Influence Of Liquid Properties Research Articles

Influence of Liquid Properties and Design Parameters on Mass Transfer in Gas–Liquid Flow through a Miniaturized Reactor

This paper presents the results of oxygen absorption from air in various liquid media within a rectangular milli-channel equipped with exchangeable staggered herringbone-like mixing inserts. We have determined the volumetric liquid-side mass transfer coefficient kLa using three different liquid substances (water, ethanol, and polypropylene glycol) in a range of superficial liquid velocities of 0.047–0.210 m s–1 and superficial gas velocities of 0.012–0.210 m s–1. From this data, we derived an empirical kLa-correlation. Overall, kLa values ranging from 0.036–0.515 s–1 were obtained, and the correlation predicts kLa with a coefficient of determination of R2 = 0.93. We have also examined the influences of changing the static mixer design parameters on the mass transfer performance and evaluated the mixer efficiency by taking the power consumption into account. Depending on liquid properties, the right choice of a mixer design leads to a significant improvement in mass transfer and/or efficiency.

Hydrodynamics and gas-liquid mass transfer in an oscillatory flow reactor: Influence of liquid properties

Liquid properties, such as, surface tension and viscosity are important parameters as they control gas-liquid mass transfer in bioprocesses. An oscillatory flow reactor provided with smooth periodic constrictions (OFR-SPC) was considered to evaluate its potential for mass transfer performance in non-pure gas-liquid systems. The effect of surface tension and viscosity on the volumetric (kLa) and liquid-side mass transfer coefficients (kL), interfacial area, (a), gas holdup (εG) and bubbles’ dynamics were investigated under different operational conditions (oscillation amplitude (x0) and frequency (f) and superficial gas velocity (ug)). Two liquid phases, ethanol and sucrose aqueous solutions covering a range of surface tension and viscosity values were used. For the bubble size distribution (BSD) measurements an image analysis technique was used. A Design of Experiment (DoE) methodology was implemented in this work to establish the relation of x0, f, ug, surface tension and viscosity with kLa. According to the results, changes in the liquid properties and operational conditions showed marked effects on bubble’s size and mass transfer. However, surface tension and viscosity had no significant influence on εG, contrary to the reported for common contactors, where εG increased in the presence of ethanol and decreased at moderate/high viscosities. Moreover, it was found that increasing the oscillatory movement notably improved kL, and kLa (2–6-fold), either in ethanol or sucrose solutions, compared to common reactors, even with moderate power consumption (∼105 W m−3). This improvement resulted from the bubbles’ breakage, which originates bubbles with small and approximately the same size (homogeneous regime) enhancing a, instead, lower oscillations resulted in large bubbles (heterogeneous regime). The results demonstrate that the OFR-SPC can ensure outstanding mass transfer rates, with potential and feasibility for use in gas-liquid bioprocesses, where mass transfer and liquid properties are important.

The influence of liquid properties on flow structure, bubble dynamics and mass transfer in a laboratory bubble column: Experimental analysis versus numerical modelling and computation

Based on detailed experiments with optical shadowgraphy in a bubble column, the influence of liquid viscosity on bubble behaviour was numerically computed with the Euler/Lagrange approach including mass transfer. Fluid flow and sub-grid-scale-turbulence (SGS) was obtained by Large Eddy Simulation (LES) including a k-transport equation. Bubbles were tracked by a point-mass approach, considering all relevant forces. For the lift coefficient a composite correlation was applied considering viscosity. An experimentally-based bubble dynamics model was considered, randomly generating eccentricity, motion angle and Sherwood numbers. SGS turbulence acting on bubble motion was modelled through a Langevin-type approach. Two-way coupling was considered in momentum and SGS turbulence. The bubble column (diameter 140 mm; height 710 mm) contained either pure water or water-glycerol mixtures. Bubbles were injected through 4 needles yielding a distribution with a mean diameter 3.6 mm. The numerical results demonstrated the enormous effect of accounting for bubble dynamics and the possibility to adapt this model for different liquid properties, although not yet generalised. Overall, good agreement between simulations and measurements was found for non-reactive and reactive cases. This concerns local properties, spatial distributions of the velocities of both phases and the temporal evolution of the pH-value when modelling bubble dynamics properly.

