简介：Inthispaper,wedescribetheestimationoflow-altituderefractivitystructurefromsimulationandrealground-basedGPSdelays.Theverticalstructureoftherefractiveenvironmentismodeledusingthreeparameters,i.e.,ductheight,ductthickness,andductslope.Therefractivitymodelisimplementedwithaprioriconstraintsontheductheight,thickness,andstrength,whichmightbederivedfromsoundingsornumericalweather-predictionmodels.Araypropagationmodelmapstherefractivitystructureintoareplicafield.Replicafieldsarecomparedwiththesimulationobserveddatausingasquarederrorobjectivefunction.Aglobalsearchforthethreeenvironmentalparametersisperformedusingageneticalgorithm.Theinversionisassessedbycomparingtherefractivityprofilesfromtheradiosondestothoseestimated.Thistechniquecouldprovidenear-real-timeestimationoftheductingeffect.Theresultssuggestthatground-basedGPSprovidessignificantatmosphericrefractivityinformation,despitecertainfundamentallimitationsofground-basedmeasurements.Radiosondesaretypicallylaunchedjustafewtimesdaily.Consequently,estimatesoftemporallyandspatiallyvaryingrefractivitythatassimilateGPSdelayscouldsubstantiallyimproveover-estimatescausedbyusingradiosondedataalone.

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简介：Inthispaper,wepresentathreedimensionalnumericalinvestigationofheattransferinaparabolictroughcollectorreceiverwithlongitudinalfinsusingdifferentkindsofnanofluid,withanoperationaltemperatureof573Kandnanoparticleconcentrationof1%involume.Theoutersurfaceoftheabsorberreceivesanon-uniformheatflux,whichisobtainedbyusingtheMonteCarloraytracingtechnique.Thenumericalresultsarecontrastedwithempiricalresultsavailableintheopenliterature.AsignificantimprovementofheattransferisderivedwhentheReynoldsnumbervariesintherange2.57×104≤Re≤2.57×105,thetube-sideNusseltnumberincreasesfrom1.3to1.8times,alsothemetallicnanoparticlesimproveheattransfergreatlythanothernanoparticles,combiningbothmechanismsprovidesbetterheattransferandhigherthermo-hydraulicperformance.

简介：High-temperaturePhaseChangeMaterial(PCM)isusedasathermalstoragemediumofaheat-pipereceiverinanadvancedsolardynamicsystem.Withbothvoidcavityandnaturalconvectionconsidered,thermalperformanceoftheheat-pipereceiverisnumericallyanalyzedundergravity.TheresultsindicatethatthePCMcontainedintheintegratedheatpipeperformsanaveragingfunctionofheatloadings.Thethermalperformanceoftheheat-pipereceiverisstableandreliable.Whenaheatingcycleisstable,thetemperaturefluctuationsbothonheat-pipewallandinPCMcanisterremainlessthan13Kthroughoutasunlightandeclipsecycle.TheutilityofPCMisessentiallyimproved.ThemaximummeltingratioofPCMis92%.Undergravity,PCMmeltsmorequicklywiththeeffectofnaturalconvection.Naturalconvectionacceleratestheprocessofphasechanges.Numericalresultsarecomparedwiththeexperimentalresultsconcerned.Theaccuracyofnumericalmodelundergravityisverified.TheexperimentforthePCMcanisteronthegroundcanbewellpreparedwithournumericalsimulation.