Surface Tension Of Fluid Research Articles

Development of models for surface tension of alcohols through symbolic regression

The study of models for the correlation of the surface tension of fluids is a crucial issue in various fields of chemical industries. Usually, seeking for appropriate models is an arduous process that relies too much on the researcher's inventiveness. The main advantage of symbolic regression (SR) is being a straightforward method which automatizes the searching for models, and provides precise and trustworthy models for the researcher to work with. Although in this work we apply SR to develop correlation models for the surface tension of alcohols, the methodology is clearly applicable to any other thermodynamic property or any other family of fluids. We employ a database set of 87 alcohols, with a total quantity of 3570 data that have been carefully selected and filtered in previous works. We consider all the parameters which have a physical meaning for the model, and make a correlation study in order to select the most representative ones: temperature, critical temperature, critical pressure, critical volume, molar volume and acentric factor. Then we make the comparison for the best models obtained with SR (attending to accuracy and complexity of the model) and the usually employed polynomial regression models, obtaining lower errors (1−R2) with SR. Afterwards, we analyze and optimize the models offered by SR which include the least number of parameters possible and provide the highest accuracy. The best models offer values under 7.8% for MAPD (the lowest one is 6.8%), and under 0.07 for 1−R2 (the lowest one is 0.04).

Reminiscent capillarity in subnanopores

Fluids in large and small pores display different behaviors with a crossover described through the concept of critical capillarity. Here we report experimental and simulation data for various siliceous zeolites and adsorbates that show unexpected reminiscent capillarity for such nanoporous materials. For pore sizes D exceeding the fluid molecule size, the filling pressures p are found to follow a generic behavior kBT ln p ∼ γ/ρD where γ and ρ are the fluid surface tension and density. This result is rationalized by showing that the filling chemical potential for such ultra-small pores is the sum of an adsorption energy and a capillary energy that remains meaningful even for severe confinements. A phenomenological model, based on Derjaguin’s formalism to bridge macroscopic and molecular theories for condensation in porous materials, is developed to account for the behavior of fluids confined down to the molecular scale from simple parameters.

A new one-parameter correlation for the surface tension of saturated liquids

In this paper, we proposed a new one-parameter correlation for the surface tension of saturated fluids. This new correlation requires only the critical temperature as inputs and is tested by using the REFPROP data for 72 saturated fluids including refrigerants, alkanes and some other simple fluids such as argon, carbon dioxide, etc. It is found that this correlation well stands in the whole temperature range from the triple point to the critical point with high accuracy for 59 liquids with average absolute deviations (AADs) less than 5%, 50 liquids with AADs less than 3%, and 13 liquids with AADs less than 1%. These results are clearly better than those of the other available correlations. This correlation can be used to estimate the value of the surface tension of the corresponding liquids at any temperature point from the triple point to the critical point.

Fluid viscosity but not surface tension, determines the tamponade effect of intravitreal fluids in a novel in vitro eye model of retinal detachment

PurposeTo determine the effect of varying surface tension and viscosity of fluids used as tamponade in an in vitro eye model of retinal detachment. MethodsWe used an in vitro eye model simulating retinal detachment. Fluids with varying surface tension and identical viscosity, and fluids with varying viscosities and identical surface tension were used as tamponade agents to prevent retinal detachment in the model, to determine which of these properties affects each fluid's effectiveness as a retinal tamponade. ResultsThe membrane (simulating retinal detachment) changes over time in a vitro eye model were not affected by varying surface tension given constant fluid viscosity. However, membrane changes were proportional to the viscosity of the fluid, given constant surface tension. ConclusionsThe tamponade effect of an intravitreal fluid against retinal detachment may not be related as previously assumed, solely to surface tension, but rather is proportionally related to its viscosity.

