Packing parameters

Figure C2.3.5. Mesoscale stmctures deriving from surfactants nominally exhibiting shapes corresponding to various packing parameter ranges.

Packer fluid Packing material Packing parameters Packings... 

The packing parameter ( ) (m) reflects the influence of the Hquid flow rate as shown in Figure 20. reflects the influence of the gas flow rate, staying at unity below 50% of the flooding rate but beginning to decrease above this point. At 75% of the flooding velocity, = 0.6. Sc is the Schmidt number of the Hquid. 

Fig. 20. Improved packing parameters ( ) for liquid mass transfer (a) ceramic Raschig rings (b) metal Raschig rings (c) ceramic Bed saddles (d) metal PaH...

The expanded version of the van Deem ter equation is used to help understand the relationships between the packing parameters and the gas flow. 

Figure 9-21G. Generalized pressure drop correlation for non-foaming systems for IMTP metal random packing. Parameter of curves is pressure drop in inches of water/foot packed height. Numbers in parentheses are mm of water/meter of packed height. Used by permission of Norton Chemical Process Products Corp., Bull-IHP-1, 12/91 (1987).

NH3-Air-H20, C12-H20, C02 in alkaline solutions, etc. Likewise, data for commercially available packings is well documented, such as packing factors, HETP, HTU, etc. Packing parameters are discussed in Chapter 8. 

The molecular descriptors refer to the molecular size and shape, to the size and shape of hydrophilic and hydrophobic regions, and to the balance between them. Hydrogen bonding, amphiphilic moments, critical packing parameters are other useful descriptors. The VolSurf descriptors have been presented and explained in detail elsewhere [8]. The VolSurf descriptors encode physico-chemical properties and, therefore, allow both for a design in the physico-chemical property space in order to rationally modulate pharmacokinetic properties, and for establishing quantitative structure-property relationships (QSPR). 

It is well known that the aqueous phase behavior of surfactants is influenced by, for example, the presence of short-chain alcohols [66,78]. These co-surfactants increase the effective value of the packing parameter [67,79] due to a decrease in the area per head group and therefore favor the formation of structures with a lower curvature. It was found that organic dyes such as thymol blue, dimidiiunbromide and methyl orange that are not soluble in pure supercritical CO2, could be conveniently solubihzed in AOT water-in-C02 reverse microemulsions with 2,2,3,3,4,4,5,5-octafluoro-l-pentanol as a co-surfactant [80]. In a recent report [81] the solubilization capacity of water in a Tx-lOO/cyclohexane/water system was foimd to be influenced by the compressed gases, which worked as a co-surfactant. 

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