Dependence Of Dynamic Viscosity Research Articles

New mathematical models for the load factor of slip pairs of the ship propulsion complex for non-Newtonian lubricants

The method of boundary variation was applied to the solution of the boundary value problem with respect to the Reynolds differential equation for the lubricating layer in the sliding bearings of ship power plants and auxiliary ship equipment, which made it possible to obtain analytical representations for the hydrodynamic pressure, shear stresses, as well as the integral characteristics of the lubricating layer. This made it possible to build new, easy-to-use mathematical models for the load factor (carrying force factor) of the sliding pairs of the ship propulsion complex, considering the non-Newtonian properties of lubricants, i.e. in the case of the dependence of dynamic viscosity on pressure and temperature. Mathematical models take into account geometric parameters of bearings, operational parameters: relative radial clearance and relative eccentricity, angular velocity; as well as viscosity characteristics of lubricants, in particular, dynamic viscosity and piezo coefficient of viscosity of lubricants. A criterion for the applicability of lubricants for given operating characteristics and bearing parameters has been developed, which uses the viscosity characteristics of lubricants. The research results are illustrated in the form of tables and graphs.

Viscosity model for the middle fraction of Atasu-Alashankou oil sludge

The temperature dependence of dynamic viscosity was calculated on the basis of a new cluster-association equation, which was derived within the framework of the concept of chaotic particles. It was shown that the degree of cluster association naturally decreases with an increase in temperature, on average corresponding to the arrangement of three to four cluster particles in the association. For the first time, the values of the activation energy per monomer were obtained when assigning the activation energy to the average number of clusters.

New empirical correlations for the viscosity of selected organic phase change materials

Although there are many methods and instruments for measuring viscosity, it is still difficult to determine a reliable value of the dynamic viscosity of complex chemicals such as paraffins and fatty acids. This is due to the complex and heterogeneous structure of these compounds in the case of commercial products. On the other hand, the measuring instrument should be selected very carefully, including its measuring principle and measuring range. This paper presents results of viscosity measurements of three organic PCMs (phase change materials) obtained in four different research institutions. Commercial products: paraffin, myristic acid (97%) and mixture of palmitic acid (55%) and stearic acid (45%) were selected as PCMs. Four different viscometers, namely Fungilab V-Pad, Rheotest LK 2.2, Rheometer Anton Paar MCR 102, and Brookfield DV-II + Pro have been used to determine temperature dependent dynamic viscosity of the tested PCMs. Using a large database of present measurement results, correlations were developed to calculate the dynamic viscosity of fatty acids and paraffins, which predict the experimental data within a band of ±20%.

Viscosity Anomalies of Magnetic Fluid Stabilized by a Double Layer of Surfactant in Water

Purpose to study the temperature dependence of the viscosity of a water-based magnetic fluid.Method. Consists of measuring the dynamic viscosity of a magnetic fluid based on cobalt ferrite particles stabilized in water by a double layer of surfactant. Lauric acid (first layer) and a mixture of lauric acid and sodium dodecyl sulfate (second layer) were used as a stabilizer. Measurements were performed using a Brookfield DV-II+Pro rotational viscometer equipped with a coaxial cylinder system. The measuring system of the viscometer was thermostated using a KRIO-VT-12-1 thermostat.Results. The temperature dependences of dynamic viscosity were measured for three samples of magnetic fluid based on cobalt ferrite particles of various concentrations in the temperature range 0–90C°. The obtained temperature dependences of viscosity are radically different from the temperature dependences both predicted by known theories and experimentally observed for kerosene-based magnetic fluids. According to well-known theoretical models, the ratio of the viscosity of the magnetic fluid to the viscosity of the base medium is a certain universal function of particle concentration. Different models offer different types of this feature. But it clearly follows from them that the viscosity ratio should not depend on temperature. For magnetic fluids based on kerosene, it has been experimentally established that its relative viscosity decreases with increasing temperature. However, according to the results obtained, the relative viscosity of a water-based magnetic fluid does not decrease with increasing temperature, but increases significantly. That is, the viscosity of a water-based magnetic fluid decreases more slowly with increasing temperature than the viscosity of water.Conclusion. The observed dependencies completely contradict the known patterns, both theoretical and experimentally established for kerosene-based magnetic fluids. The results obtained may be useful for the further development of the theory of aqueous colloidal solutions with particle stabilization by a double layer of surfactants.

ДОСЛІДЖЕННЯ В’ЯЗКІСНО-ТЕМПЕРАТУРНИХ ВЛАСТИВОСТЕЙ ВАЖКИХ НАФТ ЯБЛУНІВСЬКОГО РОДОВИЩА УКРАЇНИ

Viscosity-temperature properties of high-viscosity oils from 3 wells of the Yablunovsky field (Poltava region, Ukraine) were studied using a rotary viscometer. According to the nature of the curves of the dependence of dynamic viscosity and shear stress on the shear rate, the nature of the flow of these oils is established, which is of practical importance for effect evaluating of various methods of action on the rheological behavior of these oils during their extraction and transportation.

