Liquid Dynamic Viscosity Research Articles

Experimental determination and theoretical modeling of isobaric vapor–liquid equilibria, liquid mass density, surface tension and dynamic viscosity for the methyl butyrate and tert-butanol binary mixture

The purpose of this work is to provide consistent experimental measurements on the vapor–liquid equilibria (VLE) at the isobaric conditions of 50.00, 75.00 and 94.00kPa, as well as experimental determinations of the liquid mass densities, the surface tensions and the dynamic viscosities at 298.15K and 101.3kPa of the methyl butyrate + tert-butanol binary system within the whole composition range. For these goals, a Gillespie-type cell is used to carry out the VLE measurements, whereas an oscillating densimeter, a maximum differential bubble pressure tensiometer, and a rotating viscometer are used to quantify the remaining physical properties. The thermodynamical quality of the reported VLE data is validated by Fredenslund’s consistency test. Based on the VLE results, this zeotropic binary mixture exhibits a positive deviation from Raoult’s law. Furthermore, the validated data are correlated with three activity coefficient models (i.e., Wilson, NRTL, and UNIQUAC), with the Wilson equation being the most accurate one. Excess volumes, surface tensions, and liquid viscosities data are correlated by Redlich–Kister-type expansions, and the Grunberg–Nissan equation is also applied to viscosity modeling. The calculated excess volumes display a positive deviation from the ideal solution model. Regarding surface tensions, this system showcases both negative and positive deviation, althouhg slight, from the linear behavior while exhibiting the linear trend at a molar fraction of methyl butyrate of 0.758. In addition, this bimodal deviation is adequately predicted by the Chunxi model with the Wilson parameters determined from the VLE data. Finally, the dynamic viscosities data obey a strictly monotonic mole dependence predicted by Eyring’s theory, although without high accuracy. These results also reflect some interesting phenomena related to competitive association effects, which are discussed.

Dynamic viscosity of low GWP refrigerants in the liquid phase: An empirical equation and an artificial neural network

This study presents a simple correlation for describing the temperature and pressure dependence of the liquid dynamic viscosity of low GWP refrigerants, namely HydroFluoroOlefins (HFOs) and HydroChloroFluoroOlefins (HCFOs). The model has 3 input parameters (i.e., reduced temperature, reduced pressure, and acentric factor) and 6 coefficients which were regressed on 794 experimental data collated from the literature for 7 alternative refrigerants (i.e., R1233zd(E), R1234yf, R1234ze(E), R1234ze(Z), R1224yd(Z), R1336mzz(E), and R1336mzz(Z)). Moreover, a multi-layer perceptron neural network for the liquid dynamic viscosity of the studied fluids was developed from the selected dataset. The artificial network has the same 3 input parameters of the correlation and one hidden layer with 19 neurons. The results of the proposed correlation proved that it is an accurate model for calculating the dynamic viscosity of the studied liquid refrigerants, despite its simplicity. It ensured an average absolute relative deviation of the liquid dynamic viscosity (AARD(η)) of 2.88 %, lower than that given by other literature correlations. As expected, the multi-layer perceptron neural network provided the best results for all the selected refrigerants (AARD(η) = 0.86 % for the complete dataset), proving that it can be considered a reference for the development of other models.

Experimental investigation of a supersonic close-coupled atomizer employing the phase Doppler measurement technique

Along with the growing economic importance of metal additive manufacturing by means of laser powder bed fusion, the demand for high-quality metal powders as the corresponding raw material is also increasing. However, the physics involved in supersonic close-coupled gas atomization, which is often employed for the production of these powders, are not well understood and extensive experimental data is scarce, leading to a lack of reliable predictive modeling capabilities. In this experimental study, local particle size and velocity distributions for the spray produced by a generic supersonic close-coupled atomizer are obtained using the phase Doppler measurement technique. The gas stagnation pressure and the liquid mass flow rate are varied systematically and independently. Three working liquids are considered, investigating the influence of the liquid dynamic viscosity on the atomization result. The particle size is shown to be sensitive to changes in both the gas stagnation pressure and the liquid mass flow rate. Notably, it is not an unambiguous function of the gas-to-liquid ratio. Furthermore, the effect of the liquid dynamic viscosity appears to be negligible. In conclusion, these are important insights for formulating physics-based models for the supersonic close-coupled atomization process.

