جستجوی مقالات مرتبط با کلیدواژه « Viscosity » در نشریات گروه « شیمی »

In this research, some thermophysical properties of ethylene glycol with water (H2O) and two solvent mixtures dimethylformamide/ water (DMF + H2O) were studied. The densities (ρ) and viscosities (η) of ethylene glycol in water and a mixed solvent dimethylformamide (DMF + H2O) were determined at 298.15 K, t and a range of concentrations from 0.1 to1.0 molar. The ρ and η values were subsequently used to calculate the thermodynamics of mixing including the apparent molar volume (ϕv), partial molar volume (ϕvo) at infinite dilution. The solute-solute interaction is presented by Sv results from the equation ∅_v=ϕ_v^o+S_v √m. The values of viscosity (B) coefficients and Falkenhagen coefficient(A) of the Jone-Dole equation and Gibbs free energy of activation (∆G*) for viscous flow of solution were estimated. The positive values of ϕ_v^o between 35.58 and 49.908 and Sv values from 12.54 to 8.83 indicate strong solute-solvent interactions.

In the present article, a comparative study of the rheological characteristics of nano-lubricants based on Fe2O3, Al2O3 and ZnO nanoparticles is carried out. The base fluid used is 20W40 engine oil. The nanofluid samples were prepared in the solid volume fractions (0.25%; 0.50%; 0.75% and 1%). The measurements have been performed at different temperatures, ranging between 20 °C and 60 °C and at shear rates ranging from 100 s-1 to 300 s-1. The results obtained have shown that nanofluids based on Fe2O3 and ZnO nanoparticles exhibit a non Newtonian shear thinning behaviour while the nanofluid based on Al2O3 nanoparticle exhibit a Newtonian behaviour. The Al2O3/oil nanofluid has a lower dynamic viscosity than Fe2O3/oil and ZnO/oil nanofluids. The increase in temperature leads to a reduction of more than 80% in viscosity for all nanofluids. On the other hand, the increase of the nanoparticles volume concentration clearly improves the dynamic viscosity.

This study focuses on developing a new method that represents user-accessible correlation for the estimation of water-based nanofluids viscosity. For this, an evolutionary algorithm, namely Gene Expression Programming (GEP), was adapted based on a wide selection of literature published databanks including 819 water-based nanofluids viscosity points. The developed model utilized the base fluid viscosity as well as volume fraction and size of the nanoparticles as the inputs of the model. Several statistical parameters integrated with graphical plots were employed in order to assess the accuracy of the proposed GEP-based model. Results of the evaluation demonstrate fairly enough accuracy of the developed model with statistical parameters of AARD%=11.7913, RMSE=0.3567, and SD=0.1851. Furthermore, the trend analysis indicates that the GEP calculated points satisfactorily follow the trend of the nanofluid viscosity variation as a function of different model inputs. To provide more verification, the proposed GEP model was compared with some literature theoretical and empirical correlations leading to the supremacy of the developed model here. The applied sensitivity analysis reveals that the highest impact value is assigned to the volume fraction of the nanoparticle. Moreover, the outlier’s detection by Williams’ technique illustrates that about 96.5% of the GEP estimates are in the applicability domain resulting in the validity of the proposed model in this study. At last, the results of this study demonstrate that the new method here outperforms other literature-published correlations from the standpoint of accuracy and reliability.

A successful drilling operation depends strongly on a useful drilling fluid system. Using nanoparticles (NP)s to formulate intelligent drilling fluids gives them a wide range of optimal properties under different operating conditions and resolves any operational problems. In this study, in order to provide an effective solution for improving the rheological and high pressure/high temperature (HPHT) filtration properties of the oil-based drilling fluid (OBDF), copper oxide (CuO) NPs were synthesized with dandelion morphology. CuO dandelions were characterized by using XRD, FTIR, SEM, and zeta potential measurements. A long time stabilized nanofluid (NF) was prepared and evaluated. The OBDF samples consisting of various amounts of NF ranging from 1 to 11% (V/V) were prepared. Then, the fluid loss and rheological properties of OBDF were examined. The results showed that the OBDF containing 7% (V/V) NF was appropriate to improve the rheological properties such as yield point (YP), apparent viscosity (AV), and gel strength (GS). In addition, the minimum HPHT filtration value of 2 ml was acquired for the drilling fluid containing 9% (V/V) NF. In conclusion, CuO NPs demonstrated a positive effect on the performance of the OBDF system.

Excess thermodynamic properties such as viscosity deviation (ln ∆ƞ), excess isentropic compressibility (KsE), excess molar volume (VmE), excess intermolecular free length (LfE), excess free volume (VfE), excess acoustic impedance (ZE) and excess internal pressure (ΠiE) were evaluated from the experimentally measured values of density (ρ), ultrasonic velocity (u) and viscosity (ƞ) for the binary mixtures of acetonitrile (AN) with dimethyl sulfoxide (DMSO) and with N, N-dimethylacetamide (DMA) as a function of mole fraction at temperatures- 298 K, 308 K, 318 K and 328 K. The excess values were further fitted to Redlich-Kister polynomial equation to ascertain the fitting parameters and standard deviations. The variations of excess parameters with composition and with temperature were further discussed with regard to the nature and extent of molecular interactions among the dissimilar component molecules of the investigated solvent systems. Overall positive deviation in ZE values and negative deviations in the values of LfE, VfE and KsE over the entire solvent composition range suggested the existence of strong molecular interactions between unlike molecules of the components. AN-DMA solvent system was found to exhibit a deviation more towards a stronger interaction mode as compared to AN-DMSO solvent system.

Methane is the simplest alkane and the main constituent of natural gas, shale gas, and gas hydrate. Its viscosity has both academic and industrial importance. A new model for the methane viscosity was developed based on the theory of the averaged intermolecular potential field. The derived equations of the model were fitted to 1669 experimental data points in good agreement over the parameter ranges: from 100 to 523 K with the pressure from 0.047 up to 1000 MPa. The new model also comprehensively performed better than the famous samples in comparison. The physical base, good numerical behavior, and better-comparing performance suggest that the model has considerable theoretical significance and practical application potentials.

The viscosities of binary mixtures of 1,4-butanediol with o-cresol, m-cresol and p-cresol have been determined at 303.15, 308.15, 313.15 and 318.15 K over the entire mole fraction range. The deviation in viscosity,, and excess Gibbs energy of activation (G*E) of viscous flow have been examined in terms of structural changes and interactions. The deviations/excess values were fitted to the Redlich-Kister equation to determine the fitting parameters and the root-mean square deviations. The results obtained for viscosity of binary mixtures were used to test the semi-empirical relations of Bingham, Frenkel, Kendall, HindUbbelhode, Refutas, Sutherland Wassiljiewa, Gambill, McAllister, Hind, Grunberg, Wijk, McAllister 4 body, Tamura Kurata, Katti-Chaudhri and Nhaesi.