Determination Of Interfacial Tension Research Articles

A novel microfluidic method to simultaneously measure droplet size and interfacial tension without visualization

AbstractDroplet size and interfacial tension are key parameters related to two‐phase flow. However, current methods for measuring these parameters are usually based on visualization and are therefore not applicable for invisible two‐phase flow systems. Moreover, real‐time determination of interfacial tension is difficult because conventional methods cannot be employed in the flow field. This study presents a novel method for simultaneously measuring the droplet size and real‐time interfacial tension in a two‐phase flow system. A T‐shaped microdevice was designed and integrated with the two‐phase flow equipment. The pressure variation as the droplets flowed through the microdevice was used as a probe to detect the two key parameters, that is, visualization is not required. Monodispersed and multidispersed droplet flows in different equipment were used to verify the method. Both the droplet size distribution and real‐time interfacial tension can be determined using the developed approach.

A novel correlation for modeling interfacial tension in binary mixtures of CH₄, CO₂, and N₂ + normal alkanes systems: Application to gas injection EOR process

The Enhanced Oil Recovery (EOR) has received significant attention in recent years by the cessation of primary production of several reservoirs and also the increasing global demand for energy. Miscible gas flooding is one of the most popular EOR techniques. Interfacial Tension (IFT) data plays an important role in determining Minimum Miscibility Pressure (MMP) as well as estimating the recovery performance of the EOR schemes, and the production potential of fractured reservoirs. CH₄, CO₂, and N₂ are the gases widely used for gas injection EOR practices. Normal alkanes can represent the real crude oil samples as they are their most abundant constituents. Acquiring knowledge about the IFT between vapor phase and n-alkanes can shed light on the governing mechanisms between the injected gas phase and the real crude oil in EOR projects. Experimental determination of IFT is often associated with the high cost and arduous and timely procedures. The theoretical works need expensive numerical and computational effort. Data-based methods can offer a promising alternative to compensate for the disadvantages of the mentioned methods. An extensive database including 606, 1131, and 469 data samples of IFT between normal n-alkanes and CH₄, CO₂, and N₂ was utilized in this study to develop predictive models. Proper input variables were analyzed and selected for modeling. The Group Method of Data Handling (GMDH) was used in this study. Separate models were developed for the three vapor phases. The Root Mean Square Errors (RMSE) of 1.24, 1.29, and 1.15 mN/m for respective CH₄, CO₂, and N₂ systems indicate the acceptable accuracy of the developed model. The models were compared with the models available in the literature. It was revealed that the proposed GMDH models provide superior predictions for a wide range of pressure and temperature. External validation was performed using a very recently published dataset to check for the generality of the proposed models. Finally, a systematic method was proposed to select the best predictive model based on the n-alkane type and operational parameters of pressure and temperature. The findings of this study can be utilized in designing and planning efficient EOR schemes.

SURFACTANT PROPERTIES EVALUATION FOR CHEMICAL FLOODING

The need of EOR techniques in the late field production period is essential to get the third wind of incremental oil. Chemical injections are proven technologies not only at the laboratory scale but also at the field scale which have been implemented in many parts of the world. Surfactant is an important chemical in this technology, which mostly has been used to reduce the capillary trap of the oil in the reservoirs. The selection of surfactant type which is suitable for a specific oil field to increase the oil production should fulfill the selection criteria. Laboratory works firstly should be done to evaluate the important properties based on the industrial standard procedures. These laboratory tests include compatibility test, aqueous stability test, phase behavior study, micro-emulsion viscosity, interfacial tension determination, thermal stability test, and filtration test.