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.

Numerical investigation on characteristics of interfacial wave of liquid film in gas–liquid two-phase flow using OpenFOAM

Liquid film cooling as an advanced cooling technology is widely used in space vehicles. Stable operation of liquid film along the rocket combustion inner wall is crucial for thermal protection of rocket engines. The stability of liquid film is mainly determined by the characteristics of interfacial wave, which is rarely investigated right now. How to improve the stability of thin film has become a hot spot. In view of this, an advanced model based on the conventional Volume of Fluid (VOF) model is adopted to investigate the characteristics of interfacial wave in gas–liquid flow by using OpenFOAM, and the mechanism of formation and development of wave is revealed intuitively through numerical study. The effects from gas velocity, surface tension and dynamic viscosity of liquid (three factors) on the wave are studied respectively. It can be found that the gas velocity is critical to the formation and development of wave, and four modes of droplets generation are illustrated in this paper. Besides, a gas vortex near the gas–liquid interface can induce formation of wave easily, so changing the gas vortex state can regulate formation and development of wave. What’s more, the change rules of three factors influencing on the interfacial wave are obtained, and the surface tension has a negative effect on the formation and development of wave only when the surface tension coefficient is above the critical value, whereas the dynamic viscosity has a positive effect in this process. Lastly, the maximum height and maximum slope angle of wave will level off as the gas velocity increases. Meanwhile, the maximum slope angle of wave is usually no more than 38°, no matter what happens to the three factors.

Influence of Dynamic Viscosity of a Lubricant Material on the Parameters of Adhesion Bond in the Systems of Materials "12KH2H4 - STEEL 45", "45KHN2MFA - Steel 45" when Boring and Borocement Steel 45

In this work, the regularities of the change in the shear strength of the adhesive bond τ0 and the piezoelectric coefficient β in the metal systems "12Kh2N4 (45KhN2MFA) - steel 45 + B", "12Kh2N4 (45KhN2MFA) - steel 45 + VS" were obtained during physical modeling of the shear of surfaces of small-sized samples and changes in dynamic viscosity environment of their interaction with the use of additional equipment of the SMTs-2 friction machine. It has been established that borating and boron carburizing of the surface of steel 45 leads to the absence of adhesion to the surfaces of steels 12Kh2N4 and 45KhN2MFA in certain ranges of normal pressures, at which τ0> 0 and the dynamic viscosity of liquid and grease. It was found that the parameter τ0 when lubricating surfaces is determined to a greater extent for the system "12X2H4 - steel 45", and partially for borating steel 45 and low values of dynamic viscosity μ = 0.027 Pa•s. With an increase in the dynamic viscosity of the liquid phase of the lubricant in the "12X2H4 - steel 45" system, there is a tendency to an increase in the value of τ0. It was found that the absence of modification of steel 45 with boron and boron carbide predetermines the independence of the piezoelectric coefficient from the viscosity of the liquid lubricant and the shear rate. Boring and boron carburizing steel 45 predetermines an increase in the piezoelectric coefficient by an average of 1.6 times with an increase in dynamic viscosity from 0.027 Pa•s to 0.19 Pa•s at a shear rate of 10.16±0.8. At shear rate = 5.08±0.6 mm/s, the piezoelectric coefficient is relatively constant in the systems under study. With the transition to contact through a grease lubricant, there is an ambiguous manifestation of the rate of change of the piezoelectric coefficient.

