Physical Properties Of Fluid Research Articles

Taylor-Couette flow with mixed convection heat transfer and variable properties in a horizontal annular pipe

Taylor-Couette flows in a horizontal annular gap between finite coaxial cylinders in rotor-stator configuration are numerically investigated. The inner cylinder (rotor) rotates at a constant angular velocity while the outer cylinder (stator) is at rest. They are limited at their extremities by two fixed walls that prevent axial fluid-flow. In addition, a heat transfer is generated by an imposed temperature difference, with the rotor hotter than the stator while the end-walls are adiabatic. The fluid physical properties are temperature dependent. This non-linear physics problem, with a strong coupling of the conservation equations and boundary conditions, is solved by a finite volume method with numerical schemes of second order space and time accuracies. The radius and aspect ratios and the Taylor, Grashof, and Prandtl numbers are the control parameters. The developed numerical code has been tested for different meshes and perfectly validated. Extensive calculations have been made in large ranges of the Taylor and Grashof numbers to analyze the Taylor-Couette flow in convection modes. The results highlight the dynamic and thermal instabilities generated in the Taylor-Couette flow from the appearance of Ekman cells to the Taylor vortex propagation in the entire annulus. The combined effect of these vortices with the secondary flow improves the heat transfer. Furthermore, the influence of the physical properties in the radial direction is more marked in the vicinity of the walls. Finally, we propose an empirical correlation of the Nusselt number in the studied parameter ranges.

A Fractal Model for Thermal Dispersion Coefficients of Porous Media

The thermal dispersion coefficient is an important parameter to characterize heat and mass transfer in porous media, which is related to the physical properties of fluid and the structure of porous media. The pore-throat structure model for fractal porous media was established, and the local head loss and the velocity dispersion effect were studied for the fluid changing from the turbulent state to the laminar state around the pore-throat structure. The thermal dispersion coefficient formula was derived under the influences of the micropore-throat structure and the velocity dispersion effect. The results show that, the thermal dispersion coefficient is directly proportional to the pore-throat ratio, the number of pore-throat structures and the tortuous fractal dimension, and is inversely proportional to the porosity and the area fractal dimension. Furthermore, in the range of 1~150, the pore-throat ratio has a significant influence on the velocity dispersion effect, and the fluid has a local head loss around the pore-throat structure, which leads to an enhancement of the velocity dispersion effect and an increase of the thermal dispersion coefficient.

Geochemical rationalisation for the variable oil quality in the Orcutt reservoir, California, USA

The relationship between fluid physical properties and hydrocarbon compositions was investigated on a suite of eleven heavy oil samples from the Orcutt Field, onshore Santa Maria Basin in California. The physical properties of oils display a considerable range across the reservoir, with viscosity varying from 46.3 to 611,150 centipoises at 20 °C and API gravity from 16.3 to 25°. Not surprisingly, the molecular composition of the Orcutt Field oils is also highly variable.Present-day fluid physical properties in the field are determined by the mixing of multiple petroleum charges. The bulk of the oil volume in place was generated by source rocks of the Monterey Formation in the early oil window stage of petroleum generation. The mixing of biodegraded and non-biodegraded oils indicates at least two oil charge events, punctuated by episodes of biodegradation. Oil viscosity decreases towards the Orcutt Frontal fault and Solomon Hills fault, which bound the Orcutt anticlinal structure to the northeast. These faults appear to be conduits for a separate diamondoid-rich light oil or condensate charge responsible for localised improvements in oil viscosity towards the NE and in the crest of the structure.Data from this study show the profound impact of charge mixing and in-reservoir alteration on physical properties of oils within a single accumulation.

Dipping into a new pool: The interface dynamics of drops impacting onto a different liquid.

When a drop impacts onto a pool of another liquid, the common interface will move down at a well-defined speed for the first few milliseconds. While simple mechanistic models and experiments with the same fluid used for the drop and pool have predicted this speed to be half the impacting drop speed, this is only one small part in a rich and intricate behavior landscape. Factors such as viscosity and density ratios greatly affect the penetration speed. By using a combination of high-speed photography, high-resolution numerical simulations, and physical modeling, we disentangle the different roles that physical fluid properties play in determining the true value of the postimpact interfacial velocity.