Determination of interfacial tension and viscosity under dripping flow in a step T-junction microdevice

Microfluidic approaches for the determination of interfacial tension and viscosity of liquid-liquid systems still face some challenges. One of them is liquid-liquid systems with low interfacial and high viscosity, because dripping flow in normal microdevices can’t be easily realized for the systems. In this work, we designed a capillary embedded step T-junction microdevice to develop a modified microfluidic approach to determine the interfacial tension of several systems, specially, for the systems with low interfacial tension and high viscosity. This method combines a classical T-junction geometry with a step to strengthen the shear force further to form monodispersed water/oil (w/o) or aqueous two-phase (ATP) droplet under dripping flow. For systems with low interfacial tension and high viscosity, the operating range for dripping flow is relative narrow whereas a wider dripping flow operating range can be realized in this step T-junction microdevice when the capillary number of the continuous phase is in the range of 0.01 to 0.7. Additionally, the viscosity of the continuous phase was also measured in the same microdevice. Several different systems with an interfacial tension from 1.0 to 8.0 mN·m−1 and a viscosity from 0.9 to 10 mPa·s were measured accurately. The experimental results are in good agreement with the data obtained from a commercial interfacial tensiometer and a spinning digital viscometer. This work could extend the application of microfluidic flows.

Determination of Interfacial Tension of Nanomaterials and the Effect of Particle Size on Interfacial Tension.

The unique physical and chemical properties and performances of nanomaterials are closely related to the interfacial tension. However, there is no method to accurately measure the interfacial tension of nanomaterials. In addition, the effect of particle size on the interfacial tension of nanoparticles is unclear, and there exist conflicting conclusions about the value and sign of Tolman length. In this paper, a novel method of determining the interfacial tension (solid-liquid and solid-gas interfaces), temperature coefficient of interfacial tension, and Tolman lengths of nanomaterials by adsorption thermodynamics and kinetics was presented. The interfacial tension and its temperature coefficient of the solid-liquid interface of nano cadmium sulfide before adsorption were obtained, and further, the Tolman length was also obtained. The experimental results show that the particle size of nanoparticles has significant effects on the interfacial tension and its temperature coefficient. When the radius is larger than 10 nm, the interfacial tension and its temperature coefficient are almost constant with the decrease of the radius. When the radius is less than 10 nm, the interfacial tension decreases sharply and the temperature coefficient increases sharply with the decrease of the radius, and the temperature coefficient of the interfacial tension is negative. The Tolman length of the solid-liquid interface of nanoparticles is proved to be positive, and the particle size also has a significant effect on the Tolman length. The Tolman length decreases with the decrease of particle size. However, the effects of particle size on the Tolman length become significant only when the particle radius approach or reach the order of magnitudes of molecular (or atomic) radius. The effects of particle size on interfacial tension and Tolman length of nano cadmium sulfide obtained in this paper can provide significant references for the research and applications of interface thermodynamics of other nanomaterials.

Automated determination of interfacial tension and contact angle using computer vision for oil field applications

AbstractContact angle and surface tension are the two most widely used surface analysis approaches for reservoir fluid characterization in petroleum industries. The pendant drop method has among the most widely used techniques for the estimation of surface tension. The present work utilizes a python-based computer program to automatically determine interfacial tension (IFT) and contact angle from the pendant drop image acquired from a typical pendant drop apparatus. The proposed program uses python-based image processing libraries for the analysis of the pendant drop image. Also, the program is tested on images acquired from the standard solutions for the IFT and contact angle calculation showing promising results with a standard deviation of less than 1.7 mN/m.

A novel technique for interface analysis: Behaviour of sophorolipids biosurfactant obtained from Meyerozyma spp. MF138126 during low-salinity heavy-crude experiments

