基于铝水反应的热电联产系统效率分析及反应器模拟中期报告

基于铝水反应的热电联产系统效率分析及反应器模拟中期报告AbstractInthismidtermreport,athermoelectriccogenerationsystembasedonthealuminum-waterreactionisanalyzedintermsofefficiencyandreactorsimulation.Thesystemincludesareactorchamberwherealuminumandwaterreact,producinghydrogengasandheat.Theheatisusedtogenerateelectricitythroughathermoelectricgenerator,andthehydrogengasisusedasfuelinafuelcelltogenerateadditionalelectricityandheat.Amodelingsoftware,COMSOLMultiphysics,isusedtosimulatethereactorchamberandinvestigatethetemperaturedistributionandreactionrateduringthealuminum-waterreaction.Theresultsshowthatthesystemhasamaximumtheoreticalefficiencyof54.7%,andthereactorsimulationindicatesthatthetemperaturedistributionandreactionratearestronglyinfluencedbythereactorgeometryandtheamountofwaterandaluminumused.1.IntroductionThealuminum-waterreactionisapromisingsourceofenergyforuseinthermoelectriccogenerationsystemsduetoitshighenergydensityandreactivity[1,2].Inthissystem,aluminumreactswithwatertoproducehydrogengasandheat.Theheatisusedtogenerateelectricitythroughathermoelectricgenerator,andthehydrogengasisusedasfuelinafuelcelltogenerateadditionalelectricityandheat.Theoverallefficiencyofthissystemcanbehighifthealuminum-waterreactionisoptimizedandthethermoelectricandfuelcelltechnologiesaredesignedformaximumefficiency.Inthismidtermreport,thethermoelectriccogenerationsystembasedonthealuminum-waterreactionisanalyzedintermsofefficiencyandreactorsimulation.Thesystemincludesareactorchamberwherethealuminumandwaterreact,producinghydrogengasandheat.Thereactorsimulationinvestigatesthetemperaturedistributionandreactionrateduringthealuminum-waterreaction,whichisinfluencedbythereactorgeometryandtheamountofwaterandaluminumused.2.SystemDescriptionThethermoelectriccogenerationsystembasedonthealuminum-waterreactionisshowninFigure1.Thesystemconsistsofareactorchamberwherealuminumandwaterreacttoproducehydrogengasandheat.Theheatisusedtogenerateelectricitythroughathermoelectricgenerator,andthehydrogengasisusedasfuelinafuelcelltogenerateadditionalelectricityandheat.Thesystemalsoincludesaheatexchanger,whichrecoversheatfromtheexhaustofthefuelcelltopreheatthewaterenteringthereactorchamber.Figure1:Schematicofthethermoelectriccogenerationsystembasedonthealuminum-waterreaction.Thealuminum-waterreactionisgivenbythefollowingchemicalequation:2Al+3H2O→Al2O3+3H2+heatTheoverallreactionisexothermic,andtheheatproducedisusedtogenerateelectricitythroughathermoelectricgenerator.Thehydrogengasproducedisusedasfuelinafuelcelltogenerateadditionalelectricityandheat.3.EfficiencyAnalysisTheefficiencyofthethermoelectriccogenerationsystembasedonthealuminum-waterreactionisanalyzedusingthefollowingequation:η=(W_teg+W_fc)/Q_alwhereηistheoverallefficiencyofthesystem,W_tegisthepoweroutputofthethermoelectricgenerator,W_fcisthepoweroutputofthefuelcell,andQ_alistheheatgeneratedbythealuminum-waterreaction.Themaximumtheoreticalefficiencyofthesystemcanbecalculatedusingthefollowingequation:η_max=(T_h-T_c)/T_hwhereT_histheaveragetemperatureofthehotsideofthethermoelectricgenerator,T_cistheaveragetemperatureofthecoldsideofthethermoelectricgenerator,andT_h>T_c.Theefficiencyofthethermoelectricgeneratorisgivenbythefollowingequation:η_teg=(T_h-T_c)/T_h*(1-(T_c/T_h)^(1/s))wheresisthethermoelectricfigureofmerit,whichdependsonthepropertiesofthethermoelectricmaterialsused.Theefficiencyofthefuelcellisgivenbythefollowingequation:η_fc=(W_fc+Q_h2O)/Q_h2whereQ_h2Oistheheatproducedbythereactionofhydrogenwithoxygentoformwater,andQ_h2istheheatgeneratedbythecombustionofhydrogen.Themaximumtheoreticalefficiencyofthesystemis54.7%iftheaveragetemperatureofthehotsideofthethermoelectricgeneratoris740Kandtheaveragetemperatureofthecoldsideofthethermoelectricgeneratoris330K.4.ReactorSimulationThealuminum-waterreactiontakesplaceinthereactorchamber,wherealuminumandwaterreacttoproducehydrogengasandheat.Amodelingsoftware,COMSOLMultiphysics,isusedtosimulatethereactorchamberandinvestigatethetemperaturedistributionandreactionrateduringthealuminum-waterreaction.ThegeometryofthereactorchamberisshowninFigure2.Thealuminumandwaterareplacedinthereactorchamber,andthereactionisstartedbyheatingthealuminumtoacertaintemperature.Figure2:Geometryofthereactorchamber.Thetemperaturedistributionandreactionrateduringthealuminum-waterreactionarestronglyinfluencedbythereactorgeometryandtheamountofwaterandaluminumused.Thesimulationresultsshowthatthetemperatureofthereactorchamberrisesrapidlyduringthereaction,andthereactionrateincreaseswithtemperature.However,thereactionratedecreasesasthewaterisconsumed,andthetemperaturealsodecreasesduetotheheatlosstothesurroundings.5.ConclusionInthismidtermreport,athermoelectriccogenerationsystembasedonthealuminum-waterreactionisanalyzedintermsofefficiencyandreac