High-pressure Viscosity Measurements Research Articles

Two-capillary viscometer for temperatures and pressures relevant to CO2 capture, transport, and storage—operation and improved analysis at high pressure

High-pressure viscosity measurements are crucial for understanding CO2 transport and storage because CO2 is often transported as a supercritical fluid, at a high pressure and temperature above its critical point. In this study, we extended the operational range of our new two-capillary viscometer to handle pressures up to 20 MPa, focusing on the behaviour of CO2 at temperatures around 300 K. The analysis model is based on the low-pressure principle, which relied on virial descriptions of density and viscosity, proved inadequate under these conditions. Therefore, we introduced a modified hydrodynamic model as a function of density that is suitable for viscosity measurements at high pressure and liquid states. The modified model bypasses the need for a density virial correction. We conducted initial viscosity tests on pure CO2 at five isotherms: 280.01 K, 298.15 K, 300.01 K, 323.15 K, and 348.15 K to validate the performance of the new two capillary viscometer and the modified model at high pressures. The experimental viscosities agreed with the model predictions and comparable within the estimated uncertainty of the data. In addition, we thoroughly explained the calibrations and the analysis of uncertainty estimation. The uncertainty analysis showed a maximum extended combined uncertainty of 1.3% (k = 2) within all thermodynamic states—gas, liquid, and close to the critical region.

A two-capillary viscometer for temperatures up to 473 K and pressures up to 100 MPa—operation and verification at low pressure

In this paper, we described the design and construction of a new two-capillary viscometer with several novel technical solutions for viscosity and density measurements. Our design, which is based on the low-pressure principle, featured numerous improvements in hardware and procedure that allowed the greatly extended range of pressure. The new design adopted a (2 × 2) capillary configuration, utilizing different combinations of four capillaries to enable viscosity measurements with a wide range of flow rates, temperatures, and pressures. The design temperature range is 213 K–473 K, and the pressure range is up to 100 MPa. The viscometer was specifically designed for measuring the viscosity of pure CO2 and CO2-rich mixtures, addressing the scarcity of data in conditions relevant to carbon capture, transport, and storage. Our facility is capable of viscosity measurements in different thermodynamic states; gaseous, liquid, supercritical, and critical regions. A commercial densimeter is integrated to measure density under the same temperatures and pressures. We aimed for a total uncertainty target of better than 0.03%. The performance of the viscometer was validated by measurements with pure CO2 at 298.15 K and zero density. We observed a deviation of less than 0.03% between the reference viscosity of CO2 of this work and accurately calculated data using ab initio quantum mechanics with a standard uncertainty of 0.2%. Our primary focus in this paper was to provide a detailed description of the design and construction of the apparatus, emphasizing improvements and introducing new solutions to other research groups in constructing similar instruments suitable for low- and high-pressure viscosity measurements with high accuracy.

High pressure viscosity measurements of ternary (methane + propane + heptane) mixtures

Prediction of thermophysical properties for natural gas mixtures close to the mixture's critical point and cricondenbar (the maximum pressure at which two fluid phases can co-exist) is challenging but important as often natural gas processes operate close to these conditions. Here we present a comprehensive study of the viscosity of (CH4 + C3H8 + C7H16) mixtures with heptane fractions up to 15 mol%. Accurate measurements of saturated-phase and compressed-fluid (single phase) viscosities, at temperatures from 200 K to 423 K and pressures up to 35 MPa, are presented. The collected data were compared with the prediction of the extended corresponding states (ECS) model, with relative deviations spanning between (−20 to 11) % from the model. Additionally, pure component parameters needed for the residual entropy scaling (RES) model were fit to literature data and then applied predictively to mixtures viscosity without any additional fit parameters. The relative deviation of the measured viscosities from values calculated with the RES model is generally within 15%. This work demonstrates that no current model satisfactorily predict mixtures viscosity, and that high quality experimental data are needed to anchor the methods used to design and optimize natural gas processing.