YNAMIC VISCOSITY OF THE LUBRICANT AND ITS EFFECT ON STEEL MATERIALS WITH BORON

In this work, the regularities of the change in the shear strength of the adhesive bond τ0and the piezoelectric coefficient β in the metal systems "12Kh2N4 (45KhN2MFA) -steel 45 + B", "12Kh2N4 (45KhN2MFA) -steel 45 + VS" were obtained during physical modeling of the shear of surfaces of small-sized samples and changes in dynamic viscosity environment of their interaction with the use of additional equipment of the SMTs-2 friction machine. It has been established that boridingand boron carburizing of the surface of steel 45 leads to the absence of adhesion to the surfaces of steels 12Kh2N4 and 45KhN2MFA in certain ranges of normal pressures, at which τ0> 0 and the dynamic viscosity of liquid and grease. It was found that the parameter τ0when lubricating surfaces is determined to a greater extent for the system "12X2H4 -steel 45", and partially for borating steel 45 and low values of dynamic viscosity μ = 0.027 Pa•s. With an increase in the dynamic viscosity of the liquid phase of the lubricant in the "12X2H4 -steel 45" system, there is a tendency to an increase inthe value of τ0. It was found that the absence of modification of steel 45 with boron and boron carbide predetermines the independence of the piezoelectric coefficient from the viscosity of the liquid lubricant and the shear rate. Вoridingand boron carburizing steel 45 predetermines an increase in the piezoelectric coefficient by an average of 1.6 times with an increase in dynamic viscosity from 0.027 Pa•s to 0.19 Pa•s at a shear rate of 10.16±0.8. At shear rate = 5.08±0.6 mm/s, the piezoelectric coefficient is relatively constant in the systems under study. With the transition to contact through a grease lubricant, there is an ambiguous manifestation of the rate of change of the piezoelectric coefficient

LLE, VLE and dynamic viscosity for the furfural + nonane mixture at low pressure: Measurements and modeling

This work reports new experimental data for the furfural + nonane mixture for the temperature range between 303.25 K and 441.55 K at low pressure. Vapor-liquid equilibria (VLE), liquid–liquid equilibria (LLE), and dynamic viscosity (µ) are reported and modeled under isobaric condition. Experimental data measurement is done using the same validated equipment applied in authors previous work. The expanded uncertainties for boiling temperature, viscosity- temperature, liquid–liquid temperature and dynamic viscosity are around 0.21 K, 0.12 K, 0.42 K and 0.0881 mPa∙s (0.95 level of confidence). After data is collected, phase equilibria are modeled using a modified Peng-Robinson equation of state coupled with the Huron Vidal and NRTL mixing rules. Also, dynamic viscosity is modeled using a generalized logistic function type in order to describe all the composition domains. The average absolute relative deviation using the models LLE, VLE, and viscosity is around of 0.01 %, 2.39 %, and 2.93 %. The results indicate that the new data can be modeled using the selected models.

The internal flow behaviors during Taylor cone formation of pulsating electrohydrodynamic jet printing

The toroidal vortex inside the Taylor cone is one of the most interesting features in electrohydrodynamic (EHD) jet printing. However, due to the considerable difficulty in capturing the microscopic internal fluid flow from the experiment, many aspects of the printing process are still not fully understood. Here, we present a numerical study on the Taylor cone formation process of pulsating EHD jet printing under the variations of several key operational parameters and liquid properties, namely, electric voltage, nozzle height, liquid surface tension coefficient, and liquid dynamic viscosity. In addition to the electrohydrodynamic motion of the liquid–gas interface, we focus our attention to the time evolution of the liquid flow and vortex inside the Taylor cone. The intensity of the vortex is evaluated by analyzing the absolute value of the swirling strength throughout the formation process. By virtue of examining the electric field distribution, interface charge density, velocity field, and the absolute value of the swirling strength from the numerical data, we elucidate the influences of the aforementioned parameters on Taylor cone formation and internal flow behaviors. Eventually, a scaling law of λ2max∝Boe/Ca2 between the maximum absolute value of the swirling strength and the dimensionless variables electric bond number Boe and capillary number Ca is proposed, which applies to all the parameters investigated in this work.

In-line measurements of the physical and thermodynamic properties of single and multicomponent liquids.

