Temperature dependence of the surface tension for binary mixtures ofn-butanenitrile +n-alkanes

The differential capillary-rise method was used to determine the orthobaric surface tension of binary liquid mixtures ofn-butanenitrile mixed withn-pentane,n-hexane, andn-heptane, throughout the composition range. at 293.15, 303.15, 313.15, 323.15, 333.15. and 343.15 K. Furthermore, the system withn-hexane was also studied al 263.15 K. i.e., 19 K above its upper critical solution temperature, over the whole composition range. For each binary system the surface tension changes regularly with both temperature and composition between the values of the pure components. The results are discussed in terms of deviations from surface ideality and related to the large positive deviations observed for bulk properties of the same systems.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Surface tension of pentafluoroethane (HFC-125)

A set of accurate surface-tension data for HFC-125 has been obtained experimentally with both an absolute capillary rise technique and a differential capillary rise technique in the temperature range of 233.15–333.15 K. The purity of the experimental HFC-125 sample is 99.98 wt%. The two sets of experimental results with an absolute capillary rise method agree well with each other and, also, with the experimental results with a differential capillary rise method. The absolute deviations of experimental results with these two methods are within 0.01 mN · m^–1. The relative deviation are within 0.2%. A van der Waals surface-tension correlation is also proposed.     

The influence of variable surface tension on capillary-gravity waves

Periodic gravity-capillary waves propagating at a constant velocity at the surface of a fluid of infinite depth are considered. The surface tension is assumed to vary along the free surface. A numerical procedure is presented to solve the problem with an arbitrary distribution of surface tension on the free surface. It is found that there are many different families of solutions. These solutions generalize the classical theory of gravity-capillary waves with constant surface tension. An asymptotic solution is presented for a particular distribution of variable surface tension.     

Surface tension of aqueous binary solutions at low temperatures

The paper is concerned with measurements of the surface tension of aqueous binary solutions at low temperatures. The effects of both temperature and concentration on the surface tension of CaCl₂, NaClO₃, and propylene glycol have been investigated. A differential capillary-rise method was employed for the measurements. The results showed that the surface tension of CaCl₂ and NaClO₃ increases monotonically as the concentration of the solution increases, while for the propylene glycol solution the surface tension decreases with increasing concentration. The surface tension of the testing liquids was found to be an almost-linear function of temperature from 20°C to just above the freezing temperature. Equations for the surface tension of the three aqueous binary solutions as a function of temperature and concentration are presented. Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5–8, 1995, Tokyo, Japan.     

Measurements of the surface tension of four halogenated hydrocarbons,CCl3F,CCl2F2, C2Cl3F3, and C2Cl2F4

By means of the capillary rise method, we have measured the surface tension of four different kinds of halogenated hydrocarbons, namely, trichlorofluoromethane (CCl₃F; R 11), dichlorodifluoromethane (CCl₂F₂; R 12), trichlorotrifluoroethane (C₂Cl₃F₃; R 113), and dichlorotetrafluorethane (C₂Cl₂F₄; R 114). Under the coexistence of the sample liquid with its saturated vapor in equilibrium, the measurements have been performed within the maximum uncertainty of 0.12 mN · m^–1 at temperatures from 273 K up to near the critical point of the respective substances. Under the same experimental conditions, two sets of surface tension data have been obtained with two different Pyrex glass capillaries whose inner radii were 0.1536±0.0004 and 0.1724±0.0005 mm, respectively. The two sets of data were in agreement within 0.1 mN · m^–1. The data were represented by van der Waals-type correlations with a standard deviation of 0.10 mN · m^–1 for CCl₃F, 0.04 mN · m^–1 for CCl₂F₂, 0.08 mN · m^–1 for C₂Cl₃F₃, and 0.07 mN · m^–1 for C₂Cl₂F₄, respectively.     

