Accuracy Of Surface Tension Measurements Research Articles

Quantifying facility performance during thermophysical property measurement of liquid Zr using Electrostatic Levitation

Density, thermal expansion coefficient, surface tension and viscosity of liquid Zr at high temperatures were measured by oscillating droplet method in two Electrostatic Levitation (ESL) facilities. The ground-based tests at NASA MSFC ESL were conducted in vacuum and the space-based tests at JAXA ELF were conducted in Argon atmosphere with both results reported as a function of temperature. The accuracy and precision of each set of the measurement techniques has been reported using a detailed uncertainty analysis on both facilities. The uncertainties associated with each measurement were used to characterize performance for each facility. Zr samples processed in microgravity showed heavy influence of oxidation which lowered the natural frequency and thus significantly affecting the accuracy of surface tension measurement. The ground-based results are comparable to previously reported literature values.

Measurement of the surface tension of liquid Ga, Bi, Sn, In and Pb by the constrained drop method

Abstract The effect of the droplet size on the accuracy of surface tension measurement by the sessile drop method is discussed for liquid metals through a simulation by using the Laplace equation. It is found that with increasing size of the droplet, a higher accuracy of the measured value of the surface tension can be obtained. In order to make a large droplet of liquid metals, the constrained drop method with a special crucible shape was applied to measure the surface tension of liquid Ga, Sn, Bi, In, and Pb. The uncertainty of the measured surface tension was within 1%. The temperature dependences of the surface tension of liquid Ga, Sn, Bi, In, and Pb were obtained in the present experiment as follows: Ga: σGa = 737 − 0.062T mN/m (823 ≤ T ≤ 993K) Sn: σSn = 579 − 0.066T mN/m (723 ≤ T ≤ 993K) Bi: σBi = 417 − 0.070T mN/m (773 ≤ T ≤ 873K) In: σIn = 600 − 0.082T mN/m (673 ≤ T ≤ 993K) Pb: σPb = 499 − 0.089T mN/m (757 ≤ T ≤ 907K)

Registration of high-frequency waves on the surface by the interference methods

Capillary waves are frequently used to measure the surface tension of liquids. However, this approach has not found wide application in the manufacture of modern commercial tensiometers because of the limitations imposed by capillary wave excitation techniques and the labor input associated with its practical implementation. In this paper we introduce a modified version of the capillary wave method which allows one to avoid the existing limitations and disadvantages. The distinguishing features of the proposed technique are as follows: acoustic wave generation and application of an interferometry technique for 3D surface profile reconstruction. A dynamic speaker with controlled vibration frequency and amplitude is used to produce acoustic vibrations. Application of a conventional Fizeau interferometer and the spatial phase shifting method makes it possible to perform surface form measurements with a high accuracy. For calculating wavelengths and the damping co-efficient, the surface profile is fitted with a decaying cylindrical wave equation. The accuracy of surface tension measurement by the modified capillary wave technique is 0.3 %. Owing to the non-contact way of wave generation and the small amounts of the examined fluid, the proposed method can be used in different studies.

Модификация метода капиллярных волн

Capillary waves are frequently used to measure the surface tension of liquids. However, this approach has not found wide application in the manufacture of modern commercial tensiometers because of the limitations imposed by capillary wave excitation techniques and the labor input associated with its practical implementation. In this paper we introduce a modified version of the capillary wave method which allows one to avoid the existing limitations and disadvantages. The distinguishing features of the proposed technique are as follows: acoustic wave generation and application of an interferometry technique for 3D surface profile reconstruction. A dynamic speaker with controlled vibration frequency and amplitude is used to produce acoustic vibrations, which are transferred via waveguides and create the local source of pressure oscillations on the fluid surface. Application of a conventional Fizeau interferometer and the spatial phase shifting method makes it possible to perform surface form measurements with an accuracy of 5 nm. For calculating wavelengths and the damping coefficient, the surface profile is fitted with a decaying cylindrical wave equation. The accuracy of surface tension measurement by the modified capillary wave technique is 0.3 % , and the measured values coincide with the known values of these parameters determined using other measuring instruments. Owing to the non-contact way of wave generation and the small amounts of the examined fluid, the proposed method can be used in biological, magnetic fluids studies and rheological investigations in physical chemistry.

Surface tension measurement of glass melts using sessile or pendant drop methods

The drop shape (sessile or pendant) method is widely used to measure the surface tension of glass melts. The accuracy of surface tension measurement has been improved by applying the technologies of video-image digitization and best-fitting algorithms. An accurate surface tension can be determined using hundreds of edge points from drop profiles and the best-fit with the drop profiles from the Young–Laplace equation. In this study, we examine the accuracy of measuring the surface tension of glass melts using the sessile or pendant drop methods. Experimental data show that the accuracy of surface tension measurement using the pendant drop method (±3 mN/m) is better than that obtained by using the sessile drop method (±9 to ±20 mN/m, depending on the contact angle).

