Critical Fluid Research Articles

An analytical solution for nonlinear vibration of functionally graded porous micropipes conveying fluid in damping medium

This paper presents an analytical solution for nonlinear free vibration of functionally graded porous micropipes conveying fluid embedded in viscous damping medium. By applying Von-Kármán's nonlinear strain relations, strain gradient theory and Hamilton's principle, the nonlinear governing equations of motion are derived in the presence of viscous damping medium. The nonlinear governing equations of motion are discretized and converted to a set of nonlinear ordinary differential equations by using Galerkin's method. For the first time, closed-form expressions are obtained for nonlinear frequency, critical fluid velocity and damped time response of the functionally graded porous micropipe conveying fluid by employing the homotopy analysis method. In addition, the convergence control parameter is considered to diminish the error of the damped vibration response. The effects of the geometrical properties of the micropipe and the viscous damping medium on the vibration of the functionally graded porous micropipe conveying fluid are investigated. The results show that the optimum value of the convergence control parameter dramatically decreases the error of the homotopy solution. Also, the vibration period is increased by the increment of the fluid velocity, damping coefficient, porosity volume fraction, power-law exponent and the length of the functionally graded porous micropipe conveying fluid.

Modeling of Phase Coexistence via Thermodynamic Potentials

Thermodynamic potentials can be used to study various phase phenomena. In particular, they can be used to determine the phase coexistence of a liquid and vapor for a simple van der Waals fluid, which relates the interactions and size of particles (molecules/atoms) represented by spheres as simple constants a and b, respectively. Phase coexistence at a given temperature for a simple fluid is determined using Newton’s method, thermodynamic potentials, and the conditions of phase coexistence. From this information, we are able to construct a phase diagram of the vapor and liquid densities versus the temperature. The constructed phase diagram shows how the simple van der Waals fluid predicts the occurrence of a critical point (point at which the fluid is no longer simply characterized as a gas or liquid but rather a liquid and gaseous fluid or critical fluid) as opposed to the ideal gas law. This phase diagram can then be further used to study homogeneous (a pure solution or solution containing a single molecule/atoms) and inhomogeneous (mixture or solution containing multiple molecules/atoms or a substrate/wall) nucleation by classical density functional theory in statistical mechanics.

Genesis of Graphite in Betul Belt, Madhya Pradesh, India: Inferences Based on Petrographic and Other Studies

Betul belt is known for its volcanic massive sulphide type of mineralization in the geological circles of India. But here the betul belt has been presented with a different qualification, which is graphite mineralization. The graphite mineralization is popularly known within the proterozoic sediments of Aravalli Supegroup of rocks in South Rajasthan and in its extension in the Jhabua and Alirajpur districts of Madhaya Pradesh. The graphite mineralization in Betul belt is confined to the supracrustals enclosed within the granite gneisses and has been brought on the national map after the recently explored blocks by geological survey of India, which were auctioned for the commercial exploitation. This paper briefly discuses the possible mechanism of formation and the nature of mineralization of graphite here in this belt, essentially based on the inferences drawn from petrography supported by scanning electron microscopic and XRD data. It is concluded that major proportion of the graphite mineralization here is accumulated due to progressive metamorphism of the organic matter deposited along with various sediments, while a considerable component has been contributed by the precipitation from super critical graphite rich fluids.

Studies on the Physical and Chemical Characteristics, Super Critical Fluid Extracting and Spray Drying for an Instant Tea of Mulberry Leaves (Morus Alba L.)

Studies on the Physical and Chemical Characteristics, Super Critical Fluid Extracting and Spray Drying for an Instant Tea of Mulberry Leaves (Morus Alba L.)