Microfluidic devices are becoming increasingly important in various fields of pharmacy, flow chemistry and healthcare. In the embedded microchannel, the flow rates, the dynamic viscosity of the transported liquids and the fluid dynamic properties play an important role. Various functional auxiliary components of microfluidic devices such as flow restrictors, valves and flow meters need to be characterised with liquids used in several microfluidic applications. However, calibration with water does not always reflect the behaviour of the liquids used inthe different applications. Therefore, several National Metrology Institutes (NMI) have developed micro-pipe viscometers for traceable inline measurement of the dynamic viscosity of liquids used in flow applications aspart of the EMPIR 18HLT08 MeDDII project. These micro-pipe viscometers allow the calibration of any flow device at different flow rates and the calibration of the dynamic viscosity of the liquid or liquid mixture used under actual flow conditions. The validation of the micro-pipe viscometers has been performed either with traceable reference oils or with different liquids typically administered in hospitals, such as saline and/or glucose solutions or even glycerol-water mixtures for higher dynamic viscosities. Furthermore, measurement results ofa commercially available device and a technology demonstrator for the inline measurement of dynamic viscosity and density are presented in this paper.

Semi-empirical correlations and an artificial neural network for liquid dynamic viscosity of low GWP refrigerants

In this work, simple semi-empirical correlations to describe the temperature and the pressure dependence of the dynamic viscosity of low GWP refrigerants, namely HydroFluoroOlefins (HFOs) and HydroChloroFluoroOlefins (HCFOs), in the liquid phase are presented. Firstly, the experimental liquid dynamic viscosity data available in scientific literature and databases were collected and statistically analyzed. From the data collected for low pressures, the Latini et al. (2002, 1990) correlation for the dynamic viscosity of liquid refrigerants in saturated conditions was re-fitted and constants expressly dedicated to the studied low GWP refrigerants were obtained. Then, the proposed temperature-dependent correlation was modified to represent liquid dynamic viscosity dependence on pressure. In addition, an artificial neural network was developed to predict the dependence of the liquid viscosity of the studied refrigerants on temperature and pressure. This model was trained, validated, and tested for the selected dataset. The results of the proposed correlations and the multi-layer perceptron neural network were compared with the liquid viscosity calculations provided by some of the most well-known literature correlations and REFPROP 10.0, proving the accuracy of the proposed models for engineering applications.

How dynamic adsorption controls surfactant-enhanced boiling

Improving boiling is challenging due to the unpredictable nature of bubbles. One way to enhance boiling is with surfactants, which alter the solid–liquid and liquid–vapor interfaces. The conventional wisdom established by previous studies suggests that heat transfer enhancement is optimized near the critical micelle concentration (CMC), which is an equilibrium property that depends on surfactant type. However, these studies only tested a limited number of surfactants over small concentration ranges. Here, we test a larger variety of nonionic and anionic surfactants over the widest concentration range and find that a universal, optimal concentration range exists, irrespective of CMC. To explain this, we show that surfactant-enhanced boiling is controlled by two competing phenomena: (1) the dynamic adsorption of surfactants to the interfaces and (2) the increase in liquid dynamic viscosity at very high surfactant concentrations. This dynamic adsorption is time-limited by the millisecond-lifetime of bubbles on the boiling surface—much shorter than the timescales required to see equilibrium behaviors such as CMC. At very high concentrations, increased viscosity inhibits rapid bubble growth, reducing heat transfer. We combine the effects of adsorption and viscosity through a simple proportionality, providing a succinct and useful understanding of this enhancement behavior for boiling applications.

Experimental measurement of thermophysical properties of some commercial phase change materials (PCM) for air conditioning applications

This paper presents the measurement of liquid phase density, thermal diffusivity, thermal conductivity, and dynamic viscosity of five commercial PCM (RT2HC, RT5HC, OM05-P, OM08, CrodaTherm9.5) in the temperature range 2 − 30 °C. The density of RT2HC, RT5HC, OM05-P is 23-24% lower than water, that of OM08 is 6% higher than water and that of CrodaTherm9.5 is 14% lower than water. The thermal diffusivity of RT2HC, RT5HC, OM05-P is 22-24% lower than water, that of OM08 is around a half of water and that of CrodaTherm9.5 is 38-40% lower than water. The thermal conductivity of the five PCM is 72-74% lower than water. The dynamic viscosity of RT2HC, RT5HC, OM05-P and OM08 is 2 − 3 times higher than water, and that of CrodaTherm9.5 is from 7.4 to 8.3 times higher than water. The five PCM are expected to provide convective heat transfer performance significantly lower than water .