Design and accuracy of pendant drop methods for surface tension measurement

Drop shape techniques are extensively used for surface tension measurement. The accuracy of surface tension measurements using a pendant drop setup depends mainly on the drop shape. As the pendant drop shape becomes close to spherical, the performance of drop shape techniques deteriorates. It is important to consider how to optimize the pendant drop design and how to quantify the accuracy of the surface tension measurements. In this paper, the design and accuracy of pendant drop methods is considered in detail. Dimensional analysis is used to describe similarity in pendant drop shapes and to express the problem using appropriate dimensionless groups. A quantitative criterion called shape parameter is then used to express quantitatively the difference in shape between a given experimental drop and a spherical shape. The shape parameter is found to depend only on two dimensionless groups: the dimensionless volume and the Bond number. A critical shape parameter (minimum value of the shape parameter that guarantees a specified accuracy) is shown to depend only on Bond number. A set of experiments were performed with pure liquids to illustrate the change of the critical shape parameter with the Bond number. Results show that high accuracy is indeed reachable independent of the algorithms used.

Simultaneous Measurement of Contact Angle and Surface Tension Using Axisymmetric Drop-Shape Analysis-No Apex (ADSA-NA)

Axisymmetric drop-shape analysis-no apex (ADSA-NA) is a recent drop-shape method that allows the simultaneous measurement of contact angles and surface tensions of drop configurations without an apex (i.e., a sessile drop with a capillary protruding into the drop). Although ADSA-NA significantly enhanced the accuracy of contact angle and surface tension measurements compared to that of original ADSA using a drop with an apex, it is still not as accurate as a surface tension measurement using a pendant drop suspended from a holder. In this article, the computational and experimental aspects of ADSA-NA were scrutinized to improve the accuracy of the simultaneous measurement of surface tensions and contact angles. It was found that the results are relatively insensitive to different optimization methods and edge detectors. The precision of contact angle measurement was enhanced by improving the location of the contact points of the liquid meniscus with the solid substrate to subpixel resolution. To optimize the experimental design, the capillary was replaced with an inverted sharp-edged pedestal, or holder, to control the drop height and to ensure the axisymmetry of the drops. It was shown that the drop height is the most important experimental parameter affecting the accuracy of the surface tension measurement, and larger drop heights yield lower surface tension errors. It is suggested that a minimum nondimensional drop height (drop height divided by capillary length) of 1.7 is required to reach an error of less than 0.2 mJ/m(2) for the measured surface tension. As an example, the surface tension of water was measured to be 72.46 ± 0.04 at 24 °C by ADSA-NA, compared to 72.39 ± 0.01 mJ/m(2) obtained with pendant drop experiments.

Identifying rotation and oscillation in surface tension measurement using an oscillating droplet method

AbstractWe proposed a new approach to identify the frequencies of droplet rotation and m=±2 oscillation that degrade the accuracy of surface tension measurement by an oscillating droplet method. Frequencies of droplet rotation and m=±2 oscillation can be identified by a phase unwrapping analysis of time dependence of the deflection angle for the maximum diameter of the droplet image observed from above. The present method was validated, using test data with given frequencies. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(7): 421–430, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20214

Measurement of the surface tension of liquid Ga, Bi, Sn, In and Pb by the constrained drop method

Abstract The effect of the droplet size on the accuracy of surface tension measurement by the sessile drop method is discussed for liquid metals through a simulation by using the Laplace equation. It is found that with increasing size of the droplet, a higher accuracy of the measured value of the surface tension can be obtained. In order to make a large droplet of liquid metals, the constrained drop method with a special crucible shape was applied to measure the surface tension of liquid Ga, Sn, Bi, In, and Pb. The uncertainty of the measured surface tension was within 1%. The temperature dependences of the surface tension of liquid Ga, Sn, Bi, In, and Pb were obtained in the present experiment as follows: Ga: σGa = 737 −0.062T mN/m (823 ≤ T≤ 993K)Sn: σSn = 579 −0.062T mN/m (723≤ T≤ 993K)Bi: σBi = 417 −0.070T mN/m (773 ≤ T≤ 873K)In: σIn = 600−0.082T mN/m (673 ≤ T≤ 993K)Pb: σPb = 499 −0.089T mN/m (757 ≤ T≤ 907K)

Improvements in Surface Tension Measurements of Liquid Metals Having Low Capillary Constants by the Constrained Drop Method

Accurate measurements of surface tension of liquid metals having low capillary constants (the ratio between density (r) and surface tension (s), r/s) have been attempted using the constrained drop method. High accuracy of surface tension measurements was obtained by making a large axi-symmetric liquid drop and adopting a developed image capturing system composed of a high-resolution charge-coupled device (CCD) camera, an additional CCD camera to adjust the level of the metal drop and a He‐Ne laser.