Rheological behaviour of CaO–MgO–SiO2–Al2O3–B2O3 system with varying B2O3 content up to 30 wt% at basicity of 0.4

A comprehensive theoretical and experimental study describing the effect of B2O3 (0–30 wt%) on softening, liquidus, and crystallization temperatures, flow behaviour, and dynamic viscosity of the glass-based oxide system SiO2(64.64–43.21 wt%)-MgO(10 wt%)-CaO(15.86–7.29 wt%)-Al2O3(9.50 wt%)-B2O3 with a constant basicity of 0.4 was carried out. The experimental data was obtained up to 1550 °C using a high-temperature rheometer and were supported by the study of the internal structure by means of scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray powder diffraction analysis, and Fourier transform infrared spectroscopy. The increasing addition of boron oxide caused a decrease in the start and end softening and liquidus temperatures. At 1550 °C, the systems exhibited Newtonian behaviour, with a dynamic viscosity increasing exponentially with a decreasing temperature and decreasing with increasing B2O3 content. The amorphous character of the samples and the formation of structural units [BO2O−] and [BO3] and [BO4], confirmed by complementary analyses, led to a decrease in the degree of polymerization of the silicate structure. The theoretical insight into the dependence of dynamic viscosity on the temperature and composition was realized based on molecular dynamics. Furthermore, the prediction of viscosity as a function of temperature (1230–1550 °C) and the change in chemical composition (0–30 wt% B2O3) was performed using artificial neural networks.

Magnetohydrodynamic micropolar nanofluid flow over a vertically elongating sheet containing gyrotactic microorganisms with temperature-dependent viscosity

Magnetohydrodynamic bioconvective micropolar nanofluid flow with migrating microorganisms opens up an intriguing new field in materials science. The distribution of particles during processing, such as metal casting, polymer extrusion, etc., can affect material characteristics and final product quality. So, the current research examines magnetohydrodynamic micropolar nanofluid flow over a vertically extending material in the presence of swimming microorganisms. The mathematical model also considers the temperature dependence of dynamic viscosity with thermal radiation using the Rosseland approximation, Brownian diffusion, and the thermo-migration of microscopic particles. Similarity variables are used to convert the partial derivatives to ordinary derivatives. Then the Runge-Kutta-Gill method is used with the shooting technique to obtain a numerical solution to the resulting set of equations. Various tables and graphs are included to illustrate the impact of the emerging parameters on the flow fields. Results show that an increase in the material parameter improves fluid mobility but decreases the skin friction coefficient, whereas the magnetic field term exhibits the opposite behaviour due to friction induced by the Lorentz force. The analysis shows that the thermal field significantly expands as the thermo-migration of tiny particles and Brownian motion get stronger.

Modeling viscosity of SiO2-Al2O3-CaO based slags using Arrhenius and VFT models as well as the CALPHAD method

The first step of modeling the viscosity of slags is to choose a temperature-related viscosity model which plays a significant role in determining the framework of the entire model. In the present work, two temperature-related viscosity models, the Arrhenius and the VFT (Vogel-Fulcher-Tammann) models are compared for calculating the viscosity of slag systems taking the experimental data for the SiO2-Al2O3-CaO system as basis. The results show that the VFT model shows a better performance in describing experimental data for the temperature dependence of dynamic viscosity among all the investigated systems compared to the Arrhenius model. Such a good performance by the VFT model is explained by the actual network structure of liquid oxide systems described well by this model. Moreover, a linear relationship between the two semi-empirical parameters of the VFT model (ln A and T0) is found for the first time, which can decrease the number of independent parameters when modeling the viscosity of slags by this model. In addition, the viscosities of the CaO-Al2O3 and SiO2-CaO systems are modelled by the combined VFT-CALPHAD (CALculation of PHAse Diagrams) model over wide temperature and composition ranges.

Rheological Characteristics of Fe–C–Cr(Ni) Alloys

The principal objective of this project was to investigate the rheological properties of Fe-C-Cr and Fe-C-Ni-based low-alloy steels using an Anton Paar high-temperature rotational viscometer up to 1550 °C. The emphasis was placed on determining the liquidus temperatures and evaluating the flow and viscosity curves and the temperature dependence of dynamic viscosity. All were studied depending on the change in the content of chromium (0.010-4.863 wt%), nickel (0.001-4.495 wt%), and carbon (0.043-1.563 wt%). It was shown that the dynamic viscosity decreases with increasing nickel content and increases with increasing carbon and chromium content. The experimental data of the flow curves were fitted using the Herschel-Bulkley model with a good agreement between the measured and calculated values. Characterization of the internal structure was performed by SEM and EDX analyses, confirming non-significant changes in the microstructure of the original and remelted samples. The phase composition of the selected samples was also determined using JMatPro 12.0 simulation software (Sente Software Ltd., Guildford, UK).

