Resistance of Bulk Poppy Seeds to Airflow

The resistance to airflow of bulk poppy seeds, expressed as pressure drop across unit depth of bed, was measured in the ranges of 6·21–18·37% d.b. of moisture content, 558·3–592·7 kg m−3 of bulk density, 0–10% of fines content, 250–1000 mm of bed depth and 0·03–0·08 m3 s−1 m−2 of airflow rate. The pressure drop through the poppy seed beds increased with an increase in airflow rate, bed depth, bulk density and fines content and with a decrease in moisture content. The pressure drop was observed to increase more rapidly with increasing airflow rates than with increasing bed depth. An increase in the moisture content range of 6·21–18·37% d.b. resulted in about 24·67% decrease in pressure drop, while an increase in bulk density by about 6·16% caused an increase in pressure drop by about 28·25% and an increase in fines content by 10% caused an increase in pressure drop by about 30·08%. A non-linear regression procedure was used to fit the Sheddʹs equation and the Hukill and Ives equation to the experimental pressure drop data obtained and to develop a statistical model. The models were compared using the coefficient of determination, mean relative percent deviation and standard error of the estimate. The Sheddʹs equation provided a higher value for the coefficient of determination and lower values for the standard error of the estimate and the mean relative percent deviation than the Hukill and Ives equation. The developed statistical model was found to predict satisfactorily the pressure drop across poppy seed beds within the experimental range of study.