Air-Flotation, Pneumatic Conveying Velocities, and Airflow Relationships for Coffee Fruits and Coffee Beans

Abstract

Air-flotation and -conveying velocities for coffee fruits, pulp, and beans determined and calculated using the pitot-tube formula, under normal air conditions, compare favorably with values in work done with other crops and fit closely in the Sturtevant pneumatic conveying curve developed by Westinghouse (8). Air-conveying velocities of 5,683, 5,750, 4,925, and 5,455 feet per minute were obtained for green fruits, ripe fruits, pulp, and pulped washed beans, respectively. Ripe coffee fruits offer a higher resistance to airflow than the green ones. The higher the moisture content in parchment coffee the higher the resistance to airflow. A straight-line relationship results when the static pressure, in inches of water, is plotted logarithmically versus the airflow for coffee fruits and beans.