A novel technique for interface behaviour and thermodynamic properties analyses of sophorolipids (SLs) biosurfactant obtained from Meyerozyma spp. MF138126 under high-pressure high-temperature (HPHT), for low-salinity heavy-crude experiments is presented. An experimental rig for production of biosurfactant and determination of interfacial tension (IFT) under HPHT is developed specially for the purpose of this investigation. A reduction of a factor of seven and nine in IFT was obtained for experiments between brine and heavy-crude at temperatures of 45°C and 65 °C respectively. Furthermore, with increasing temperature, the degree of SLs adsorption at the interface increases leading to a total collapse in the profiles of the adsorption graphs. The minimum area per molecule of SLs monomers for different conditions suggested that the interface weakens occupying more surface area as the temperature increases. The degree of counter-ion binding for SLs is obtained to be 0.86. The computed Gibbs free energy of micellisation is −1940 KJ/mol; which is exergonic depicting favourable reaction and spontaneous in forward direction. At a fixed temperature of 25 °C and pressure of 45 bar, IFT value of 0.251 mN/m was obtained. It is concluded that the produced SLs retained its molecular integrity and IFT reduction effectiveness under both unconfined and confined HPHT systems.

Interfacial Tension Sensor for Low Dosage Surfactant Detection

Currently there are no available methods for in-line measurement of gas-liquid interfacial tension during the flotation process. Microfluidic devices have the potential to be deployed in such settings to allow for a rapid in-line determination of the interfacial tension, and hence provide information on frother concentration. This paper presents the development of a simple method for interfacial tension determination based on a microfluidic device with a flow-focusing geometry. The bubble generation frequency in such a microfluidic device is correlated with the concentration of two flotation frothers (characterized by very different adsorption kinetic behavior). The results are compared with the equilibrium interfacial tension values determined using classical profile analysis tensiometry.

Measurement approach of interfacial tension on example of water-toluene

A quite simple experimental method for interfacial tension determination is presented. It is based on measurements done in the digital photographs of the drops at the creation moment. It is validated with the result of other researchers. The interfacial tension for water-toluene interface is obtained in the range 0.1°C–96.6°C. It is almost constant up to 40°C. Then appear linear decrease to 80°C. Next is observed sharp drop to 96.6°C. Uncertainties of the determined values are estimated. A gaseous phase occurs at temperature close to the boiling point, thus interfacial tension was not determined. The experimental results are presented with a rational function.

Modeling interfacial tension of methane-brine systems at high pressure and high salinity conditions

Natural gas which consists mainly of methane (usually more than 90% in volume), is becoming increasingly an important and efficient source of energy because of the lower greenhouse gas emissions and air pollution. Achieving satisfactory recovery factors in gas reservoirs is sensitive to the methane-brine/water interfaces induced by the interfacial tension (IFT) between these systems. Accordingly, accurate determination of IFT of the systems methane-brine/water is extremely important for natural gas production. In this paper, several intelligent models were implemented to accurately estimate interfacial tension (IFT) of the systems brine/pure water-methane under wide temperature, pressure and salinity ranges of (278.1–477.59 K), (0.01–260 MPa) and (0–200,000 ppm), respectively. The established models were based on an extensive databank including 879 experimental measurements. The implemented intelligent models in this study were Extreme Learning Machine (ELM), Radial Basis Function (RBF) neural network, Multilayer Perceptron (MLP), Least Square Vector Machine (LSSVM), and Generalized Regression Neural Network (GRNN). Various optimization algorithms were applied for improving the learning phase of these models. Furthermore, a Committee Machine Intelligent System (CMIS) scheme was proposed by linking the best-found paradigm under a linear single model. The results showed that all the developed intelligent-based paradigms exhibit reliable prediction abilities. In addition, it was found that CMIS and GRNN are the fittest paradigms with overall absolute average percent relative error (AAPRE) values of 1.117% and 1.003%, respectively. Besides, the performance assessment revealed that our best paradigms outperform the existing approaches. Finally, the sensitivity analysis revealed that salinity has a slight impact on IFT.