Influence of Liquid Properties on Gas-Liquid Flow Regimes and Pressure Drop in a Flat Microchannel

Influence of Liquid Properties on Gas-Liquid Flow Regimes and Pressure Drop in a Flat Microchannel

Influence of liquid properties on the oblique splashing threshold of drops

This report investigates how different splashing mechanisms affect the oblique splash threshold of drops impacting a dry solid surface. The splashing behaviors of water, ethanol, and a water/ethylene glycol solution are observed over a wide range of drop diameters (0.7 mm < D < 2.2 mm) and Weber numbers (10 < We < 1040), and several published models are tested in order to predict the thresholds between deposition, one-sided splashing, and two-sided splashing. We found that the splash threshold of liquids that exhibit the corona splashing mechanism can be readily predicted by existing models. However, for liquids such as water that exhibit prompt splashing, the oblique splash threshold is not successfully predicted by any presently established correlation. Hence, our findings identify a critical knowledge gap in the drop impact field, since the behavior of water is of fundamental importance to countless engineering problems. Finally, combining our own results with others reported in the literature, we address some contradictory reports about the influence of liquid viscosity on the splash threshold and demonstrate that the presence or lack of thin-sheet in different experiments could explain the contradictions present in the literature.

Experimental study of single Taylor bubbles rising in vertical and slightly deviated circular tubes

This paper reports an experimental study of single Taylor bubbles rising in stagnant water-glycerin mixtures inside slightly deviated cylindrical tubes. The inclination angles studied were 0°, 2.5°, 5°, 7.5°, 10° and 15° from the vertical. The rise bubble velocity and the shape of the bubbles at two vertical orthogonal planes that intersect at the tube axis were measured by using a pulse-echo ultrasonic technique. Thus, the liquid films draining at the top, bottom and lateral sides of the bubbles were observed. The experimental results indicated that for all liquid mixtures studied, the bubble velocity increased when the inclination angle was increased, and that the bubble velocity was independent of the bubble length. The influence of liquid properties and of tube diameter on the bubble movement and shape were evaluated for deviated angles ranging from 0° to 15°. Different correlations to predict the drift velocity of Taylor bubbles rising in inclined tubes were tested for this particular range of inclination.

High-frequency vibration analysis of LiTaO3 piezoelectric plates excited by lateral electric fields produced by surface electrodes under viscous liquid loadings for sensing

In this work, the coupled thickness-shear and flexural vibrations of the LiTaO3 piezoelectric plates excited by lateral electric fields produced by surface electrodes under viscous liquid loadings are modeled and analyzed based on Mindlin’s plate theory. The influences of liquid properties on the admittance characteristics and frequency shifts of the piezoelectric bulk acoustic wave devices operate in the lateral field excitation (LFE) mode are examined. In addition, the effects of the structure parameters, such as the electrode gap width, electrode/plate mass ratio and the electrode width, on the frequency sensitivity are investigated. It is shown that with the increasing electrode/plate mass ratio R, the sensitivities of the device on liquid viscosity and density increase first and then decrease, there is a maximal sensitivity when R is with a certain value. The varying trends of the frequency shifts with various liquid properties and sensitivities with various structural parameters are verified by the FEM simulations. The results are crucial to obtain good vibration characteristics and sensitivities for liquid-phase LFE piezoelectric sensors by using LiTaO3 piezoelectric crystals.

A numerical study on the influence of liquid properties on gas-focused micro-jets

A numerical study on the influence of liquid properties on gas-focused micro-jets

Influence of Liquid Properties on Energy Conversion During Crown Evolution Following Drop Impact Upon Films

Abstract The energy conversion is proposed to analyze the effects of liquid properties on the formation of an ejecta sheet, prompt splashing, and crown evolution. The incompressible laminar Navier–Stokes equations coupled with the volume-of-fluid (VOF) model are solved numerically in an axisymmetric frame to simulate the impact process. Based on the energy conversion curves and liquid–gas interface shapes, the Weber number is shown to be the main dimensionless quantity controlling the impact process, especially with regard to crown evolution. However, the Reynolds number does have some influence on the drop impact process, especially during the stage of ejecta sheet formation and prompt splashing. By studying energy conversion during the impact process, the crown evolution is shown to be accelerated significantly with decreasing Weber number, but is hardly affected by the Reynolds number. A linear relation is found between the time to the moment of crown stabilization (when the crown height reaches its maximum value) and the square root of the Weber number. The relationship between the Weber number and the energy distribution at the moment of crown stabilization is also studied.