Particle swarm optimization based numerical study for pressure, flow, and heat transfer over a rotating disk with temperature dependent nanofluid properties

In the era of nanotechnology and advanced manufacturing, many industrial applications involve the flow control over the rotating disk. Rotating machineries, computer storage devices, dynamic filtration processes, gas turbine engines, bio inspired electro-catalysis processes are a few of them. Considering the wide applications of flow over rotating permeable disks, this paper presents the investigation of flow, temperature and pressure characteristics of water-based titanium oxide nanofluid with temperature dependent properties. The quadratic Boussinesq approximation is considered to incorporate the density variations due to temperature change. The numerical computation is carried out using metaheuristic based hybrid shooting technique. Temperature dependent dynamic viscosity and thermal conductivity models for nanofluid are considered and the numerical results for velocity components, pressure and temperature distributions are investigated. The investigation unveiled reduction in skin friction and heat transfer rate with increasing value of quadratic convection parameter. The suction parameter is found to be very significant in terms of increasing heat transfer rates. An 80% increase in local Nusselt number is observed for a small change in suction parameter from −1 to −1.5.

On rheological properties of environmentally friendly inorganic systems and their modeling by artificial neural networks

This work aims to investigate the rheological properties, namely dependence of dynamic viscosity on temperature, chemical composition, and shear rate, of environmentally friendly inorganic systems using a high-temperature rotational viscometer up to 1550 °C. The liquidus and start and end softening temperatures of these systems were also studied. The environmentally hazardous calcium fluoride in the amount of up to 6 wt% was substituted by other components (B2O3, TiO2, and Na2O) to preserve the original utility properties of the investigated systems (low liquidus temperatures and viscosities). The effect of alternative additives ranging from 2 to 6 wt% on the required properties was more beneficial than that of fluoride. The most significant reduction in liquidus temperature of up to 185 °C was achieved by adding 6 wt% B2O3 while maintaining a low viscosity value. The addition of CaF2 (up to 6 wt%) had the least effect, lowering the liquidus temperature by only 22 °C as compared to the original system. In the case of TiO2 addition, the dependence of viscosity on chemical composition was non-linear and complex to predict with existing models. Therefore, it was modeled using artificial neural networks. The predicted viscosity values for a given temperature and chemical composition were in good agreement with the experimentally obtained values, as the maximum relative error between the measured and calculated viscosity values was less than 5%. The characterization of the internal structure of the investigated systems was performed by Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses and Scanning Electron Microscopy (SEM).

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.

Non-Newtonian Flow of Structured Systems. XXXIV. Dependence of Dynamic Viscosity and Dynamic Elasticity on Strain Amplitude in Aqueous Latex Suspension

Non-Newtonian Flow of Structured Systems. XXXIV. Dependence of Dynamic Viscosity and Dynamic Elasticity on Strain Amplitude in Aqueous Latex Suspension

Density and Viscosity of Glycolic, Lactic, and Malic Acid Esters

Densities and viscosities were measured as a function of temperature for 12 esters of glycolic, dl-lactic, and dl-malic acids and linear chain alcohols C1–C5. The density and kinematic viscosity were obtained using a pycnometer and a Pinkevitch capillary viscometer in a temperature range of 293.15–363.15 K with accuracies of 0.1 and 0.35%, respectively. The obtained data were used for dynamic viscosity calculation. It was demonstrated that the viscosity–temperature dependence of esters was described by the ASTM D341 model with an average absolute relative deviation of 1%. The temperature dependence of dynamic viscosity was fitted using the Arrhenius-like equation and Vogel–Fulcher–Tammann (VFT) model. It was found that the adjustable parameters A and B have the similar value for compounds in one homologous series. These parameters were taken as constant for each series of esters of the corresponding acids. The dynamic viscosity–temperature dependence of esters was better described by the VFT model than the Arrhenius-like equation. The capabilities of some group-additivity methods for predicting density have been reviewed and compared with experimental results.

Viscosity and Rheological Properties of Graphene Nanopowders Nanofluids.

The dynamic viscosity and rheological properties of two different non-aqueous graphene nano-plates-based nanofluids are experimentally investigated in this paper, focusing on the effects of solid volume fraction and shear rate. For each nanofluid, four solid volume fractions have been considered ranging from 0.1% to 1%. The rheological characterization of the suspensions was performed at 20 C, with shear rates ranging from to , using a cone-plate rheometer. The Carreau–Yasuda model has been successfully applied to fit most of the rheological measurements. Although it is very common to observe an increase of the viscosity with the solid volume fraction, we still found here that the addition of nanoparticles produces lubrication effects in some cases. Such a result could be very helpful in the domain of heat extraction applications. The dependence of dynamic viscosity with graphene volume fraction was analyzed using the model of Vallejo et al.

