Capillary Constant Research Articles

Capillary constant and surface tension of isobutane–hydrogen solution in temperature range of 298–348 K

We presented the results of measuring of the capillary constant of isobutane–hydrogen solution in the temperature range of 298.15–348.15 K at pressures from the saturation pressure of pure isobutane up to 4 MPa. The surface tension of the solution was determined. The equations approximating the concentration and pressure dependences of the capillary constant and surface tension are constructed.

Oscillations of the Helium II – Vapor Interface during Motion in a Channel of a Relatively Large Diameter

The article considers the motion of superfluid helium in a U-shaped cylindrical channel with a diameter significantly larger than the helium capillary constant in the approximation of an inviscid incompressible fluid. When a heat flux is applied near the end-face section of one of the channel elbows, a vapor layer emerges near the heater, and the helium II – vapor interface begins to move. The purpose of the calculation is to determine the interface position as a function of time. The heat transfer in a liquid is described using the semi-empirical Gorter-Mellink theory. The processes in the vapor are analyzed based on the methods of molecular kinetic theory. The influence of the gravity field is studied. The system of equations is reduced to an ordinary second-order differential equation, which is solved numerically. Various process development scenarios depending on the heat flux are obtained. The occurrence of oscillations is described, and the influence of parameters on the oscillation amplitude and frequency is analyzed. In this way, the previously obtained experimental data have been interpreted.

Study of Surface Wettability of Mineral Rock Particles by an Improved Washburn Method.

The surface wettability of rocks in underground reservoirs affects the distribution of fluids in the reservoir, so the wettability of reservoir minerals is a key factor for crude oil recovery from reservoirs. In this paper, the wettability of quartz sand with different particle sizes in different polar solvents was determined by Washburn's capillary rise method, and the C·cos θ values were calculated first. Next, the experimentally obtained macroscopic contact angle of water on the quartz surface of 15.0° was substituted into C·cos θ to obtain a linear equation between the particle size of quartz sand and the capillary constant C. The particle sizes of oil sand and mineral powder were then substituted into the equation to obtain their capillary constants C. Then, based on the Owens-Wendt-Rabel-Kaelbe (OWRK) equation and the obtained contact angles of solvent on quartz sand, oil sand, and mineral powder, the surface free energy of quartz sand with different particle sizes is calculated as 76.09, 76.65, and 76.42 mN/m, respectively, which are close to the literature results. In addition, the surface free energy of oil sand with different particle sizes was 23.22, 23.45, and 23.63 mN/m, and the results indicated that the polarity of oil sand was low. Meanwhile, the surface free energies of kaolinite, illite, feldspar, and montmorillonite were 61.59, 32.85, 35.87, and 25.91 mN/m, respectively. By the improved Washburn method in this paper, the wettability of different solvents on the surface of reservoir rocks was investigated, and the surface free energy of specific solid particles was calculated, which is important for studying the extraction of crude oil from subsurface reservoir rocks.

ASSESSMENT OF THE PORE DIAMETER MEASURED IN GAS-LIQUID DISPLACEMENT POROMETRY: EFFECT OF THE CAPILLARY CONSTANT

ASSESSMENT OF THE PORE DIAMETER MEASURED IN GAS-LIQUID DISPLACEMENT POROMETRY: EFFECT OF THE CAPILLARY CONSTANT

Capillary constant and surface tension of hydrogen and helium solutions in n-butane (R600)

The results of measuring the capillary constant of n-butane + hydrogen and n-butane + helium solutions are presented. The measurements were carried out by a differential version of the capillary rise method in the temperature range of 138–408 K at pressures from the saturation vapor pressure of a pure solvent to 4 MPa. The uncertainty of the calculated values is uc(a2)=0.019 mm2 (n-butane + helium solution) and uc(a2)=0.015 mm2, uc(γ)=0.034 mN/m (n-butane + hydrogen solution).The surface tension of the n-butane + hydrogen solution was determined. Equations are proposed that describe the concentration and pressure dependences of the capillary constant and surface tension. A qualitatively different effect of small additions of hydrogen and helium on the surface tension of n-butane has been established.