One-Pot Super Critical Fluid Synthesis of Spinel MnFe2O4 Nanoparticles and its Application as Anode Material for Mg-ion Battery

In present study, the synthesis of spinel MnFe2O4 nanoparticles using a facile one-pot super critical fluid method and their application for Mg-ion battery application as anode materials is reported. The synthesized MnFe2O4 nanoparticles were well characterized for their structure and morphology using XRD, SEM, TEM and EDS analysis. The average particle size of materials was less than 50 nm with spinel structure. The main feature of magnesium ion battery is its high specific capacity and large volumetric energy density, which makes it a promising alternative to Li-ion batteries. The spinel MnFe2O4 material has been used as an anode material for Mg-ion batteries. At different C-rates (0.05C to 2C), electrochemical charge-discharge behaviour has been observed. In first cycle of the phase-pure spinel structured anode, an initial specific capacity of 195.82 mAh/g, 139.70 mAh/g, 25.04 mAh/g and 14.16 mAh/g were obtained at C rate of 0.05C, 0.1C, 1C and 2C, respectively. A possible phase conversion reaction of the anode resulted in a decrease in specific capacity with increasing C-rate.

The hybrid ergodic lattice gas model for critical fluids and the molecular nature of the critical point

This paper introduces the hybrid ergodic lattice gas model as a conceptually simple, computationally cheap, yet accurate model that predicts macroscopic fluid pressure along the critical isotherm of a fluid accurately. A key concept is the hybrid evaluation of the properties: the kinetic and repulsive pressure components are calculated from equations of state, representing the ‘global’ nature of these values, whereas the attractive pressure component is calculated from the ‘local’ particle arrangement, in which particle clusters are identified using unsupervised machine learning. The proposed method captures the fluid pressure of the ideal gas regime and near the critical point, and is much more accurate then the Peng Robinson equation of state for liquid states. The predicted molecular structure is then used to identify three distinct stages of molecular behavior along the isotherm: I. cluster formation, II. cluster consolidation, and III. supercluster growth. Specifically, the critical point is shown to correspond to the state in II. where clusters merge together to form a single supercluster, corresponding to the percolation threshold of a cubic site lattice. The foundation of the model in a lattice gas opens the door for the analytical analysis of near-critical fluids using percolation theory and probabilistic analysis. As an example, a lattice-based derivation of a van der Waals attractive term is given. Finally, the lattice fluid is shown to be related to random networks, but deviates from the classical Erdős and Rényi’s G(N, L) model in that the critical point is found at a degree of 〈k〉 = 2 rather than the classical result of 〈k〉 = 1.

Super-Critical Fluid: An Overview on Analytical Applications

Abstract:: Super Critical Fluid is the emerging technique that consists of super solvent, which is considered a benefit over many other conventional solvents. The main component utilized in it is Carbon Dioxide [CO2], which possesses dual state properties such as effusion through solid and other dissolving materials like liquid which results in unique applications bidden with no limitations. The varying temperature and pressure are the important parameters optimized and thus enhance its solvent properties. Higher Co-efficient of diffusion, reduction in time, higher compressibility, etc. is some of the major advantages of SCF-CO2 over the conventional solvents. Over and above, it is a green approach and a super solvent. Here we have discussed the multifarious applications of the SCF-CO2 extraction in fields and areas extended, but not limited to, Food, Environmental, Analysis, Metal-Cation Extraction, as well as Extractions, Forensics, Pharmaceuticals, Toxins, and Botanical Samples.

A technology review of recycling methods for fiber-reinforced thermosets

The rapidly rising demand for fiber-reinforced plastics (FRPs) has led to large volumes of manufacturing and end-of-life waste. Recycling fiber-reinforced thermosets is very difficult owing to their complex structure and heterogeneity. Landfill and incineration have become the most commonly used methods for eliminating non-degradable FRP waste, which adversely affects the environment and ecology. The purpose of this review is to evaluate end-of-life FRP recycling technologies in terms of optimizing the reuse/recycling of resources and eliminating waste, thereby improving FRP waste management. The technical progress made in the recycling of thermosetting composites is reviewed, including mechanical, thermal (pyrolysis and fluidized-bed), and chemical (critical fluid and low-temperature solvent) methods. The technical feasibility of each method was compared, and the economic and environmental impacts were considered. The challenges and opportunities facing the establishment of a composite recycling market in the future are examined. Finally, we provide a comprehensive summary of the scope of each recycling method.