Study on Relations of High-Pressure Viscosity Properties and the Polymer Behavior of Various Viscosity Index Improver-Blended Oil (Part 2)

Using high-pressure viscosity measurements of 23 kinds of VII-blended oil reported in Part 1, a high-pressure viscosity prediction formula for VII-blended oil was derived. This equation is expressed in a so-called Barus formula, and the pressure-viscosity coefficient is the secant pressure-viscosity coefficient αB(p)-Bl (= ln(ηpt / ηot) /P) in each ln(ηpt) ‒ P relation curve. The calculation formula of αB(p)-Bl is composed of the corresponding base oil value αB(p)-Bf, the polymer coil itself pressure-viscosity coefficient αPm and the polymer concentration wPm (wt%). In relation to mentioned above, the volume fraction of one polymer molecule in hydrodynamically equivalent sphere, and the volume fraction of the hydrodynamic volume occupied in 100 cm3 of VII-blended oil at critical concentration c* of polymer coil were investigated. It was also found that the viscosity index VIo-Bl in the atmospheric pressure of the VII-blended oil drops with pressure. For this reason, the effect of temperature on the ln(ηpt) ‒ P relation curve, the influence of polymer type and base oil in ηi ‒ P ‒ t relationship, and the influence of polymer type on atmospheric pressure viscosity ηot ‒ t relationship were discussed.

Density, Viscosity, and Derivative Properties of Diethylene Glycol Monoethyl Ether Under High Pressure and Temperature

The measurement of densities (ρ) of the pure component diethylene glycol monoethyl ether (2-(2-ethoxyethoxy)ethanol) has been carried out using a vibrating-tube densimeter (Anton Paar DMA HPM) along temperatures varying from 293.15 to 353.15 K and pressures from 0.1 to 70 MPa with an expanded uncertainty of 0.5 kg·m–3. High-pressure dynamic viscosity (η) measurements were performed with a falling body viscometer at pressure values up to 70 MPa and within a temperature range from 293.15 to 353.15 K with an expanded relative uncertainty of 0.03η. The dynamic viscosity was determined at 0.1 MPa, thanks to an Ubbelohde capillary viscometer, with an expanded relative uncertainty smaller than 0.01η. Density experiments were adjusted using a Tait-like equation and modeled by employing the perturbed-chain statistical associating fluid equation of state (EoS). Moreover, high-pressure dynamic viscosity experimental data were correlated using the Vogel–Fulcher–Tammann (VFT) equation.

Design of a high-pressure viscosity-measurement system using two pressure balances

In this paper, a new high-pressure viscosity measurement system using a capillary method is reported. In this system, two pressure balances are used to generate stable pressure and flow field in the capillary. The volumetric flow rate was measured by calculating the change in the piston fall rate. To check the effectiveness of the method, the viscosity of bis(2-ethylhexyl) sebacate was measured at pressures of up to 200 MPa. Differential pressure and volumetric flow rate had a linear relationship at all temperature and pressure conditions, indicating that the Hagen–Poiseuille law can be applied in this method. The viscosity–pressure dependence is in agreement with other published reports. Thus, we confirmed that the newly developed high-pressure viscosity measurement system can accurately evaluate the pressure dependence of viscosity.

High-Pressure Viscosity Measurements for the Binary Mixture HFE-7500 + Diisopropyl Ether

In this work, high-pressure viscosity measurements for seven compositions of the binary mixture (x) HFE-7500 + (1 – x) diisopropyl ether were carried out. A set of 163 points have been measured cov...

In situ observation of gelation of methylcellulose aqueous solution with viscosity measuring instrument in the diamond anvil cell

Gelation of methylcellulose aqueous solution was investigated by a high-pressure viscosity measurement device which consisted of diamond anvil cell, microscope and CCD. And the temperature and pressure dependence of the viscosity of methylcellulose aqueous solution was measured utilizing a rolling-ball technique. The results showed that sol-gel thermal transition of methylcellulose solution occurred at the temperature of 53 °C under atmospheric pressure. Upon compression, it was indicated that the viscosity showed a dramatic change in the vicinity of the pressure of 500 MPa. Parabolic phase diagram of methylcellulose aqueous solution was constructed, and it showed that the melting point was an increasing function of pressure at the first stage and an decreasing function of pressure at the final stage. The mechanism of sol-gel transformation of methylcellulose aqueous solutions was also discussed, it might be assumed that both hydrogen and hydrophobic bonds were involved with the gel formation in the case of methylcellulose aqueous solution.