Flow visualization of two-phase R-245fa at low mass flux in a plate heat exchanger near the micro-macroscale transition

Two-phase R-245fa flow in a plate heat exchanger (PHE) is experimentally investigated to understand the unique flow regimes found during adiabatic operation at low mass flux. A transparent PHE replica with 3.4 mm hydraulic diameter is 3D-printed for flow visualization using high-speed videography. Observed flow regimes support that the thermofluidic characteristics peculiar to PHE operation are due to the macro-microscale transitional two-phase flow from the coexistence of fluid inertial forces and surface tension effects, corresponding to the operating conditions. Maximum stable bubble diameter is bigger at low mass flux than at high mass flux, and the bubbles can become big enough to be fully confined in the millimeter-scale PHE channel to be deformed or elongated. This represents the main thermo-physical characteristics of two-phase flow in mini- and microchannels, which is different from turbulent mixing flow found at high-mass-flux operation or in channels of conventional macroscale. Flow morphology involving bubble coalescence and breakup dynamics is captured and analyzed in relation to the fluid properties and geometric obstructions provided by the heat exchanger channel. Current observations validate some previously published findings that suggest potential microscale boiling mechanisms in PHEs.

Thermal Marangoni-driven dynamics of spinning liquid films

Spin coating of thin films of viscous liquids on a rotating substrate is a core technological component of semiconductor microchip fabrication. The thinning dynamics is influenced by many physical processes. Specifically temperature gradients affect thin liquid films through their influence on the local fluid surface tension. We show here experimentally and numerically that adding a static temperature gradient has a significant effect on the equilibrium film thickness and height profile reached in spin coating. Our results suggest that thermal gradients can be used to control film height profile dynamics.

Surface and Bulk Stresses Drive Morphological Changes in Fibrous Microtissues

Engineered fibrous tissues consisting of cells encapsulated within collagen gels are widely used three-dimensional in vitro models of morphogenesis and wound healing. Although cell-mediated matrix remodeling that occurs within these scaffolds has been extensively studied, less is known about the mesoscale physical principles governing the dynamics of tissue shape. Here, we show both experimentally and by using computer simulations how surface contraction through the development of surface stresses (analogous to surface tension in fluids) coordinates with bulk contraction to drive shape evolution in constrained three-dimensional microtissues. We used microelectromechanical systems technology to generate arrays of fibrous microtissues and robot-assisted microsurgery to perform local incisions and implantation. We introduce a technique based on phototoxic activation of a small molecule to selectively kill cells in a spatially controlled manner. The model simulations, which reproduced the experimentally observed shape changes after surgical and photochemical operations, indicate that fitting of only bulk and surface contractile moduli is sufficient for the prediction of the equilibrium shape of the microtissues. The computational and experimental methods we have developed provide a general framework to study and predict the morphogenic states of contractile fibrous tissues under external loading at multiple length scales.

A semi-implicit and unconditionally stable approximation of the surface tension in two-phase fluids

We focus on the energy conservation of two-phase fluids, where the change in kinetic energy is balanced by the gravitational potential and the surface energy related to surface tension. We introduce an unconditionally stable approximation in the sense that the total energy does not increase with any time step. An analysis is presented to prove the unconditional stability property of the scheme, and numerical results are given to confirming the analysis.

Rumen CO2 species equilibrium might influence performance and be a factor in the pathogenesis of subacute ruminal acidosis

This experiment was conducted to explore rumen carbon dioxide (CO2) species equilibrium. Three lactating, fistulated cattle were consecutively exposed to three dietary treatments tailored to produce low rumen pH and increase the risk of subacute ruminal acidosis (SARA) by reducing physically effective neutral detergent fiber (Low peNDF), increasing rumen degradable starch (High RDS) or both (Combined). Under these conditions, high and varied rumen concentrations of the CO2 associated to water or dissolved CO2 (dCO2) were found. The results suggest that the activity of dCO2 and bicarbonate (HCO3−) represents an important component of the rumen environment. Rumen CO2 holdup was associated with high dCO2 and HCO3− activity as well as changes in the viscosity and surface tension of the rumen fluid. All dietary treatments produced low rumen pH, <5.5 for >3 h/d, a condition associated with SARA, but clinical SARA was observed only during CO2 holdup. This pilot study highlights the possible role of CO2 holdup and rumen CO2 species in cattle performance and nutritional diseases. In the future, better estimations of CO2 species might help clarify these findings.

Surface tension of ethylene glycol-based nanofluids containing various types of nitrides

This paper focuses on an experimental study of the surface tension of nanofluids based on ethylene glycol with various types of nitride nanoparticles. Samples were prepared using a two-step method with mass content between 1 and 5% of particles. Nanofluids contain three types of nitride nanoparticles: aluminum nitride, silicon nitride and titanium nitride with various particle average sizes. Surface tension of nanofluids was investigated at a constant temperature of 298.15 K with two different techniques: du Noüy ring method and pendant drop method. It is presented that experimental values obtained with both methods are in good agreement with each other. Also, results obtained during this study show that the addition of this type of nanoparticles does not have a significant impact on the surface tension of base fluid for the concentrations and diameters of nitride nanoparticles considered.

