Physical Properties Of Fluid Research Articles

PHYSICS AND TACTILE PERCEPTION OF FLUID‐COVERED SURFACES

ABSTRACTLittle is known about the linkage between the physical properties of fluids and how they are perceived. Therefore, 15 fluids with diverse rheologies were characterized physically by three participants via a novel “force plate” (FP) device. Perceptual ratings were made by 20 participants, of 27 “sensory” attributes (e.g., oily) and 14 “emotional” attributes (e.g., arousing). Factor analyses decomposed 14 physical measures obtained from the FP into factors approximating friction, normal vibration, and tangential vibration; the sensory attributes into watery, textured, slick, silken and viscous factors; and the emotional attributes into factors labeled pleasant, sensual and harsh. Pleasant and harsh were related to textured and silken. Fluids perceived as more watery elicited greater normal and tangential vibration and less friction, whereas high viscous scores were associated with lower vibration factor scores and increasing friction. These results emphasize the complex perceptual nature of fluid‐coated surfaces as compared with dry, solid surfaces.PRACTICAL APPLICATIONSIn developing consumer products that are fluid‐based (e.g., various foods or cosmetic preparations), it is desirable to reach an end goal in terms of how the fluid feels. This is achieved primarily by altering the physical composition of the fluid. The reported research established relationships between the percepts and physical composition of a diverse set of fluids. These relationships allow early insights concerning how one might formulate a product to produce a given, desirable, percept.

Measurements of liquid film flow as a function of fluid properties and channel width: Evidence for surface-tension-induced long-range transverse coherence

We study experimentally the influence of the transverse dimension on film flow in relatively wide channels with sidewalls. Large deviations from two-dimensional predictions are observed in the primary instability and in the post-threshold traveling waves, and the deviations are presently shown to depend strongly on fluid physical properties. Measurements for a wide range of fluid properties are found to correlate with the Kapitza number, which represents the ratio of capillary to viscous stresses. These observations point to an unexpected long-range effect of surface tension that provides transverse coherence to the flow.

3-D CFD Parametric Study of the Impact of the Fluid Properties and Delivery Conditions on Flow and Heat Transfer in Grinding

Fluids have an important role in grinding. Correct fluid application results in enhanced process stability, better work piece quality, and tool life. This paper shows that Computational Fluid Dynamics (CFD) models can be used to simulate the fluid flow and heat transfer in a grinding process, replacing numerous experiments that are expensive, time-consuming, and have limited capabilities. The most important properties of created 3-D model are described, along with results obtained. The results show very detailed distributions of temperatures, pressures, and flow rates in and around the grinding region. The data obtained is essential in studying the influence of the grinding fluid on the grinding process, as well as in determining the best fluid composition and supply parameters for a given application. The results agree well with experimental global flow rates and temperature values and show the feasibility of 3-D CFD-based simulations in grinding applications. The parametric studies of influence of several fluid physical properties on useful flow rates and temperatures were presented as well.

Fully implicit compositional thermal simulator using rigorous multiphase calculations

Simulation of the in-situ combustion process is one of the most complex simulations amongst other reservoir flow simulations. Accurate simulation of the process is critical to obtain a successful implementation of the in-situ combustion process. Several factors impact performance of the simulation of this process. First are all the numerical models used for different sub-processes, such as reactions, fluid phase behavior, heat loss to surrounding formations and fluid physical properties. In the previous numerical models of the in-situ combustion process, very simplified models were used for the phase behavior of the fluid. Recent studies show that the fluid phase behavior model has a great effect on the results of the simulation. In this work, a novel simulator is presented, which uses a rigorous phase equilibrium model for fluid phase behavior calculations. The numerical model is developed in such a way that different models for the phenomena mentioned above can be replaced easily. The other affecting parameter is the solution scheme of the simulator. Previous studies indicated that the more implicit the solution scheme, the better the performance of the simulator. The presented simulator uses a full implicit solution scheme to solve the equations. The applicability of this method is examined through two synthetic reservoirs.