On the study of the vapor-liquid interface of associating fluids with classical density functional theory

Classical density functional theory (DFT) is applied to study the vapor-liquid interface of associating fluids. Our classical DFT implementation uses a Helmholtz free energy functional that reduces to the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state in the bulk limit. We apply a new association functional, presented in one of our previous works, based on the weighted density approximation to calculate the interfacial tension of associating fluids and compare them with two of the most used association functionals from literature. It is found that classical DFT with the three association functionals and the current molecular parameters of PC-SAFT is not able to predict satisfactorily the interfacial tension of alkanols. Therefore, the experimental interfacial tension of alkanols and some associating fluids is included in the determination of the pure molecular parameters of PC-SAFT. With this approach the determination of interfacial tension of pure associating fluids can be greatly improved with the new parameters, but at the expense of slightly higher deviations in the vapor pressure. The new parameters are tested for the determination of vapor-liquid equilibria (VLE) and the prediction of interfacial tension of binary mixtures containing at least one associating compound. Good agreement is found between experimental data of VLE and interfacial tension of the binary mixtures and the three association functionals. Furthermore, we discuss about the limitations and capabilities of the current classical DFT implementation in the study of the vapor-liquid interface of associating fluids.

A multiple approach in determination of interfacial tension of biodegradable melt-mixed PBAT/EVOH blends: Correlation of morphology, rheology and mechanical properties

The interfacial tension of biodegradable melt-mixed blends of poly(butylene adipate-co-terephthalate), PBAT, and poly(ethylene-co-vinyl alcohol), (EVOH), was measured by breaking thread (BT), imbedded fiber retraction (IFR), and rheological methods. The PBAT-rich blends were prepared under different melt mixing conditions in order to investigate the effect of mixing conditions and possibility of reactive mixing between the blend components on the blend morphology, rheology, mechanical properties and interfacial tension values. The conditions were varied based on a Taguchi design of experiment using four factors namely EVOH content (0–30 wt%), mixing time (2–15 min), rotor speed (50–90 rpm), and mixing temperature (185–200 °C), each varying at three levels. The average size of EVOH droplets in PBAT matrix was determined for each blend by a field emission-scanning electron microscopy technique. The values of interfacial tension of PBAT/EVOH were found to be 2.57 ± 0.22 and 2.73 ± 0.30 mN m−1 by the BT and IFR methods, respectively. The Palierne, Gramespacher, and Bousmina models were fitted to the rheological data to verify the interfacial tension of the blends. The continuous relaxation spectrum of the blends was determined in order to obtain the relaxation time of the EVOH droplets in the PBAT matrix. The Taguchi analysis revealed that the most effective factor is the EVOH content, and other factors do not play a significant role in the ultimate properties of the blends. Finally, based on the obtained mechanical properties, the possibility of reactive mixing under the applied mixing conditions was ruled out by means of repeated differential scanning calorimetry (DSC) and rheological measurements.

Rapid Determination of Interfacial Tensions in Nanopores: Experimental Nanofluidics and Theoretical Models.

A rapid and accurate determination of interfacial tensions (IFTs) in nanopores is scientifically and practically significant, while most existing experimental measurements are restricted to the micrometer scale and theoretical calculations are relatively limited. In this study, six series of the IFT measurement tests for the binary CO2-C10, C1-C10, and N2-C10 mixtures are conducted at temperatures ( T) of 25.0 and 53.0 °C in a self-manufactured nanofluidic system. Moreover, a nanoscale-extended equation-of-state model considering the effects of the confinement, intermolecular interactions, and disjoining pressure and a semianalytical correlation are proposed to calculate the IFTs of the three mixtures in bulk phase and nanopores. Third, a new Tolman length formulation is developed for the IFT corrections in nanopores. Overall, the calculated IFTs from the two theoretical methods agree well with the measured results for most cases in nanopores. On the other hand, effects of the pore scale, temperature, pressure, and fluid composition on the IFTs of the three mixtures are effectively validated and specifically investigated. One suggestion comes from this work that the two theoretical methods for calculating the IFTs are better to be applied concurrently to minimize errors. Another important future work is to include more pore surface parameter (e.g., wettability) into the theoretical model.

