Loose random packing

Figure 9.19 Typical dependence of the porosity, s, of a bidisperse PS with loose random packing of globules size of on partial volume of the larger particles X, and K=D ID2.

For a particulate system with a relatively narrow size distribution and the loose random packing pattern, a approaches to 0.268 at around 1.38,... 

Figure 19.21 Dependence of porosity of a random packing of spherical particles in a cylinder container according to 1 [104], 2 [105], (3), (4) for loose and dense packings by [102], Solid lines correspond to calculations using Equation 9.42a through Equation 9.42c.

Zou and Yu (1996) studied both loose and dense random packing of monosized nonspherical particles and found that the porosity was strongly dependent on both the particle shape and the packing method. The initial porosity of loose and dense random packings can be expressed as... 

The voidage of irregular particles has to be determined empirically at present (Cumberland and Crawford, 1987). For random packing, e.g. particulate material poured into container and then tapped, voidage is generally in the range = 0.40 (loose) < e < 0.36 (dense). 

Experiment shows that heat is absorbed as iodine dissolves. The regular, ideally packed iodine crystal gives an iodine molecule a lower potential energy than does the random and loosely packed solvent environment. We see that the second factor, tendency toward minimum energy, favors precipitation and growth of the crystal. 

Columns, scrubbers, reactors, and similar process vessels, particularly those containing packed beds, either structured or random (or loose-fill), can be susceptible to internal fires when they are opened to the atmosphere for internal... 

In Figure 1, a is plotted vs. ax for a face-centered lattice (a close-packed lattice) and for a simple cubic lattice (a loose-packed lattice). We notice that (1) the dependence of a on ax can be regarded as being practically the same for both lattices and that, (2) tx undergoes a rapid change around x = xc, which is the point at which a = 0 (Fig. 1). However, p/a does not attain the value it would have for the case of the unrestricted random walk model at x = xc, since at this point, p/a > 1 (Fig. 2), while for unrestricted chain pja = 1. Moreover, the dependence of p/a on ax is not the same for the two lattices while a as a function of ax is practically independent of the lattice. 

Figure 21. Cellulose microfibrils in the primary wall and Sj portion of the secondary wall from a longitudinal tracheid. Note the loosely packed ana randomly arranged microfibrils in the primary wall (P). The S layer (S) consists of tightly packed, parallel microfibrils. 12,000X...

---