The prediction of surface tension in mixtures of cryogenic liquids

Recently we showed how a fluid model for predicting thermodynamic properties could be used to correlate surface tension of organic liquids. We apply the model here to predict the surface tension of the cryogenic binary mixtures of methane, carbon monoxide, argon and nitrogen.⁵     

A generalized equation for surface tension from the triple point to the critical point

A three-parameter generalized equation is proposed for surface tension from the triple point to the critical point. This equation not only fits the data well but also is good for interpolation between the normal boiling point and the critical point. This equation is also good for extrapolation to the triple point. This equation has been tested using the surface tension of water from the triple point to the critical point. The constants of this equation obtained using orthobaric surface tensions are given for a number of compounds. The isobaric surface tensions determined at a pressure of 1 atm do not differ significantly from the orthobaric surface tensions. Such data also have been used in obtaining equations from the triple to the critical point.Nomenclature T _c Critical temperature, K - T _t Triple point, K - T _m Melting point, K - T _r Reduced temperature, K - X (T _c-T)/T _c - Surface tension, dyne · cm^–1;10^–3N · m^–1 - _m Surface tension at the melting point - _f Surface tension at T _r=0.9 - _t Surface tension at the triple point - Relative deviation 100[ _obsd– _calcd]/ _obsd - Standard deviation [( _obsd– _calcd)²/(No. points—No. parameters)]^0.5     

液体表面张力系数与浓度的关系实验研究

为探究液体表面张力与液体浓度的关系,利用压阻式力敏传感器,采用拉脱法,测试室温下水及不同浓度的蔗糖水、盐水、酒精、肥皂水的表面张力系数。实验结果表明:蔗糖水和盐水的表面张力系数随浓度的增大而增加,而酒精、肥皂水的表面张力系数随浓度的增大而减小。     

Simultaneous measurement of surface tension and kinematic viscosity using thermal fluctuations

We have developed a surface laser-light scattering apparatus to measure simultaneously surface tension and kinematic viscosity. In this method, we can obtain the surface properties by the laser heterodyne detection of light scattered from thermally excited capillary waves (called ripplon), which are typically of low amplitude (1 nm) and a characteristic wavelength (100m). Two gratings (d=100 and 200m) were employed to select the wave number of the capillary waves and to produce a reference beam for heterodyne detection. It was found through an experimental study on water that this contact-free method has considerable potential for application to measurements under extreme conditions such as high temperatures and high pressures.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

未变性胶原生物表面活性剂的表面张力及其表面吸附

研究了一种未变性胶原生物表面活性剂(CBS)水溶液的表面张力和表面吸附性质。结果表明,CBS水溶液的表面张力随CBS浓度的增大而降低,最终趋于平缓,达到55.92 mN/m。在等电点附近,CBS表面静电荷降低,使其表面张力显著降低。在低温下,CBS溶液的表面活性较好,当温度继续升高(35℃),由于变性作用,CBS溶液的表面张力急剧增大。CBS水溶液的吸附属于Langmiur型吸附,根据γ-lgC、Γ-C以及C/Γ-C拟合曲线计算得到饱和吸附量相似,分别为1.86×10-10,1.97×10-10和2.03×10-10 mol/cm2。吸附自由能为-3.53kJ/mol,表明其在标准状态下可以自发进行。     

Surface tension of helium-oxygen and helium-ethane solutions

The capillary constant has been measured, and the surface tension of gassaturated solutions of He-O₂ and He-C₂H₆ has been calculated in the temperature range from the solidification temperature to approximately 0.9T _C , whereT _C is the critical temperature of the solvent. Measurements have been carried out along isotherms at pressures from the saturation pressure of the pure solvent to 5 MPa. Equations approximating the baric dependence of the capillary constant and the concentration dependence of the surface tension are proposed. Adsorption is determined. The data obtained are discussed within the framework of the method of a finite-thickness layer. It is shown that for the investigated solutions the approximation of a monomolecular surface layer is not justified even at temperatures lower than the normal boiling point.     

Inviscid instability of an unbounded shear layer: effect of surface tension, density and velocity profile

The inviscid temporal stability analysis of an unbounded shear layer of two fluids of different density is investigated. Two background velocity profiles are considered: the piecewise-linear profile and the more realistic error-function profile. The disturbance kinetic energy is analyzed to physically understand the mechanism that causes instability. The surface-tension effect is investigated extensively. Surface tension is found to destabilize the neutrally stable waves that exist when surface tension is absent. This surface-tension-induced unstable mode is generally weaker than the dominant mode and extremely less evident when the density and/or viscosity difference increases. Short-wavelength instability is observed with a background viscosity jump at the interface. A comparison between the two velocity profiles is presented. The piecewise-linear profile does not match the more realistic results obtained with the error-function profile in the short wavelength range, especially in nonhomogeneous shear-layer flows; however, the phase-speed results are in a good agreement with those of the error-function profile.     