CFD study of drag and lift coefficients of non-spherical particles

The prediction of correct drag and lift forces acting on immersed bodies is vital for optimized efficiency and industrial economics. Particulate suspensions involving non-spherical particles are extensively used in the chemical and medical industry. In recent years, the hydrodynamics of non-spherical particles have attracted much attention. The hydrodynamic forces acting on these particles are the function of particle size, shape, orientation, and the physical properties of fluid. In the current research, the drag and lift coefficient of non-spherical particles of disc and prolate shapes at different inclination angles and Reynolds number (Re) is calculated using the simplified Eulerian approach of computational fluid dynamics (CFD). The method adopted for simulation is first validated for a simple case of sphere. The effect of orientation and Re on drag and lift coefficient (CD and CL, respectively) is studied and compared with the available data. It is found that CD and CL increase as the angle of inclination increases, but decrease with Re. CD and CL are smaller for prolate at given Re and orientation than for the case of disc. The effects of finite size geometry cause some deviation in results from the literature. The results obtained with this simple and less computationally intensive method agree well with highly resolved numerical simulations with minor deviations.

Modeling of nanoparticle fluid microscopic plugging effect on horizontal and vertical wellbore of shale gas

Shale gas is an important part of realizing the modern multi-energy system as a kind of unconventional energy with huge reserves for human energy needs. Adding nanomaterials to plug shale pores is an effective method to improve shale gas development. However, the dynamic migration of nanoparticles in shale pores, the time-space process of plugging, and the mapping relationship between permeability under different wellbore conditions are unclear. In this paper, a fluid-solid coupling nano-blocking model based on pore characteristics, fluid physical properties, and discrete element parameters is established considering the nano-scale effects. In order to ensure the rationality of the nanoparticle force, codes were written to modify the flow resistance. Pore ratio with perpendicular and parallel to shale bedding and channel bending degree model is established, and their rationality is verified through experiments. Particle concentration, size, particle release mode and shape factors for plugging efficiency were discussed with different wellbore conditions. Results indicate the plugging gap between horizontal and vertical wells narrowed by 43.76% as particles increased from 1 wt% to 5 wt%. Increasing the particle size has a greater impact on plugging efficiency of vertical well pores. In the multi-scale particle release mode, the particle plugging effect is increased by 90.44% and 94.22% compared with vertical and horizontal wells, respectively. The research results can provide nano plugging solutions in drilling fluid for shale gas development.

Improving Battery Pack Safety with an Innovative Fluid for Thermal Management

<div class="section abstract"><div class="htmlview paragraph">Efficient and safe Lithium-Ion Batteries have undoubtedly become the Holy Grail of the electric vehicle industry. Any OEM’s technical roadmap is currently focused on increasing battery lifetime, energy density, or above all on safety. The battery is definitively becoming a way to differentiate electric vehicle performance. Battery safety is central; any fire is unacceptable and can damage OEM’s image and Battery Electric Vehicle (BEV) acceptance. Therefore, solutions must be developed to cope with this dramatic issue. This paper presents a battery thermal management system, helping to increase battery lifetime, but, above all, making the battery pack safer. This system relies on the use of an innovative dielectric fluid in direct contact with electrochemical cells. Fluid physical properties are designed to accurately maintain the battery pack at a specific temperature in a daily life (fast charging and fast acceleration). Experimental and numerical results demonstrate the performance and the versatility of this solution. The key innovation relies on the fluid behavior when exposed to extreme heat generated during a battery thermal runaway event. Its specific chemical structure prevents fire propagation, even in a severe scenario where common fluids are getting ignite and catch on fire. Electrochemical cells abuse tests have been carried out on several types of cells, such as 21700 cylindrical cells or pouch cells with higher capacity. During nail penetration and overcharging events triggered in tests, it was demonstrated thermal events were avoided. The solution developed is ready to be implemented on a large scale and can be used by any battery pack designer as a tool to improve safety.</div></div>

