Abstract
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.
Highlights
Grains and cereals are important staple foods that are cropped seasonally and have to be properly processed and stored to meet the market demand throughout the year
The purpose of this study was to investigate the influence of the moisture content of the solids on the pressure drops through packed beds of four widely consumed staple grains, namely soy, barley, lentils and oats, with moisture contents ranging from the equilibrium moisture up to 0.24 g.g-1
An investigation concerning the influence of the moisture content of the solids on the pressure drop through packed beds of biological particles was carried out for moisture levels varying from the equilibrium moisture up to 0.24 g g-1
Summary
Grains and cereals are important staple foods that are cropped seasonally and have to be properly processed and stored to meet the market demand throughout the year. Aeration in silos is commonly used to improve the storability of grains, because forced ventilation helps to keep uniform temperatures throughout the silo, and contributes to avoiding moisture migration and removing the odours of the stored grain masses, and can be used to apply fumigation (Khatchatourian & Savicki, 2004; Khatchatourian et al, 2017). The static pressure requirements of the fan used for aeration, drying or cooling of a packed bed of grains, is determined by the resistance of the packed grains to the airflow. The pressure drop across a homogeneous packed bed of granular material can be predicted by Forchheimer’s equation, given by (Coulson & Richardson, 2002):
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