Foam volume ratio

Surfactant Oil phase Foam volume after x minutes, x = 30 min Foam volume ratio oil/no oil... 

The value of the 1.0X 1.5X brine foam volume ratio at 75 C may be taken as a measure of the sensitivity of surfactant foaming properties to aqueous phase salinity. Values of this ratio determined at 75 C in the presence of decane are summarized below ... 

Surfactant 30 min Foam Volume (cc) Foam Volume Ratio 30 min l min. 

PhenoHc MicrobaUoons appHcations in plastics take advantage of low density, porosity, and surface-to-volume ratio to produce lightweight parts. Probably the most notable example is the syntactic foam. 

Fig. 35. Maximum foaming volume of styrene diviaylben2ene copolymers containing 8.8 wt % CO2 as a function of divinylben2ene content and temperature. Numbers beside curves indicate wt % divinylben2ene, VJVthe ratio of final volume to initial volume at temperature t (258).

Cf, C y, and Cq are the concentrations of the substance in question (which may be a colligend or a surfactant) in the feed stream, bottoms stream, and foamate (collapsed foam) respectively. G, F, and Q are the volumetric flow rates of gas, feed, and foamate respectively, is the surface excess in equilibrium with C y. S is the surface-to-volume ratio for a bubble. For a spherical bubble, S = 6/d, where d is the bubble diameter. For variation in bubble sizes, d should be taken as YLnid fLnidj, where n is the number of bubbles with diameter dj in a representative region of foam. 

Many aromatic steroids submitted to the Birch reduction contain hydroxyl groups which are deprotonated to the corresponding alkoxides during the reduction, particularly if a tertiary alcohol is used as the proton donoi. The steroidal alkoxides and the one derived from the proton donor often precipitate and cause foaming of the reaction mixture, as was noted by Wilds and Nelson. These alkoxides can be kept in solution by adding an excess of the proton donor alcohol to the mixture the alcohol also assists in dissolving the starting hydroxylic steroid. A particularly useful reaction medium for hydroxylic steroids contains ammonia, tetrahydrofuran and -butyl alcohol in the volume ratio of 2 1 (Procedure 2, section V). This mixture... 

The area of colloids, surfactants, and fluid interfaces is large in scope. It encompasses all fluid-fluid and fluid-solid systems in which interfacial properties play a dominant role in determining the behavior of the overall system. Such systems are often characterized by large surface-to-volume ratios (e.g., thin films, sols, and foams) and by the formation of macroscopic assembhes of molecules (e.g., colloids, micelles, vesicles, and Langmuir-Blodgett films). The peculiar properties of the interfaces in such media give rise to these otherwise unlikely (and often inherently unstable) structures. 

Oxidisable organic materials of high surface to volume ratio (carbon powder, foamed elastomers, lampblack, sawdust) react very violently, even at -78°C, with perchloryl fluoride, which should be handled with the same precautions as liquid oxygen. 

Tuerker and Mavituna immobilized Trichoderma reesei within the open porous networks of reticulated polyurethane foam matrices. Growth pattern, glucose consumption, and cellulase production were compared with those of freely suspended cells. The method of immobilization was simple and had no detrimental effect on cell activity. Hundreds of similar projects could be cited. Not all rated the use of polymethane as the preferred technique. If a statistical analysis were conducted on aU the immobilization literature, we are sure that no single technique would be dominant. However, the combination of ease of immobilization, cost of materials, flow-through properties, control of flux rate through the immobilizing membrane, high surface-to-volume ratio, and other factors make polymethane a viable substratum for the continuous production of proteins. 

In foaming, the ratio of foam volume produced to the volume of liquid used to make the foam. Also termed the expansion ratio . 

In foaming, the ratio of gas volume to liquid volume in a foam, expressed as a percentage. Also termed the foaming power . 

The most important parameters characterising a polyhedral foam are expansion ratio, dispersity and foam stability. The expansion ratio n is the ratio between the foam volume V and the volume of the liquid content Vl in it... 

The common understanding of foam stability usually refers to the ability of a foam to maintain its main parameters constant with time, i.e. bubble size, liquid content (expansion ratio) and total foam volume. Foam lifetime is most often used as the simplest measure of foam stability. 

A great advantage of mixing foam generators is the possibility to regulate both foam expansion ratio and dispersity, though within a narrow range of alterations. For example, at constant ratio of gas and liquid volumes the dispersity of foam increases when the consumption of liquid and gas rises [45]. 

