Accurate Viscosity Research Articles

Accurate viscosity measurement of nitrates/nitrites salts for concentrated solar power

Hitec (NaNO3-NaNO2-KNO3) and Solar salt (NaNO3-KNO3) are two of molten salts extensively used in Concentrated Solar Power (CSP). Viscosity plays an essential role in process of heat transfer for CSP system. However, it has some certain deviation and unsatisfactory errors among different reports; additionally, it still lacks the data close to melting point, which also makes another barrier for their application. In this work, accurate viscosity data of Hitec and Solar salt with 2.5% uncertainty were systematically measured using an optimized rotational coaxial cylinder in a wide temperature range that fill in the blanks of the existing data. Meanwhile, relevant viscosity were explicitly summarized and particularly analyzed based on the experimental data. Viscosity of the specific components of emerging ternary nitrates (Ca(NO3)2-NaNO3-KNO3, LiNO3-NaNO3-KNO3 and Ca(NO3)2-LiNO3-KNO3 mixtures) having potential applications for CSP systems were measured in the high temperature areas for the first time.

Evaluation of Existing Viscosity Data and Models and Developments of New Viscosity Model for Fully Liquid Slag in the SiO2-Al2O3-CaO-MgO System

Metallurgical properties of slag are determined to a great extent by its viscosity. High-temperature viscosity measurements are time-consuming and expensive. It is necessary to develop an accurate viscosity model for blast furnace slag in the SiO2-Al2O3-CaO-MgO system using reliable viscosity data. This paper describes a systemic evaluation procedure to determine the viscosity data to be used for model development. 1780 viscosity data from 10 to 65 wt pct SiO2, 3.5 to 40 wt pct Al2O3, 2 to 60 wt pct CaO, and 2 to 38 wt pct MgO in the SiO2-Al2O3-CaO-MgO system have been accepted for model evaluation after critical reviews. The existing 14 viscosity models in SiO2-Al2O3-CaO-MgO system is also reviewed and evaluated. Based on the structure of alumina-silicate slag and evaluated viscosity data, a new viscosity model has been proposed for the system SiO2-Al2O3-CaO-MgO. A new term “probability,” based on the basic oxide and electronegativity, is introduced to calculate the integral activation energy of slag. The model has been evaluated and compared with existing viscosity models in three different composition ranges in SiO2-Al2O3-CaO-MgO system for different applications. The new model reports an outstanding agreement between predictions and experimental data. The industrial implications of the new model have also been discussed in ironmaking and steelmaking processes.

Liquid Viscosity Measurement Using a Vibrating Flexure Hinged Structure and a Fiber-Optic Sensor

A novel viscosity measurement system based on a miniature 3D printed parallelogram flexure hinge structure and a fiber-optic sensor is developed. Lorentz forces are applied to excite the structure vibration at various frequencies, and the fiber-optic sensor is used to measure the amplitude and phase responses without the electromagnetic interference. The system is modeled as a single oscillator by taking into account the liquid-induced mass and damping as well as the additive stiffness due to the liquid viscoelasticity. By curve fitting of the experimentally obtained amplitude and phase responses based on the analytical model, the viscosity and the additive stiffness can be obtained. This method can help differentiate the effect of the viscosity and elasticity on the response of the sensing structure. By implementing this method, accurate viscosity measurements over a large range of 1–1045 $\text {mPa} \cdot \text {s}$ are demonstrated with the errors of <3.7% for all the test samples. It is also confirmed in the experiment that the liquid-induced additive stiffness is strongly related to the liquid storage modulus.

State-of-the-art ab initio potential energy curve for the krypton atom pair and thermophysical properties of dilute krypton gas.

