ranges of heat transfer rate, output temperature, size, etc (Kays and London, 1984) Design engineers working on another thermal system, such as air conditioning or indoor heating, may simply select the condenser, evaporator, or other types of heat exchangers needed, rather than design these

Selection is clearly a much less involved process, as compared to design The requirements and specifications of the desired component or equipment are matched with whatever is available If an item possessing the desired characteris-tics is not available, design is needed to obtain one that is acceptable for the given purpose Because selection is often used as part of the overall system design, the two terms are sometimes interchanged We are mainly concerned with the design

of thermal systems and, as such, selection of components needed for a system will be considered only as a step in the design process, particularly during the synthesis of the various parts

FIGURE 1.5 Common types of heat exchangers (a) Concentric pipe parallel-flow,

(b) concentric pipe counter-flow, (c) cross-flow with unmixed fluids, (d) fin-tube compact heat exchanger cores, (e) shell-and-tube (Adapted from Incropera, F.P and Dewitt, D.P., 1990.)