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Int.Agrophysics,2001,15,247-254INTERNATIONALAgrophysicswww.ipan.lublin.pl/int-agrophysicsEffectofthetriticalegrainmoisturecontentonthespontaneousheatingofgrainandonthepressureagainstthesilowallE.KusinskaDepartmentofEngineeringandMachinery,UniversityofAgriculture,Doswiadczalna44,20-236LublinReceivedOctober9,2000;acceptedMay29,2001Abstract.Theauthorpresentstheresultsofstudiesonthetemperatureandhorizontalpressureoftriticalegraininamodelsilo.Thestudiesincludedgrainwithaninitialmoisturecontentof13,16and18%w.b.Thegrainstoragedurationwas25days.Thestudyshowedthatgraintemperatureisaffectedbyitsinitialmoisturecontent.Thehighesttemperaturevalueswereobservedingrainwithaninitialmoisturecontentof18%w.b.Also,ahigherinitialmoisturecontentresultsingreaterincreasesinpressure.Keywords:triticale,moisturecontent,silo,heatingINTRODUCTIONTemperatureandmoisturecontentarethemostimportantfactorsaffectinggrainqualityinthecourseofitsstorage.Seasonalanddiurnalvariationintemperaturehaveanegativeeffectonstoredgrain,causewatermigrationandchangesinitsdistributionwithinthematerialstored.Theaccuratepredictionofmoisturecontentandthetemperatureofgraininstorageisnecessaryfortheeffectivecontroloftheprocessofventilation,appliedtoprovideoptimumstorageconditionsforgrainandtheminimizingofconditionsforinfestationbyinsects[2].Thefreemigrationofwaterdependsonanumberoffactors-thekindandqualityofgraininstorage,thesizeandshapeofthegrain,itstemperature,initialmoisturecontent,andatmosphericconditions.Italsodependsonthedurationofstorage,aswellasonthesorptiveanddiffusivepropertiesofthegrain.Thosefactorscausetheprocessofwatermigrationtobeunstable.Watertendstomigratefromwarmertocoolerareaswithingrainmass.Themigrationrateisfasteringrainwithahighermoisturecontentthanindrygrain[10].EFFECTSOFWATERMIGRATIONINPLANTMATERIALSNumerousauthorshavetriedtodescribethephenomenonofwatermigration.HolmanandCarter[10]studiedtheprocessinoveradozensoybeanvarietieswithdifferentbeansizes.Theyshowedthatwatermigrationtakesplaceinallsoybeanvarieties,whichresultsfromwateraccumulationinhigherlayersofmaterialinstorage.Schmidt[19]conductedexperimentsinvolvingmeasurementsofthewheatgrainmoisturecontentduringstorage.HefoundthatwatermigrationgenerallybeginsinthesecondhalfofSeptemberoratthebeginningofOctober.HellevangandHirning[9]performedastudyon16varietiesofbeansofvarioussizesduringtheperiodfromApriltoAugust.Theyobservedanaveragemoisturecontentdropby2.56%intheupperlayeranda0.45%increaseinthelayerlocated0.6to1.8mbelow.Knowledgeofchangesoccurringinthecourseofcerealgrainstorageisveryimportantforpracticalpurposes.Theapplicationofasuitablemodelforthecalculationanddeterminationofthequantitativeandqualitativedistributionofwaterandtemperaturewithinthegrainmassinstorage,thegrainbeingacommercialcommodity,canhelptheproperstorageofvariouscerealsunderavarietyofclimaticconditions.AnumericalmodelforthecalculationofwatermigrationwithingrainmassinstoragehasbeendevelopedbyKhankari[11].Hederivednon-linearequationsdescribingthetemperature,moistureandrateoffreeconvection,usingcurrentweatherdata.Thenumericalmodelforthecalculationofwatermigrationwasusedforthecalculationoftemperatureandmoisturedistributioningrain,forconditionsprevalentinMinnesota.Themodelwasbasedontheassumptionthatnaturalairconvectionistheprevalentphenomenonwithingrainmass.Themathematicalmodelwasthentestedexperim...