Viscosity Of Pure Fluids Research Articles

Some experimental and theoretical studies of diethylene glycol diethyl ether and 2-alkanol mixtures

Experimental density and dynamic viscosity data for the diethylene glycol diethyl ether +2-alkanol (C3 to C6) mixtures have been published at 293.15 K, 303.15 K, 313.15 K, and 323.15 K and at pressure of 0.1 MPa. Excess molar volume and deviation in dynamic viscosity were obtained from experimental data and correlated with Redlich–Kister equation, from the values obtained, the interaction forces were studied. Perturbed chain-statistical associating fluid theory equation of state was used for modeling the density for pure fluids and mixtures. Free volume theory coupled to Perturbed chain-statistical associating fluid theory equation of state was used to modeling the viscosity of pure fluids and mixtures; in the case of binary mixtures, we proposed a simple mixing rule and used the Pourabadeh et al. mixing rule. Good results in the prediction and correlation of experimental liquid density and dynamic viscosity for binary mixtures were obtained, 0.12% and 2.28%, respectively.

Viscosity analysis of enriched SAE50 by nanoparticles as lubricant of heavy-duty engines

In this study, effective parameters on viscosity of a suitable oil for lubrication of heavy-duty engines (vehicles that are in use in construction, farm, and logging equipment, semi-trucks, delivery trucks, etc.) are studied. SAE50 as a single-degree engine oil is examined in present experimental work. The mentioned engine oil is enriched by MgO and MWCNT nanoparticles (NPs). The nanofluid was prepared in six solid volume fractions (SVF) and in temperature range of 25–50 °C. The results showed the viscosity dependence on shear rate, so nanolubricant has a non-Newtonian behavior. 2–4% Viscosity reduction in concentrations of 0.0625% and 0.125% reported in comparison with viscosity of pure fluid. Also sensitivity analysis of viscosity measurement was lower than 1% for all investigated conditions. To lower experimental costs, a mathematical correlation was proposed to predict the viscosity. The R2 was considered as criterion for accuracy of proposed correlation. Having amount of 0.9995 for R2 shows accommodation of correlation predictions with experimental results. Also maximum deviation of < 3% indicates that the proposed correlation has a high accuracy.

Acoustic absorption measurement for the determination of the volume viscosity of pure fluids / Messverfahren für die akustischen Absorption zur Bestimmung der Volumenviskosität reiner Fluide

Abstract A realistic description of fluid mechanical and acoustic processes requires the volume viscosity of the medium to be known. This work describes how the volume viscosity of pure fluids can be determined by measuring acoustic absorption with the pulse-echo method. The challenge in realizing such a measurement method lies in the separation of the different dissipative effects that superimpose on absorption. Diffraction effects ultimately cause a dissipation of acoustic energy and acoustic reflector surfaces have a small, but finite transmission coefficient. Further, influences of the transducer (in particular its frequency response), as well as the system’s electrical components have to be taken into account. In contrast to the classical approach relying on the amplitude ratio, the absorption is determined by the moments of the amplitude spectrum. The measurement system applied is originally designed for precision measurements of the sound velocity by means of the propagation time difference of two acoustic signals.

Reference Values and Reference Correlations for the Thermal Conductivity and Viscosity of Fluids.

In this paper, reference values and reference correlations for the thermal conductivity and viscosity of pure fluids are reviewed. Reference values and correlations for the thermal conductivity and the viscosity of pure fluids provide thoroughly evaluated data or functional forms and serve to help calibrate instruments, validate or extend models, and underpin some commercial transactions or designs, among other purposes. The criteria employed for the selection of thermal conductivity and viscosity reference values are also discussed; such values, which have the lowest uncertainties currently achievable, are typically adopted and promulgated by international bodies. Similar criteria are employed in the selection of reference correlations, which cover a wide range of conditions, and are often characterized by low uncertainties in their ranges of definition.

Viscosity of pure fluids—Enskog-2σ model

In this work, we propose a new kinetic theory model (Enskog-2σ model) to analyze and predict the viscosity of simple fluids. The model is based on the Enskog formulation and makes use of two effective diameters to represent two aspects of molecular interactions in Enskog's treatment; namely, the effective diameter representing the excluded volume of a molecule and the effective diameter accounting for the increased probability of collision in comparison to the dilute gas. We have tested the model by analyzing the viscosity of five simple fluids (Ar, CH4, N2, CO2 and SF6) of increasing complexity at supercritical temperatures. The new Enskog-2σ model outperforms previous approaches based on Enskog theory in terms of its correlative ability. We demonstrate that the effective diameter associated with the excluded volume exhibits a universal behaviour as a function of reduced temperature. The conformal behaviour can be achieved by means of a single fluid-dependent length scaling parameter. We make use of this finding to develop a general model that allows the prediction of the viscosity of one fluid from the knowledge of the viscosity of a reference fluid, which in this work was chosen to be Ar. The accuracy of the predicted viscosity depends on the way in which the length scaling parameter was estimated. If the length scaling parameter is obtained from the knowledge of viscosity along a single isotherm, the accuracy of the predicted viscosity is similar to the uncertainty of the original correlation over its entire supercritical range. If a single viscosity value is used to estimate the length scaling parameter, the viscosities of supercritical CH4, N2, CO2 and SF6 are predicted with the maximum deviation of 3.3%, 4.2%, 9.9% and 10.5% respectively over the entire range of validity of the Enskog-2σ model.