Assessment of brain tumors by magnetic resonance dynamic susceptibility contrast perfusion-weighted imaging and computed tomography perfusion: a comparison study.

To investigate the association and agreement between magnetic resonance dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) and computed tomography perfusion (CTP) in determining vascularity and permeability of primary and secondary brain tumors. DSC-PWI and CTP studies from 97 patients with high-grade glioma, low-grade glioma and solitary brain metastasis were retrospectively reviewed. Normalized cerebral blood flow (nCBF), cerebral blood volume (nCBV), capillary transfer constant (nK2) and permeability surface area product (nPS) values were obtained. Variables among groups were compared, and correlation and agreement between DSC-PWI and CTP were tested. All DSC-PWI and CTP parameters were higher in high-grade than in low-grade gliomas (p < 0.01 and p < 0.001). Metastases had greater DSC-PWI nCBV (p < 0.05), nCTP-CBF (p < 0.05), nCTP-CBV (p < 0.01) and nCTP-PS (p < 0.0001) than low-grade gliomas and more elevated nCTP-PS (p < 0.01) than high-grade gliomas. The correlation was strong between DSC-PWI nCBF and CTP nCBF (r = 0.79; p < 0.00001) and between DSC-PWI nCBV and CTP nCBV (r = 0.83; p < 0.00001), weaker between DSC-PWI nK2 and CTP nPS (r = 0.29; p < 0.01). Bland-Altman plots indicated that the agreement was strong between DSC-PWI nCBF and CTP nCBF, good between DSC-PWI nCBV and CTP nCBV and poorer between DSC-PWI nK2 and CTP nPS. DSC-PWI and CTP CBF and CBV maps were comparable and interchangeable in the assessment of tumor vascularity, unlike DSC-PWI K2 and CTP PS maps that were more discordant in the analysis of tumor permeability. CTP could be an alternative method to quantify tumor neoangiogenesis when MRI is not available or when the patient does not tolerate it.

Capillary constant and surface tension of propane (R-290) with small additives of hydrogen

A differential variant of the capillary rise method was used to measure the capillary constant and to determine the surface tension of a propane (R-290) + hydrogen system. The measurements were carried out for 13 isotherms in the temperature range 95–355 K at pressures from the saturated vapor pressure of pure propane up to 4 MPa. Equations are proposed that describe the concentration and pressure dependences of the capillary constant and surface tension. It is shown that an increase in the concentration of hydrogen in the solution leads to a decrease both of the capillary constant and the surface tension.

Evaporation front propagation over a non-isothermal surface

The experiments are performed on R21 freon at a reduced pressure of 0.04 under conditions of natural convection. The propagation velocity of a self-sustaining evaporation front over a heat transfer surface is measured in the presence of a substantial temperature gradient along the heat transfer surface. The stabilization of the front propagation velocity is shown in accordance with the isotherm propagation velocity. The experiments show that when the evaporation front propagates over a heat-transfer surface with a significant temperature gradient, the stabilization of the front velocity occurs on a scale of the order of the capillary constant.

Observation of Reduced Homeostatic Metabolic Activity and/or Coupling in White Matter Aging.

