Pressure versus airflow characteristics were determined for various densities and cut sizes of green tobacco leaves with leaf surfaces oriented either parallel or perpendicular to the airflow. The flowrate measurement device consisted of a fan,PVC pipe, orifice plate, sealing apparatus, and a plenum. Graphs of pressure gradient versus superficial velocity showed a nearly linear log-log relationship. Three equations were used to fit the data: the power equation, ASAE standard equation, and Ergun equation. The Ergun equation provided the best fit in most cases. Analysis of variance of equation parameters with experiment variables showed that the pressure gradient was a function of the leaf density squared. The only other factor affecting thepressure gradient was the leaf orientation. For a given velocity, leaves oriented perpendicular to the airflow had a pressure gradient about 10 times greater than that of the leaves oriented parallel to the airflow.
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