Modeling Alkane and Haloalkane Mixture Viscosities in a Three-Parameter Corresponding States Format

The fundamental structure of the model is based upon a detailed and innovative conformality analysis of the viscosity surfaces of pure fluids similar to that proposed for thermodynamic properties [G. Scalabrin et al. Fluid Phase Equilib. 170:23 (2000); Int. J. Refrig. 26:35 (2003)], resulting in the introduction of a new specific scaling parameter ψ for viscosity, defined by a single experimental viscosity value. The model structure is based on two reference fluids for which pure-fluid viscosity dedicated equations (VDE) are available, which in this work are ethane and propane. The model is then extended to mixtures following the classical corresponding states (CS) one fluid model using mixing rules without interaction parameters. This gives the model a predictive character. It can be reliably applied in a wide range of pressure–temperature values, in both liquid and vapor phases, due to the validity ranges of the reference equations. The investigated mixtures include binary and multicomponent systems of both light and heavy n-alkanes and halogenated alkanes including R134a, R125, R152a, R143a, R22, R142b, R32, and R124 as components. For both families of fluids, the accuracy in terms of absolute average deviation (AAD) is within 2.68% in the vapor phase and 3.0% in the liquid phase. The model has also been validated for strongly azeotropic mixtures such as R32–R290 and R134a–R290 giving interesting results by fitting the interaction parameters on a limited subset of data. The effectiveness of the proposed procedure is enhanced by the comparison with a recently published advanced theoretical model.

Particle‐Laden Drop Impacting on Solid Surfaces

This paper presents an experimental study of the effects of particles on spreading and retracting of a single drop impacting on a smooth surface. The results are reported for particle concentrations from 0 to 0.30, different liquids (mixtures of water and glycerin), Reynolds number from 6.1 to 2700 Weber number from 0.0084 to 180, and four different surfaces (thermal oxide coated silicon wafer, silicon wafer, 1,1,1,3,3,3, hexamethyl disilazane (HMDS) coated silicon wafer, and Teflon® film). Drops laden with polystyrene particles coated with calcium phosphate are observed to behave differently from pure liquids, especially on thermal oxide coated silicon wafer, which is the most hydrophilic surface studied. It was found that pure fluid viscosity is more important than apparent viscosity of the particle‐laden fluid in setting the spreading and retraction. At an impact speed of 2 m/sec, the rebound behavior on the Teflon® surface depends on particle volume fraction.

An improved extended corresponding states method for estimation of viscosity of pure refrigerants and mixtures

The extended corresponding states method for calculating the viscosity of pure refrigerants and mixtures is investigated. The accuracy of pure fluid viscosity values is significantly improved by introducing a third shape factor evaluated using available pure fluid viscosity data. A modification to the method of Huber and Ely (Fluid Phase Equilibria, 1992, 80, 45–46) is proposed for estimation of the viscosity of mixtures; this modification eliminates the possibility of discontinuities at the critical point, ensures that the pure component viscosity is provided in the limit of a component mole fraction approaching 1, and improves the overall accuracy of the method. The method has been applied to 12 pure refrigerants including three hydrocarbons and mixtures. The average absolute deviations between the calculated and experimental viscosity values are within 4% for all of the pure fluids and most of the mixtures investigated.

Short-time dynamics of colloidal suspensions.

We report numerical simulations of the velocity autocorrelation function ~VACF! for tagged particle motion in a colloidal suspension. We find that the asymptotic decay follows the theoretical expression for the VACF of an isolated particle, but with the suspension viscosity replacing the pure fluid viscosity ~at long times the suspension behaves, so far as a tagged particle is concerned, like a fluid with the suspension viscosity—as an ‘‘effective fluid’’ !. While physically appealing, this observation is hard to reconcile with a recent theoretical prediction that at long times the VACF in a suspension should be the same as the VACF at infinite dilution. It also differs, in a rather subtle manner, from a scaling rule which has been used in the analysis of experimental and computer simulation results. From the scaling behavior of the VACF we conclude that effective fluid behavior only occurs on a time scale somewhat longer than the time taken for transverse momentum to diffuse a particle radius. This contrasts with the findings of earlier workers who concluded that effective fluid behavior is already observed at much shorter times. @S1063-651X~96!03909-8# A colloidal suspension can be considered as a mixture in which the particles of one component are much bigger than those of all the others. If the size difference is sufficiently large, the smaller components can be thought of as forming fluid which occupies the space between the big particles. The larger particles are often referred to as Brownian particles, named after the botanist Robert Brown, who was the first to observe the apparently random motion of small particles suspended in water. Starting with Brown’s observation, our understanding of these systems has evolved in an interesting series of historical jumps. It was not until over seventy years later that Einstein @1# proposed that the motion of the Brownian particles ~Brownian motion! arose from the accumulated effects of individual collisions between Brownian particles and the particles of the host fluid. This was strong evidence that fluids were molecular in nature, a view not universally accepted at that time. Einstein was also able to make progress with the theory of transport processes in Brownian suspensions. First he derived the expression for the diffusion coefficient D0 of a spherical particle in the dilute limit @2#

