Surface tension saturation

DTAB and PSS. The behavior of mixed DTAB-PSS solutions is very different from that of DTAB-PAMPS. We will recall here results obtained for f = 100% and Mw = 75 000.19 First, for given surfactant and polymer concentrations, the decrease of surface tension is much smaller for PSS (Figure 3). Second, there is no evidence of surface tension saturation above a certain polymer concentration and the CAC depends on polymer concentration.19 For a... 

The ability of the surfactant to increase its translational entropy lowers the surface tension. However, we note that this expression is only valid for insoluble surfactants at low concentrations, so the tendency for y to become negative at large a is just an indication that these approximations are breaking down. For soluble surfactants, one cannot consider fixed Ng. Rather, one has to equate the chemical potentials of the surfactants on the surface and in the bulk. For small concentrations, the surface tension is still reduced in a linear manner, but at large concentrations, the reduction in surface tension saturates due to the formation of micelles in the bulk this is discussed in Chapter 8. 

The methods discussed above have been used extensively in the literature, recent example of which is a calculation of the surface tension of six common water models at different temperatures.Particular noteworthy is the recent detailed calculation of the surface tension at the liquid/vapor interface for a series of alcohols by MC simulations, using many of the mechanical and thermodynamics methods described above. The surface tension, saturated liquid densities, and the critical points compare well with experiments. 

On a microscopic scale (the inset represents about 1 - 2mm ), even in parts of the reservoir which have been swept by water, some oil remains as residual oil. The surface tension at the oil-water interface is so high that as the water attempts to displace the oil out of the pore space through the small capillaries, the continuous phase of oil breaks up, leaving small droplets of oil (snapped off, or capillary trapped oil) in the pore space. Typical residual oil saturation (S ) is in the range 10-40 % of the pore space, and is higher in tighter sands, where the capillaries are smaller. 

Adsorption may occur from the vapor phase rather than from the solution phase. Thus Fig. Ill-16 shows the surface tension lowering when water was exposed for various hydrocarbon vapors is the saturation pressure, that is, the vapor pressure of the pure liquid hydrocarbon. The activity of the hydrocarbon is given by its vapor pressure, and the Gibbs equation takes the form... 

A complication now arises. The surface tensions of A and B in Eq. IV-2 are those for the pure liquids. However, when two substances are in contact, they will become mutually saturated, so that 7a will change to 7a(B) and 7b to 7B(A). That is, the convention will be used that a given phase is saturated with respect to that substance or phase whose symbol follows in parentheses. The corresponding spreading coefficient is then written 5b(A)/a(B)-... 

Referring to Fig. IV-4, the angles a and /3 for a lens of isobutyl alcohol on water are 42.5° and 3°, respectively. The surface tension of water saturated with the alcohol is 24.5 dyn/cm the interfacial tension between the two liquids is 2.0 dyn/cm, and the surface tension of n-heptyl alcohol is 23.0 dyn/cm. Calculate the value of the angle 7 in the figure. Which equation, IV-6 or IV-9, represents these data better Calculate the thickness of an infinite lens of isobutyl alcohol on water. 

Equations for vapor pressure, liquid volume, saturated liquid density, liquid viscosity, heat capacity, and saturated Hquid surface tension are described in Refs. 13, 15, and 16. 

Nitrile latices are used ia a wide variety of appHcations, including production of dipped nitrile mbber products. In the principle use of paper saturation, adhesives and fiber bonding, small particle size and optimum surface tension is desirable to achieve rapid penetration and setup or dryiag. 

There are three types of Hquid content in a packed bed (/) in a submerged bed, there is Hquid filling the larger channels, pores, and interstitial spaces (2) in a drained bed, there is Hquid held by capillary action and surface tension at points of particle contact, or near-contact, as weU as a zone saturated with Hquid corresponding to a capillary height in the bed at the Hquid discharge face of the cake and (3) essentially undrainable Hquid exists within the body of each particle or in fine, deep pores without free access to the surface except perhaps by diffusion or compaction. 

Fig. 9. Surface tension between Hquid water and steam along the saturation line.

T — T (4) the ratio of the solute concentration and the equiUbrium concentration, c A, which is known as relative saturation or (5) the ratio of the difference between the solute concentration and the equiUbrium concentration to the equiUbrium concentration, s — [c — c which is known as relative supersaturation. This term has often been represented by O s is used here because of the frequent use of O for iaterfacial energy or surface tension and for variance ia distribution functions. 

In porous and granular materials, Hquid movement occurs by capillarity and gravity, provided passages are continuous. Capillary flow depends on the hquid material s wetting property and surface tension. Capillarity appHes to Hquids that are not adsorbed on capillary walls, moisture content greater than fiber saturation in cellular materials, saturated Hquids in soluble materials, and all moisture in nonhygroscopic materials. 

Surface Tension (N/m) of Saturated Liquid Refrigerants. . . 2-361 Velocity of Sound (m/s) in Gaseous Refrigerants at... 