Effects on droplet generation in step-emulsification microfluidic devices

Step emulsification technology is an important breakthrough for the industrial application of microfluidic devices. In this paper, the influences of microdevice structures and physical properties of fluids on the droplet (around 1 mm in size) generation in a step emulsificator with a single microchannel are studied. Through the analysis of the interface evolution process during droplet generation, we found that increasing the width of the terrace (0.4–1.0 mm) and the size of the collection cavity, decreasing the viscosity of the dispersed phase (0.89–54.61 mPa·s) result in the increase in the range of the dripping flow regime, obtaining a larger emulsion flux of the microdevice. The prediction equation for the droplet size is proposed by considering the inertial and viscous forces of the dispersed phase: Dh=1.63Oh0.17We0.14+D0h-0.47Oh0.24. Finally, the relationship between the satellite droplet size formed by the neck rupture and the manipulation variables is presented.

Hydrodynamic study of the oil flow in a protective relay coupled to a power transformer: CFD simulation and experimental validation

The present study aimed at performing a hydrodynamic analysis of the safety device's behavior in a gas relay, using computational fluid dynamics techniques and experimental data validation obtained in a protective relay pilot unit (PRP) using different safety flaps geometries for fault detection within high-power transformers. The proposed methodology was carried out in four stages: (i) development of computational meshes from the three-dimensional geometry of the protective relay and safety flaps; (ii) specification of the physical properties of fluids, boundary conditions, and fluid dynamic models; (iii) obtaining speed profiles, flap angle, oil flow and system pressure difference; and (iv) comparison of simulated and experimental data. The devices installed in the relay showed satisfactory performance for failures caused by the oil volumetric expansion. It was observed that from the flap 10° tilt, the orifice ceases to be the preferred path oil, reducing detection sensitivity of the flow. Using the CFD (computational fluid dynamics) computational tool, it was possible to understand the flow behavior within the relay, allowing to detect quickly and efficiently cases of failure with oil expansion.

Two-phase solid/liquid mixture of water/carbon nanotubes at the equilibration phase of atomic structures: Atomic value effects in a microchannel using the molecular dynamics method

Carbon nanotube (CNT) effects on H2O (basefluid) are described in our computational study. Molecular Dynamics (MD) method are used in our study with a LAMMPS simulation package. Technically, H2O/CNT nanofluid simulated with DREIDING and Tersoff force fields in which this selection is appropriate for the atomic study of these structures. For the atomic manner of H2O/CNT nanofluid, we reported quantities, such as total temperature, energy, atomic density, atomic velocity, and atomic temperature profiles of the simulated nanofluid. The nanoparticles cause the phase change in lower simulation time steps. Numerically, this phenomenon time varies from 701,000 to 512000-time steps when CNT nanoparticles are added to H2O base fluid. Additionally, this nanoparticle causes to increase the density, velocity, and maximum temperature values. Our calculations indicate that CNT nanoparticles affect the base fluid physical properties and can be used for thermal conductance procedures with high efficiency.

Theoretical Atomization Model of Liquid Sheet Generated by Coaxial Swirl Injectors

This paper describes the atomization process of a liquid sheet generated by a coaxial swirl injector and it establishes a theoretical breakup model to predict the Sauter mean diameter (SMD) in the entire spray field. The two stage breakup model, which includes Kelvin-Helmholtz (K-H) and Rayleigh-Taylor (R-T) instability, is established and combined with the dispersion relation obtained by linear stability analysis. The theoretical expression to predict the SMD is then determined by full wavelength integration. The validity of the present model is first verified; the results predicted by the theoretical model showed good agreement with previous experimental data. Subsequently, effects of fluid physical properties and flow parameters on the SMD are also investigated. The related conclusions are compared and concur well with the existing literature.

A numerical study of heat transfer enhancement by helically corrugated tubes in the intermediate heat exchanger of a very-high-temperature gas-cooled reactor

We numerically investigate heat transfer enhancement by helically corrugated tubes (HCTs) in the intermediate heat exchanger (IHX) of a very-high-temperature gas-cooled reactor (VHTR). A comparison with heat transfer in a smooth tube shows that HCTs have better heat transfer over the full IHX temperature range. The helical corrugations strengthen the intensity of the turbulence and create rotational flow, which better mixes the fluid and improves the synergy between the velocity field and the temperature gradient field. The effects of tube structural parameters and fluid physical properties on the Nusselt number (Nu), friction factor, and performance evaluation criterion (PEC) were also analyzed. The corrugations have optimal heights for the maximum Nu and PEC. Nu decreases as the corrugation pitch increases, whereas the PEC shows the opposite trend. The best heat transfer enhancement is 1.69 for e/d = 0.03 and p/d = 0.4, and the best overall performance is 1.13 for e/d = 0.01 and p/d = 0.8, both of which are in the high-temperature region.

