Solving Problems in Thermal Engineering: A Toolbox for Engineers PDF
Preview Solving Problems in Thermal Engineering: A Toolbox for Engineers
Power Systems Viktor Józsa Róbert Kovács Solving Problems in Thermal Engineering A Toolbox for Engineers Power Systems Electrical power has been the technological foundation of industrial societies for many years. Although thesystems designed to provide and apply electrical energy have reached a high degree of maturity, unforeseen problems are constantly encountered, necessitating the design of more efficient and reliable systems based on novel technologies. The book series Power Systems is aimed at providing detailed,accurateandsoundtechnicalinformationaboutthesenewdevelopmentsin electrical power engineering. It includes topics on power generation, storage and transmission as well as electrical machines. The monographs and advanced textbooks in this series address researchers, lecturers, industrial engineers and senior students in electrical engineering. ** Power Systems is indexed in Scopus** More information about this series at http://www.springer.com/series/4622 ó ó á Viktor J zsa R bert Kov cs (cid:129) Solving Problems in Thermal Engineering A Toolbox for Engineers 123 Viktor Józsa Róbert Kovács Department ofEnergy Engineering Department ofEnergy Engineering Faculty of MechanicalEngineering Faculty of MechanicalEngineering BudapestUniversity of Technology BudapestUniversity of Technology andEconomics andEconomics Budapest, Hungary Budapest, Hungary ISSN 1612-1287 ISSN 1860-4676 (electronic) Power Systems ISBN978-3-030-33474-1 ISBN978-3-030-33475-8 (eBook) https://doi.org/10.1007/978-3-030-33475-8 ©SpringerNatureSwitzerlandAG2020 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart 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 orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained hereinorforanyerrorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregard tojurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland to the memory of our young colleague, Gergely Novotni and to my wife, Ági, and our daughter, Julianna Viktor Józsa to my beloved parents Róbert Kovács Preface Thermal analysis is often omitted in practical research and industrial applications due to its secondary importance, hoping that heat will find its way in or out while theequipmentisfullyfunctional.Themarketpulliscruel,therearestrictdeadlines which usually does not allow a few extra days and engineer hours to spend. Therefore,thermalengineersarerarelyemployedinsmallcompanieswhoactually have serious thermal problems, leading to significant losses. In most cases, this viewpoint is initially viable and safe. The reliable operation will be guaranteed if enough tests were performed with the equipment. Nevertheless, malfunctions, crashes, and other events are often originated from thermal problems, and they comeupafterweeks,months,oryearsofuse.Theprincipalaimofthepresentbook is providing practical tools for solving thermal problems at all levels from the beginner to the researcher. It is always better to have a rough estimate in a paper (yes, even today, papers help a lot in solving complex problems to have a good overview from a distance of our eyes) than entirely omitting thermal evaluations since one does not have the background or confidence in using the state-of-the-art calculation tools. Solving thermal problems require abstract thinking since a small temperature difference does not hurt during testing, does not have color, odor, direction, and others.Furthermore,thetimescaleofthermalproblemsisusuallyexceededthatof chemical, fluid dynamical, and mechanical problems of the same physical size by ordersofmagnitude.Therefore,oldchurchesandcastleswiththickwallsvarytheir inside temperature marginally over the year while a tree trunk floating on a river maytravelkilometersinanhour.Insteadofdiggingdeepintothemodernmethods whichmightbeobsoleteinfewyearsoradecade,themainfocusofthisbookison discussing the necessary viewpoint to solve thermal problems, emphasizing the state-of-the-art challenges what should be solved for reliable operation or estima- tion, and modernly, ensure smart energy use. This latter criterion became standard since the beginning of the century; however, most of our current buildings, machines were designed earlier when these requirements were secondary, calling for a different design philosophy. vii viii Preface Thisbookisdividedintosixchapterswhicharelooselyconnectedbutrepresent different tools for solving thermal problems. Chapter 1 is focusing on the general approach of thermal