Transvascular water exchange plays a key role in the functional integrity of the blood-brain barrier (BBB). In white matter (WM), a variety of imaging modalities have demonstrated age-related changes in structure and metabolism, but the extent to which water exchange is altered remains unclear. Here, we investigated the cumulative effects of healthy aging on WM capillary water exchange. A total of 38 healthy adults (aged 36-80 years) were studied using 7T dynamic contrast enhanced MRI. Blood volume fraction (vb ) and capillary water efflux rate constant (kpo ) were determined by fitting changes in the 1 H2 O longitudinal relaxation rate constant (R1 ) during contrast agent bolus passage to a two-compartment exchange model. WM volume was determined by morphometric analysis of structural images. R1 values and WM volume showed similar trajectories of age-related decline. Among all subjects, vb and kpo averaged 1.7 (±0.5) mL/100 g of tissue and 2.1 (±1.1) s-1 , respectively. While vb showed minimal changes over the 40-year-age span of participants, kpo declined 0.06 s-1 (ca. 3%) per year (r = -.66; P< .0005), from near 4 s-1 at age 30 to ca. 2 s-1 at age 70. The association remained significant after controlling for WM volume. Previous studies have shown that kpo tracks Na+ , K+ -ATPase activity-dependent water exchange at the BBB and likely reflects neurogliovascular unit (NGVU) coupled metabolic activity. The age-related decline in kpo observed here is consistent with compromised NGVU metabolism in older individuals and the dysregulated cellular bioenergetics that accompany normal brain aging.

Prediction of survival and progression in glioblastoma patients using temporal perfusion changes during radiochemotherapy

BackgroundThe aim of this study was to investigate changes in structural magnetic resonance imaging (MRI) according to the RANO criteria and perfusion- and permeability related metrics derived from dynamic contrast-enhanced MRI (DCE) and dynamic susceptibility contrast MRI (DSC) during radiochemotherapy for prediction of progression and survival in glioblastoma. MethodsTwenty-three glioblastoma patients underwent biweekly structural and perfusion MRI before, during, and two weeks after a six weeks course of radiochemotherapy. Temporal trends of tumor volume and the perfusion-derived parameters cerebral blood volume (CBV) and blood flow (CBF) from DSC and DCE, in addition to contrast agent capillary transfer constant (Ktrans) from DCE, were assessed. The patients were separated in two groups by median survival and differences between the two groups explored. Clinical- and MRI metrics were investigated using univariate and multivariate survival analysis and a predictive survival index was generated. ResultsMedian survival was 19.2 months. A significant decrease in contrast-enhancing tumor size and CBV and CBF in both DCE- and DSC-derived parameters was seen during and two weeks past radiochemotherapy (p < 0.05). A 10%/30% increase in Ktrans/CBF two weeks after finishing radiochemotherapy resulted in significant shorter survival (13.9/16.8 vs. 31.5/33.1 months; p < 0.05). Multivariate analysis revealed an index using change in Ktrans and relative CBV from DSC significantly corresponding with survival time in months (r2 = 0.843; p < 0.001). ConclusionsSignificant temporal changes are evident during radiochemotherapy in tumor size (after two weeks) and perfusion-weighted MRI-derived parameters (after four weeks) in glioblastoma patients. While DCE-based metrics showed most promise for early survival prediction, a multiparametric combination of both DCE- and DSC-derived metrics gave additional information.

Destruction of waves and formation of rivulets on the surface of a heated liquid film at Re = 10

The mechanism of transformation of developed naturally formed waves into thermocapillary-wave structures in the vertical flow of a heated water film was studied experimentally. The motion of large waves whose width significantly exceeds the distance between the thermocapillary rivulets (transverse inhomogeneities of thickness and temperature), which have already formed in the residual film layer in front of the incoming large wave was studied in detail. It is shown that combination of thermocapillary and inertial effects in a wavy liquid film leads to deformation of large waves and their decay into the waves of a smaller width. Various scenarios of large wave destruction are considered. It is found out that when medium and small waves move, the thermocapillary forces change the distance between their crests, adjusting them to the distance between the forming structures in the residual layer.The regime maps, where the flow is divided into two zones: the region of deformation of three-dimensional waves and the region of developed rivulet flow, have been plotted for different heat fluxes.Various scenarios of changes in three-dimensional waves occur in the region of their deformation. In the region of developed rivulet flow, the motion of waves obeys the general laws. Waves propagate only along the rivulets with the average inter-rivulet distance equal to five capillary constants. Between the rivulets, the film is smooth. The amplitude of waves (the maximal film thickness) in the rivulets and their velocity increase as they move along the heater.