A Low-power Liquid-fuelled Burner Using a Novel Atomization Concept

ABSTRACTThe design of and experimental results for a low-power heating oil burner, operating between 1.25 and 5.1 kW with exhaust gas emissions within the normative regulations for domestic usage, are presented. In contrast to common domestic heating oil burners, the atomization and combustion sections are spatially separated to allow the implementation of a novel atomization concept for low-power liquid-fuelled burners proposed in a previous study. The main working principle for spray generation is the secondary atomization of a droplet chain impinging on a pin downstream. Through pulse-width modulation (PWM) of the droplet generator, modulation of the spray flowrate over a wide range with constant spray quality was achieved. Phase-Doppler anemometry measurements under non-reacting conditions were performed to obtain the droplet size distribution of the spray. Three model liquids were used to determine the influence of liquid properties on the droplet size distribution. The Sauter mean diameter (SMD) values obtained for all liquids and operation parameters studied are in the range of 10% of the primary droplet diameter, which is 30 µm for the setup in this study.

Bubble formation from an orifice in liquid cross-flow

The formation of gas bubbles by submerged orifices in a cross-flowing liquid is encountered in many industrial applications. It is therefore important to understand the dynamics of bubble formation and to accurately predict the bubble detachment characteristics under such situations. In the present work, the process is numerically studied using the Local Front Reconstruction Method (LFRM), a Front Tracking Direct Numerical Simulation method that enables the simulation of interface merging and breakup. Experiments of bubble formation subjected to cross-flow induced shear are also performed to provide data for the validation of the numerical simulations. The predictions of the bubble shape and the detached bubble volume obtained by the numerical model show good agreement with the experimental results. The validated numerical model is then used to study the effects of volumetric gas flow rate and fluid physical properties on the bubble detachment characteristics under various shear rates in the quasi-static bubble growth regime. The simulation results show that the shear flow advances the bubble detachment and decreases the bubble size. Consequently, the bubble formation frequency and the detached bubble size can be controlled by exerting different shear rates. At higher shear rates, the simulated bubbles are highly deformed due to the drag force created by the tangential liquid flow and the influence of liquid properties on the bubble detachment characteristics becomes less significant.

Influence of liquid properties on atomization characteristics of flow-blurring injector at ultra-low flow rates

Atomization and efficient evaporation at extremely small flow rates is an additional challenge for liquid fueled small-scale combustor and burner applications. In the present study, experiments are conducted to investigate the effects of liquid properties on atomization of flow-blurring atomizer at ultra-low liquid flow rate (2.78–41.7 μL/s). Shadowgraphy, backlight imaging technique and laser based spray visualization methodology were employed for atomization characterization. Formation of three different atomization regimes namely bubble bursting, weak spray and fully developed spray was observed with a gradual increase in airflow rate (8.33–83.3 mL/s). Prompt mode of atomization in weak spray regime produces coarse droplets, while a sudden reduction in droplet size is observed in fully developed spray regime. Fine atomization in fully developed spray regime is attributed to flow-blurring effect due to air recirculation and thereby formation of highly turbulent two-phase flow inside the injector. This investigation reports that the criterion proposed in literature is not sufficient to achieve enhanced atomization through flow-blurring phenomenon. Experiments demonstrate that viscosity has marginal effect on atomization, however, surface tension dominates the atomization characteristics in a flow-blurring atomizer. Meanwhile, Weber number appears an appropriate parameter to predict the atomization regime transition.