EFFECT OF SUPERCRITICAL FLUID EXTRACT OF ZINGIBER OFFICINALIS IN THE MANAGEMENT OF DIABETES AND ITS RELATED COMPLICATIONS

Diabetes mellitus is referred as diabetes which is the metabolic disorder. Major symptoms of diabetes include increased urination & thrust, head ache, high degree of sudden weight loss. Due to increase in blood glucose levels it causes trigger of various pathways which ultimately leads to various diabetic complications. Pathways like which includes Polyol Pathway, Hexosamine Pathway, Activation of PK-C (Protein Kinase-C), & formation of Advance Glycation End Products. For the diagnosis of diabetes two major tests are done blood glucose level and Glycated hemoglobin content (HbA1c). Ayurveda is the super bank for various molecules to treat any disease. Here we have chosen the super critical fluid extract of Ginger that is Zingiber Officinale. In our study we have used Streptozotocin induced diabetes mellitus model by using rats. Our result showed promising effects in the streptozotocine induced diabetes and immunomodulatory activity was also shown by the extract. Overall in conclusion it Zingiber Officinale supercritical fluid extract can be considered as source of multitalented molecules which can be proven better for the management of diabetes and its related

EFFECT OF SUPERCRITICAL FLUID EXTRACT OF ZINGIBER OFFICINALIS IN THE MANAGEMENT OF DIABETES AND ITS RELATED COMPLICATIONS

Diabetes mellitus is referred as diabetes which is the metabolic disorder. Major symptoms of diabetes include increased urination & thrust, head ache, high degree of sudden weight loss. Due to increase in blood glucose levels it causes trigger of various pathways which ultimately leads to various diabetic complications. Pathways like which includes Polyol Pathway, Hexosamine Pathway, Activation of PK-C (Protein Kinase-C), & formation of Advance Glycation End Products. For the diagnosis of diabetes two major tests are done blood glucose level and Glycated hemoglobin content (HbA1c). Ayurveda is the super bank for various molecules to treat any disease. Here we have chosen the super critical fluid extract of Ginger that is Zingiber Officinale. In our study we have used Streptozotocin induced diabetes mellitus model by using rats. Our result showed promising effects in the streptozotocine induced diabetes and immunomodulatory activity was also shown by the extract. Overall in conclusion it Zingiber Officinale supercritical fluid extract can be considered as source of multitalented molecules which can be proven better for the management of diabetes and its related

Influence of diffusion and viscosity on the field asymmetry of the effect of gravity in the critical fluid

A brief review of the results of studies of the effect of gravity in inhomogeneous substance near a critical state of a critical fluid (CF) has been presented in paper, based on the data of light scattering, refractometry, and slow neutron transmission methods.Based on these data, the field-altitude asymmetry of various properties of an inhomogeneous substance has been analyzed, namely order parameter Dr(z), scattered light intensity I(z), density gradient dr(z)/dz of the substance. It had been shown that the field-altitude asymmetries of the scattered light intensity I(z)~dr/dm(h) and the density gradient dr(z)/dz~dr/dh(h) of the substance are diametrically opposite. The different altitudinal asymmetry of these quantities dr/dh(h) and dr/dm(h) is explained in paper by the altitude asymmetry of the derivative of the chemical potential dm/dh, and hence with the altitude asymmetry of the chemical potential Dm(h)>>h in the external field h.To the present time, the physical mechanism of the altitude asymmetry of the gravity effect has not been studied. In this regard the mechanism of the formation of the vertical asymmetry of the internal critical field Dm(h) has proposed in paper to be associated with the kinetic characteristics of the inhomogeneous critical fluid: the diffusion coefficients D (h) and viscosity coefficients h(h), when the system passes from a homogeneous state to an inhomogeneous one under the action of an internal asymmetric fields |DU(z)|= |Dm(z)|>>|h=rcgz/Pc|. For this purpose, a high-pressure cell with a height L, with a critical filling density of the substance is considered in paper.It has been shown that when the system is under critical density filling by substance =rc the critical level of substance z = 0 with the critical density rc at the critical temperature Tc is realized above the middle of the sample with an inhomogeneous substance. Based on the literature data of P-V-T-measurements and the gravity effect in benzene and ethane, the values of the altitudinal change in the internal critical field have been found. It has been shown that the value of the critical internal inhomogeneous field in the inhomogeneous critical fluid significantly exceeds the variable of the Earth's gravity |DU(h,Tc)|= |Dm(h,Tc)>>|h| It has been also shown that the magnitude of this field according to the cubic law depends on the critical temperature Tc of the substance: |Dm(z,Tc1)/|Dm(z,Tc2) » (Tc1/Tc2)3.

