Mathematical modelling of heat and moisture transfer of wheat stored in plastic bags (silobags)

ANALIA GASTON; RITA ABALONE; RICARDO BARTOSIK; JUAN RODRIGUEZ

BIOSYSTEMS ENGINEERING

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2009 vol. 104 p. 72 - 85

1537-5110

A bidimensional finite element model that predicts temperature distribution and moisturemigration of wheat stored in silobags due to seasonal variation of climatic conditions isdescribed. The model includes grain respiration and calculates carbon dioxide and oxygenconcentrations during storage as well as the associated dry matter loss.The model validation was carried out by comparing predicted with measured temperatureand moisture content (MC) data. The temperature standard errors of the model validationwere 1.94 C at the bottom, 1.35 C in the middle and 1.20 C at the top layer. The modelpredicted moisture increase in the top grain layer during storage ranging from 1.0 to 1.5%w.b., while the measured increase ranged from 0.4 to 0.8% w.b.Predicted average CO2 and O2 concentrations were compared with measured data. For drywheat (12.5% w.b.), after 100 days of storage, differences in concentrations were 1.8 and0.6% points for CO2 and O2, respectively. For wet wheat (16.4% w.b.), the model predictedthe total consumption of O2 after five days while the observed O2 data never dropped below5%. The difference between the measured and predicted CO2 concentration for the fifth daywas 1.1%. For the range of MCs considered in this work, the change in CO2 concentrationduring storage was satisfactorily predicted by use of White et al. (1982) estimation of CO2production rate, but prediction of O2 concentration was poor for wet grain.