A numerical study on the influence of liquid properties on gas-focused micro-jets

In this paper we present a numerical study on the influence of liquid properties on gas-focused micro-jets, such as used for sample delivery in serial femtosecond crystallography. The study is based on solving mixture formulation of Newtonian, compressible two-phase model with the finite volume method and algebraic volume of fluid for treatment of the phase-interface. The density, viscosity and surface tension of the focused fluid span around the material properties of pure water in the range of ±30%, thus representing a large range of possible sample delivery fluids. Fixed liquid and helium gas flow rates are used for jet focusing and the length, diameter, velocity and temperature of the jet are assessed as a function of material properties of the liquid. A thicker and slower jet is observed in case of increased density and surface tension of the focused fluid, while change in liquid viscosity has no effect on flow characteristics.

Effect of liquid properties on laser ablation of aluminum and titanium alloys

In order to study the effect of liquid properties on laser ablation in liquids, aluminum 5A06 and titanium TB5 targets were irradiated by single-pulse infrared laser in isopropanol, distilled water, glycerin and as a comparison, in air, respectively. Craters induced by laser ablation were characterized using scanning electron and white-light interferometric microscopies. The results show that for liquid-mediated ablation, craters with porous surface structures were formed in aluminum target through phase explosion, while no micro-cavities were formed in titanium target owing to high critical temperature of titanium. In addition, ablation rates of aluminum and titanium targets vary with types of ambient media in accordance with such sequence: air<isopropanol<water<glycerin. Further, the influence of liquid properties on material-removal mechanisms for laser ablation in liquid is discussed. It is concluded that the density, thermal conductivity and acoustical impedance of liquid play a dominant role in laser ablation efficiency.

Influence of liquid properties on the performance of S0-mode Lamb wave sensors: A theoretical analysis

Sensors based on thin film electroacoustic (TEA) devices have emerged as a promising alternative to quartz crystal microbalance and surface acoustic wave devices, in view of sensibility, miniaturization and easy integration. TEA devices include quasi-shear film bulk acoustic resonators (QS-FBAR) and S0 mode Lamb wave resonators (S0-LWR) based on AlN films. Despite the work done on the application of TEA devices as in-liquid biological and chemical sensors, a theoretical framework for S0-LWRs properly describing their sensing mechanisms is still needed. Here we validate a finite element analysis model on QS-FBARs and study the sensing mechanisms of S0-LWRs in liquid media. We show that S0-LWRs can sense changes in the dielectric permittivity of the liquid and demonstrate different sensitivities to viscosity and density. A complementary assessment of the S0-LWRs losses, dependent in a non-specific manner on the square root of the density viscosity product, provides the ability to discriminate density from viscosity changes on the entire device surface. Finally, with an S0-LWR optimization study we show that resolution improves with the decrease of the membrane thickness; however, a trade-off between sensitivity, quality factor and membrane fragility has to be considered.

Mathematical Model of Foam Flowing Characteristics by Snap-Off Mechanisms at Steady State in Porous Media

Flow characteristics and regeneration processes of foams were influenced by lamella properties and pore-throat structure in porous media. In this article, porous media was simplified as a bunch of constricted capillary tubes according to grain size, pore-throat radius, and immobile water saturation in porous media. Based on an analysis of forces upon liquid lamella, a mathematical model of foam migration and regeneration at steady state was established according to the mass conservation law and the momentum conservation law in porous media. The model could be used to calculate some important parameters in porous media, such as pressure distribution, shearing stress, lamella morphology, liquid-layer thickness, regeneration bubble size, etc. A series of flow experiments were carried out to investigate the influence of liquid properties and pore-throat structure on flow characteristics and resistance behavior of foams in porous media. The experimental results showed that pressure distribution monotonously decreased along porous media. The theoretical results were in good agreement with the experimental results. Foam structure, that is, foam quality was an important factor upon foam resistance behavior in porous media. The strongest resistance ability of foams was achieved at foam quality of 85% in porous media.