Capillary constant and surface tension of liquefied gases saturated with helium

The effect of helium on the capillary constant and surface tension of liquefied gases is examined. Experimental data are analyzed in the framework of the finite thickness layer method. It is noted that owing to its low solubility and considerable surface activity, helium, depending on the kind of solvent and state parameters, may act as a surface-active and an inactive substance. The possibility to use the concept of thermodynamic similarity in describing the properties of the liquid–gas interface in solutions is discussed.

Surface tension in bulk and bounded liquids

The paper is aimed at theoretical studying the following problems and its relation to the available experimental data: 1) the coefficient of surface tension and capillary constant in bulk and spatially bounded liquids in a wide range of thermodynamic parameters (temperature, density, pressure, etc.), including the critical region; 2) influence of size effects on surface tension and capillary constant in liquids with a varying spatial dimensionality, namely from the “surface” 2D-state to the “bulk” 3D-state, and then to regular 4D-state where the fluctuation effects may be neglected in liquids like water with the Ginzburg number, Gi < 1; 3) comparison the obtained results and empirical approach to the water surface tension in a wide intervals of thermodynamic variables, including confined supercooled water; 4) medical application of results for surface tension, using similarity between processes of carcinogenesis and nucleation.The theoretical formulas are proposed for dependence of surface tension and capillary constant in bulk and confined liquids on temperature, density, pressure, and size variables in a wide vicinity of the critical region. The agreement of theoretical and experimental data for the temperature dependence of surface tension and capillary constant appears to be quite satisfactory. The 2D↔3D dimensional crossover for surface tension and capillary constant is analyzed. The surface tension of liquids with a relatively small Ginzburg number, including bulk water, is studied with taking into account the dimensionality crossover from 3D-systems to 4D-systems, where the Landau mean-field theory is valid. The empirical formula for surface tension of pure water is discussed together with the Tolman correction and the fluctuation theory of phase transitions. The consequences of the similarity hypothesis of nucleation and carcinogenesis are discussed.

Influence of a Perpendicular Electrostatic Field on Aerodynamic-Force-Induced Primary Disintegration of a Thin Plane Jet of Dielectric Liquid

The disintegration of a plane nonconductive jet of a high-permittivity liquid has been studied. The jet moves with constant velocity in a gas that is quiescent at infinity in the presence of a perpendicular electrostatic field. Initially, the boundaries of the jet are parallel to each other. Its thickness is much smaller than the capillary constant. The gas density has been included into the list of governing parameters. The case has been considered when aerodynamic forces arising from wave disturbance of the gas–liquid interface make a greater contribution to the dynamics of the liquid than capillary forces. It has been shown that when the jet is aerodynamically unstable, the application of a perpendicular electric field with moderate intensity considerably decreases fragments of the jet after disintegration.

Theoretical Basis of Formation Highly Organized Porous Structure of Aerated Concrete

Theoretical principles of the formation of highly organized porous structure of cellular concrete are developed, based on model concepts of the dynamics of the expanding gas cavity in the liquid phase as a single control cell. The peculiarities of controlling the formation of cellular structure of aerated concrete based on the balance of forces in a three-phase disperse system on the model "gas pore - molding mixture" are revealed and a coalescing-aggregate scheme for porosity formation of the aerated concrete mixture is proposed. It is shown that, in accordance with the refined Rayleigh-Plesset equation, the determining factor in the formation of the cellular structure of aerated concrete is the pressure over the mixture to be poroused, the effect of the porosity being achieved by reducing the external pressure to the vacuum level. The division of pores by size in anaerated concrete mixture is proposed. The maximum pore size is determined by the capillary Laplace constant. The prospects of aerated concrete technology are associated with a decrease in the maximum and average size of cellular pores, as well as methods for eliminating pores of air entrainment and segmented pores. Reducing of the size of the pores will be reflected in the decrease of the Bond quantity and in the increase of the importance of capillary forces in the formation of the porous structure of aerated concrete. The concepts of the types of cellular structures are developed, depending on the average density and their boundaries for cellular concrete are established.