Improvers of Pressure-Viscosity Coefficients of Two-Phase Liquid-Solid Lubricants

The prediction of the pressure-viscosity coefficient, α, is one of the most important properties for Elastohydrodynamic lubrication (EHL) condition; thereby, the need for improvers to aid its measurement and performance is necessitated. This article presented two phase liquid – solid lubricants of PTFE and MoS2 solution in SAE 30 oil at varying compositions. The lubricants tested are SAE #30, SAE #30 plus PTFE and SAE #30 plus MoS2. High-pressure viscosity measurement was done at pressure up to 1.5 GPa and temperature range at 20°C to 100°C. Viscosity indices are calculated from the measured viscosity at 40 and 100 oC using ASTM D 2270. However, an attempt to predict α for the blended lubricants using the relationship between pressure-viscosity coefficient and Walther’s logarithm of kinematic viscosity at atmospheric pressure was used. The pressure-viscosity coefficient of two phase liquid – solid lubricants were successfully predicted and the influence of solid lubricant concentration, and temperature on the lubricants viscosity were determined, and compared with SAE #30 oil. The properties and viscosity of mixtures obtained are optimal lubricant factors which optimze the measurement and performance of the highest EHL pressure-viscosity coefficient of the mixtures, and also enhance the better chance to improve the lubrication of machine element than the SAE #30 conventional engine oil.

Viscosity Measurements of Two Potential Deepwater Viscosity Standard Reference Fluids at High Temperature and High Pressure

This paper reports high-pressure viscosity measurements for Krytox GPL 102 lot K2391 and tris(2-ethylhexyl) trimellitate (TOTM). These two viscous liquids have recently been suggested as potential deepwater viscosity standard (DVS) reference fluids for high temperature, high pressure viscosity studies associated with oil production from ultradeep formations beneath the deepwaters of the Gulf of Mexico. The measurements are performed using a windowed, variable-volume, rolling-ball viscometer at pressures between 7 and 242 MPa and temperatures between 314 and 527 K with an expanded uncertainty of 3% at a 95% confidence level. The viscosity results are correlated using an empirical temperature/pressure-dependent function and a modified Vogel–Fulcher–Tammann (VFT) Equation. The present viscosity data for TOTM and Krytox GPL 102 lot K2391 are in good agreement with the available reported data in the literature at lower temperatures and pressures. The viscosity values of TOTM and Krytox GPL 102 lot K2391 are 9....

High-Pressure Viscosity Measurements of Polyalphaorefins at Elevated Temperature

High-Pressure Viscosity Measurements of Polyalphaorefins at Elevated Temperature

Contributing to accurate high pressure viscosity measurements: Vibrating wire viscometer and falling body viscometer techniques

Two new techniques for measuring viscosities at high pressure have been implemented at the TERMOCAL laboratory in order to obtain accurate values of thermophysical properties such as viscosity, especially at high pressures.A vibrating-wire viscometer has been developed to accurately measure viscosities over the working ranges T=(283.15 to 423.15)K and p=(0.1 to 140)MPa. The setup of the equipment includes calibration with toluene and its validation with n-dodecane.A falling body viscometer able to measure viscosities at T=(253.15 to 523.15)K and p=(0.1 to 140)MPa is also presented in this work. Results of calibration with toluene and its verification with n-heptane and n-dodecane are reported.The detailed uncertainty budgets for both techniques are included in this work. Moreover, the paper studies the compatibility of the results obtained using both techniques according to their corresponding uncertainties in order to obtain reliable data. New viscosity measurements of 1,2,4-trimethylbenzene and 2,2,4-trimethylpentane have been performed and included in the paper.

Temperature and Pressure Dependence of the Viscosities of Krytox GPL102 Oil and Di(pentaerythritol) Hexa(isononanoate)

This work reports high-pressure viscosity measurements on two viscous liquids that may prove useful as high-temperature, high-viscosity reference materials, Krytox GPL102 and di(pentaerythritol) hexa(isononanoate). The perfluoropolyether oil, Krytox GPL102, is the subject of a round-robin comparison of high-pressure viscosity measurements on a specific sample being made by a group of laboratories worldwide employing a variety of viscometric techniques. Viscosity data are reported between (0 and 95) °C, at pressures to 226 MPa and viscosities between (6 and 4182) mPa·s. For the more viscous di(pentaerythritol) hexa(isononanoate), data are reported between (0 and 90) °C, at pressures to 203 MPa and viscosities between (34 and 2269) mPa·s. Correlations are provided using modified Vogel–Fulcher–Tammann (VFT) equations for both substances, a modified Litovitz equation for Krytox GPL102 and a modified Barlow-Lamb equation for di(pentaerythritol) hexa(isononanoate). Glass temperatures are estimated to be (178.2 and 218.1) K, respectively, based on the Angell equation relating the VFT parameters to Tg. Thermodynamic scaling is applied to both the experimental and reduced viscosities. The scaling parameters found are consistent with previous work on chain molecular compounds and esters.