Viscosity and Interfacial Tension of Ternary Mixtures Consisting of Linear Alkanes, Alcohols, and/or Dissolved Gases Using Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

Ternary mixtures consisting of liquids and dissolved gases with either two solvents or solutes are characterized by determining their liquid dynamic viscosity ηL and interfacial tension σ using surface light scattering (SLS) and equilibrium molecular dynamics (EMD) simulations in the temperature range between (298 and 573) K and for mole fractions of the dissolved gas up to 0.20. The four ternary mixtures of interest are n-hexadecane + n-octacosane + carbon dioxide (CO2), n-hexadecane + nitrogen (N2) + CO2, as well as 1-hexadecanol + n-octacosane with CO2 or water (H2O). With SLS, ηL and σ of the two ternary mixtures containing n-hexadecane are accessed with average relative expanded experimental uncertainties (coverage factor k = 2) of ur(ηL) = 0.021 and ur(σ) = 0.019. EMD simulations are performed for all four ternary mixtures and give access to ηL and σ with average relative expanded statistical uncertainties (k = 2) of ur(ηL) = 0.15 and ur(σ) = 0.061. The influence of the dissolved gases is investigated by comparing the thermophysical properties of the ternary mixtures to those of the pure solvent or the binary subsystems. The results for the ternary mixture consisting of n-hexadecane, n-octacosane, and CO2, which include a variation of the composition of the binary subsystem, i.e. the solvent mixture, have shown the reduction of both properties, due to dissolving CO2, to be independent of the solvent composition. For the ternary mixture consisting of n-hexadecane, N2, and CO2, the reduction in both properties can be estimated by adding up the reduction determined for the binary subsystems, i.e. n-hexadecane with dissolved N2 or CO2, which suggest that the presence of a further solute does not influence the impact of a dissolved gas.

Viscosity and Interfacial Tension of Binary Mixtures Consisting of an n-Alkane, Branched Alkane, Primary Alcohol, or Branched Alcohol and a Dissolved Gas Using Equilibrium Molecular Dynamics Simulations

This study aims to characterize binary mixtures consisting of a liquid with a dissolved gas by determining their dynamic viscosity and interfacial tension using equilibrium molecular dynamics (EMD) simulations in the temperature range between (298 and 573) K and for solute mole fractions up to 0.20. With the help of a systematic variation of solvent and solute molecules, the influence of their molecular characteristics, e.g., in form of size, shape, or polarity, on the thermophysical properties of the mixtures is discussed. For this, eight different alkanes and alcohols with a carbon number between 12 and 40 as solvents and seven solutes in form of hydrogen, helium, methane, water, nitrogen, carbon monoxide, or carbon dioxide are studied. Using EMD simulations, the liquid dynamic viscosity is determined in the slightly compressed liquid phase close to saturation conditions. Simulations at vapor–liquid-equilibrium (VLE) are performed to determine the interfacial tension and to calculate the solute molecules at the vapor–liquid interface. To check the applicability of the EMD simulations, data for the dynamic viscosity and interfacial tension from this work are compared to experimental data of binary mixtures with the same solutes and similar solvents. The results from this work show that the impact of the dissolved gas on the thermophysical properties is strongly depending on its molecular characteristics. For example, the properties of mixtures containing dissolved He are usually within combined uncertainties with the ones of the pure solvent. In contrast, dissolving CO2 leads to a pronounced reduction in both properties at comparable solute mole fractions. For the molecular characteristics of the solvent, the carbon chain length is shown to influence mainly the interfacial tension and the polarity mainly influences the viscosity.