The role of the critical compressibility factor in the equation of state for the critical fluid

Based on the literature data of PVT measurements, the amplitudes of the equations of the critical isotherm D0(Zk), the critical isochore Г0(Zk), the phase boundaries В0(Zk) are expressed in terms of the critical factor of compressibility of the substance Zk=PkVk/RTk in the entire fluctuation region near the critical point. By doing so, a phenomenological method has been used for calculating the values of the critical exponents of the fluctuation theory of phase transitions based on the introduction of small parameters into the equations of the fluctuation theory. 
 It has been shown that, within the limits of the PVT measurement errors, these dependences D0(Zk) and В0(Zk) on the compressibility factor are linear, and Г0 practically does not depend on the compressibility factor Zk.
 The relationship of these amplitudes with the amplitudes a and k of the linear model of the system of parametric scale equations of state of substance near the critical point has been established. It has been shown that the dependences k(Zk) and а(Zk) are also linear in the entire fluctuation region near the critical point. The obtained dependences k(Zk) and а(Zk) agree with the known relationship between the amplitudes of the critical isotherm D0(Zk), critical isochore Г0(Zk), phase boundaries В0(Zk) Aerospace Institute of the National Academy of Sciences of Ukrainewithin the framework of the system of parametric scaling equations.
 The relations а(Zk), k(Zk) make it possible, on the basis of a linear model of the system of parametric scale equations of state of substance, to determine such important characteristics of the critical fluid as the temperature and field dependences of the correlation length Rc(T,m) and the fluctuation part of the thermodynamic potential Ф(T,m) in the entire fluctuation region near the critical point.
 Then, based on the form of the fluctuation part of the thermodynamic potential Ф(T,m)~Rc(T,m)-3, the results obtained allow one to calculate the field and temperature dependences of the thermodynamic quantities for a wide class of molecular liquids in the close vicinity of the critical point (DP<10-3, Dr<10-2, t<10-4), where precision experiments are significantly complicated, and its can also be used when choosing the conditions for the most effective practical application of the unique properties of the critical fluid in the newest technologies.

Screening of fluoride analysis as a biochemical parameter in the orthodontic treatment using fixed appliances

Saliva is a critical and useful biological fluid necessary for good health and for the appropriate execution of mouth activities. Orthodontic biomaterials have a complex relationship with many components, including the oral environment. Treatment with fixed orthodontic appliances may causes dental caries. As a result, it is necessary to comprehend how orthodontic therapy and various fluoride regimens affect the chances of developing dental cavities as well as individual risk factors. Usage of fluoride will tend to reduce the caries in the patients diagnosed with the fixed orthodontic treatment. The aim of this study was to screen the biochemical parameter of the fluoride levels in the patients undergone and completed the treatment of orthodontic fixed appliances. In this study, 35 patients have been visited on day 1 as well as day 35 and categorized as T0 and T1 groups. Saliva samples were collected and fluoride levels were measured between T0 and T1 groups. Using the fluoride kit with the spectrophotometer, fluoride levels were measured. The results confirmed similar fluoride levels between T0 (26.11 ± 4.86) and T1 (27.71 ± 4.40) groups. There was no significant association observed in this study (p = 0.56). Fluoride might have no role in the patients undergoing orthodontic treatment.