Laminar convective heat transfer of supercritical CO2 in horizontal miniature circular and triangular tubes

Laminar mixed convective heat transfer of supercritical CO 2 in horizontal miniature tubes with circular or triangular cross section was investigated numerically. The distributions of the velocity, temperature and wall shear stress inside the circular or equilateral triangular tubes with the hydraulic diameters less than 1.0 mm under cooling condition, with and without gravity, were obtained. The effects of the sharply varied physical properties of supercritical CO 2 and the geometrical characteristics of tubes on the fluid flow and heat transfer were examined. It is found that the buoyancy is significant and enhances the heat transfer, especially near the pseudocritical point, unless the fluid and the tube wall are under the thermal equilibrium condition. More interesting transport phenomena and the detailed explanations to the physics were given. The results of this work benefit in the design and optimization of the high efficiency compact supercritical CO 2 heat exchangers. ► We model laminar flow and heat transfer of supercritical CO 2 in miniature tubes. ► We examine the flow and heat transfer behaviors in circle/triangular tubes under cooling condition. ► Buoyancy is significant that changes the flow patterns and enhances the heat transfer. ► Buoyancy depends on the variations of fluid physical properties and tube shape.

A digital PLL circuit for resonator sensors

AbstractResonant mechanical sensors are powerful tools for measuring, e.g., physical properties of fluids. Suitable systems for real-time monitoring of a sensor’s resonance behavior are, e.g., oscillator circuits and phase-locked loop circuits. In this contribution, we present a novel specific digital phase-locked loop circuit with the ability to determine damping, as well as resonance frequency, and providing automatic compensation of spurious parallel capacitances of the sensor. Instead of a phase-frequency detector, the system measures phase and amplitude of the sensor signal with a 16-bit ADC and uses this information to control a numerically-controlled oscillator. Due to the used 4-channel digital synthesizer, the sensor can be excited with up to three frequencies at the same time facilitating enhanced performance in terms of simultaneous measurement of higher order resonances and compensation of spurious capacitances.

Mass transfer in pressure-driven membrane separation processes, Part II

Following on from the work presented in Part I, this Part II paper presents a new mathematical description for water and solute transfer in pressure-driven membrane separation processes, the Molecular Trap (MT) model. This model incorporates the outcomes from the Analytical Solution-Diffusion Pore-Flow (ASDPF) model, which explains the effects of the operational conditions on membrane microstructure and the permeated fluid physical properties, with the solute molecular properties. The new theory, which is found to be qualitatively in agreement with the experimental findings, may be useful for further process understanding and future development.

A Fast Optical Method for the Determination of Liquid Levels in Microplates

Parallel liquid handling systems are widely used in different applications of life sciences. In order to avoid false positive or negative results which lead to higher costs due to the replication of the experiments it is necessary to monitor the process and success of liquid delivery. An easy method for the determination of the liquid levels in microplates has been developed and evaluated. The optical method bases on the measurement of the liquid level using CCD cameras followed by special algorithms for the evaluation and visualization of the measured data. The proposed method was tested in changing environmental lighting for two different liquids. These tests confirm our approach towards optical liquid level determination for smallest volumes in microplates and also show the challenges regarding environmental lighting and different physical properties of fluids.

Systematic investigation of droplet generation at T-junctions

Droplet microfluidics has attracted much attention in recent years. For many droplet-based applications, researchers want to predict the size of the droplets in a certain experimental condition. To meet this need, van Steijn and colleagues proposed an elegant theoretical model that predicts the volume of droplets generated in a common channel configuration for forming a steady-state, continuous stream of droplets, the T-junction geometry. To determine the accuracy of this model in predicting droplet volume, we performed a systematic experimental study over two orders of magnitude in capillary number. We found that this model, albeit elegant, has a limited range of interfacial tension over which it can predict accurately the droplet volume. Our experimental results, together with fluid dynamic simulations, allowed us to highlight the importance of physical fluid properties when employing theoretical models.

Numerical investigations on internal temperature distribution and refrigeration performance of reciprocating active magnetic regenerator of room temperature magnetic refrigeration

A two-dimension porous medium model for a reciprocating active magnetic regenerator (AMR) of room temperature magnetic refrigeration has been developed. The thermal diffusion effect, heat flux boundary effect and variable fluid physical properties are considered in the model. In the paper, we compare the numerical results of the porous medium model with the experimental data and the calculation results of one-dimension Schumann model to validate our model. Our model can simulate the operation of the reciprocating AMR effectively. With the present model, the internal heat exchange between the two phases is numerically investigated. The two dimensional temperature distributions of the magnetic refrigerant and the refrigeration performance of AMR are obtained, and the influence of the heat flux boundary effect and the variable fluid properties on them is discussed. AMR can achieve a maximum refrigeration capacity of 293.7 W with a corresponding coefficient of performance ( COP) of 5.4.