2D MoSe2-based nanofluids prepared by liquid phase exfoliation for heat transfer applications in concentrating solar power

Concentrating solar power (CSP) is one of the most promising environmentally-friendly sources of energy for meeting global energy demands. One line of research intended to improve this kind of solar plants involves increasing the efficiency of the heat transfer fluid (HTF) used, one option being the use of nanofluids. Consequently, this study involves a methodology based on liquid phase exfoliation to prepare stable nanofluids based on 2D MoSe2. A surfactant was used to modify the ratio of the components of the fluid's surface tension in order to obtain a stable nanofluid. Five nanofluids were prepared based on MoSe2 nanosheets, Dowtherm A heat transfer fluid and the Triton X-100 surfactant. The stability of the nanofluids was analysed for a month. Lastly, their thermal properties were characterized. The best nanofluid presented improvements of 7% in isobaric specific heat, 4% in diffusivity and 11% in thermal conductivity. Therefore, these nanofluids would appear to provide a good starting point for creating an alternative to the conventional HTFs used in thermosolar plants. The study highlights the importance of optimizing the parameters of the ratio of the surface tension components, the kind of surfactant added and the methodology used to prepare the nanofluid.

Surface tension for pure fluids by molecular thermodynamic model and PHTC equation of state

ABSTRACT In this study, the modified square well model is combined with perturbed-hard-trimer-chain (PHTC) EOS to correlate the surface tension of normal alkanes and refrigerant fluids. The performance of the proposed model has been evaluated by calculating the surface tension of 15 hydrocarbons range within 112–440 K and pressures up to 4.72 × 10−6 MPa. From 251 data points examined the average relative deviation (ARD) of the correlated and calculated densities and surface tension from the experimental ones was found to be 1.63% and 2.46%. Besides, some surface thermodynamic functions such as the surface entropy (SS ) and surface enthalpy (HS ) of studied liquids were also computed via our method. The ARD (in %) were found to be equal to 3.94 and 2.44, respectively. Finally, our method has also been employed to estimate the critical temperature of 15 hydrocarbons with ARD (in %) equal to 7.92. Abbreviations R13: Chlorotrifluoromethane, R12: Dichlorodifluoromethane, R143a: Ethane, 1,1,1-trifluoro

Hybrid GMDH-type neural network to predict fluid surface tension, shear stress, dynamic viscosity & sensitivity analysis based on empirical data of iron(II) oxide nanoparticles in light crude oil mixture

The effects of different parameters including nanoparticles mass fraction and temperature were investigated on rheological behavior and surface tension of iron(II) oxide/light crude oil nanofluid. Iron(II) oxide was dispersed in light crude oil by using ultrasonic processor. TEM images was provided in order to assess the size and morphology of iron(II) oxide nanoparticles. In addition, DLS analysis and Zeta potential test were performed on nanofluid for estimation of nanoparticles size distribution within the basefluid and stability of nanoparticles, respectively. The results of this study showed that for iron(II) oxide/light crude oil nanofluid the value of surface tension reach to its minimum value at the condition where nanoparticles mass fraction was chosen to be 2.0 wt% and temperature was set on 70 °C. These results showed that for iron(II) oxide/light crude oil nanofluid the rheological behavior of nanofluid is non-Newtonian at temperature of 40 °C and the suspension behave as a rheoplexy fluid in which by increasing the shear rate higher dynamic viscosity of nanofluid observed. Furthermore, nanofluid behaves as a Newtonian fluid for the temperature of higher than 55 °C. Finally, a comprehensive correlation was obtained for estimation of relative dynamic viscosity of nanofluid by hybrid group method of data handling (GMDH)-type neural network method. The correlation presented in this study shows that for the relative dynamic viscosity of iron(II) oxide/light crude oil as a function of nanoparticles mass fraction and temperature, the amount of the total deviation of calculated data from experimental values is less than 10%.

