Volume fraction of the pores

Cake Dryness In dewatering, usually the cake needs to be as diy as possible. Cake diyness is commonly measured by the solids fraction by weight W or by volume ,. The moisture content is measured by the complement of W or ,. The volume fraction of the pores and void in the wet cake is measured by the cake porosity (= 1 — ,) whereas the volume fraction of the liquid in the pores of the cake is measured by the saturation S. For welf-defined solids in the cake with sohd density (bone diy) p, and hquid density Pl, and given that the cake volume... 

If the volume fraction of the pores is /, the number of pores appearing in unit cross-section... 

Generally, porous materials have the porosity of 0.2-0.95. The porosity means the fraction of pore volume to the total volume. Let us consider a sample of total volume V. The volume of the solid phase is Vs, and the volume of the pore phase (the holes) is Vp, where V=VS +VP. The volume fraction is normalized variable that is generally more useful. The volume fraction of the pore phase is commonly called the porosity, and is denoted as ( )= Vp/V. The solid volume fraction is then described as 1-( )29. 

Another approach is to scale the A-term contribution to a so-called effective particle diameter as has been proposed by Vallano and Remcho [19], They defined an effective particle diameter from the perfusive EOF velocity within each volume fraction of the pore size distribution of the particles. Their model allows inclusion of both the intraparticle EOF and a pore size distribution. However, both this approach as well as Eq. (10) are more or less empirical. 

It is clear from Figure 3.12 that the amount of liquid penetration depends strongly on the liquid contact angle. In addition, since capillary pressures vary inversely with asperity size, the amount of liquid penetration also depends on the size of the asperity. These trends are shown in Figure 3.13 (page 65) where the volume fraction of the pore filled by liquid is plotted vs the contact angle for... 

A completely different approach is the so-caUed continuous pore size distribution proposed by Munch and Holzer [69], which is (from a statistical point of view) not a distribution function but a function of volume fractions. It is driven by the idea of a geometric implementation of porosimetry measurements with respect to image data. It is based on the determination of volume fractions of the pore phase which can be covered by a sphere with fixed radius rs > 0. 

Porosity is characterized by the volume fraction of pores, and their size, shape, and distribution. In ceramics, porosity can vary from 0 to >90% of the total volume of the material. Figure 11.1 shows how the electrical and thermal conductivities change with porosity. If the spherical pores are isolated, the conductivities decrease linearly with the volume fraction of the pores. On the other hand, in the case of porosity being continuous, there is almost a sudden decrease of conductivities to a very low value, and for larger values of porosity, the decrease becomes gradual. 

It is generally believed (refs.2,3) that the strength of a given mortar or cement is related to the pore size distribution as opposed to the volume fractions of the pores. The pore size distribution is governed by the nature of the starting materials and by the mode of mixing and compacting (ref. 4). 

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