Влияние перпендикулярного электростатического поля на вызванный аэродинамическими силами первичный распад тонкой плоской струи жидкого диэлектрика

AbstractThe disintegration of a plane nonconductive jet of a high-permittivity liquid has been studied. The jet moves with constant velocity in a gas that is quiescent at infinity in the presence of a perpendicular electrostatic field. Initially, the boundaries of the jet are parallel to each other. Its thickness is much smaller than the capillary constant. The gas density has been included into the list of governing parameters. The case has been considered when aerodynamic forces arising from wave disturbance of the gas–liquid interface make a greater contribution to the dynamics of the liquid than capillary forces. It has been shown that when the jet is aerodynamically unstable, the application of a perpendicular electric field with moderate intensity considerably decreases fragments of the jet after disintegration.

Capillary constant and surface tension of propane (R-290) with helium dissolved in it

The differential capillary method is employed for the measurement of the capillary constant. Based on the knowledge of this parameter, the surface tension of propane (R-290) + helium is calculated. The measurements are performed in a temperature interval from 120 to 350 K at pressures in the range from the saturation pressure of pure propane up to 4 MPa. Equations are proposed for the dependence of the surface tension on temperature, pressure, and concentration. It is shown that in the considered range of values of the parameters small additions of helium into propane may lead both to a decrease and an increase of the surface tension of the solution.

Regimes of Intensified Heat Transfer during Evaporation of Thin Horizontal Liquid Layers at Reduced Pressures

The influence of structures formed during the evaporation and boiling of a liquid (n-dodecane) in thin horizontal layers on heat transfer has been analyzed. Structures shaped with the shapes of funnels and craters are formed at low pressures in liquid layers with thicknesses above the capillary constant under the action of a vapor recoil force. Increasing pressure leads to the onset of bubble boiling. It is established that the formation of these structures in the regime of intense evaporation at low reduced pressures leads to an about 70% increase in the heat-transfer coefficient at analogous layer thicknesses in comparison to the case of bubble boiling.

Режимы с интенсификацией теплообмена при испарении в тонких горизонтальных слоях жидкости при пониженных давлениях

AbstractThe influence of structures formed during the evaporation and boiling of a liquid (n-dodecane) in thin horizontal layers on heat transfer has been analyzed. Structures shaped with the shapes of funnels and craters are formed at low pressures in liquid layers with thicknesses above the capillary constant under the action of a vapor recoil force. Increasing pressure leads to the onset of bubble boiling. It is established that the formation of these structures in the regime of intense evaporation at low reduced pressures leads to an about 70% increase in the heat-transfer coefficient at analogous layer thicknesses in comparison to the case of bubble boiling.

Accuracy of Axisymmetric Drop Shape Analysis in Determining Surface and Interfacial Tensions.

Axisymmetric drop shape analysis (ADSA) has been used in a broad range of applications for determining surface tensions of air-liquid surfaces and interfacial tensions of liquid-liquid interfaces. However, it is well-known that the accuracy of ADSA deteriorates upon the reduction of drop volume. Here, we systematically compared different criteria and parameters in evaluating the accuracy of ADSA upon reducing drop volume. By scrutinizing the dependence of ADSA accuracy on various parameters, including the capillary constant (c), the Bond number (Bo), the Worthington number (Wo), and the shape parameter (Ps), we concluded that the classical Bond number failed to predict the accuracy of drop shape analysis at very small drop volumes. Thus, we proposed a replacement of the classical Bond number, called the Neumann number Ne ≡ (ΔρgR0H)/γ. The design rationale of this new dimensionless number lies in the use of the geometric mean of the radius of curvature at the drop apex (R0) and the drop height (H) as the new characteristic length (L) to represent the drop size, that is, L = (R0H)1/2. It is found that the Neumann number is capable of evaluating the accuracy of ADSA. Moreover, we have demonstrated the usefulness of the local Neumann number, Nez ≡ (ΔρgR0/γ)z, in evaluating the contribution of the local drop profile to the accuracy of ADSA.