Numerical analysis of hydrodynamic fine fragmentation of corium melt drop during fuel-coolant interaction

Hydrodynamic fine fragmentation of melt drops is important in increasing melt-coolant contact area, and thus directly affects heat transfer, oxidation and solidification. The interfacial instabilities incurred by relative flow and density gradient are the dominant factors for melt drops deformation and fragmentation. In this study, we modelled melt drop breakup behavior using a meshless Lagrangian MPS method, and validated the numerical model with the experimental results. Then, the melt fragments amount, size distribution and normalized perimeter were analyzed under different Weber numbers. The results indicate that the melt drop breakup process could be divided into two phases: initial deformation and fragmentation phase governed by flow inertial force and the subsequent fragments coalescence phase under the impact of fluid surface tension. Fragments amount increased in fragmentation phase but decreased in coalescence phase. The amount of fragments with smaller size (d/d0 < 0.04) was significantly larger at high Weber number cases, but the amount of large-scale fragments (d/d0 > 0.05) was equivalent among different weber number cases. The maximum fragments perimeter reached 20 times of the initial melt drop perimeter for case of We = 2618, which was about 3.3 times of that at We = 291.

Effects of thermocapillarity on the dynamics of an exterior coating flow of a self-rewetting fluid

The effects of thermocapillarity on the dynamics of an exterior coating flow of a self-rewetting fluid on a vertical fibre are investigated theoretically. Whereas surface tension decreases linearly with temperature for most fluids, the surface tension of a self-rewetting fluid exhibits a well-defined minimum. We developed an evolution equation for the interface in the framework of the long wave approximation. Linear stability analysis and numerical simulations on the nonlinear evolution have been performed to investigate the effects of thermocapillarity for axisymmetric disturbances. The results showed that thermocapillarity plays different roles in the stability and dynamics depending on the value of difference between the temperature at the interface, Θ¯i, and the temperature corresponding the minimum of the surface tension, Θ0. The results of linear stability analysis showed that the thermocapillarity is destabilizing or stabilizing as Θ¯i-Θ0 is negative or positive. At the nonlinear stage, for Θ¯i-Θ0<0 more pronounced beads-like structures are observed due to the reinforcement between the thermocapillarity and the Rayleigh-Plateau instability. However, for Θ¯i-Θ0>0 the thermocapillarity weakens the tendency of formation of beads due to the Rayleigh-Plateau mechanism.

Effect of self-rewetting fluids on the liquid/vapor phase change in a porous media of two-phase heat transfer devices

This paper presents an experimental study of the phase change phenomenon in a porous medium. The tested working fluids are pure water and butanol aqueous solutions with different concentrations. In contrast to ordinary fluids, the surface tension of self-rewetting fluids exhibits a positive gradient beyond a certain temperature value. The experimental results indicate that the use of self-rewetting fluids (water/butanol) as working fluid significantly improves the performance of the capillary evaporator by decreasing the casing temperature. To explain the heat transfer enhancement mechanism, the phase change phenomenon is visualized for the two working fluids. It is shown that as the applied power increases, the shape of the vapor pocket that developed within the porous wick also increases for pure water until it reaches a stable shape. With respect to self-rewetting fluids, the shape of the vapor pocket decreases with increasing applied power allowing more efficient mass and heat transfers. Wettability, capillary pressure and Marangoni forces are the factors related to surface tension and contact angle that seem to be responsible for this heat transfer improvement for self-rewetting fluids.

Surface tension and intrinsic amyloid fluorescence of serum and cerebrospinal fluid samples in Alzheimer´s disease.

Surface tension of biological fluids can be influenced by changes in oligomerization or aggregation of surfactant peptides or proteins. Amphiphilic peptides of amyloid-β or other amyloidogenic peptides/proteins display properties of surfactants, oligomerization and aggregation increase also their fluorescence intensity compared with native structures. Results/methodology: We estimated surface tension and native/ThioflavinT-based/intrinsic amyloid fluorescence intensity in serum and cerebrospinal fluid samples for their evalution as diagnostic biomarkers for Alzheimer´s disease (AD). Our results indicate that values of surface tension are not a suitable biomarker for AD. However, the ratio of ThioflavinT-based fluorescence to intrinsic amyloid fluorescence in cerebrospinal fluid appears to be an acceptable supportive diagnostic biomarker for AD (its sensitivity was 61.1%, and the specificity 70.8% when compared with aged controls).

