Prediction of pressure drop through packed beds of granular materials: influence of moisture reduction and air velocity

Abstract

The influence of the moisture content of the solids on the pressure drop through packed beds of soy, barley, lentils and oats was investigated. The properties of the grains and the packed beds were determined varying the moisture contents of the solids between the equilibrium moisture content and 0.24 g g-1 (mass of water per mass of dry solid). The pressure drops were measured as a function of the aeration velocity under different moisture contents of the solids. It was observed that a reduction in the moisture content caused a decrease in the particle dimensions but did not affect their shape. Due to the reduction in size caused by the moisture removal, the packed beds become denser and less permeable to the airflow, resulting in an increase in the pressure drop. In the moisture range investigated, the pressure drops increased by more than 39% for lentils, soy and barley, and by about 24% for oats, indicating that the energy consumption during aeration could rise significantly. The parameters of the Forchheimer’s equation were modified to take into account the influence of the moisture content of the solids on the pressure drops. For each particle, empirical equations were proposed and shown to be adequate to accurately predict the pressure drop of the packed beds as a function of the moisture content and aeration velocity.

Heat and Mass Transfer during Sorghum Grains Drying in a Thick Fixed Bed with and without Change of Airflow Direction

“…Regardless of whether a conventional or reversal airflow configuration is employed, modelling thick-layer grain drying using the two-fluid model approach is a challenging task. This is mainly due to the substantial changes in the grains and packed bed properties, such as size, shape, porosity, and density, as moisture is removed [13][14][15]. Therefore, it is crucial to investigate the influence of grain´s moisture content on its physical properties and the properties of the packed bed to address this challenge effectively.…”