Effects Of Liquid Physical Properties Research Articles

Component Effects in Binary Droplet Impact Behaviors on the Heated Plate: Comparison Study of Ethanol/Propanol and Ethanol/Water Droplets and Observation of Novel Bubble Shrinkage Phenomenon

This work aims to investigate the effect of liquid physical properties on the behavior of binary droplets impact on the heated smooth aluminum alloy plate with a high-speed imaging system. Two groups of mixed solutions with similar boiling point differences are selected as the working liquid, in which the low-boiling-point components are both ethanol and the high-boiling point components are propanol and water, respectively. Compared to the ethanol/propanol binary droplets, the experimental results show that the ethanol/water binary droplets have diverse impact phenomena and significantly broad transition boiling regimes, as well as the reduced droplet residence time and increased Leidenfrost temperature point. With the decreasing ethanol content in ethanol/water binary droplets, these effects become more prominent. For secondary atomization, the ethanol/water binary droplet undergoes parent droplet breakup into fragment droplets with larger diameters (Ds > 0.3 mm). Both binary droplets produce satellite droplets with small diameters (Ds < 0.3 mm) by puffing and ejection. In terms of the ethanol/propanol binary droplet impact, the probability of puffing is higher and the satellite droplet diameters are small. In the ethanol/water binary droplet impact, the probability of ejection is higher and the satellite droplet diameter distribution is wider. When an ethanol/water binary droplet of 25 vol.% ethanol content impacts the heated wall at Ts = 120 °C, a novel large bubble shrinkage phenomenon occurs at the late stage of droplet evaporation. This phenomenon is proposed to be relevant to the increasing surface tension and saturation temperature with decreasing ethanol content, as well as the decreasing ambient temperature above the top surface of the bubble.

Cavitation-induced shock wave behaviour in different liquids

This paper follows our earlier work where a strong high frequency pressure peak has been observed as a consequence of the formation of shock waves due to the collapse of cavitation bubbles in water, excited by an ultrasonic source at 24 kHz. We study here the effects of liquid physical properties on the shock wave characteristics by replacing water as the medium successively with ethanol, glycerol and finally a 1:1 ethanol–water solution. The pressure frequency spectra obtained in our experiments (from more than 1.5 million cavitation collapsing events) show that the expected prominent shockwave pressure peak was barely detected for ethanol and glycerol, particularly at low input powers, but was consistently observed for the 1:1 ethanol–water solution as well as in water, with a slight shift in peak frequency for the solution. We also report two distinct features of shock waves in raising the frequency peak at MHz (inherent) and contributing to the raising of sub-harmonics (periodic). Empirically constructed acoustic pressure maps revealed significantly higher overall pressure amplitudes for the ethanol–water solution than for other liquids. Furthermore, a qualitative analysis revealed that mist-like patterns are developed in ethanol–water solution leading to higher pressures.

A modeling study of different kinds of sessile droplets on the horizontal surface with surface wettability and gravity effects considered

Droplet phase change is important for energy storage and saving technology. The initial profile of the droplet is extremely important for its vaporization or solidification on a horizontal surface. To understand the effect of liquid physical properties on droplet profile, a theoretical model was developed in this study, based on the Young-Laplace equation with gravity effect specially considered. After the model was experimentally validated by comparing the geometric shape of water droplets, it was further used for predicting droplet shapes of other materials, and thus analyzing the influence of different physical properties, such as temperature, pressure, surface wettability, etc. Results show that the results of this model agree well with the experimental data. The maximum and average deviations are less than 4.5% and 1.5%, respectively. For all kinds of droplets on the fixed surfaces, when the temperature increases, the droplet contact radius increases and height decreases. The droplets of nitrogen and carbon dioxide are more sensitive to temperature than ethanol and ethylene glycol droplets. For 20 μL droplets on the surface of contact angle 150°, when the temperature changes from 273.15 K to 293.15 K, the droplet contact radiuses increase by 30.6% for carbon dioxide, 1.2% for ethanol and 0.67% for ethylene glycol, and the droplet heights decrease by 42.9%, 2.5%, 1.1%, respectively. Results of this study are meaningful for predicting the phase change process of droplets on the horizontal surface by controlling their initial profiles.

