PH—Postharvest Technology: Airflow Resistance of Paddy and its Byproducts

Designers of grain cooling and drying systems require data on airflow resistance of grains and oilseeds for the accurate selection of fans, for assessment of filling depths in storage bins, and mathematical prediction of pressure and airflow patterns in the stored mass. An experimental study was performed to determine the resistance to airflow (expressed as pressure drop per unit depth of bed for a known airflow rate) of paddy and its byproducts. Effects of the parameters such as moisture content, airflow rate, direction of airflow (both vertical and horizontal) and fines and chaff content on the resistance to airflow were studied. The resistance to airflow of paddy increased with an increase in fines and chaff content and a decrease in moisture content. The pressure drops developed by the three paddy varieties tested, were different at the same airflow rates because of differences in physical dimensions and properties among them. The highest pressure drop was observed in broken grains and the lowest in parboiled paddy than the other paddy constituents like raw paddy, raw rice and parboiled rice. The resistance to airflow of paddy and its byproducts in the horizontal direction was 0·19–0·31 times the resistance to airflow in the vertical direction.