Simultaneous compressed liquid viscosity and density measurements of n-alkanes at temperatures between (291 and 353) K and pressures up to 50 MPa

Compressed liquid density (ρ) and dynamic viscosity (η) were simultaneously measured for pure liquid n-alkanes (n-hexane, n-heptane, n-octane, n-nonane, and n-decane) in the temperature range from (291 to 353) K and pressure up to 50 MPa by an experimental system using a coil capillary tube viscometer (CCTV) coupled with a vibrating tube densimeter (VTD). The reliability and validation of this measuring system were verified by determining and comparing both dynamic viscosity and density data of ethanol published in the international literature. The maximum viscosity deviation was 8 μPa ∙ s for viscosity and 0.87 kg ∙ m−3 for density. The measurements were carried out with a relative expanded uncertainty (k=2) of 1.00 % for the measurements of dynamic viscosity and 0.20 % for the measurements of density considering the impurities of the chemical compounds). Both dynamic viscosity and density data were represented using two empirical models, obtaining a maximum deviation of 2.49 % for the dynamic viscosity and 0.12 % for the density with the experimental data. Finally, the isothermal compressibility and isobaric thermal expansivity were calculated from the empirical models at the reported conditions.

Viscosity and Interfacial Tension of Binary Mixtures Consisting of Linear, Branched, Cyclic, or Oxygenated Hydrocarbons with Dissolved Gases Using Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

In the present study, the influence of the molecular characteristics of the solvent and solute on the dynamic viscosity and interfacial tension of binary mixtures consisting of a liquid with a dissolved gas is investigated using surface light scattering (SLS) and equilibrium molecular dynamics (EMD) simulations. In detail, binary mixtures consisting of linear, branched, cyclic, or oxygenated hydrocarbons and the solutes hydrogen, helium, methane, water, carbon monoxide, or carbon dioxide are studied in the temperature range between (298 and 573) K and for solute mole fractions up to 0.2. With SLS, the liquid dynamic viscosity and interfacial tension of the binary mixtures could be accessed in macroscopic thermodynamic equilibrium with average expanded uncertainties (coverage factor k = 2) of (2.4 and 2.3)%, respectively. While EMD simulations were able to predict the influence of the dissolved gases on the interfacial tension of the binary mixtures, the simulations fail to represent the influence of the dissolved gas on the viscosity. Due to the systematic variation of the solvent and solute molecules, the influence of the molecular characteristics, e.g., in the form of size, shape, or polarity, on the thermophysical properties of the mixtures is discussed. Dissolving carbon dioxide, e.g., leads to a reduction of both properties by up to 60% compared to the properties of the pure solvent. Dissolved helium, on the other hand, has only a small influence on the properties of the pure solvent. The influence of dissolved water was found to be negligible in mixtures with an alkane but strongly increases both properties when dissolved in an alcohol, which may be explained by the formation of hydrogen bonds.

Thermodynamic Properties of {Diethyl Phosphate-Based Ionic Liquid (1) + Ethanol (2)} Systems, Experimental Data and Correlation

In this work, three solutions consisting of ionic liquid and ethanol were considered for forward-looking use in absorption refrigeration technology. It is proposed to use the following ionic liquids as absorbents: 1-ethyl-3-methylimidazolium diethyl phosphate (abbreviated as [EMIM][DEP]), 4-ethyl-4-methylmorpholinium diethyl phosphate ([EMMOR][DEP]), and 1-ethyl-1-methyl-pyrrolidinium diethyl phosphate ([EMPYR][DEP]). Since the thermodynamic and physicochemical properties of working fluids determine the efficiency of the refrigerator while looking for alternative operating fluids, it is crucial to perform their extensive characteristics. Therefore, in this work, (vapor + liquid) phase equilibria (VLE), liquid density (ρ), and dynamic viscosity (η) were determined for the ethanolic solution of the three mentioned diethyl phosphate-based ionic liquids. The isothermal VLE was measured by an ebulliometric method within a temperature range from T = (328.15 to 348.15) K with an increment of 10 K and pressures up to 90 kPa. Non-random two-liquid (NRTL) equation with temperature-dependence parameters was used to correlate experimental data. Physicochemical properties including liquid density and dynamic viscosity were determined at temperatures from (293.15 to 338.15) K at ambient pressure over the whole concentration range. These properties were correlated using empirical equations. From experimental density and viscosity data, the excess molar volumes and the deviations from additivity were determined and correlated using the Redlich–Kister-type equation. Two of the tested ILs, [EMMOR][DEP] and [EMPYR][DEP], were synthesized and characterized using NMR analysis. The thermophysical characterizations of pure compounds, including glass transition temperature (Tg) and heat capacity at the glass transition temperature (ΔgCp), have been determined using a differential scanning calorimetry technique (DSC) at atmospheric pressure. The work presented is a combination of basic studies on the effect of the cation structure of an ionic liquid on the properties of their solutions with ethanol, with the possibility of future application of the tested systems in a viable refrigeration system.