Nonlinear dynamics and manipulation of dripping in capillary flow focusing

In this study, we carried out experimental and numerical investigations on the dripping dynamics in axisymmetric capillary flow focusing. For the direct numerical simulations, we solved the Navier-Stokes equations coupled with a diffuse interface method. For the experiments, we observed both periodic and non-periodic dripping modes at different focused and focusing liquid flow rates. The non-periodic dripping that results in polydispersed droplets downstream the orifice can be attributed to the nonlinear dynamics of the flow; thus, we constructed numerical plots of the streamlines and temporal evolutions of the focused liquid cone in different modes. We identified a phase diagram of the dripping regimes in the plane of mainly dimensionless parameters, which led us to further investigate the effects of liquid physical properties, such as viscosity and interface tension, on the mode transition. For suppression of the nonlinear dynamics, we proposed a geometrical optimization that imports a guiding rod positioning along the axis of the capillary tube. Here, we conducted a numerical analysis on the manipulation of the dripping process, as well as scaling analysis on the appearance of the nonlinear dripping. We expect this study to provide an insight into the underlying physical mechanisms of dripping in flow focusing, which are advantageous in the generation of monodispersed microdroplets for various applications.

Numerical Models for Viscoelastic Liquid Atomization Spray

Atomization spray of non-Newtonian liquid plays a pivotal role in various engineering applications, especially for the energy utilization. To operate spray systems efficiently and well understand the effects of liquid rheological properties on the whole spray process, a comprehensive model using Euler-Lagrangian approaches was established to simulate the evolution of the atomization spray for viscoelastic liquid. Based on the Oldroyd model, the viscoelastic linear dispersion relation was introduced into the primary atomization; an extended viscoelastic version of Taylor analogy breakup (TAB) model was proposed; and the coalescence criteria was modified by rheological parameters, such as the relaxation time, the retardation time and the zero shear viscosity. The predicted results are validated with experimental data varying air-liquid mass flow ratio (ALR). Then, numerical calculations are conducted to investigate the characteristics of viscoelastic liquid atomization process. Results showed that the evolutionary trend of droplet mean diameter, Weber number and Ohnesorge number of viscoelastic liquids along with axial direction were qualitatively similar to that of Newtonian liquid. However, the mean size of polymer solution increased more gently than that of water at the downstream of the spray, which was beneficial to stable control of the desirable size in the applications. As concerned the effects of liquid physical properties, the surface tension played an important role in the primary atomization, which indicated the benefit of selecting the solvents with lower surface tension for finer atomization effects, while, for the evolution of atomization spray, larger relaxation time and zero shear viscosity increased droplet Sauter mean diameter (SMD) significantly. The zero shear viscosity was effective throughout the jet region, while the effect of relaxation time became weaken at the downstream of the spray field.

Single phase flow characteristics of FC-72 and ethanol in high aspect ratio rectangular mini- and micro-channels

Single phase flow friction factor of FC-72 and ethanol in mini-and micro-channels are experimentally investigated in the present study. High aspect ratio rectangular channels are selected, the hydraulic diameters of which are 571 µm, 762 µm and 1454 µm, and the aspect ratios are 20, 20 and 10 respectively. Degassed ethanol and FC-72 are used as working fluids. All the friction factors acquired in the 571 µm and 762 µm channels agree with the conventional friction theory within ±20%–±25%. In the 1454 µm channel, however, deviations from the conventional theory occur and a modified empirical correlation of friction factor as a function of Reynolds number is proposed. Early transition from laminar to transitional flow is captured. Besides, effects of liquid physical properties are discussed. Lower viscosity and higher liquid density are responsible for the higher friction factor of FC-72. The influence of liquid properties weakens as the Reynolds number increases.

New froth behaviour observations and comparison of experimental sieve tray entrainment data with existing correlations