TABLE 2-360 Surface Tension (N/m) of Saturated Liquid Refrigerants ... 

The physical properties of saturated fluorocarbons and their analogous hydrocarbons differ in many respects [4 5] Sahirated fluorocarbons have the lowest dielectric constants, surface tensions, and refractive indexes of any liquids at room... 

Saturated fluorocarbons have the lowest surface tensions of any organic liquids and can completely wet almost any surface. Perfluonnated amines and ethers also... 

Cantor (1895) has indicated that the deiv-point, or temperature at which vapour condenses on a solid surface, must be different from the saturation temperature for the vapour over the surface of its own liquid, because of the different surface tensions between (vapour)/(solid) and (vapour)/(liquid). 

For a bubble to be formed in a liquid, such as steam in water, for example, it is necessary for a surface of separation to be produced. Kelvin has shown that, as a result of the surface tension between the liquid and vapour, the vapour pressure on the inside of a concave surface will be less than that at a plane surface. As a result, the vapour pressure Pr inside the bubble is less than the saturation vapour pressure P, at a plane surface. The relation between Pr and P, is ... 

Huid Saturation temperature Isat [°C] Liquid density Pl [kg/m ] Liquid specific heat rp,L [J/kg K] Vapor density Pg [kg/m ] Latent heat of vaporization h-LG [kJ/kg] Surface tension (TX id [N/m]... 

In this table the parameters are defined as follows Bo is the boiling number, d i is the hydraulic diameter, / is the friction factor, h is the local heat transfer coefficient, k is the thermal conductivity, Nu is the Nusselt number, Pr is the Prandtl number, q is the heat flux, v is the specific volume, X is the Martinelli parameter, Xvt is the Martinelli parameter for laminar liquid-turbulent vapor flow, Xw is the Martinelli parameter for laminar liquid-laminar vapor flow, Xq is thermodynamic equilibrium quality, z is the streamwise coordinate, fi is the viscosity, p is the density, <7 is the surface tension the subscripts are L for saturated fluid, LG for property difference between saturated vapor and saturated liquid, G for saturated vapor, sp for singlephase, and tp for two-phase. 

In order to take into account the effect of surface tension and micro-channel hydraulic diameter, we have applied the Eotvos number Eo = g(pL — pG)d /(y. Eig-ure 6.40 shows the dependence of the Nu/Eo on the boiling number Bo, where Nu = hd /k] is the Nusselt number, h is the heat transfer coefficient, and k] is the thermal conductivity of fluid. All fluid properties are taken at the saturation temperature. This dependence can be approximated, with a standard deviation of 18%, by the relation ... 

On the meniscus surface the deviation of vapor pressure from the saturation pressure Psat depends on the surface tension a, liquid density p( gas constant R, temperature T, and radii of curvature r. When p( > -Psat(T) < (2[Pg.354]

Kakiuchi et al. [75] used the capacitance measurements to study the adsorption of dilauroylphosphatidylcholine at the ideally polarized water-nitrobenzene interface, as an alternative approach to the surface tension measurements for the same system [51]. In the potential range, where the aqueous phase had a negative potential with respect to the nitrobenzene phase, the interfacial capacity was found to decrease with the increasing phospholipid concentration in the organic solvent phase (Fig. 11). The saturated mono-layer in the liquid-expanded state was formed at the phospholipid concentration exceeding 20 /amol dm, with an area of 0.73 nm occupied by a single molecule. The adsorption was described by the Frumkin isotherm. 

Brown (1967) noted that a vapor bubble in a temperature gradient is subjected to a variation of surface tension which tends to move the interfacial liquid film. This motion, in turn, drags with it adjacent warm liquid so as to produce a net flow around the bubble from the hot to the cold region, which is released as a jet in the wake of the bubble (Fig. 4.10). Brown suggested that this mechanism, called thermocapillarity, can transfer a considerable fraction of the heat flux, and it appears to explain a number of observations about the bubble boundary layer, including the fact that the mean temperature in the boundary layer is lower than saturation (Jiji and Clark, 1964). 

W-3 CHF correlation. The insight into CHF mechanism obtained from visual observations and from macroscopic analyses of the individual effect of p, G, and X revealed that the local p-G-X effects are coupled in affecting the flow pattern and thence the CHF. The system pressure determines the saturation temperature and its associated thermal properties. Coupled with local enthalpy, it provides the local subcooling for bubble condensation or the latent heat (Hfg) for bubble formation. The saturation properties (viscosity and surface tension) affect the bubble size, bubble buoyancy, and the local void fraction distribution in a flow pattern. The local enthalpy couples with mass flux at a certain pressure determines the void slip ratio and coolant mixing. They, in turn, affect the bubble-layer thickness in a low-enthalpy bubbly flow or the liquid droplet entrainment in a high-enthalpy annular flow. 

---