A new reference krypton-krypton interatomic potential energy curve was developed by means of quantum-chemical ab initio calculations for 36 interatomic separations. Highly accurate values for the interaction energies at the complete basis set limit were obtained using the coupled-cluster method with single, double, and perturbative triple excitations as well as t-aug-cc-pV5Z and t-aug-cc-pV6Z basis sets including mid-bond functions, with the 6Z basis set being newly constructed for this study. Higher orders of coupled-cluster terms were considered in a successive scheme up to full quadruple excitations. Core-core and core-valence correlation effects were included. Furthermore, relativistic effects were studied not only at a scalar relativistic level using second-order direct perturbation theory, but also utilizing full four-component and Gaunt-effect computations. An analytical pair potential function was fitted to the interaction energies, which is characterized by a depth of 200.88 K with an estimated standard uncertainty of 0.51 K. Thermophysical properties of low-density krypton were calculated for temperatures up to 5000 K. Second and third virial coefficients were obtained from statistical thermodynamics. Viscosity and thermal conductivity as well as the self-diffusion coefficient were computed using the kinetic theory of gases. The theoretical results are compared with experimental data and with results for other pair potential functions from the literature, especially with those calculated from the recently developed ab initio potential of Waldrop et al. [J. Chem. Phys. 142, 204307 (2015)]. Highly accurate experimental viscosity data indicate that both the present ab initio pair potential and the one of Waldrop et al. can be regarded as reference potentials, even though the quantum-chemical methods and basis sets differ. However, the uncertainties of the present potential and of the derived properties are estimated to be considerably lower.

Viscosity and density measurements of aqueous amines at high pressures: MDEA-water and MEA-water mixtures for CO2 capture

Viscosity and density are thermophysical properties crucial to characterizing any kind of fluid such as aqueous amines. These blends are becoming more and more relevant for their CO2 capture potential, such that having accurate viscosity and density measurements would prove useful. Densities and viscosities of these mixtures at atmospheric pressure may be found in the literature although it is more difficult to find values at high pressures, these potentially proving interesting when seeking to provide a full description of these fluids.Viscosity and density measurements at high pressures (up to 120MPa) and at temperatures between 293.15K and 353.15K of MDEA+water and MEA+water mixtures (both from 10% to 40% amine mass fraction) are presented in this work. Density measurements were performed with an Anton Paar DMA HPM densimeter with an expanded uncertainty (k=2) less than ±0.7kg·m−3. A falling body technique was used to measure viscosities at high pressures due to its sturdiness in terms of corrosion. Details of this latter equipment are presented, including calibration using n-dodecane and uncertainty calculations, which give a relative expanded uncertainty (k=2) of less than ±2.4% for the highest viscosity and ±2.9% for the lowest.

A methodology to evaluate statistical errors in DNS data of plane channel flows

Direct numerical simulations (DNS) provide useful information for the understanding and the modeling of turbulence phenomena. In particular, new methodologies recently allowed the achievement of high Reynolds number in DNS of the benchmark plane channel flow. In this scenario, estimating the statistical errors associated with DNS is a difficult but necessary task. Here, we present a methodology to evaluate the statistical errors of the second-moment DNS data. In this methodology, the momentum balance equation is used to calculate the mean velocity profile by considering the Reynolds stress tensor provided by DNS. This error evaluation was applied to different plane channel flow databases available in the literature. We show that using the Reynolds stress statistics obtained from standard DNS can lead to significant discrepancies for turbulence modeling. One interesting consequence of this approach is that we are able to compute the Reynolds shear stress from the converged first order statistic. This information can be used, for instance, to extract a more accurate turbulent viscosity for turbulence modeling purposes. Moreover, the new methodology seems to be a promising path to formulate a convergence criterion for future plane channel DNS.

Monitoring of the Dilution of Motor Oil with Diesel Using an Advanced Resonant Sensor System

In modern light-duty Diesel vehicles the particulate filters in the exhaust system require periodic regeneration to prevent plugging. The regeneration procedure is a major cause of dilution of engine oil with diesel fuel. In order to investigate the effect of the operation conditions of the engine on the fuel content in the oil, a precise and fast in-line measurement system is required. In this contribution a resonant sensor system for determination of diesel content by measuring the viscosity of the oil is tested. A commercial off-the-shelf quartz tuning fork resonator is used as sensor element and evaluated using a universal analyzer for resonant sensors developed for fast and precise acquisition of resonant sensor responses. The experiments presented in this paper show that fuel concentration in the range of 0.2 % can be determined within seconds. The obtained results are compared to that obtained with an accurate lab bench viscosity and mass density meter.