On the other hand a comparison of the ratio between the volumes of real Plateau border and cylindrical border model, obtained by Pertsov et al. [85], with the ratio (rh /rn)2, evaluated from the dodecahedral model [83] indicates that these ratios correlate well only when n > 640 but when n < 300 they differ by almost 30%. However, it should be noted that the method for calculating border volume in [85,86] at low foam expansion ratio differs from the real volume by 10%. Besides, all values of expansion ratio given in the tables of [86] are twice higher. This means that the interpolation equations for calculating the corrections of the volume and hydro- and electrical conductivities in the cylindrical border model must be corrected. The Plateau border cross-section area is determined by Eq. (1.19) when the contact angle between film and border surface is small 6 (or 1 in radians). 

The foam expansion ratio or its reciprocal value the foam liquid volume fraction, called also relative or volume density of a foam, is used as a basic parameter characterizing the liquid to gas ratio in the foam. 

Pertsov et al. [9] have also calculated the average (by volume) ultimate equilibrium foam expansion ratio n, at which there is neither liquid flowout from nor liquid suck in the foam... 

Based on the studies of border and film shape in the dodecahedral model Kruglyakov et al. [18] and Kachalova et al. [19] have proposed an expression for foam expansion ratio, using a cylindrical border model with the same cross-sectional radius of curvature. The volume of excess vertex parts was considered in order to estimate the effect of the longitudinal radius of curvature on the border shape... 

The simplest technique for determination of the average by volume expansion ratio (and density) is the direct measurement of the total foam volume and the liquid volume in it (or its mass). Using barbotage methods for foam production the foaming process can be run until the initial solution is completely transformed into foam. Foam expansion ratio and its density are calculated by the formula... 

Another technique for foam expansion ratio determination involves taking samples and can be applied also for foams produced by foam generators. The precision of these direct volume-mass methods depends to a considerable extent on foam uniformity with respect to its expansion ratio and on the sampling conditions [20,21,22], The relative error in the evaluation of n for low expansion ratio foams (n < 100) is about 1-2%. However, for high expansion ratio foams (n > 1000) these methods become inapplicable. 

Here R is the average bubble radius nb is border expansion ratio (foam volume to border liquid volume ratio), assuming that the initial border expansion ratio nb = 0 n = nf is film expansion ratio. 

Chemin [21] and Chistyakov et al. [44] have determined the change in bubble number in a unit contact area ns with time and have shown that the rate of the decrease in cell number dnjdr depends linearly on ns for all foam expansion ratios studied. Similarly to the lg R(r), this dependence consists of two parts. This is an expected result, since at constant foam volume the average bubble size Ry and their number Nb are related by the expressions... 

In a system obtained from 1% NaDoS solution + 1.75% NaCI + kerosene (at W/O ratio 1 1) the increase in the concentration of pentanol and at SAD not much less than zero, a maximum in the stability of the O/W emulsion is observed. At SAD = 0, there is a sharp decrease in stability while at SAD > 0, the stability of W/O emulsion increases. Similarly changes the volume and stability of the foam (Fig. 7.19). In the presence of kerosene the foam volume and stability fall down to zero at SAD > 0. In the presence of oil the foam volume and stability reach a minimum at SAD = 0, then increase at SAD > 0. Similar decrease in foam stability with the increase in SAD is observed when the salt concentration in the following systems is raised NaDoS + alcohol + a complex foaming agent (Coatex + isooctane W/O =... 

The duration of establishing a steady-state regime depending on foam stability is usually of the order of seconds or minutes. The maximum foam volume Vr mM increases with the rise in the volumetric gas rate Q. The ratio VFmax/Q or H,mx/Q remains constant within a large range of gas rates [13]. Other authors suggest that constant should be the quantity (Hmax -ao)/Q or Vq IQ (where ao = const) [13,115]. At relatively high rates of gas supply all the expressions practically coincide. 

Foam compressibility has been considered by Siehr [3], He studied a foam of expansion ratio 100 prepared from a diluted potato juice. 100 cm3 of the foam were placed into a vertical pipe, closed at the bottom and was subjected to compression. At pressure dump the foam volume was reversed to its initial value, i.e. the process was entirely reversible. At Ap= 12.5, 24.0 and 48.0 kPa, the volume decreased from 100 cm3 to 90, 81 and 69 cm3, respectively. At ambient atmospheric pressure of 101.3 kPa and the above values of Ap, the calculated foam volume (not accounting for pa and the foam liquid volume) should be 89, 80.8 and 67.8 cm3, respectively. The calculated volumes, corresponding to the experimentally obtained, are derived at po = 106.5 kPa (Ap = 106.5 - 101.3 = 5.2 kPa), accounting for the liquid volume. Therefore, foam compressibility is in accord with the equation of state of the foam (the error being ca. 5%). 

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