Air distribution from ventilation ducts under grain

Abstract

Using experimental measurements and simulations, air pressures in perforated ventilation ducts under bulks of grain were related to air distribution through the grain above the ducts. In shallow grain layers and at high velocities, the static pressure in the duct close to the fans was up to 20 times that at the distant end when the air was sucked into the ducts, so producing a large difference in airflow through the grain bulk at opposite ends of the duct. When air was blown into the ducts the air distribution improved considerably, although a regain of static pressure occurred at the distant end of the duct of up to 4 times that at the fan end. In blowing systems, air distribution was acceptable at moderate air velocities in a duct of constant cross section but was improved by reducing the diameter of the ducting in stages along the store, by increasing the grain depth, by introducing partial barriers into the duct or by using ducts with higher internal friction.