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.

Structural and dynamical properties of liquid Al-Au alloys

We investigate temperature- and composition dependent structural and dynamical p roperties of Al-Au melts. Experiments are performed to obtain accurate density and viscosity data. The system shows a strong negative excess volume, similar to other Al-based binary alloys. We develop a molecular-dynamics (MD) model of the melt based on the embedded-atom method (EAM), gauged against the available experimental liquid-state data. A rescaling of previous EAM potentials for solid-state Au and Al improves the quantitative agreement with experimental data in the melt. In the MD simulation, the admixture of Au to Al can be interpreted as causing a local compression of the less dense Al system, driven by less soft Au--Au interactions. This local compression provides a microscopic mechanism explaining the strong negative excess volume of the melt. We further discuss the conentration dependence of self- and interdiffusion and viscosity in the MD model. Al atoms are more mobile than Au, and their increased mobility is linked to a lower viscosity of the melt.

Prediction of viscosity of water-based Al2O3, TiO2, SiO2, and CuO nanofluids using a reliable approach

Nanoparticles are usually used in the form of nanofluids that consist of nanoparticle and a base fluid. Nanofluids have been used in many industrial processes like engine cooling and enhanced oil recovery because of their properties. One of these properties is viscosity that is very important especially for chemical and petroleum engineering applications. Some empirical and theoretical models have been developed for viscosity prediction of nanofluids, but they have low accuracy or small condition ranges of applicability. Regarding these reasons, there is a huge interest for accurate viscosity prediction of nanofluids using a simple, rapid, accurate, and comprehensive modeling approach. In this study, Least Squares Support Vector Machines (LSSVM) is used as a powerful tool for viscosity prediction of water-based nanofluids of Al2O3, TiO2, SiO2, and CuO. The results of the model were in excellent agreement with experimental data with a very good coefficient of determination of 0.998. The results show that the proposed LSSVM model has a very good performance in comparison to the other existed models. Furthermore, model capability for viscosity trends prediction was checked against nanoparticle volume fraction and temperature changes and it shows very good agreement with experimental data. Finally, leverage approach is utilized to find the outliers and check the applicability domain of the proposed model.

Viscosity Model for Iron Blast Furnace Slags in SiO2–Al2O3–CaO–MgO System

Operational performance of ironmaking processes is determined to a great extent by its slag viscosity. A simple and accurate viscosity model for blast furnace (BF) slags has been developed based on the Urbain model using the critically evaluated experimental data reported by the authors and other researchers. A total number of 2958 viscosity measurements from 582 compositions in the SiO2–Al2O3–CaO–MgO system have been collected from 34 publications. These data have been critically reviewed for developing a viscosity model for ironmaking slags. The model has been significantly revised by consideration of alumina behavior in this system and re‐optimization of the parameters using large quantity and high quality data. The new model has less number of parameters, but better performance in the viscosity predictions. Applications of the new viscosity model on BF operation have been discussed.

MBR activated sludge viscosity measurement using the Delft filtration characterization method

Viscosity measurements play an important role in activated sludge (AS) characterization, especially with respect to Membrane BioReactor (MBR) operation where low and high shear rates (velocity gradients) occur near the membrane surface and on the bioreactor tank due to the mixing, respectively. Moreover, viscosity plays a role in terms of energy consumption (e.g. pumping and mixing). Therefore, an accurate viscosity relationship as a function of total suspended solids (TSS) and temperature can help to model the behavior of the AS. A total number of 10 municipal and 11 industrial MBR plants throughout Europe were investigated during the period 2007–2009 using the Delft Filtration Characterization method (DFCm). Unlike other literature studies, AS rheology was measured on site, exploiting the resemblance of the DFCm to a tubular rheometer and compared against the results of a rotational rheometer. A new rheological model for the viscosity of AS was developed maintaining the same mathematical structure as previous rheological models made for MBRs. The model proposed in this study is valid for TSS and temperature ranges of 5–20gL−1 and 10–25°C, respectively. This model proves that the DFCm unit can be used as a ‘cheap’ rheometer and produce the same results as a rotational rheometer for AS viscosity characterization.

