Coefficient surface tension

The presence of 0.004—0.0062% Te in a welding rod or wke produces a positive surface tension coefficient which enhances the heat transfer to the... 

The eigenfrequency spectrum of the surface modes of a hollow sphere with gas inside is well known (e.g., see Ref. [109] as well as our Appendix A). If we pretend for a moment that the surface tension coefficient a is curvature independent, the possible values of the eigenfrequency oo are found by solving the following equation ... 

As a particular example, one can consider the homogeneous nucleation in the pure water vapor at 25° C. The surface tension coefficient of water is a = 71.96 N/m at this temperature. Table 5.1 shows some characteristics of the new phase. When the oversaturation is p/p =8.1, the critical nucleus of 0.5 nm radius is seen to comprise 18 water molecules. The equihbrium pressure of such nuclei is not high (approximately 10 bar). Since the water vapor pressure in real clouds is usually no more than 0.1% over that of the saturated vapor, it is unrealistic to expect in the rea sonable time scale the homogeneous formation of water drops in Earth s atmosphere. 

Several other experimental findings support the existence of a microceliular structure in oligomeric foams. Thus, Oween and Denis ) observed an anomalous pattern (in the expression of the authors) for certain types of silicone surfactants the liquid foam system consists of gas bubbles the sizes of which differ by several orders of magnitude. The possibility of formation of very small gas bubbles after a marked reduction of the surface tension coefficient in poly-lurethane formulations has been reported by Dubyaga and Tarakanov ). 

A liquid forms an interface with another fluid. At the surface, the molecular layers are different in density than the bulk of the fluid. This results in siuface tension and interfacial phenomena. The surface tension coefficient, a, is the force per unit length of the circumference of the interface, i.e., N/m, or the energy per unit area of the interface area. 

The surface tension coefficient [Pg.118]

The dynamic interaction between flow and drops and bubbles floating in the flow may deform or even destroy them. This phenomenon is important for chemical technological processes since it may change the interfacial area and the relative velocity of phases and cause transient effects. In this case, the viscous and inertial forces are perturbing actions, and the capillary forces are obstructing actions. The bubble shape depends on the Reynolds number Re = aeU,p/p and the Weber number We = aeU2p/cr, where p, and p are the dynamic viscosity and the density of the continuous phase, a is the surface tension coefficient, and ae is the radius of the sphere volume-equivalent to the bubble. 

Various thermal hydrodynamic phenomena are analyzed, which are related to the dependence of the surface tension coefficient on temperature. Thermo-gravitational and thermocapillary convection in a fluid layer is studied. The problem of thermocapillary drift of a drop in an external temperature-gradient field is considered, as well as other, more complicated problems. 

If the surface tension coefficient is not constant along the interface between two nonmixing fluids, then there arise additional tangential stresses on the interface they are referred to as capillary stresses and can substantially affect the motion of the fluid or even solely determine it in the absence of gravitational and... 

Statement of the problem. Let us consider the motion of a viscous fluid in an infinite layer of constant thickness 2h. The force of gravity is directed normally to the layer. The lower plane is a hard surface on which a constant temperature gradient is maintained. The nonuniformity of the temperature field results in two effects that can bring about the motion of the fluid, namely, the thermogravitational effect related to the heat expansion of the fluid and the appearance of Archimedes forces, and the thermocapillary effect (if the second surface is free) produced by tangential stresses on the interface due to the temperature dependence of the surface tension coefficient. 

This equation is valid in the entire flow field even if the material properties vary discontinuously across phase boundaries. In Eq. (1), p and p are density and viscosity, v is the velocity field, p is pressure, and /is the body force. The effects of the interfacial tension are accounted for by the last term in Eq. (1). In this term, 5 is two or three dimensional delta function, cr is surface tension coefficient, k is the curvature of two-... 

Polysiloxanes, [-O-Si(RR )-], are linear resins that can be branched or crosslinked into elastomers. They have high compressibility, permeability to gases, low T and viscosity, exceptional weather-ability, low surface tension coefficient and are relatively expensive. Siloxane polymers or copolymers have been incorporated into engineering or specialty resins to improve processability, toughness, HDT, solvent and weather resistance. 

From Surface Tension Coefficients Among the different approaches used to calculate the surface tension coefficient, Vj, the most useful seems to be the parachor method [Sugden, 1924 Van Krevelen, 1976 Wu, 1982]. This parameter was defined as [Sugden, 1924] ... 

The subscript d and p refer to dispersive and polar components of the surface tension coefficients. Eq 4.38 is called the harmonic-mean... 

V surface tension coefficient PBMA polybutyl methacrylate... 

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