Analysis of the instability of pipes conveying fluid resting on two-parameter elastic soil under different boundary conditions

In this study, the dynamic behaviour of a fluid conveying pipe resting on a two-parameter elastic foundation was investigated under four different boundary conditions. In the analyses, the fluid conveying pipe was modelled as an Euler-Bernoulli beam, and the equation of motion that describes the dynamic behaviour of the beam was obtained. The critical velocities and the complex frequencies of the system were obtained using the Differential Transform Method. The critical flow velocities and the corresponding instability forms that may induce pipe failure under four different boundary conditions were investigated in detail. The results of this study showed that the fluid conveying cantilevered and clamped-pinned pipes are more stable than the pinned-pinned pipe, but less stable than the clamped-clamped pipe; the elastic foundation increases the natural frequency and the critical fluid velocity, and induces stability of the pipe; it is easier for a fluid conveying pipe without elastic foundation to lose stability compared to a fluid conveying pipe resting on elastic foundation; increasing elastic foundation parameters increase the critical flow velocity and stability of the pipe, and delays the occurrence of divergence and flutter instabilities of the pipe.

A Thermo-Hydraulic Investigation of the Unprecedented TMRS Upper Neutron Spallation Target

Abstract The next-generation neutron spallation target station, the Target–Moderator-Reflector System (TMRS) Mk. IV, will be installed in 2021. This iteration features an unprecedented, water-cooled, third internal target aptly named the upper target. With the upper target designed completely by analysis, a complementary empirical investigation was undertaken to ascertain target conformance to those computational results which deemed the cooling efficacious. Three facets of the target were designated for verification: displacement under hydraulic load, critical fluid velocities, and the characteristic heat transfer coefficient (HTC). With the potential for flow maldistribution under excessive displacements, static pressure testing was performed. Discrepancies of an order of magnitude became evident between empirical and simulated displacements, 1.499 mm versus 0.203 mm, respectively. A closed-water flow loop reproducing the flow parameters intrinsic to the TMRS Mk. IV was constructed. Utilizing particle image velocimetry, global fluid dynamics were observed to be analogous to computer simulation. Furthermore, crucial velocities such as those at the point of beam impingement were met or exceeded, thus satisfying cooling requirements by a preponderance. A graphite susceptor mirroring nominal beam geometry was coupled to a solenoid coil to replicate a prodigious peak heat flux of 169 W/cm2 via induction heating. Matching peak heat flux within 3% engendered a HTC of 80% that of simulation. Consistent with analysis, the local HTC sufficiently mitigated nucleate/flow boiling. In summary, the analytically derived upper target design empirically demonstrated sufficient cooling despite quixotic beam conditions and unforeseen displacements.

Observation of heat transfer due to variable thermophysical properties of sub-, near- and super- critical fluids in porous media by magnetic resonance imaging

Local velocity and temperature profiles are measured non-invasively using nuclear magnetic resonance (NMR) imaging (MRI) in porous media with a sub-, near-, and supercritical fluid. Heat transfer is driven by natural convection via heating from below. The C2F6 fluid fills the pore spaces in a packed bed of encapsulated phase change material (PCM). As the PCMs melt, 1H signal intensity increases with temperature. Physical properties of C2F6, e.g. thermal diffusivity, vary substantially at the critical point, affecting the rate and magnitude of heat transfer. The changes in bead signal, e.g. temperature, are imaged and measured over time at 27 bar (sub-critical), 32, 34 and 36 bar (near-critical), and 66 bar (supercritical). Despite velocity profile similarities, the temperature in the packed bed varies significantly with thermal diffusivity, the magnitude of which decreases and increases with temperature around the critical point. NMR spatially and temporally captures the resulting dynamic heat transfer processes.