Structural viscosity model for aluminosilicate slags

Based on the structure of aluminosilicate slag, a new model has been proposed for viscosity calculation of aluminosilicate slags. Contributions of bridging oxygen (O0), non-bridging oxygen (O−) and free oxygen (O2−) to viscous activation energy were modelled. Compositions of three types of oxygen were calculated from optical basicity values by combining the Toop–Samis model with a correlation between reciprocal of optical basicity and polymerisation extent proposed by Ottonello and Moretti. Charge compensation equilibrium among charge compensated Al, cations for modifying network and Al with no charge compensating cations was considered. The model has been applied in calculations of viscosity of the Al2O3–CaO–MgO–SiO2 system. Good agreement between calculated and measured viscosity with a mean deviation of less than 25% was achieved. Since most viscosity measurements for molten slag at high temperature ware subject to an experimental uncertainty of 25%, the present model could provide accurate viscosity values for slag systems investigated.

Rheological characterization and finite element modeling of an extrusion process of a WC–Co compound

The use of hard metals, in particular for cutting tools, is becoming wider. Their manufacturing cost, higher than traditional steel, is compensated by an increased lifetime. This work involves the rheological characterization of a WC–Co compound, in order to evaluate its viscosity for different values of strain rate. Following this characterization, the data are implemented in a FEM code, in order to simulate the extrusion processes of such compounds to manufacture hard metal bars. This study highlights the importance of an accurate viscosity evaluation of these mixtures and the correct setting of FEM parameters in order to predict successfully extrusion processes. As an example, an analysis is presented for the case of cutting tools with helical holes for the passing of fluid coolant.

Viscosity of bimodal suspensions with hard spherical particles

We analyze two equations for their ability to predict the viscosity of bimodal suspensions with hard spherical particles. The equations express the viscosity as a function of the particle loading and the packing (or, volume) fraction at which the viscosity diverges (viscosity threshold). The latter is found from previously published experimental studies for a variety of sphere diameter ratios and fractions of small particles in total solids. A comparison between the viscosity thresholds and the maximally random jammed packing verifies their interconnection and permits accurate viscosity prediction of bimodal suspensions.

Temperature-dependent viscosity model of HPAM polymer through high-temperature reservoirs

Polymer flooding in high temperature reservoirs usually has shown poor performance because the injected polymeric solution tends to experience severe thermal degradation and ineffective in-situ sweep behavior. For the simulation results under such reservoirs, the real observation is likely to be out of estimation due to the absence of accurate viscosity model. The aim of this study was therefore to modify an existing numerical reservoir simulator to model HPAM hydrolysis, which is caused by thermal degradation in high temperature reservoirs, by employing the concept of half-life decomposition. The term ‘half-life’ has been proposed in numerical simulations to describe the kinetics of thermal decomposition of unstable polymers. This work analyzed rheological properties considering thermal hydrolysis with the goal of establishing an in-situ viscosity calculation for high temperature reservoirs. Comparison of the conventional Flory–Huggins’ model to the proposed viscosity model allowed us to evaluate hydrolysis and the long-term stability of the polymer according to temperature. The results obtained using the new viscosity model indicated that polymer concentration loss was proportional to the initial concentration. However, viscosity reduction was more severe than concentration loss at higher initial polymer injection concentrations and was exaggerated as the initial concentration increased. Due to polymer decomposition at high temperatures, application of polymer flooding is limited at high-temperature reservoir.