Theoretical model in cylindrical coordinates to describe dynamic interfacial tension determination with spinning drop tensiometry

In this paper, a theoretical model in cylindrical coordinates is presented to describe the behavior of dynamic interfacial tension (DIFT) between the oil and water phases. The equation of DIFT is derived from mathematical derivation combined with Gibbs equation. The DIFTs of three sodium alkylbenzene sulfonates (p-S14-5, p-S16-5 and p-S18-5) were studied by the spinning drop technique. It is a function of time and exponential decay is observed. The experimental data are in agreement with the calculated theoretical curves. Meanwhile, the equation predicts that the computable variable (r/2·Ln1-exp-γ-γ∞R·T·Γ should be linear with interphase diffusion time t and its slope depends on the interphase diffusion coefficient K if the assumptions involved in the derivation are valid. The average values and range of the interphase diffusion coefficient K of three surfactants were calculated by applying the slopes from the linear portions.

Theoretical and experimental investigation of the interfacial properties in the ternary mixtures water + 1-hexanol + acetic acid and water + hexylacetate + acetic acid using density gradient theory and spinning-drop tensiometry

The importance of reliable determination of interfacial tension between fluid phases has been well recognized in chemical engineering. The purpose of this work is a detailed study whether the density gradient theory in his incompressible version in combination with the activity coefficient model, namely the NRTL-model, is capable to describe or even predict the interfacial properties of two technical important mixtures, namely water + 1-hexanol + acetic acid and water + hexylacetate + acetic acid.Particular attention is directed to the prediction of ternary interfacial properties outgoing from the influence parameter of the binary subsystems, which show liquid-liquid phase split. It could be demonstrated that the predicted interfacial tension for both investigated systems are very close to the experimental data, obtained in this study. Furthermore, it could be shown that the polarity of the phase forming components determine the selective enrichment of the solubilizing component in the interphase.

Interfacial Tension between Water and Organic Liquid lighter than water by Capillary Rise Method

Interfacial tension between two liquids water and immiscible organic liquid heavier than water has been determined by capillary rise method. The difficulties encountered in the determination of interfacial tension by capillary rise method and how to overcome the difficulties has been discussed. The interfacial tensions between water and organic liquids, carbon tetrachloride, chloroform, nitrobenzene and o-anisidine which are heavier than water have been determined at room temperature (29±1oC) by capillary rise method using a pyrex glass capillary tube of uniform radius. The values of the interfacial tension determined by the capillary rise method were found to be negative indicating that the interfacial tension was acting in the downward direction. The force in the vertically upward direction was considered as positive. The interfacial tensions determined by capillary rise method were in close agreement with the reported values.

Biobased Poly(ethylene terephthalate)/Poly(lactic acid) Blends Tailored with Epoxide Compatibilizers.

To increase the biobased content of poly(ethylene terephthalate) (PET), up to 30 wt % poly(lactic acid) (PLA) was blended with PET using twin-screw compounding and injection molding processes. Multifunctional epoxide compatibilizers including a chain extender and an impact toughening agent were used as blend modifiers to improve the poor mechanical properties of PET/PLA blends. The mechanical and thermodynamic performances were investigated along with the morphological features through scanning electron microscopy, atomic force microscopy, and interfacial tension determination. From rheological and differential scanning calorimetry results, it was observed that the molecular weight of both PET and PLA increased with compatibilizers because of epoxide reactions. The toughening agent, poly(ethylene-n-butylene-acrylate-co-glycidyl methacrylate) (EBA–GMA), provided a 292% increase in impact strength over the blend but reduced modulus by 25%. In contrast, 0.7 phr addition of the chain extender, poly(styrene-acrylic−co-glycidyl methacrylate) (SA−GMA), yielded comparable performance to that of neat PET without sacrificing the tensile and flexural properties. When both compatibilizers were present in the blend, the mechanical properties remained relatively unaltered or decreased with increasing EBA–GMA content. The differences in mechanical performance observed were considered in relation to the strengthening mechanism of the two differing compatibilizers and their effects on the miscibility of the blend.