A thorough understanding of the hydrodynamics in tray columns is required to optimise column and tray design for specific operating capacities and conditions. Liquid transported by the rising gas to the tray above, defined as entrainment, is one way of measuring the tray column capacity limit. Entrainment correlations available in the literature have been developed with predominantly air/water data, because of the limited availability of non-air/water data. In this work an experimental setup was constructed to measure entrainment, tray pressure drop and weeping for various gas and liquid systems. The experimental entrainment data for three systems, namely air/water, air/ethylene glycol and air/silicone oil, is compared to existing correlations. The effect of liquid physical properties on entrainment under flow factors ranging from 1.6kg0.5/(m0.5s), for a 415mm tray spacing to 4.0kg0.5/(m0.5s) for a 615mm tray spacing within a liquid flow range of 2.9–112m3/(hm) was observed. The experimental results showed a somewhat complex dependency of entrainment on liquid physical properties. At gas flow factors of 2.2kg0.5/(m0.5s) for the 415mm tray spacing, entrainment reached a maximum in the froth regime and then decreased with increasing liquid rates. Notably, the liquid viscosity – not included in previously developed correlations – significantly influences the entrainment behaviour. Existing entrainment correlations agree better with the air/water data than with the air/ethylene glycol or air/silicone oil data.

Effect of viscosities on structure and instability of sprays from a swirl atomizer

The breakup phenomena of liquid spray sheets and jets are encountered in daily life as well as in various industrial applications. The onset of instability has a direct impact on the downstream spray development, and thus it is necessary to investigate the effect of liquid physical properties on this instability. The present paper focuses on the effects of liquid viscosity on the spray characteristics and instability during the transient operation of a swirl atomizer in a trigger sprayer via experiments. In the experiments, water–glycerol mixtures were used to simulate fluids with a wide range of viscosities. The transient displacement of the dispensing piston was measured. A high-speed digital video camera was used to visualize the near-nozzle spray structure. The digital images of the sprays were further processed in order to analyze the spray angle and the surface waves on the spray cone. By using the spatiotemporal diagrams, the surface wave temporal frequency was also analyzed for fluids with different viscosities. From the experimental results, it is seen that the fluid viscosity plays a critical role in controlling the liquid sheet breakup and atomization. More viscous fluids result in smaller average spray cone angles. The spray cone developed very fast during the early stage for less viscous fluids, while for the most viscous liquid, a very small cone angle with little breakup and atomization was observed. As the liquid viscosity increases, the cone collapses earlier with larger droplets in the end stage. In addition to the spray cone angles, the surface wave temporal frequency was also calculated from the recorded images. The results show that the surface wave temporal frequency depends on the dispensing time and the fluid viscosity, and is almost independent of the location in the near nozzle liquid cone. The results also indicate that the surface wave temporal frequency decreases with time.

207 気流による液泡分裂に関する液体物性の効果(流体工学(乱流・混合・拡散))

To reduce the greenhouse gases, bio fuels are developing as an alternative fuel instead of fossil fuels. As carbon dioxide and so on are the causes of global warming, low carbon combustion is one of the crucial issues to conserve the global environment. Liquid atomization technology should contribute to the field of fuel combustion and others, such as the cooling of exhausted warm water at geothermal power plants and so on. A liquid bubble contains gas in a liquid drop. So, it has a larger surface area than a liquid drop of the same mass. It could have the advantage for fuel combustion and cooling of exhausted warm water. In order to apply it in these areas, effects of liquid physical properties for liquid bubble breakup due to airstreams were investigated. Experiments were conducted using a horizontal air-suction-type wind tunnel. Liquid and air were fed to a nozzle, and uniformly sized liquid bubbles were produced. The liquids used in the experiment were water and several kinds of ethanol in water solutions. The breakup processes and characteristic breakup patterns were precisely observed using a digital high-speed video camera. The displacement of liquid bubbles in the airstream was measured in the entire process. The deformation rate was also measured. The author has been studying on the deformation and breakup of liquid bubbles and liquid drop, such as breakup [1-3], displacement [4, 5], deformation [6, 7]. The liquid bubble has many important scientific applications such as the cooling of warm exhausted water, fuel combustion [8], and a compound liquid jet [9]. It is also useful for the study of structure of collapsing liquid drops and liquid bubbles by shock waves. By comparing a structure of collapsing liquid bubbles with liquid drops, the collapsing mechanism was revealed in a high-speed airstream behind a shock wave [10-12]. If liquid bubbles are used to combust bio-ethanol fuel, biodiesel fuel (BDF), and glycerin which is a by-product of BDF, more effective combustion could be obtained than in the case of liquid droplets. The experiment was conducted to investigate the effects of liquid physical properties for liquid bubbles breakup due to airstreams. The breakup pattern is impacted due to surface tension, and viscosity of liquid. Several characteristic deformation and breakup patterns are observed. Some of them are never observed for liquid drops. The breakup processes and characteristic breakup patterns are precisely observed. The displacement of liquid bubbles in the airstream is measured in the entire process. The deformation rate, that is, a time variation of liquid bubble diameters is also measured. These data are obtained by analyzing the breakup processes recorded by the digital high-speed video camera.