Intrinsic viscosity and conformational parameters of xanthan in aqueous solutions: Salt addition effect

The intrinsic viscosity and conformational parameters of xanthan in aqueous solutions were investigated at 25°C as a function of salt nature (NaCl and KCl) and concentration (up to 3×10−1mol/L). The viscometric parameters were evaluated by applying semi-empirical equations proposed by Rao and Wolf. The results show that the new model proposed by Wolf provides accurate intrinsic viscosity values comparable with those obtained by using traditional methods. The experimental data were modeled with Boltzmann sigmoidal equation. The stiffness parameter, hydrodynamic volume and viscometric expansion factor were determined and discussed. With increasing salt concentration, the hydrodynamic volume and the viscometric expansion factor decrease and the critical overlap concentration increases, reaching limiting values above a given salt concentration. The high Huggins constant values suggest the existence of aggregates for salt concentrations above 5×10−2 and 3×10−3mol/L for NaCl and KCl, respectively. Stiffness parameter was determined by Smidsrød and Haug method as being 5.45×10−3, indicating a rigid conformation for xanthan macromolecules in solution.

Group contribution modeling of viscosity during urethane reaction

Abstract Based on experimental viscosity data collected from single material and binary system mixtures, a group contribution method was introduced to estimate viscosities of a range of polyol oligomers and urethane polymers at temperatures from 25 to 150°C. Use of mixture rules then extends the estimation method to multi-component reacting systems. Mixture viscosity data were used to determine the Gibbs free energy (G) in the Grundberg-Nissan equation which can be used to estimate mixture viscosities with correction for some non-idealities. The resulting model is able to accurately predict mixture viscosities based on binary interaction. The goal of this work is to estimate the viscosities of urethane-forming reactions; accurate viscosity information is critical as an intermediate step to predict how successful a foam formulation would be and to ultimately estimate the final physical properties of the foam.

REPRESENTATION OF IONIC LIQUID VISCOSITY-TEMPERATURE DATA BY GENERALIZED CORRELATIONS AND AN ARTIFICIAL NEURAL NETWORK (ANN) MODEL

Ionic liquid (IL) viscosity (η)-temperature (T) data (at atmospheric pressure) are represented by an artificial neural network (ANN) model and the reduced forms of the Arrhenius, Vogel-Tamman-Fulcher (VTF), Arrhenius + higher order T-terms, and VTF + higher order T-term models. Training the data of 73 liquids (comprised of 5 cations and 32 anions) at 654 data points by a 2-7-1 neural network model (with inverse reduced temperature with respect to 323.15 K and logarithm of viscosity at 323.15 K as input neurons) yielded an overall percent deviation () of 6.6% and a coefficient of determination (R 2 ) equal to 0.9. The other four models, in contrast, yielded values of and R 2 ranging between (21.2% and 21.7%) and (0.80 and 0.81), respectively. Testing the models with the data on an additional set of 8 ILs at 82 points yielded values of and R 2 comparable to those in the case of training. The results obtained show that the neural network scheme provides reasonably accurate viscosity estimates. On the other hand, the other four models could be used for design purposes, providing for approximate calculations. [Supplementary materials are available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resources: supplementary data tables.]

Viscosity Ratio Measurements with Capillary Viscometers

Viscosity ratio measurements made with capillary viscometers exploit the accurate values of the viscosity of helium calculated ab initio. Accurate values of the argon-to-helium viscosity ratio are now used for primary acoustic gas thermometry and for the most accurate redeterminations of the Boltzmann constant. Accurate viscosity ratio measurements enable the calibration of laminar flow meters with surrogate gases and their use with process gases. We review ratio viscometers that comprise one, two, and four capillaries. A single capillary is a ratio viscometer when it is used to measure multiple gases sequentially, while two- and four-capillary viscometers are instruments intended for ratio measurements. We consider gases and Newtonian liquids, with a focus on the two-capillary gas viscometer and its extension to pressures up to 100 MPa. A single-capillary viscometer could measure the ratio (viscosity of liquid water)/(viscosity of gaseous helium) thereby reducing the uncertainty of the liquid viscosity scale relative to the international system of units.