more information - www.cambridge.org/9781107015302 BUOYANCY EFFECTS ON NATURAL VENTILATION This book describes in depth the fundamental effects of buoyancy, a key force in driving air and transporting heat and pollutants around the interior of a building. This book is essential reading for anyone involved in the design and operation of modern sustainable, energy- efficientbuildings,whetherastudent,researcher,orpractitioner.The bookpresentsnewprinciplesinnaturalventilationdesignandaddresses surprising,little-knownnaturalventilationphenomenathatareseldom taughtinarchitectureorengineeringschools.Despiteitsscientificand appliedmathematicssubject,thebookiswritteninsimplelanguageand containsnodemandingmathematics,whilestillcoveringbothqualitat- iveandquantitativeaspectsofventilationflowanalysis.Itis,therefore, suitabletobothnon-expertreaderswhojustwanttodevelopintuition ofnaturalventilationdesignandcontrol(e.g.,architectsandstudents) andthosepossessingmoreexpertisewhoseworkinvolvesquantifying flows(e.g.,engineersandbuildingscientists). Dr.TorwongChenvidyakarnisSeniorTutorandLecturerintheArchi- tecturalInnovationandManagementProgramatShinawatraInterna- tionalUniversity,Thailand.Healsocurrentlyworksasabuildingcon- sultant and publishes internationally. Previously, Dr. Chenvidyakarn wasChairofTechnicalTeachingintheDepartmentofArchitectureat the University of Cambridge, where he lectured on building physics, buildinginnovation,architecturaldesign,andenvironmentaldesignin the Department of Architecture and Department of Engineering. He alsoheldafullFellowshipinArchitectureatMagdaleneCollegeanda DirectorshipofStudiesinArchitectureatMagdaleneandDowningCol- leges,Cambridge.HereceivedtheHappoldBrilliantAwardforExcel- lenceintheTeachingofBuildingPhysicsintheContextofaLowCarbon Economy from the Chartered Institution of Building Services Engin- eers,UK.Dr.Chenvidyakarncarriesoutresearchintheareaofsustain- ablebuildings,withparticularinterestsinthephysicsofnaturalvent- ilation,heatingandcooling,andtheimpactsofclimatechangeonthe designandmanagementofthebuiltenvironment.Aformerresearcher attheBP(BritishPetroleum)InstituteintheUnitedKingdom,hehas beenaguestlecturer/designcriticatanumberofuniversities. Buoyancy Effects on Natural Ventilation Torwong Chenvidyakarn FormerFellowandDirectorofStudiesinArchitecture, UniversityofCambridge,andSeniorTutor,Architectural InnovationandManagementProgramme,Shinawatra InternationalUniversity 32AvenueoftheAmericas,NewYork,NY10013-2473,USA CambridgeUniversityPressispartoftheUniversityofCambridge. ItfurtherstheUniversity’smissionbydisseminatingknowledgeinthepursuitof education,learningandresearchatthehighestinternationallevelsofexcellence. www.cambridge.org Informationonthistitle:www.cambridge.org/9781107015302 (cid:2)C TorwongChenvidyakarn2013 Thispublicationisincopyright.Subjecttostatutoryexception andtotheprovisionsofrelevantcollectivelicensingagreements, noreproductionofanypartmaytakeplacewithoutthewritten permissionofCambridgeUniversityPress. Firstpublished2013 PrintedintheUnitedStatesofAmerica AcatalogrecordforthispublicationisavailablefromtheBritishLibrary. LibraryofCongressCataloginginPublicationData Chenvidyakarn,Torwong. Buoyancyeffectsonnaturalventilation/byTorwongChenvidyakarn. pages cm Includesbibliographicalreferencesandindex. ISBN978-1-107-01530-2(hardback) 1.Naturalventilation. 2.Buoyantascent(Hydrodynamics) I.Title. TH7674.C47 2013 697.9ʹ2–dc23 2013007957 ISBN978-1-107-01530-2Hardback CambridgeUniversityPresshasnoresponsibilityforthepersistenceoraccuracyof URLsforexternalorthird-partyInternetWebsitesreferredtointhispublication anddoesnotguaranteethatanycontentonsuchWebsitesis,orwillremain, accurateorappropriate. Contents Preface pageix Acknowledgements xv 1 Introduction ...................................... 1 1.1. Themodellingquest 3 1.2. Water-bathmodelling 5 1.3. Thetheoreticalbasis 9 1.4. Applicabilityofwater-bathmodelling 14 1.5. Thecasesexamined 16 2 Somepreliminaries................................ 18 2.1. Variousconservationlaws 18 2.1.1. Conservationofmass 18 2.1.2. Conservationofthermalenergy 20 2.1.3. Conservationofbuoyancyflux 21 2.2. Equilibriumandneutrallevel 23 2.3. Bernoulli’stheorem 26 2.4. Effectiveopeningarea 27 2.5. Applicationofthebasicprinciples 30 v vi Contents 3 Sourcesofidenticalsign........................... 34 3.1. Residualbuoyancy 35 3.1.1. Mixingventilation 36 3.1.2. Displacementventilation 43 3.2. Thelocalisedsource 51 3.2.1. Plumetheory 51 3.2.2. Sealedenclosure 58 3.2.3. Ventilatedenclosure 62 3.2.4. Transientresponses 69 3.2.5. Multiplelocalisedsources 78 3.3. Thedistributedsource 96 3.3.1. Steady-stateflowregime 98 3.3.2. Evolutiontosteadystate 103 3.4. Acombinationofthelocalisedsourceandthe distributedsource 116 4 Sourcesofoppositesign........................... 126 4.1. Flushingwithpre-cooledair 127 4.2. Pre-cooledventilationofoccupiedspaces 143 4.2.1. Coolingtoaboveambientair temperature 144 4.2.2. Coolingtobelowambientair temperature 156 4.3. Maintainedsourceofheatandinternal cooling 165 4.3.1. Distributedsourceofheatanddistributed sourceofcooling 169 4.3.2. Localisedsourceofheatanddistributed sourceofcooling 175 4.3.3. Localisedsourceofheatandlocalised sourceofcooling 183 Contents vii 5 Somecommonflowcomplicationsarisingfrom morecomplexgeometries ......................... 190 5.1. Openingsatmorethantwolevels 191 5.1.1. Multiplestacks 191 5.1.2. Multiplesideopenings 204 5.2. Multipleconnectedspaces 218 5.2.1. Multi-storeybuildings 218 5.2.2. Spacesconnectedsideways 230 Finalremarks 247 References 249 Index 257