Development of endodontic sealers containing antimicrobial-loaded polymer particles with long-term antibacterial effects

ObjectiveThe objective of this study is to prepare new dental resins with a long-lasting antimicrobial activity. Specifically, this study evaluates an approach for controlling infection in root canals using sealers containing polyhydroxyethyl methacrylate trimethylolpropane trimethacrylate (polyHEMA/TMPT) particles loaded with cetylpyridinium chloride (CPC). In addition, the physical properties of sealers containing CPC-loaded polyHEMA/TMPT particles (CLP) are determined. MethodsPolyHEMA/TMPT particles with 10 (10%-CLP) and 25wt.% CPC (25%-CLP) with different particle sizes were fabricated and incorporated in HEMA-based sealers. CPC-release profiles were evaluated over 14 days of immersion in water, followed by 14 days of storage and 14 days of water immersion. The antibacterial activity of these sealers against Enterococcus faecalis in dentinal tubules was assessed using a root-canal-infection model. Their sealing abilities were evaluated by fluid filtration and physical properties were tested according to the ISO 6876 standard. The long-term antibacterial activity of the cured sealer containing 25%-CLP (∼21μm particle diameter) was re-assessed after 1 year of storage. ResultsAfter 28 days of immersion, 25%-CLP exhibited a higher and sustained CPC release unlike 10%-CLP. Residual bacteria in root dentinal tubules were eradicated by obturation with 25%-CLP-containing sealers. The incorporation of 25%-CLP (∼21μm) had no adverse effects on the sealing ability and physical properties of the sealer and resulted in long-term antibacterial activity. SignificanceThe incorporation of CPC-loaded particles in HEMA resins yielded endodontic sealers with long-term bactericidal activity against E. faecalis in root canals. These sealers can potentially be used to prevent recurrent apical periodontitis.

CFD Study of Cuttings Transport through Vertical Wellbore

Cuttings transportation from the bit up the annulus to the surface is one the essentialfunctions that are performed by drilling fluid. Predication of drilling fluid efficiency totransport cuttings in the annulus is very complicated due to numerous parameters that haveaffected drilling operations. Computational Fluid Dynamics (CFD) is widely used as anumerical technique in handling complex multiphase flow problems in differentoperational conditions.The present work has taken the advancement of CFD to computationally analyse theinfluence of the effects of various parameters like drilling fluid rheology, flow rate, piperotation, cuttings density, shape, concentration and drilling fluid- cuttings particle couplingregimes on the cuttings transport in a vertical wellbore. The CFD simulation was carriedout by using transient solver of ANSYS-FLUENT CFD commercial code.The dense discrete phase model (DDPM) is suggested in this work to overcome themain shortcomings of Eulerian–Eulerian and CFD-DEM approaches in simulating drillingfluid-cuttings flow. Also, some of the experimental investigations were involved indetermining the fluid physical properties and essential input data to perform the CFDsimulations. Regarding the results validation and verification, well agreement has beenachieved between results obtained in this study with those reported in other studies

How a sticky fluid facilitates prey retention in a carnivorous pitcher plant (Nepenthes rafflesiana)