problems, which is recommended to start with for beginners andindustrialengineers.Itdiscussesthefundamentalconceptsofathermalsystem, including boundaries, and basic calculation methods for estimating the thermal behavior. Chapter 2 is the summary of the governing equations of heat conduction to provide a framework of advanced modeling. It gives a brief overview of the mathematical structure of particular models, including heat conduction, fluid mechanics, diffusion and mechanics, situating them onto the same thermodynamic ground. It mostly uses the approach of Classical Irreversible Thermodynamics but also presents its possible extensions. Chapter 3 is focusing on thermal problems in energy engineering through several examples, concentrating on renewable technologies. To minimize our ecologicalfootprint,weneedefficientmachinesforagiven purpose.However,the losses are often realized as heat transfer or dissipation to the ambient. As our presentmachineswhichweusetodaywilllikelyremaininservicefordecades,their retrofit for efficient use of thermal energy is the problem of the present to solve. Hence,besidessolarandwindapplications,combustionisalsodiscussedregardless that is unpopular in the media. The space industry has exploded since the introduction of private companies in the past decade with viable plans to make commercial use of space resources. Hence,Chap.4isdedicatedtodiscussingthethermalbalanceanditschallengesin space. Nevertheless, most of the content can be directly applied to vacuum appli- cations on Earth as well. Chapter 5 focuses on the experimental proofs of non-Fourier thermal conduc- tion.Thatis,itincludeslowandroomtemperaturemeasurementsinwhichvarious phenomena are observed, such as second sound and ballistic propagation. It was initially measured in cryogenic conditions, which is usually far from applications. Nevertheless, the non-Fourier behavior was proven to be present even in room temperature under unsteady conditions, requiring heterogeneous materials or nano-sized objects. Typically, composites and layered structures from distinct materials fall into this category. Since the appearance of the non-Fourier behavior dependsontheparticularlengthandtimescales,oneshouldbeawareofthese,and that advanced thermal conduction models exist which are likely to appear in commercial simulation software codes in the near future. NumericalmethodsarediscussedinChap.6,focusingontheimplementationof boundary conditions both from numerical and analytical aspects. Furthermore, a particular way of error estimation is demonstrated on a conservative system which makes apparent how easy to obtain stable, but unphysical solutions. It affects all software.Therelevanceofthischapteristhatsimulationmodulesareavailableina rapidlyincreasingnumberofengineeringsoftware.Itisoftenafewclicksona3D drawingtogetathermalanalysiswithaconvergentresult.However,theusermust beawarethatthemodelalways remains anestimate oftherealprocess.Therefore, careful validation and method analysis are required prior to making any decision Preface ix based on a colorful result to avoid spectacular mechanical, thermal, and financial failures. Theproblemswhichwefeelinourskinrangefromthesizeofourplanetdown to the nano-size scale in the semiconductor industry where the continuum-based physics is still applicable. Consequently, understanding the governing logic and using the appropriate mathematical tools allow us to build a versatile knowledge independent of the given application and available software in the market. Wishing you joy and persistence in your life and career, Budapest, Hungary Viktor Józsa Róbert Kovács Acknowledgements TheauthorsthankTamásFülöp,PéterVán,MátáysSzücs,GregoryKowalski,and the BME Combustion Research Group for their valuable ideas, and their support. The work was supported by the grants National Research, Development and InnovationOffice—NKFIH116197(116375),124366(124508),123815,KH130378, FK124704, and FIEK-16-1-2016-0007, New National Excellence Program of the Ministry of Human Capacities ÚNKP-19-4-BME-213, the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, and the NVIDIA Corporation withthedonationoftheQuadroP6000whichwasusedforthecalculationspresented inChap.4.TheresearchreportedinthispaperwassupportedbytheHigherEducation Excellence Program of the Ministry of Human Capacities in the frame of NanotechnologyresearchareaofBudapestUniversityofTechnologyandEconomics (BMEFIKP-NANO). We would like to thank the Elsevier, APS, and Taylor&Francis for the permission to reuse the relevant figures. xi
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