液态纯铁1 550℃的粘度及表面张力与结构的相关性

用θ-θ液态金属X射线衍射仪研究了液态纯铁在1 550℃的结构,根据实验所得双体分布函数,利用Iida和Reynolds的公式对液态纯铁的动力粘度和表面张力进行了计算.结果表明,液态纯铁在1 550℃的动力粘度η=6.44mPa@s,表面张力γ=2.04N/m;根据公式r/η= ,液态纯铁的动力粘度和表面张力之间吻合较好;液体结构、动力粘度和表面张力三者间存在密切联系.     

A new variant for measuring the surface tension of liquid metals and alloys by the oscillating drop method

The theoretical background of the oscillating drop technique for measuring surface tension is briefly presented and the different analysis procedures are cited. A new method is described for obtaining oscillation frequencies by fast fourier transformation (FFT) of the pyrometer voltage signals from temperature measurements at the top of the levitated sample. The results on the first experiments on liquid nickel are in a good agreement with the hterature data.Paper presented at the Fourth International Workshop on Subsecond Thermophysics. June 27–29, 1995, Köln, Germany.     

高温液相添加剂对纳米LiBr溶液表面张力和沸腾温度的影响

通过在纳米溴化锂(LiBr)溶液中添加表面活性剂降低溶液沸腾温度,从而有助于大幅度应用工业余热、废热等低品味热源。尽管影响沸腾温度的因素较多,但是溶液的表面张力是一个重要的因素,首先对异辛醇(C8H18O)、壬醇(C9H20O)和癸醇(C10H22O)3种高沸点液相添加剂对纳米LiBr溶液的表面张力的影响做了深入研究,并进一步研究了相对应的沸腾温度。并且通过实验发现随着烷醇中烷基数增加,表面张力更低,使得沸腾温度也进一步降低。     

Surface tension,coexistence curve,and vapor pressure of binary liquid-gas mixtures

The objective of this paper is to present measurements of the vapor pressure, capillary coefficient, and refractive index of four binary mixtures, CO₂-SF₆, R14-SF₆, SF₆-R13B1, and SF₆-R22, at liquid-vapor equilibrium at different average concentrations. The measuring temperature range covered the entire liquid-vapor region from the triple line up to the critical point. The capillary coefficient was determined by means of the capillary rise method; the refractive index, by measuring the angle of refraction of a light beam passing through a prism and the sample. In order to obtain the liquid-vapor densities of pure substances the Lorentz-Lorenz relation can be used. However, in applying this relation to calculate the liquid-vapor densities of a mixture, one may need the concentrations of both the liquid and the vapor phase, which are, for the most part, quite different from the average concentration of the mixture. Calculating the concentrations of both fluid phases with the aid of an equation of state and comparing with measurements, we could show that the molar refraction coefficient of the mixtures can be simply determined from the average concentration and the molar refraction coefficients of their pure components. The surface tension of the mixtures could then be calculated from the measured capillary coefficient and the refractive index with the aid of the Lorentz-Lorenz relation.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Surface-tension effects in suspended-level capillary viscometers

The results of an experimental study of surface-tension effects in kinematic capillary viscometers of the suspended-level type are presented. These results are deduced from a comparison with measurements obtained with a special Ostwald viscometer in which surface-tension effects are negligibly small. It is shown that surface-tension effects in suspended-level viscometers are sensitive to the shape of the capillary exit. Recommendations how to minimize these effects are discussed.     

Fully implicit finite element method for the modeling of free surface flows with surface tension effect

A new approach based on the use of the Newton and level set methods allows to follow the motion of interfaces with surface tension immersed in an incompressible Newtonian fluid. Our method features the use of a high‐order fully implicit time integration scheme that circumvents the stability issues related to the explicit discretization of the capillary force when capillary effects dominate. A strategy based on a consistent Newton–Raphson linearization is introduced, and performances are enhanced by using an exact Newton variant that guarantees a third‐order convergence behavior without requiring second‐order derivatives. The problem is approximated by mixed finite elements, while the anisotropic adaptive mesh refinements enable us to increase the computational accuracy. Numerical investigations of the convergence properties and comparisons with benchmark results provide evidence regarding the efficacy of the methodology. The robustness of the method is tested with respect to the standard explicit method, and stability is maintained for significantly larger time steps compared with those allowed by the stability condition. Copyright © 2016 John Wiley & Sons, Ltd.