Bubble size distribution and gas holdup in bubble columns employing non‐Newtonian liquids: A CFD study

AbstractThe hydrodynamics involved with the rise of air bubbles in shear‐thinning non‐Newtonian liquids in bubble columns was investigated using computational fluid dynamics (CFD). In bubble columns, the bubble size distribution (BSD) and gas holdup significantly affect the mass transfer rates and the reactor design. Consequently, the influence of superficial gas velocity, flow index, consistency index, sparger bubble size, and yield stress were analyzed on a local and global scale. The bubble sizes and the coalescence and breakage phenomena were incorporated using the homogeneous discrete method of the population balance model (PBM). The bubbles underwent coalescence during ascent and exhibited bimodal distribution. The radial homogeneity of the gas phase increased axially. Moreover, the zones of low liquid dynamic viscosity produced zones of a high gas holdup. Though the dual effect of viscosity on gas holdup was non‐existent, the gas holdup surged after 35.1 mPa s at the mid‐zone and remained constant thereafter. The noteworthy differences in simulation results put further emphasis upon the importance of sparger bubble size in CFD modelling. A decrease in the overall gas holdup and the axial air velocity with yield stress was observed. CFD simulation proved capable of providing results in reasonable agreement with experiments.

Physicochemical characterization and activity coefficients at infinite dilution of molecular compound in poly(ethylene glycol)dimethyl ether and the eutectic mixture composed of poly(ethylene glycol) with cyclic carbonate

This work is focused on determining the effectiveness of using hitherto unexplored extractants in separation processes. It is proposed to use poly(ethylene glycol) and the eutectic mixture composed of poly(ethylene glycol) with cyclic carbonate as separating agents in desulphurization of model fuel (heptane/thiophene) and alkanes from aromatic hydrocarbons (heptane/toluene) processes. The selected glycol was poly(ethylene glycol)dimethyl ether with an average molecular weight of M = 250 g·mol−1 (abbreviated as PEG250DME). The second component of the mixture was ethylene cyclic carbonate (abbreviated as EC). These components create a non-crystallizing mixture at a temperature below T = 203 K in the range of 25–40% ethylene carbonate, thus a mixture with the following composition 30% of EC and 70% of PEG250DME (wEC = 0.331) was investigated. For this purpose, the extensive research on the infinite dilution activity coefficients for 45 molecular compounds including alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, ethers, pyridine, thiophene, acetone, acetonitrile, and 1-nitropropane in both PEG250DME and {[PEG250DME] + [EC], wEC = 0.331} were determined. The experiment was performed at a temperature range from T = (308.15 to 338.15) K with an increment of 10 K using gas–liquid chromatography (GLC). Based on the experimental data, the infinite dilution capacity and selectivity of the PEG250DME and DES: {[PEG250DME] + [EC], wEC = 0.331} are presented to evaluate the effectiveness of using them as an extractant in the separation of aliphatic from aromatic hydrocarbons and sulfur compounds from alkanes. Obtained selectivity and capacity values for different separation processes are compared with the literature data for other separating agents presented in the available literature reports. From the temperature - dependence of the infinite dilution activity coefficient, the partial molar excess Gibbs energy, ΔG1E,∞, enthalpy ΔH1E,∞ and entropy term TrefΔS1E,∞ at infinite dilution were calculated and discussed. Additionally, the liquid density and dynamic viscosity of pure PEG250DME and it’s eutectic mixture with EC as a function of temperature were determined. Both of the physicochemical parameters are important from a technological point of view.