An Induction Balance for Investigation of the Surface Properties of Water

A precision induction balance is described. The balance can be used to study the isotherms of compression and expansion of organic monolayers and physicochemical processes on the water surface, such as organic liquid spreading, adsorption of substances, film evaporation, etc. The balance includes an inductive transducer and a recording system based on virtual instruments installed under MS Windows using standard PC multimedia facilities. This provides a high sensitivity and accuracy of surface-tension measurements (as high as several hundredths of a millinewton per meter).

Surface tension of pentafluoroethane and 1,1,1,2,3,3,3-heptafluoropropane

The surface tension of pentafluoroethane (HFC-125) and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) has been measured in the present work. The measurements were conducted at vapor–liquid equilibrium conditions. Thirty-nine data points have been obtained by the differential capillary rise method (DCRM) in the temperature range from 243 to 340 K for HFC-227ea, and 20 data points from 248 to 323 K for HFC-125. The temperature uncertainty is within ±20 mK. The accuracy of surface tension measurements is estimated to be within ±0.15 mN m −1. Also correlations of the surface tension data are proposed.

Surface tension of trifluoroiodomethane (CF3I)

Abstract The surface tension of trifluoroiodomethane (CF3I) has been measured in the present work. The measurements were conducted under equilibrium conditions between the liquid and its saturated vapor. Thirty data points have been obtained by differential capillary rise method (DCRM) in the temperature range from 243 to 344 K. The temperature uncertainty is within ±10 mK. The accuracy of surface tension measurements is estimated to be within ±0.1 mN m−1. The correlation of surface tension also has been proposed, the RMS deviation is 0.58%.

Experimental surface tensions for HFC-32, HCFC-124, HFC-125, HCFC-141b, HCFC-142b, and HFC-152a

The surface tension of six alternative refrigerants, i.e., HFC-32 (CH, F, ). HCFC-124 (CHClFCF,), HFC-125 (CHF2CF3). HCFC-14lb ICH,CCI,F). HCFC-142b (CH3CCIF2), and HFC-152a (CH3CHF2), has been measured in the present study. The measurements were conducted under equilibrium conditions between the liquid and its saturated vapor. The differential capillary-rise method (DORM) used two glass capillaries, with inner radii of 0.3034 ± 0.0002 and 0.5717 ±0.0002 mm, respectively. Temperatures in the range from 270 to 340 K were considered. The accuracy of surface tension measurements is estimated to be within ±0.2 mN · m−1. The temperatures are accurate to within ±20 mK. The temperature dependence of the resultant data were successfully represented by van der Waals' correlations to within ±(1.1 mN m−1 for each substance. Available surface tension data are compared with the present data.

Considerations on the Pendant Drop Method: A New Look at Tate's Law and Harkins' Correction Factor

New considerations on the pendant drop method, which include a thorough analysis of the detachment conditions, are presented in this paper. It is shown that Harkins' empirical correction factor F can be derived from a momentum balance written just before release. The geometrical parameters to be used in the calculation are obtained via a numerical simulation of the shape of the pendant drop. The agreement with the tabulated values coming from our experimental data on refractory metals is remarkable. Finally, the consequences in terms of accuracy of surface tension measurements are discussed.

Effect of static deformation and external forces on the oscillations of levitated droplets

The oscillations of an aspherical droplet subjected to different external forces are considered. For an arbitrary shape deformation, it is shown that the frequency spectrum splits into (2l−1) peaks for a mode l oscillation, and the splitting of the frequency spectrum is calculated for mode 2, 3, and 4 oscillations. The deformation is then treated as a consequence of a general external force, and the frequency split is obtained in terms of the external force parameters. Droplets levitated by acoustic, electromagnetic, and combined acoustic-electromagnetic forces are considered in particular, and it is shown that the effects of asphericity adequately explain the splitting of the frequency spectrum observed commonly in experiments. The interpretation of spectra with regard to accurate surface tension measurement using the oscillations of levitated droplets is discussed, and the results applied to some previous experimental results. It is shown that the accuracy of surface tension measurements can improve if the asphericity caused by the levitating force, and the resulting frequency split, are taken into account.

Measurements of the surface tension for n-hexane and n-octane.

The surface tension of two alkanes, namely n-hexane(C6H14), are investigated for temperatures from 273 K to 463 K in the present study. Under the coexistence of the sample liquid with its saturated vapor in equilibrium, the surface tension has been measured by the capillary rise method. At the same experimental condition, two sets of surface tension data have been independently obtained with two different Pyrex glass capillaries I and II whose inner radii are 0.1516±0.0004 and 0.1703±0.0005 mm, respectively. The purities of samples are not less than 97 % for n-hexane and 99 % for n-octane. The accuracy of surface tension measurements is estimated better than ±0.20 mN/m. The temperature dependence of the present results has been represented by van der Waals-type correlation with a standard deviation of 0.14 mN/m for n-hexane and 0.12 mN/m for n-octane, respectively. The uncertainty of the present correlations is estimated to be ±0.2 mN/m.