A FRACTAL MODEL FOR NUCLEATE POOL BOILING OF NANOFLUIDS AT HIGH HEAT FLUX INCLUDING CHF

A fractal model for nucleate pool boiling of nanofluids at high heat flux and critical heat flux (CHF) is developed based on the fractal distribution of nanoparticles and nucleation sites on boiling surfaces in this paper. The formula of calculating high heat flux and CHF for nanofluids in nucleate pool boiling is given by taking into account heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids. The proposed model is expressed as a function of temperature of nanofluids, the effective thermal conductivity of nanofluids, the average size of nanoparticles, the fractal dimension of nanoparticles and nucleation sites, the nanoparticles volume fraction of suspension, and physical properties of fluids. No additional/new empirical constant is introduced in this fractal model. An agreement between the proposed model predictions and experimental data is found. The validity of the fractal model for nucleate pool boiling of nanofluids at high heat flux and CHF is thus verified.

Generalized similarity method in unsteady two-dimensional MHD boundary layer on the body which temperature varies with time

In this paper, the multiparametric method known as generalized similarity method is used to solve the problem of unsteady temperature two-dimensional MHD laminar boundary layer of incompressible fluid. It is assumed that outer magnetic field induction is function only from longitudinal coordinate. Magnetic field acts perpendicular to the body on which boundary layer forms. Body temperature varies with time. Further, electric field is neglected and value of magnetic Reynolds number is significantly less then one i.e. problem is considered in induction-less approximation. According to temperature differences under 50oC physical properties of fluid are constant. Introduced assumptions simplify considered problem in sake of mathematical solving, but adopted physical model is interesting from practical point of view, because its relation with large number of technically significant MHD flows. Obtained partial differential equations can be solved with modern numerical methods for every particular problem. In this paper, quite different approach is used. In the first place new variables are introduced and then similarity parameters which enable transformation of equations into universal form. Obtained universal equations and corresponding boundary conditions do not contain explicit characteristics of particular problems. Based on obtained universal equations, approximated universal differential equations of described MHD boundary layer flow problem are derived. Aproximated universal equations do not depend on the particular problems. Keywords: boundary layer, MHD, generalized similarity method, electroconductive fluid

Flow pattern and break-up of liquid film in single-channel falling film microreactors

This paper concerns an experimental investigation into the flow pattern transition and break-up mechanism of liquid film in single-channel falling film microreactors. Three major flow patterns were observed to be ‘corner rivulet flow’, ‘falling film flow with dry patches’, and ‘complete falling film flow’. The critical flow rate associated with the transition between each flow pattern was determined. Hysteresis was found, as the critical flow rate was higher when the flow pattern shifted from ‘falling film flow with dry patches’ to ‘complete falling film flow’ than it was when the flow pattern shifted in the opposite direction. There existed a minimum wetting flow rate (MWF) in order to the complete falling film flow pattern to be present. MWF was observed to increase with the width or depth of microchannel and could not be well predicted by traditional falling film correlations. Based on the obtained data, an empirical correlation has been proposed for the prediction of MWF in falling film microreactors, where the influence of fluid physical properties and channel dimension is revealed.

Experimental Study on Gas Entrainment Due to Nonstationary Vortex in a Sodium Cooled Fast Reactor—Comparison of Onset Conditions Between Sodium and Water

An innovative sodium cooled fast reactor has been investigated as part of the fast reactor cycle technology development project. In the reactor, a compact reactor vessel (R/V) with increased sodium flow velocity was designed to reduce the construction cost. One of the thermal hydraulic problems in this design is gas entrainment at the free surface in the R/V. In most of past studies, water experiments were performed to investigate the gas entrainment in the reactor. It is necessary to evaluate an influence of fluid physical property on the gas entrainment phenomena. In this study, sodium experiments were carried out to clarify the onset criteria of the gas entrainment due to a free surface vortex. Water experiments using a test section in which geometry is the same as that in the sodium tests were also performed. The gas entrainment in water slightly tended to take place in comparison with that in sodium under low velocity conditions. Overall, the onset condition map on the lateral and downward flow velocities in the sodium and water experiments were in good agreement.

