The enrichment layer usually has large gaps and high voidage
. Cracks often develop and expand in the enrichment layer.
This gives reservoir voidage
replacement ratio of 1, without significant pressure depletion of the reservoir.
The total voidage
[phi] (%) of an element is written as 
In conclusion, the type of evolved hydrocarbons and their quantity changes with heating rate, which is a measure of the heat flux to the material, indicating either the change of the reaction mechanism or occurrence of complex and/or secondary reactions due to higher heat input to oil shale or presence of a catalyzing material, enhance chemical reactions or increase in system voidage
The bed porosity or voidage
(void fraction) is calculated by measuring the bulk density of chips and is defined as
All design features combined with the axial distribution of steam voidage
(from 0% at the bottom to 80% at the top) create a very complex 3D calculational problem.
The basic premise underlying our paper is the introduction into the set of constitutive variables of the time derivative of the voidage
to characterize the inelastic effects.
It is to be noted that, in the above models, the global operating conditions are used to deduce the correlation between drag coefficient and voidage
(or bed height), which neglect the effect of local information on the drag coefficient.
Properties such as size, thickness, superficial texture, and shape, which are usually not uniform for biological particulates, are key factors in defining packed-bed properties such as permeability, local voidage
and bulk density.
parameter which is marked as [chi] was employed to characterize the three groups of accumulation body loose, as follows:
Limits of applicability of capillary model in high voidage
beds-application to fixed beds of fibers and fluidized beds of spheres," Chemical Engineering Science, vol.