A four-parameter corresponding-states method for prediction of Newtonian, pure-component viscosity

The extended Lee-Kesler (ELK) method, introduced for calculating thermodynamic properties of polar as well as nonpolar fluids and their mixtures, has been adapted to the calculation of Newtonian, pure-fluid viscosity. The method is a four-parameter, corresponding-states technique requiring as input the critical temperature, critical pressure, a size/shape parameter α, and a polar interaction parameter β. Because α and β have been previously tabulated for many fluids (for calculation of thermodynamic properties) and may also be obtained directly from the radius of gyration and a single liquid density, respectively, the method contains no adjustable parameters and is predictive in nature. ELK viscosity predictions were compared to experimental data for nonpolar and polar fluids. For 36 different nonpolar fluids and a total of 5748 different points, the comparison yielded an absolute average deviation (AAD) of 7.88% with a bias of −4.45%. Similarly, the AAD was 10.62% with a bias of −5.34% for a comparison of 15 different polar fluids involving 1500 different points. With this method, viscosities can be calculated within the range 0.55 ⩽T r⩽2.00 and 0<P r⩽10.

Influence of the porosity of a porous medium on the effective viscosity in Brinkman's filtration equation

Brinkman's filtration equation is usually used to describe the low-Reynolds-number flow in porous media in situations where velocity gradients are non-negligible. In this paper a model problem is analysed to determine the influence of the porosity of the porous medium on the effective viscosity in Brinkman's filtration equation. In the idealized problem we consider axial flow through infinite and streaked arrays of cylindrical rods. Suppose that in such porous medium the flow is described by Brinkman's filtration equation then the effective viscosity can be calculated as a function of porosity. Contrary to the Einstein correction for dilute suspensions it is shown in this paper that the effective viscosity may be less than the viscosity of pure fluid.

Viscosity renormalization in the Brinkman equation

The Brinkman equation purports to describe low-Reynolds-number flow in porous media in situations where velocity gradients are non-negligible. The equation involves modifying the usual Darcy law by the addition of a standard viscosity term whose coefficient is usually identified with the pure-fluid viscosity. It is argued instead that the porous medium induces a renormalization of viscosity, which is calculated in the dilute limit and separately in a self-consistent approximation. The effective Brinkman viscosity is found to decrease from the pore-fluid value. The calculation fails at low porosity but agrees at least in part with experiment. In addition, the relationship between the Brinkman equation and the phenomenological boundary condition of Beavers and Joseph is discussed and it is pointed out that their experimental configuration provides a simple means of measuring viscosity renormalization.

Dynamics and hydrodynamics of suspensions of translational–rotational Brownian particles at finite concentrations

We consider the hydrodynamics of a suspension of rigid particles in a continuum fluid. The motion of the fluid and particles is coupled by the introduction of hydrodynamic boundary conditions. The dynamics of the particles is governed by rigid body translational and rotational classical equations which are derived for the particles in the suspension at finite concentrations. The appropriate random forces are included, making these equations the Langevin equations for translational and rotational Brownian motion for particles in suspensions at finite concentration. For no-slip boundary conditions, the suspension velocity field is first derived to lowest order in the concentration, and the results are applied to spheres to evaluate the suspension zero frequency shear viscosity as η =η0(1+hvsc) where η0 is the pure fluid viscosity and vsc is the volume fraction of the spheres. The constant h equals 5/2 when both translational and rotational Brownian motion is allowed; h=4 if rotations are suppressed; while previous work on stationary suspensions yields h=5/2. A general effective medium theory is introduced to handle suspensions at finite concentrations. A series expansion provides a systematic method for evaluating the corrections to this effective medium theory which arise from correlated disturbances of the fluid velocity field by two or more suspended particles. The zero frequency shear viscosity and friction coefficients for spheres are obtained from the effective medium theory as η =η0(1−hcvs)−1 and ζ=ζ0(1−hcvs)−1, respectively, where ζ0 is the single sphere translational (or rotational) friction coefficient. In the static limit hydrodynamic screening vanishes to all orders in concentration for rigid Brownian spheres.