Nonlinear dynamics of fluid-conveying composite pipes subjected to time-varying axial tension in sub- and super-critical regimes

In the present work, nonlinear dynamics of a simply-supported fluid-conveying composite pipe subjected to axial tension in sub- and super-critical regimes are investigated. The tension acting on the pipe is assumed to comprise an average component and a harmonically changing disturbance component. More specifically, the nonlinear equation of motion is derived based on the Euler-Bernoulli beam theory considering the von Kármán nonlinearity for large deformation assumption, which is then truncated via the Galerkin's approach. In addition, the Kelvin-Voigt model is adopted on the pipe materials with visco-elastic structural damping. Afterwards, parametric studies are performed to evaluate the effects of the axial tension and fiber orientation angle on pre- and post-buckling frequencies, critical fluid velocities and static buckling displacements. The global dynamic behaviors of the pipe are studied through the forms of bifurcation diagrams, phase portraits, Poincaré maps, power spectral density (PSD) diagrams and linear instability maps, in both sub- and super-critical regimes. The results show that, based on symmetric layers, pipes with smaller fiber orientation angles have larger critical divergence fluid velocities but smaller static buckling displacements. Some interesting dynamical phenomena, including periodic, multi-periodic, quasi-periodic and chaotic motions, can be observed with different fiber orientation angles. Moreover, the system shows ‘soft spring’ characteristic in super-critical regime, compared with the ‘hard spring’ characteristic in sub-critical case.

The Effects of Synonym and Antonym Relations on Visual Recognition of Chinese Compound Words: Based on Behavioral and ERP Experiments

Subcritical and supercritical fluids have had a lasting impact on process engineering. The critical fluids have been a great boon to a multitude of industries, and are also an active research interest. These fluids offer a few unique features that allow them flexibility, such as temperature-pressure-dependent differential solvating capacity, in addition to being benign in terms of processes taking place under near-ambient conditions in most cases. They have been employed in extraction, encapsulation, fractionation, chromatography, and related process engineering applications that transcend the boundaries of conventional fluids. Their ability to selectively isolate the compound of interest greatly aids in minimizing downstream processing; and being a green technology, they aid in the cause of sustaining the environment as well. This chapter provides insight into the multiple domains that have benefited from critical fluids and attempts to highlight the major achievements and the way forward.

Optimization of fluid characteristics in the main nozzle of an air-jet loom

As part of the propulsion system, the fluid dynamic features of the main nozzle can immediately affect the stability and efficiency of an air-jet loom. This study aims to optimize the fluid characteristics in the main nozzle of an air-jet loom. To investigate ways of weakening the effect of airflow congestion and backflow phenomenon occurring in the sudden expansion region, the computational fluid dynamics method is employed. Three-dimensional turbulence flow models for a regular main nozzle and 12 prototypes with different nozzle core tip geometry are built, simulated, and analyzed to get the optimum performance. Furthermore, a set of modified equations that consider the direction of airflow are proposed for better estimation of the friction force applied by the nozzle. The result shows that the nozzle core tip's geometry has a significant influence on the internal airflow, affecting the acceleration tube airflow velocity, turbulence intensity, and backflow strength of the sudden expansion region, and other critical fluid characteristics as well. Several proposed models have succeeded in reducing the backflow and outperforming the original design in many different aspects. Models A-60 and C-P, in particular, manage to increase the propulsion force by 37.6% and 20.2% in the acceleration tube while reducing the maximum backflow by 57.1% and 52.2%, respectively. These simulation results can provide invaluable information for the future optimization of the main nozzle.

Dynamics of axially functionally graded pipes conveying fluid using a higher order shear deformation theory

This study presents a novel approach for addressing dynamical characteristics of fluid conveying axially functionally graded pipes. The variation of material properties of the pipe along axial direction is taken into account according to a power-law function. Owing to a unified expression for displacement field, the developed model can be recast into classical Euler – Bernoulli and Timoshenko tube models as well as a newly developed higher order shear deformable tube model; the latter satisfies zero-shear conditions on free surfaces, and hence yields more realistic results. The system of partial differential equations governing dynamics of fluid conveying axially functionally graded pipes is derived through utilization of Hamilton’s principle. Differential quadrature scheme is used to discretize the system of differential equations and generate numerical results. Detailed numerical investigations of the current fluid-solid interaction problem elucidate the effects of material gradation pattern, transverse shear deformation distribution profile along radial direction and fluid velocity on the natural frequencies of fluid conveying functionally graded pipes. The critical fluid velocity, which is a significant design parameter, can also be determined by means of developed procedures in this study.