A NEW ANALYTICAL MODEL FOR HEAT TRANSFER IN POOL BOILING

In this paper, dependence of active nucleation site density on boiling surfaces are developed. For pool boiling heat transfer, a mathematical model is derived based on statistical treatment using the probability density function of the cavity mouth radius and existing correlation for active nucleation site density, the volume of single bubble at departure, the bubble departure diameter and the bubble departure frequency. The proposed model is expressed as a function of wall superheat, the contact angle, maximum and minimum active cavities, and physical properties of fluid. It is shown that the wall heat flux can be determined by the consideration of the variation of the cavity mouth radius. A good agreement between the proposed model predictions and experimental data is found for different contact angles. It also turns out that the present model explains well the mechanism on how wettability affects the pool boiling.

Volume of Sedimentary Particles Lifted up by a Swirl Motion of Bubbling Jet

In our previous research, we mentioned about mixing of small solid sedimentary particles using a swirl motion of a bubbling jet. The lifting behaviors of the particles were classified into two types depending on the aspect ratio (LN/D) of the bath, where LN the nozzle depth and D the bath diameter. The two types of lifting behaviors were closely associated with the isolated vortex appearing for LN/D=0.2–0.4 and twin vortices appearing for LN/D=0.5–0.8. These vortices were similar to the tornado. In this study, empirical equations are proposed for the volume of sedimentary particles lifted up by a swirl motion of a bubbling jet as functions of the gas flow rate, vessel diameter, bath depth, and the physical properties of fluids.

Digital phase-locked loop circuit for driving resonant sensors

Resonant mechanical sensors are powerful tools for measuring, e.g., physical properties of fluids. Suitable systems for real-time monitoring of a sensor’s resonance behavior are, e.g., oscillator circuits and phase-locked-loop circuits. In this contribution, we present a novel specific digital phase-locked-loop circuit with the ability to determine damping, as well as resonance frequency, and providing automatic compensation of spurious parallel capacitances of the sensor. Instead of a phase-frequency detector, the system measures phase and amplitude of the sensor signal with a 16-bit ADC and uses this information to control a numerically-controlled oscillator. Due to the used 4-channel digital synthesizer, the sensor can be excited with up to three frequencies at the same time facilitating enhanced performance in terms of simultaneous measurement of higher order resonances and compensation of spurious capacitances.

Miniaturized sensors for the viscosity and density of liquids-performance and issues

This paper reviews our recent work on vibrating sensors for the physical properties of fluids, particularly viscosity and density. Several device designs and the associated properties, specifically with respect to the sensed rheological domain and the onset of non-Newtonian behavior, are discussed.

Heat transfer in counterflow heat exchangers with helical turbulators

A 3D mathematical model has been developed to investigate the heat transfer augmentation in a circular tube with a helical turbulator. Glycol–water blends of various concentrations were used in the inner tube, and pure water was used in the outer tube. Changes in fluid physical properties with temperature were taken into account, and k–ε,k-ω, and large eddy simulations were developed for turbulence modeling. The simulation results showed a nonlinear variation in Reynolds and Prandtl numbers for a long model of a heat exchanger even in the absence of a turbulator. The presence of the turbulator was found to increase the heat transfer, sometimes without inducing turbulence, but also increased the pressure drop. The results demonstrate that the model could be used as a useful tool for optimization of heat exchanger performance in the presence of a turbulator. Comparisons with experimental data showed reasonably agreement with large eddy simulation results.

A fractal analysis of dropwise condensation heat transfer

In this paper, a fractal model for dropwise condensation heat transfer is developed based on the fractal characteristics of drop size distributions on condensing surfaces. Expressions for the fractal dimension and area fraction of drop sizes are derived, which are shown to be a function of temperature difference between condensing surface and saturated vapor. The condensation heat transfer is found to be a function of the fractal dimension for drop sizes, maximum and minimum drop radii, the temperature difference, and physical properties of fluid. The predicted total heat flux from a condensing surface based on the present fractal model is compared with existing experimental data. Good agreement between the model predictions and experimental data is found, which verifies the validity of the present model.