Dynamic viscosity dependence on temperature for fuels used for diesel engine

Abstract Viscosity is an important property of fuels used for diesel engine affecting engine’s efficiency and harmful gases emission. Viscosity of liquid fuels depends especially on fuels composition and temperature. The dynamic viscosity of diesel fuel, biodiesel and blends of diesel with biodiesel, i-propanol and n-butanol was measured for temperature ranging from 293.15 K to 323.15 K and atmospheric pressure. It has been verified that well-known Arrhenius derived equations can be used to estimate with good accuracy, viscosity at different temperatures for diesel, biodiesel, diesel+biodiesel blends, but also for diesel blends with propanol and butanol. Values of activation parameters: activation energy, activation enthalpy and activation entropy for the viscous flow were derived based on linearized Eyring’s type equation. The values of the activation energy for viscous flow of fuels and fuels blends calculated based on measured values of dynamic viscosity in the temperature range of 273.15 K and 323.15 K were similar to those presented in the literature for some hydrocarbons, esters, and alcohols, respectively.

Influence of molecular mass of PEG on rheological behaviour of MWCNT-based nanofluids for thermal energy storage

This paper presents original experimental data regarding the rheological characterisation of nanofluids based on poly(ethylene glycol) s with molecular mass of either 200 or 300 g·mol−1 (i.e. PEG-200 or PEG-300) and containing 0.025–0.70 wt% of multi-walled carbon nanotubes (MWCNT). The shear rate dependence of dynamic viscosity (η) was first studied in the temperature range from 278.15 to 313.15 K. Such non-linear viscoelastic experiments revealed that, unlike the neat poly(ethylene glycol)s used as based fluids, MWCNT/PEG-200 and MWCNT/PEG-300 nanofluids exhibited a non-Newtonian pseudoplastic behaviour in the low shear rate region (even in the case of the dispersions prepared at lowest nanoparticle concentrations). Dynamic viscosities measured at ~800 s−1 were compared with the values provided by means of different theoretical or semi-empirical approaches and a good description of our experimental results was obtained (with absolute average deviations ~0.2–0.3%) by using the Maron–Pierce equation modified to take into account the presence of aggregates/agglomerates. Additionally, rheological oscillatory analyses of these nanofluids were also conducted at 288.15 K to identify the linear-viscoelastic region and deep in the analysis of the viscoelastic behaviour of designed dispersions.

Study rheological behavior of refined rapeseed oil

Extracted from rapeseed oil was subjected to purification and refining process and then characterized in terms of rheological, ie dynamic viscosity dependence study in terms of speed shear constant temperature. The results show that at 400C, 600C, 800C and 900C dynamic viscosities of oil decreases with shear rate. At higher shear rates of 20s-1 shows lower viscosity oil fluctuations, became almost constant.
 

MATHEMATICAL MODELING OF A NEW METHOD OF THERMAL PROTECTION BASED ON THE INJECTION OF SPECIAL COOLANTS

A closed mathematical model of heat and mass transfer under the non-isothermal filtration through the organized pores of coolants with a strong dependence of dynamic viscosity on temperature with further injection into a viscous gas-dynamic flotation with the formation of liquid film and evaporation under the influence of aerodynamic heat flows has been developed. The aim of the paper is to develop the physical and mathematical basis of thermal protection with the automatic supply of coolant having a strong dependence of dynamic viscosity on temperature (by 3–5 orders of magnitude when the temperature changes by 200–2500°C). Such thermal protection system allows for operating without the mass removal that preserves the geometry of the structural elements at the intensive heating, which is very relevant. To achieve this goal, a mathematical model of the automatic coolant supply with filtration through the organized pores, injection into a high-temperature gasdynamic boundary layer with the formation of the protective liquid film and evaporation is formulated. The results with respect to the mass flow rate of the coolant, the mass evaporation rate of the formed liquid film and the temperatures of the structure which in all cases remain below the evaporation temperature of the cooler have been obtained.

Thermal protection of aircraft units using film cooling with regard to unsteady heat conductivity

A simplified physical and mathematical model of combined thermal conductivity and filtering of a cooler with a strong dependence of dynamic viscosity on temperature during film cooling of bodies was developed. The model takes into account the inflow of the cooler into the gas-dynamic boundary layer and the evaporation of the resulting protective film of the cooler. Analytical solutions are obtained for the mass evaporation rate, the rate of non-isothermal filtration, and the temperature distribution in the body, taking into account filtration. The resulting relationships are calculated by iterative methods. Analytical solution of the problem permitted us to clearly establish the functional relationship of all the defining characteristics of the system for automatic cooling of bodies.