AIrflow Resistance of Seeds at Different Bulk Densities Using Erguns Equation

Airflow resistance of grains and oilseeds has been extensively studied. Traditionally the data has been presentedusing Shedds curves. However, this assumes that airflow resistance is independent of grain depth. Grain undergoescompaction during storage that changes the bulk density, porosity, and therefore the airflow resistance. Erguns equation isa function of particle size and porosity of the granular material. Airflow resistance by Erguns equation was used to predictthe pressure drop across a column of corn, soft white winter wheat, soft red winter wheat, and soybeans at three moisturecontent levels and two bulk densities. The maximum root mean square error when predicting airflow resistance using Ergunsequation was less than 23 Pa/m when the pressure drop was less than 500 Pa/m. If all data was included up to a pressure dropof 1800 Pa/m, the average root mean square error for calculating airflow resistance was 76 Pa/m. The effect of grainorientation that would be typical in storage bins was negligible, less than a 10% increase in airflow resistance over a rangeof kernel orientations that varied between -10, +10, and 20 from the angle of repose. However, the fill method andresulting bulk density increased the airflow resistance by an order of magnitude. Erguns equation, with an appropriate modelof porosity variation within a storage bin, could be utilized for the design and analysis of grain aeration systems.