?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F299%2F&rft.title=Temperature+and+Moisture+Gradients+in+Sugar+Silos&rft.creator=Lacey%2C+Andrew&rft.creator=Sorensen%2C+Mads+Peter&rft.subject=Food+and+Drink&rft.subject=Materials&rft.description=Danisco+Sugar+is+the+main+sugar+producer+in+Denmark.+The+sugar+is+extracted+from+sugar+beets+which+are+harvested+during+the+beet+campaign+September+--+December.+The+refined+sugar+is+stored+in+huge+silos+and+withdrawn+on+a+regular%2C+but+not+constant%2C+basis+for+distribution+until+the+next+campaign.+Danisco+Sugar+utilizes+several+types+of+silos+for+the+storage+of+crystalline+sugar.+They+differ+in+construction+material+e.g.+concrete+or+steel+plate+silos%2C+dimension%2C+design+with+or+without+a+central+tower+and+isolation.+Various+methods+of+filling+and+emptying+are+utilized%2C+that+is+first+in+-+last+out%2C+or+first+in+-+first+out.+The+silos+are+equipped+with+one+or+more+facilities+for+sugar+conditioning.+Those+includes+temperature+control+of+walls%2C+control+of+the+condition+of+the+air+space+above+sugar%2C+ability+to+blow+conditioned+air+through+the+bulk+sugar+etc.%0D%0A%0D%0AA+number+of+problems+arise+when+storing+sugar+for+long+periods.+Due+to+distribution+of+heat+and+moisture+the+sugar+can+%60cake'+or+harden+and+moist+sugar+is+difficult+to+empty+from+the+silos.+The+chemical+and+microbial+stability+of+the+sugar+is+influenced+by+the+temperature+and+moisture+distribution.+On+the+other+hand+under+very+dry+conditions+there+is+a+risk+of+dust+explosions.+The+object+is+to+control+the+temperature+and+moisture+content+within+a+lower+and+an+upper+limit.+Danisco+Development+Centre+wishes+to+employ+mathematical+modelling+as+a+tool+for+understanding+and+predicting+temperature+and+moisture+distribution+in+sugar+stored+in+silos.%0D%0A%0D%0AIn+moisture+migration+the+physical+processes+which+have+to+be+taken+into+account+are+diffusion+in+the+porous+bulk+sugar%2C+natural+convection+due+to+temperature+gradients%2C+forced+convection+due+to+bulk+sugar+air+conditioning%2C+conditioning+of+the+air+above+the+bulk+sugar+and+migration+of+moisture+through+concrete+silo+walls.+The+temperature+distribution+is+influenced+by+seasonal+variations%2C+the+temperature+of+the+air+space+above+the+bulk+sugar%2C+remixing+processes+when+filling+and+emptying+silos%2C+air+conditioning+and+others.+The+following+physical+properties+are+assumed+of+importance+when+formulating+models+to+describe+the+formation+of+temperature+and+moisture+gradients%3A+bulk+sugar+heat+capacity%2C+heat+conductivity%2C+density%2C+porosity%2C+tortuosity+and+sorption+isotherms.+Most+will+vary+with+the+sugar+quality+(that+is%3A+crystal+size%2C+reducing+sugar+content+and+ash+content)%2C+some+with+temperature+and+moisture.%0D%0A%0D%0AMathematical+models+for+moisture+and+heat+conduction+in+stored+cereal+grains+have+previously+been+developed.+In+modelling+moisture+and+heat+conduction+in+sugar+our+starting+point+is+to+use+the+approach+applied+in+modelling+moisture+and+heat+conduction+in+grain+and+adopt+the+model+to+the+case+of+stored+sugar%2C+including+the+possibility+of+air+conditioning.%0D%0A%0D%0AIn+our+modelling+carried+out+during+the+week+of+the+Study+Group%2C+we+used+a+number+of+simplifying+assumptions%2C+such+as+air+flow+through+the+sugar+being+dominated+by+forced%2C+and+constant%2C+convection%2C+and+having+processes+happening+fast+enough%2C+so+that+local+equilibrium+holds.+(Estimates+obtained+at+the+time+indicated+that+the+temperature+varies+very+little+over+the+length+scale+of+the+sugar+grains+and+their+interstices.)&rft.date=1998&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpostscript&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F299%2F1%2Fdanisco.ps&rft.identifier=++Lacey%2C+Andrew+and+Sorensen%2C+Mads+Peter++(1998)+Temperature+and+Moisture+Gradients+in+Sugar+Silos.++%5BStudy+Group+Report%5D+++++