Nepenthes pitcher plants grow in nutrient-poor soils and produce large pitfall traps to obtain additional nutrients from animal prey. Previous research has shown that the digestive secretion in N. rafflesiana is a sticky viscoelastic fluid that retains insects much more effectively than water, even after significant dilution. Although the retention of prey is known to depend on the fluid's physical properties, the details of how the fluid interacts with insect cuticle and how its sticky nature affects struggling insects are unclear. In this study, we investigated the mechanisms behind the efficient prey retention in N. rafflesiana pitcher fluid. By measuring the attractive forces on insect body parts moved in and out of test fluids, we show that it costs insects more energy to free themselves from pitcher fluid than from water. Moreover, both the maximum force and the energy required for retraction increased after the first contact with the pitcher fluid. We found that insects sink more easily into pitcher fluid than water and, accordingly, the surface tension of N. rafflesiana pitcher fluid was lower than that of water (60.2 vs. 72.3 mN/m). By analysing the pitcher fluid's wetting behaviour, we demonstrate that it strongly resists dewetting from all surfaces tested, leaving behind residual films and filaments that can facilitate re-wetting. This inhibition of dewetting may be a further consequence of the fluid's viscoelastic nature and likely represents a key mechanism underlying prey retention in Nepenthes pitcher plants. Statement of significanceCarnivorous Nepenthes pitcher plants secrete sticky viscoelastic fluids that prevent insects from escaping after falling into the pitcher. What physical mechanisms are responsible for the fluid's retentive function? First, insects sink and drown more readily in N. rafflesiana pitcher fluid due to its reduced surface tension. Second, once within the fluid, our force measurements show that it costs more energy to separate insects from pitcher fluid than from water. Third, the fluid strongly resists dewetting, making it harder for insects to extract themselves and covering their cuticle with residues that facilitate re-wetting. Such striking inhibition of dewetting may represent a previously unrecognised mechanism of prey retention by Nepenthes. Pitcher fluid fulfils a well-defined biological function and may serve as a model for studying the mechanics of complex fluids.

Numerical prediction of Péclet number in small-sized fixed bed reactors of spheres

Fluid dispersion in small fixed bed reactors under single phase laminar flow conditions is evaluated through accurate predictions of axial Péclet numbers Peax using Direct Numerical Simulations (DNS). The fixed bed packing is obtained through the Discrete Element Method (DEM) code Grains3D. Peax numbers are computed from steady state simulations of the flow. An additional set of equations solving the spatial distribution of the moments of the age distribution is used. This gives access to local information on dead zones or bypasses. Computations are realized with the OpenFOAM® open-source library. Results are close to the experimental data. The DEM-OpenFOAM® workflow benefits from an accurate control of the fluid physical properties and packing geometry, thus leading to a faster production of data than an experimental approach.We first explore the influence of the reactor-to-sphere diameter ratio δ (δ < 4), fluid velocity and molecular diffusivity on the Peax number. The behavior proves much more complex than any previous report, and it can be qualitatively explained by looking at the packing structure. Then, we use the DEM-OpenFOAM® workflow to quantify the uncertainty on the Peax number when repeating the packing of a δ = 4 fixed bed reactor, and we propose that the uncertainty on the Peax number decreases as a function of the reactor length to the power of −0.5.

New analytical-numerical method for modelling of tube cross-flow heat exchangers with complex flow systems

A new method for thermal calculations of cross-flow tube heat exchangers was proposed. The heat exchanger is divided into finite volumes, inside which the fluid temperatures are given by analytical formulas. The advantage of the semi-analytical method developed is that the temperature inside the finite volume can be determined at any point, unlike the finite difference method widely used in exchanger heat modelling. Even when dividing the entire tube in one heat exchanger pass into a few finite volumes, e.g. into three segments, satisfactory results are obtained. By dividing the whole heat exchanger into a small number of finite volumes, the computer calculation time of heat exchangers with complicated tube arrangement is very short. The proposed method can be used to calculate heat exchangers with a complicated flow system in which the physical properties of fluids depend on temperature. Analytical and numerical models were developed for one and two pass finned tube heat exchangers to assess the accuracy of the proposed method. A two-pass car radiator mathematical model with two rows of tubes using the proposed method was developed. The results of the car radiator and steam reheater calculations are in good agreement with the analytical or experimental results.

