ABSTRACT Knowledge of physical and aerodynamic properties of seeds and grains is useful for the design of equipments for processing, aeration, sorting and other post-harvest operations of agricultural products. To study aeration of tef seed bulk, pressure drop and physical and aerodynamic properties of tef seeds and tef seed bulk were measured or predicted as a function of moisture content. The average length and width of tef seeds were found to increase from 1.05 to 1.20 mm and 0.61 to 0.70 mm, respectively for the moisture content range considered. The geometric mean, equivalent diameters and sphericity increased from 0.73 to 0.83 mm, from 0.78 to 0.87 mm and from 69.02 to 70.83%, respectively as the moisture content increased. The thousand grain mass increased from 0.3309 to 0.3904 g, the true density decreased from 1310.03 to 1120 kg/m 3, the bulk density decreased from 806.53 to 650.63 kg/m 3, and the porosity of the tef seeds increased from 38.43 to 41.91%, as the moisture content increased. The terminal velocity of the tef seeds increased from 3.19 to 3.72 m/s and the drag coefficient decreased from 0.709 to 0.516 as the moisture contents changed from 12.01 to 25.01% (wet basis). The measured pressure drop decreased from 1.975 to 1.625 kPa/m, when loose fill method was applied, in the moisture content range studied, while the measured pressure drop decreased from 2.014 to 1.75 kPa/m, when applying the dense fill method in the moisture content range studied. The pressure drop calculated according to the Ergun’s equation using the loose fill method reduced from 1.872 to 1.468 kPa/m. The calculated pressure drop decreased from 2.044 to 1.508 kPa/m as the moisture content increased from 12.01 to 25.01% (w.b.), when dense fill method was applied. Mean relative percent errors between measured and calculated pressure drops were 8.43% and 7.36%, respectively for loose and dense fill method.
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