Effects of Liquid Physical Properties on the Forces Acting on a Pipe Bend in Gas–Liquid Slug Flow

The effects of liquid physical properties on the hydrodynamic forces acting on pipe bends in two-phase slug flow were investigated. The two properties of interest were liquid viscosity and liquid surface tension although density was also changed. Discussion will be centred around the effects of the liquid viscosity and liquid surface tension on the maximum forces acting on a pipe bend, which is important for the design of the bend support system. Comparison between the experimental results and predictions from a one-dimensional model, the piston flow model, proposed by Tay and Thorpe will be presented.

Experimental studies of liquid flow maldistribution in a random packed column

AbstractLiquid flow distribution has been a major concern when scaling up random packed columns. This study concerns the measurements of liquid flow distribution in a large scale column packed with 25.4 mm stainless steel Pall rings. The liquid flow distribution was studied with packed bed height from 0.9 to 3.5 m, liquid flow rate from 2.91 to 6.66 kg/m2·s, and gas flow rate from 0 to 3.0 kg/m2·s. In addition, three systems, water/air, aqueous detergent solution/air and Isopar/air, were used to study the effect of liquid physical properties on liquid flow distribution, and two different liquid distributors were employed to test the effect of liquid distributor design. It was found that liquid flow distribution was strongly influenced by liquid distributor design, packed bed height, gas flow rate and liquid viscosity, slightly influenced by liquid flow rate, but not by liquid surface tension.

Airblast atomization at conditions of low air velocity

Spray quality is determined by a series of measurements of drop size distribution and mean drop size. The atomizer employed is a two-dimensional design, producing a flat liquid sheet of variable thickness sandwiched between two coflowing nitrogen gas streams. The range of test conditions is chosen to simulate those typically found in a gas turbine combustor during startup, when air velocities are low. Four different liquids—tap water, heating oil, aviation kerosine (Jet-A), and a high-viscosity mixture of glycerine and distilled water—are used to investigate the effects of liquid physical properties on atomization quality. The results generally confirm those obtained in previous studies in regard to the effects of relative velocity, air/liquid mass flow ratio, and liquid physical properties on Sauter mean diameter. However, the significant dependence of mean drop size on initial liquid film thickness reported by other investigators is not observed in this study. Also, the results suggest the existence of a threshold of relative velocity below which atomization of the liquid sheet is not possible. As the relative velocity is reduced, the Sauter mean diameter eventually reaches a maximum value, and any further reduction in relative velocity results in the loss of the spray.

Compound atomization by air action. The effect of liquid properties.

The study of the effect of liquid physical properties on atomization is an important subject. In this study, the ethyl alcohol-water solution and the glycerin-water solution are used for changing the properties. The correlation between density, viscosity and surface tension of a liquid is obtained. The relationship between SMD and the liquid physical properties is clarified. How the liquid physical properties affect the atomization is examined in detail with a D7-2-2-type nozzle which was used in the former report. An experimental equation including the liqued physical properties is obtained for SMD near the singular point.

Effect of liquid physical properties and flow rates on the surface area of sprays from a pressure atomizer

AbstractThe effects of the physical properties and volume flow rate of liquids on the surface area of sprays produced by a pressure type of atomizing nozzle were determined experimentally. the specific surface area of the sprays is correlated by an equation of two dimensionless groups in terms of the variables surface tension to the −1.0 power, kinematic viscosity to the −0.4 power, and volume flow rate to the 2.4 power. The volume flow rate is correlated by an equation of two dimensionless groups containing the variables viscosity to the 0.17 power, density to the −0.58 power, and spray pressure to the 0.42 power. The conversion of compression energy to surface‐area energy appears to be constant at approximately 0.1%.

Effects of liquid physical properties on oxygen transfer in penicillin fermentation.

Effects of liquid physical properties on oxygen transfer in penicillin fermentation.

Effects of Liquid Physical Properties on Oxygen Transfer in Penicillin Fermentation

Effects of Liquid Physical Properties on Oxygen Transfer in Penicillin Fermentation