Numerical Model of Metal Transfer Using an Electrically Conductive Liquid

In order to understand the mechanism of the metal transfer process, the numerical model, which enables to calculate the time-change of liquid transfer process, was constructed. By using the model, we numerically investigated the influence of liquid properties and electro-magnetic force on the modes of liquid transfer. It is shown that liquid transfer modes depend on the pressure balance at the tip of drop. When the dynamic pressure induced by liquid flow is lower than capillary pressure due to surface tension at the tip of liquid drop, globular transfer occurs. In contrast, when the dynamic pressure of liquid flow is higher, spray transfer occurs. In the case that the electrical current flows in the liquid, electro-magnetic force significantly influences on the transfer mode and the drop detachment. Calculated results using physical properties of molten mild steel show that electro-magnetic pinch force induced by higher current than 250 A changes the transfer mode from globular to spray, for liquid flow-out from the nozzle of 1.2 mm in diameter. Whereas in real GMAW with pure argon gas shielding the transfer mode changes at around 230 A. The behaviour of drop detachment is varied by both spatial distribution and time-change of the electro-magnetic force.

Tomography measurements of gas holdup in rotating foam reactors with Newtonian, non-Newtonian and foaming liquids

Rotating solid foam reactors have already proven to show high mass transfer rates and to be a potential alternative to slurry reactors. The rotation of a foam block stirrer results in a high mass transfer and in the development of different reactor sections showing specific hydrodynamics and gas holdup distributions. In order to optimize the reactor system the hydrodynamics in a lab scale reactor are studied using γ -ray tomography, a powerful method to measure the gas holdup in three-phase reactors. The influence of liquid properties, such as viscosity and surface tension, and the rotational speed on the gas/liquid distribution in the different reactor sections is investigated. Especially the viscosity has a strong effect on the entrapment of gas bubbles in the foam block structure, while the surface tension is the dominant parameter in the outer reactor section. The influence of these parameters on the inset of foaming and the collapse of the gas/liquid dispersion is investigated. Conclusions on the mass transfer performance are drawn and recommendations for further optimizations of the reactor design and the operational conditions depending on the liquid properties are developed.

Using a circular groove surrounded inlet to generate monodisperse droplets inside a microfluidic chip in a gravity-driven manner

A new approach to generate uniform-sized nanoliter droplets inside a simple microfluidic chip was developed by using a circular groove to break off the liquid infused from the surrounded inlet. We characterized the droplet formation by using circular grooves with different diameters ranging from 1.2 to 2.4 mm. Monodisperse droplets with a very narrow size distribution (RSD < 0.56%, n = 70 droplets) can be reliably produced and the volume of droplets varied between 74 and 576 nl by using different circular grooves. Influences of liquid properties on droplet formation were also investigated, including surface tension, viscosity and density. Moreover, the transport of droplets and reliable coalescing of two neighboring droplets were realized by using Y-shaped guiding lanes with two different designs. Controlling the velocities of each droplet based on their different physical properties or slowing down the first droplet relying on a pinched segment of the guiding lane has been developed. These methods have been used to control the contact conditions of two reagents coalescing in a ‘head-to-tail’ mode.

Influence of liquid properties on flow regime and backmixing in a special bubble column

An experiment aimed to link the extent of axial mixing in a special configuration bubble column reactor with different liquid properties (water, 10% K 2CO 3 solution, 20% K 2CO 3 solution, paraffine). The experimental results proved that, increase of liquid viscosity will delay the mean residence time and weaken gas axial backmixing. Increased surface tension leads to lower flow regime transition point and higher overall gas holdup. Surface tension is the dominant factor to influence of gas axial backmixing degree. A simple RTD model for homogeneous–heterogeneous regime is developed in the column of 0.1 m diameter and the corresponding correlation of gas axial dispersion coefficients is D ag = 0.8 u g 1.89 ( ρ L / ρ w ) 3.22 ( ( 1 − ε g ) 4 / ε g ) . The model is verified by experiments with air/water/paraffine system. Good agreement is found. As a byproduct, a non-empirical formula for gas holdup results, ɛ g/(1− ɛ g) 4 = 0.579 ( u g μ/ σ) 0.918 ( μ 4 g/ ρ L σ 3) −0.252. But both correlations cannot be available for K 2CO 3 solution with addition of small quantities of surface tension in pure liquid.