The effect of ink formulation on colorimetric properties of inkjet printing considering the impact of substrates

PurposeThe purpose of this study is to investigate the changes in the performance of ink formulations caused by the addition of compounds that improve the ink’s physical properties to achieve an optimum formulation for inkjet printing, because of the importance and simplicity of this method.Design/methodology/approachInk samples were formulated using Acid Red 14 as ink colorant, different percentages of polymeric compounds including polyvinyl alcohol (PVA), polyvinylpyrrolidone and Carboxy methyl cellulose (CMC) as viscosity modifier compounds and surfactant as the surface tension enhancer. Formulated samples were adjusted in terms of fluid physical properties e.g. viscosity, density and surface tension, and the effect of used compounds on the improvement of both physical and colorimetric properties such as viscosity, surface tension, colorimetric coordinates and lightfastness has been evaluated to achieve the optimum printing inks to be printed on three different substrates.FindingsThe experimental observations showed that CMC was the most compatible compound as the viscosity modifier as its viscosity value was in the printable range of 2–22 cP. Moreover, a flow-curve test was applied to the ink samples and their Newtonian behavior was approved. Based on the spectrophotometric test results of printed samples, the samples containing PVA provided acceptable lightfastness in comparison to other ink samples on every used substrate.Originality/valueAn optimum relation between colorimetric coordinates of the printed samples and ink formulation could be considered and achieved.

Coalescence dynamic response of an aqueous droplet at an oil-water interface under a steady electric field

The electrocoalescence of an aqueous droplet at the oil-water interface in the presence of externally direct current electric fields was numerically analyzed with the finite element method by solving the Navier-Stokes and charge conservation equations. The proprietary software Comsol Multiphysics was used for this purpose, and the interface motion was captured by the Level-Set method. Good agreement was obtained between numerical and experimental results in the literature. The numerical description of droplet-interface coalescence transition from the viewpoint of flow field evolution and bridge dynamics was systematically examined, analyzed, and discussed. In the early droplet-interface merging process of CC (complete coalescence) modes, the droplet vortex pair was more strongly developed than the interface vortex pair, which gave rise to the enlargement of the droplet-interface liquid bridge and the fluid motion from the droplet to the interface. The interfacial velocity at the liquid bridge was much larger than at the other regions of the droplet surface in the upheaval CC mode. The upward velocity of the outflow-natured outer vortex pair was observed in the PC (partial coalescence) mode, leading to the formation of secondary droplets. In the jet-like PC mode, multiple outflow-natured vortex pairs simultaneously existed, forcing the droplet tail to break up into tiny satellite droplets. In the NC (non-coalescence) mode, the outflow-natured outer vortex pair was always directed upward, and with the breakup of bouncing-off droplets in the NC mode, an abnormal flow field with an irregular outflow-natured outer vortex pair was formed. Conductivity played little or no part in determining the CC-PC transition, but influenced the PC-NC transition. With the whole liquid bridge dynamics involving liquid bridge growth and decay dynamics taken into consideration, a good quartic polynomial function trend was obtained between the non-dimensional liquid bridge width W* and the non-dimensional time t*. In addition, the liquid decay dynamics and the coupling effect of the electric field and fluid physical properties (such as interfacial tension and viscosity) determine the partial coalescence process. The outcome of this work is potentially useful for optimizing the design of compact and efficient oil-water separators.

Correlation analysis based multi-parameter optimization of the organic Rankine cycle for medium- and high-temperature waste heat recovery

The present paper established a multi-parameter optimization model of the organic Rankine cycle (ORC) to recover medium- and high-temperature waste heat. The preliminary screening of 42 pure working fluids is completed according to the limitations of environment and safety requirements. Afterwards, the relationship between heat source temperature, working fluid physical properties, and system net output power are analyzed. It can be found that there is a parabola variation relationship between working fluid critical temperature and system net power output. When the net power output reaches its peak value, a further increase of working fluid critical temperature will causes the opposite effect. Furthermore, correlation analysis is introduce to investigate the variation relationship between system net output power and working fluid critical temperature, system evaporating temperature/pressure, and condensing temperature/pressure by different heat source temperatures is investigated in detail. Results show that it is not much effective to use a working fluid with great pressure ratio for the design of a high-efficiency ORC system. On the contrary, using working fluid with a high temperature ratio can always improve the system net power output. Besides, the working fluid specific heat difference/ratio, and the latent heat difference/ratio during the evaporation and condensation processes jointly influence the ORC output performance. As a result, the influence order of working fluid key properties to the system net power output is: temperature ratio＞pressure ratio＞latent heat＞specific heat.