Specific interfacial surface area

The specific interfacial surface area, S, defined as the ratio of interfacial surface area. A, to thl volume, V, is calculated from the value of correlation distance obtained by plotting the scattered intensity in the Debye fashion [ 12,38]. 

Table III shows the result of SANS analysis on fully polymerized PB/PS IPN s, seml-IPN s, and chemical blends by Fernandez et al. [ n.] The specific interfacial surface area was shown to increase with Increasing crosslink density, S decreasing in the order full-IPN s, semi-I IPN s, seml-II IPN s afid chemical blends, as expected from many earlier studies. Its value ranges from 20 to 200 m /gm, in the range of true colloids. This result is particularly important because interfacial surface area is closely related to toughness and impact strength.

Regime 5 - instantaneous reactions at an reaction plane developing inside the film For very high reaction rates and/or (very) low mass transfer rates, ozone reacts immediately at the surface of the bubbles. The reaction is no longer dependent on ozone transfer through the liquid film kL or the reaction constant kD, but rather on the specific interfacial surface area a and the gas phase concentration. Here the resistance in the gas phase may be important. For lower c(M) the reaction plane is within the liquid film and both film transfer coefficients as well as a can play a role. The enhancement factor can increase to a high value E > > 3. 

Figure 7. The specific interfacial surface area goes through a broad maximum as polystyrene content increases. (Reproduced firom ref. 18. Copyright 1988 American Chemical Society.)...

Re = Reynolds number S = fluid constant p = density t = dynamic viscosity g = aerated 0 = not aerated qg gas throughput n = stirrer speed di = impeller diameter OTR = oxygen transfer rate from gas to liquid phase Fl = mass transfer coefficient a = specific interfacial surface area ... 

Aluminum foam can be used as a porous medium in the model of a heat sink with inner heat generation (Hetsroni et al. 2006a). Open-cell metal foam has a good effective thermal conductivity and a high specific solid-fluid interfacial surface area. 

Note that in the definition of Kia, the interfacial surface area is in general based on the liquid volume. This definition is consistent with the material balances in the reactor and in particular the gas-phase balances. However, in correlations published for Kia values, most authors use a specific area Ud based on the total volume of the gas-liquid dispersion (24.12). Ud and a are connected via the gas holdup s ... 

Thus far, the discussion of reaction rate has been confined to homogeneous reactions taking place in a closed system of uniform composition, temperature, and pressure. However, many reactions are heterogeneous they occur at the interface between phases, for example, the interface between two fluid phases (gas-liquid, liquid-liquid), the interface between a fluid and solid phase, and the interface between two solid phases. In order to obtain a convenient, specific rate of reaction it is necessary to normalize the reaction rate by the interfacial surface area available for the reaction. The interfacial area must be of uniform composition, temperature, and pressure. Frequently, the interfacial area is not known and alternative definitions of the specific rate are useful. Some examples of these types of rates are ... 

FIGURE 11.11 Specific droplet surface area A (and average droplet size surfactant concentration c, obtained at approximately constant emulsification conditions for various surfactants PVA = poly(vinyl alcohol) also for soy protein a plateau value of A is reached, at about 20kg-m 3. Approximate plateau values for the interfacial tension y are 3, 10, and 20 mN-ur1 for the nonionic, caseinate, and PVA, respectively. 

The specific interfacial area (a s) can be estimated as Interfacial surface area. W L 1... 

The specific contact surface area necessitated for mass transfer in a gas-liquid dispersion or more generally in any type of gas-liquid reactor is defined as the interfacial contact area of all the bubbles or drops or phase element such as films or rivulets within a volume element divided by the volume of that element. ... 

An understanding of much of aqueous geochemistry requires an accurate description of the water-mineral interface. Water molecules in contact with> or close to, the silicate surface are in a different environment than molecules in bulk water, and it is generally agreed that these adsorbed water molecules have different properties than bulk water. Because this interfacial contact is so important, the adsorbed water has been extensively studied. Specifically, two major questions have been examined 1) how do the properties of surface adsorbed water differ from bulk water, and 2) to what distance is water perturbed by the silicate surface These are difficult questions to answer because the interfacial region normally is a very small portion of the water-mineral system. To increase the proportion of surface to bulk, the expanding clay minerals, with their large specific surface areas, have proved to be useful experimental materials. 

In these equations, a is the specific interfacial area for a significant degree of surface aeration (m2/m3), I is the agitator power per unit volume of vessel (W/m3), pL is the liquid density, o is the surface tension (N/m), us is the superficial gas velocity (m/s), u0 is the terminal bubble-rise velocity (m/s), N is the impeller speed (Hz), d, is the impeller diameter (m), dt is the tank diameter (m), pi is the liquid viscosity (Ns/m2) and d0 is the Sauter mean bubble diameter defined in Chapter 1, Section 1.2.4. 

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