Designation:D4784−93(Reapproved2015)StandardSpecificationforLNGDensityCalculationModels1ThisstandardisissuedunderthefixeddesignationD4784;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThisspecificationisadescriptionoffourmathematicalmodelsoftheequationofstateforLNG-likemixturesthatwereadoptedin1988.Thefourmodelsincludeanextendedcorrespondingstatesmodel,acellmodel,ahardspheremodel,andarevisedKlosekandMcKinleymodel.Eachofthemodelshasbeenoptimizedtothesameexperimentaldatasetwhichincludeddataforpurenitrogen,methane,ethane,propane,isoandnormalbutane,isoandnormalpentane,andmixturesthereof.ForLNG-likemixtures(mixturesoftheorthobaricliquidstateattemperaturesof120Korlessandcontainingatleast60%methane,lessthan4%nitrogen,lessthan4%eachofisoandnormalbutane,andlessthan2%totalofisoandnormalpentane),allofthemodelsareestimatedtopredictdensitiestowithin0.1%ofthetruevalue.ThesemodelsweredevelopedbytheNationalInstituteofStandardsandTechnology(formerlytheBureauofStandards)uponculminationofsevenyearsofeffortinacquiringphysicalpropertiesdata,performingextensiveexperimentalmeasurementsusingspeciallydevelopedequipment,andinusingthesedatatodeveloppredictivemodelsforuseindensitycalculations.1.Scope1.1ThisspecificationcoversLNGdensitycalculationmod-els2foruseinthecalculationorpredictionofthedensitiesofsaturatedLNGmixturesfrom90to120Ktowithin0.1%oftruevaluesgiventhepressure,temperature,andcompositionofthemixture.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.SignificanceandUs...
