Abstract
This work deals with numerical simulation of powder caking process caused by capillary condensation phenomenon. Caking consists in unwanted agglomeration of powder particles. This process is often irreversible and not easy to predict. To reproduce mechanism involved by caking phenomenon we have used the Discrete Elements Method (DEM). In the present work, we mainly focus on the role of capillary condensation and subsequent liquid bridge formation within a granular medium exposed to fluctuations of ambient relative humidity. Such bridges cause an attractive force between particles, leading to the formation of a cake with intrinsic physicochemical and mechanical properties. By considering a Representative Elementary Volume (REV), the DEM is then performed by means of a MULTICOR-3D software tacking into account the properties of the cake (degree of saturation) in order to establish relationships between the microscopic parameters and the macroscopic behaviour (tensile strength).
Highlights
At relatively higher water activities, aw > 90%, water molecules become mobile enough to form liquid bridges, subsequently, the adsorbed molecules on the solid surface form a liquidlike a meniscus [2, 3]
The liquid interface is described by two principal radii, ρ1 and ρ2, that define the capillary radius rc 1
In the presence of water vapour condensation, the particles in the Representative Elementary Volume (REV) are subjected to attractive normal forces due to the formation of capillary bounds
Summary
At relatively higher water activities, aw > 90%, water molecules become mobile enough to form liquid bridges, subsequently, the adsorbed molecules on the solid surface form a liquidlike a meniscus [2, 3]. Sumptions and analytic models to characterise the capillary bond are given below
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