Research on Heat Transfer Performance of the Open-Loop Micro Pulsating Heat Pipe with Self-Rewetting Fluids

As technology becomes increasingly miniaturized, extremely localized heat dissipation leads to the challenge of how to keep these devices from overheating. A pulsating heat pipe (PHP) is an excellent cooling device based on the phase change of a working fluid. Experiments are performed to investigate the thermal performances of a Micro Pulsating Heat Pipe (MPHP) using different working fluids. The MPHP consists of 20 parallel channels made of a copper capillary tube with an internal diameter of 0.8 mm. The MPHP is filled with ethanol, deionized water and an aqueous solution of 1-butanol as working fluids, with different filling ratios (FRs) in the range 40–70 vol.%. The 1-butanol aqueous solution is known as a self-rewetting fluid, i.e. a dilute aqueous solution of alcohols with a number of carbon atoms higher than four (such as 1-butanol and pentanol). The surface tension of self-rewetting fluids decreases gradually with an increase in temperature, reaching a minimum around 60 °C, and subsequently increases gradually at higher temperatures. Therefore, at relatively high temperature self-rewetting fluids flow towards the regions at higher temperature due to the Marangoni effect. This flow should improve the boiling phenomenon, which is very important in the heat transfer mechanism of the MPHP. The experimental results indicate that, in the case of self-rewetting fluid, the stable oscillating motion in the MPHP arises at the heat load regime lower than that with water. In addition, the effective thermal conductivity of the MPHP with the highest concentration of self-rewetting fluid is higher than that with other fluids in the high heat load regime.

Effect of surface tension, viscosity, pore geometry and pore contact angle on effective pore throat

Through experimental measurement and theoretical calculation, we have investigated the effect of surface tension, liquid viscosity and the capillary geometry (capillary gradient and tip diameter) on the effective pore throat, and the impact of the effective pore throat on pore resistance to two-phase interfaces formed from fluids with different viscosities and surface tensions. When a two-phase interface flows in channels with varied pore diameter, capillary force is insignificant in the section of the channel with an inner pore diameter greater than the effective pore throat, and the pressure drops in this section depend on capillary tip diameter, rather than the surface tension. Capillary force takes significant effect on the interface only when the pore diameter in a tapered capillary is smaller than the effective pore throat. Effective pore throat depends on fluid surface tension and the capillary geometry, but not on liquid viscosity. The higher the fluid surface tension, the larger the diameter of the effective pore throat. A channel with a large tip diameter or gradient will give a large effective pore throat diameter. Fluid viscosity only affects the magnitude of the resistant pressure drops of fluid flows in constricted capillaries, but does not affect the effective pore throat diameter. The effective pore throat and the pressure profile measured in this study can be explained by the pore contact angle, but cannot be explained by the contact angle on a flat surface of the same materials.

Effects of EOR chemicals and superficial gas velocity on bubble size and gas holdup of a bubble column

Chemical Enhanced Oil Recovery (EOR) can boost oil extraction in offshore operations, however one of the main concerns regarding its application is how the efficiency of flotation units for treating produced water is affected. The present work thus focuses on investigating the impact of EOR chemicals on the physical properties of EOR effluents and how this can affect flotation performance parameters such as bubble size and gas holdup. Design of experiments has been used to assess the influence of polymer, surfactant and sodium chloride concentrations on bubble size and gas holdup of a laboratorial bubble column. The influence of superficial gas velocity has also been assessed together with chemicals concentrations, yet at low levels in order to avoid clusters, swarms and foam. The characterization of the synthetic effluent containing polymer, surfactant and sodium chloride has indicated that the fluid behaves as a non-Newtonian fluid, what makes separation processes in flotation cells challenging. Results showed that polymer concentration of 2000 mg/L can lead to significant increases in fluid viscosity, promote a growth of more than 40% in bubble size and only increases gas holdup when surfactant is present at high concentration. Therefore, polymers are expected to be detrimental to produced water treatment. Surfactants decrease both fluid surface tension and bubble size, increasing gas holdup. For the range studied, superficial gas velocity favors gas holdup and sodium chloride concentration seems to weakly influence bubble size and gas holdup. This work highlights the fact that changes in physical properties of produced water do modify bubble size distribution and gas holdup and this must therefore be taken into account when flotation-like systems are designed to deal with EOR effluents.