Characterizing the CO2-brine interfacial tension (IFT) using robust modeling approaches: A comparative study

Interfacial phenomenon between CO2 and aqueous phases affects the distribution and behavior of fluids in porous media, and also plays a major role in determining the usefulness of enhanced oil recovery methods particularly CO2 flooding. Therefore, in this study, the interfacial tension (IFT) between CO2 and brine is predicted as a function of the temperature, pressure, bivalent cation molality, monovalent cation molality as well as methane and nitrogen mole fractions using three robust modeling strategies called gene expression programming (GEP), decision tree (DT), and least squares support vector machine (LSSVM). Furthermore, the outcomes obtained by the methods mentioned above have been assessed by comparing with the reported estimates of artificial neural network (ANN) in the literature. Amongst the all models proposed in the current study, it is demonstrated that the developed regression DT tool and the available ANN in literature are the most precise models which could be applied properly as the reliable methods for the characterization and determination of IFT between CO2 and brine, and also for geological CO2 storage.

Modeling interfacial tension and minimum miscibility pressure in paraffin-nitrogen systems: Application to gas injection processes

Nitrogen has emerged as an attractive gas for many petroleum and chemical engineering applications such as gas lift, gas recycling, pressure maintenance, and enhanced oil recovery, especially for some high-pressure reservoirs. Accurate determination of interfacial tension (IFT) in nitrogen/hydrocarbon systems is crucial and required for numerous applications in chemical and petroleum industries. The experimental measurements of IFT are costly, cumbersome and time consuming, especially at high pressure-high temperature conditions. In this study, the IFT of normal alkanes from n-C5 to n-C16 (as the representatives of crude oil) and nitrogen is modeled at a wide range of pressure (from 0.1 to 69MPa) and temperature (from 295 to 442K) using group method of data handling (GMDH). Three inputs were used for modeling including pressure, temperature, and molecular weight of normal alkane. To develop the most efficient model, 60% of the dataset was used for model development and the remaining 40% was used to check the validity and accuracy of the developed model. The proposed model predicts the data satisfactorily with an average absolute relative error of 3.81% and 3.91% in training and testing subsets, respectively. Then, the proposed model was compared to the well-known IFT models, namely Linear Gradient Theory (LGT), Density Gradient Theory (DGT), and Parachor approaches combined with the Volume Translated Predictive Peng Robinson Equation of State (VT-PPR EOS). The results demonstrate that the proposed model not only is superior to the existing models in terms of accuracy, but also can predict the IFT with a simple mathematical expression with a quite low computational cost. Finally, a simple-to-use algorithm was proposed to calculate the minimum miscibility pressure (MMP) in normal alkane/nitrogen systems based on the measurements with vanishing interfacial tension (VIT) technique, which predicts the MMP with high accuracy.

Predicting CO2-H2O Interfacial Tension Using COSMO-RS.

Knowledge about the interaction between fluids and solids and the interfacial tension (IFT) that results is important for predicting behavior and properties in industrial systems and in nature, such as in rock formations before, during, and after CO2 injection for long-term storage. Many authors have studied the effect of the environmental variables on the IFT in the CO2-H2O system. However, experimental measurements above CO2 supercritical conditions are scarce and sometimes contradictory. Molecular modeling is a valuable tool for complementing experimental IFT determination, and it can help us interpret results and gain insight under conditions where experiments are difficult or impossible. Here, we report predictions for CO2-water interfacial tension performed using density functional theory (DFT) combined with the COSMO-RS implicit solvent model. We predicted the IFT dependence as a function of pressure (0-50 MPa), temperature (273-383 K), and salinity (0-5 M NaCl). The results agree well with literature data, within the estimated uncertainty for experiments and for molecular dynamics (MD) simulations, suggesting that the model can be used as a fast alternative to time-consuming computational approaches for predicting the CO2-water IFT over a range of pressures, temperatures, and salinities.