Bridging high pressure rheology and film-forming capacity of polymer-base oil solutions in EHL

The development of high value-added lubricants which overcome more drastic operating conditions, are fuel-efficient and provide excellent performance for a long life remains a huge challenge for oil makers. This article sheds light on the tribological response of an EHD circular rolling–sliding contact for a base oil and three polymers mixed in solutions in order to understand the relationship between physico-chemistry and tribology. The final aim is to help formulators select the appropriate chemicals meeting engine specifications. Central and minimal film thickness measurements were run on a ball-on-disc tribometer and determined through white light optical interferometry. Experiments were compared with classical analytical predictions and with the results of a finite element numerical solver based on the generalized Reynolds’ equation including the modelled rheological behavior established from high-pressure and high-stress viscosity measurements and density variations. Moreover, the role played by thermal effects and variable slide-to-roll ratio were discussed.

Effect of Compression on the Relationship between Viscosity and Dielectric Relaxation Time in Hydrogen-Bonded Primary Alcohols

High pressure viscosity and dielectric measurements were carried out on two monohydroxy alcohols, 2-ethyl-1-hexanol and 5-methyl-2-hexanol, at room temperature. Analysis of the dielectric relaxation times versus viscosity revealed the breakdown of the Einstein-Debye relation above some characteristic pressure. The failure of the Einstein-Debye relation is a manifestation of pressure induced changes of supramolecular hydrogen bonded structures which occur in these liquids.

Combined High Pressure and Low Temperature Viscosity Measurement of Biodiesel

In this work, we report the measurement of the viscosity of biodiesel derived from sunflower oil and biodiesel blend with mineral diesel under combined conditions of high pressure and subambient temperature. Using a thermostatically controlled falling sinker-type viscometer, dynamic viscosity measurements were made at pressures up to 153 MPa, which are typical of those found in common-rail automotive diesel engines, and temperatures down to 0 °C. Reproducible and reliable viscosity data was obtained from sinker fall times. Calibration of the viscometer was based on n-dodecane. Biodiesel viscosities were found to increase exponentially with both rising pressure and reducing temperature. When combined with mineral diesel as a B20 blend, the viscosity was found to be less than for B100 for all temperatures considered. Both pressure and thermal freezing were found to also occur with increasing pressure and lowering temperature.

Shear Viscosity of CO2-Plasticized Polystyrene Under High Static Pressures

High-pressure shear viscosity measurements of polymer/supercritical fluid systems are numerous, but most involve pressure-gradient equipment such as a capillary or slit die with pressure drops exce...

New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure

In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1 GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

Prediction of Pressure-Viscosity Coefficient of Mixtures

The pressure-viscosity coefficient α is one of the most important property for EHL condition, however its measurement has difficulty. Therefore authors attempt to predict α for blend oils by using the relationship between pressure-viscosity coefficient and logarithm of kinematic viscosity at atmospheric pressure, which is used for single oil as ever. The pressure-viscosity coefficient of mixtures enables to predict with base oils properties and viscosity of mixture at atmospheric pressure. Test fluids are SN-HV, PBSN, DOS, BBPH and mixtures of these oils. High-pressure viscosity measurement was done at pressure up to 0.4 GPa and temperature range at 20°C to 100°C. The authors proposed the prediction method of α for mixtures.

High-pressure viscosity measurement of fatty acids and oils

The viscosities of olive oil and its constituent fatty acids were measured using a falling sinker-type high-pressure viscometer. The viscometer consists of a titanium cylindrical sinker with ferrite core and descends concentrically under the influence of gravity through a close-fitting titanium tube. The movement of the sinker was detected by electrical induction through coils surrounding the tube. For the oil and fatty acids, the calculated dynamic viscosity increased according to the model η=ηo exp (β p). The coefficients were readily obtained by linearizing experimental data for sinker fall-times and found to be dependent on the chain length and degree of saturation.