Mixture Of Droplets Research Articles

Preparation and characterization of electrospun magnetic poly(ether urethane) nanocomposite mats: Relationships between the viscosity of the polymer solutions and the electrospinning ability

The aim of this research was to obtain electrospun fibers from poly(ether urethane) (PEU) and poly(ether urethane)-iron oxide nanoparticles (PUC) based on the correlation between the rheological characteristics and the electrospinnability of the polymer suspensions. Firstly, our goal was to explore the domain of polymer concentration suitable for electrospinning using the rheological data, in order to control the formation of electrospun fibers and to avoid the defects such as beaded fibers or sprayed droplets. By increasing the polymer concentration in the system, the morphology was changed from droplets to a mixture of droplets and nanofibers, to uniform, defect free fibers, showing a randomly ordered orientation of the fibers. Then, the influence of the amount of iron oxide nanoparticles on the rheological behaviour of nanocomposites was also envisaged. The diameter of the electrospun PUC fibers decreased with the increase of the iron oxide nanoparticles content as it was revealed by scanning electron microscopy (SEM) and confocal Raman microscopy investigations. Moreover, the magnetic properties were also envisaged and it was evidenced that the electrospun nanocomposite mats displayed superparamagnetic properties with low coercivity and remanence and reversible hysteresis behaviour. These results will allow further to choose the electrospinning parameters for an optimal design of future polyurethane nanocomposite mats for targeted applications, especially those where high surface area-to-volume or length-to-diameter ratios are required.

Utilization of a biosurfactant foam/nanoparticle mixture for treatment of oil pollutants in soil.

Oil contamination has become a primary environmental concern due to increased exploration, production, and use. When oil enters the soil, it may attach or adsorb to soil particles and stay in the soil for an extended period, contaminating the soil and surrounding areas. Nanoparticles have been widely used for the treatment of organic pollutants in the soil. Surfactant foam has effectively been employed to remediate various soil contaminants or recover oil compounds. In this research, a mixture of biosurfactant foam/nanoparticle was utilized for remediation of oil-contaminated soil. The results demonstrated that the biosurfactant/nanoparticle mixture and nitrogen gas formed high-quality and stable foams. The foam stability depended on the foam quality, biosurfactant concentration, and nanoparticle dosage. The pressure gradient change in the soil column relied on the flowrate (N2 gas + surfactant/nanoparticle mixture), foam quality, and biosurfactant concentration. The optimal conditions to obtain good quality and stable foams and high oil removal efficiency involved 1 vol% rhamnolipid, 1 wt% nanoparticle, and 1 mL/min flowrate. Biosurfactant foam/nanoparticle mixture was effectively used to remediate oil-contaminated soil, whereas the highest treatment efficiency was 67%, 59%, and 52% for rhamnolipid biosurfactant foam/nanoparticle, rhamnolipid biosurfactant/nanoparticle, and only rhamnolipid biosurfactant, respectively. The oil removal productivity decreased with the increase of flowrate due to the shorter contact time between the foam mixture and oil droplets. The breakthrough curves of oil pollutants in the soil column also suggested that the foam mixture's maximum oil treatment efficiency was higher than biosurfactant/nanoparticle suspension and only biosurfactant.

How much raindrop energy is used for transportation of the two-phase splashed material?

The ejection of a mixture of solid (soil) and liquid (water) phases is one of the aspects of the energy dissipation of the impacting drop during the soil splash phenomenon. All calculations to date have only been taking into account the ejection of solid phase material and were based on significant simplifications of the measured quantities. Therefore, the aim of the study was an improved calculation of the falling drop energy transferred to the ejected material, while considering that such material was a mixture of solid soil particles and water droplets and therefore, “two-phase”. Experimental variants included combinations of soils with different textures and initial moisture contents as well as various falling water-drop energies. Two complementary methods of i)splash cup measurements and ii) image analysis based on high-speed cameras were used for the calculation of quantities i.e. the number of ejected particles, their mass, and their ejection velocity. Based on the obtained results, it was stated that the kinetic energy of ejected particles, expressed as a percentage of falling drop energy, ranged from 1 % to 14 %. This percentage depended strongly on soil texture as well as initial moisture content. The highest values were obtained for soil with the largest amount of sand fraction and the lowest for the soil with the largest amount of finer fractions. All tested soils showed a trend of a higher drop energy transferred to the splashed particles with increasing initial soil moisture content. Taking into account the varied energy of the falling drop variants, the amount of energy transferred to ejected particles was constant.

Molecular Dynamics Simulation of Spreading of Mixture Droplets on Chemically Heterogeneous Surfaces.

The dynamic spreading process of mixed droplets on chemically heterogeneous surfaces has attracted significant attention owing to its extensive industrial applications. The spreading of mixture droplets on a chemically heterogeneous surface is more complex than that for pure fluid droplets and needs to be understood further. In this study, molecular dynamic simulations were performed to investigate the dynamic spreading process of R32/R1234yf mixture droplets and water/ethanol mixture droplets of radius 4.7-6.5 nm with different compositions, on chemically heterogeneous surfaces. The variation in the relative spreading radius with time was analyzed and compared with the molecular kinetic theory. It was observed that for the R32/R1234yf mixture, the actual component mole fraction did not deviate from the nominal one in the triple contact region, and the dynamic spreading behavior was identical to that for the pure fluids. Meanwhile, the converse was true for the ethanol/water mixture. The molecular kinetic theory could accurately predict the spreading of droplets for R32/R1234yf mixtures when the mixture properties were used. However, this was not feasible for ethanol/water mixtures. It was observed that the local physical properties in the triple contact line (including the mole fraction and the lyophilic and lyophobic area ratio) play key roles in the spreading of the ethanol/water mixture droplets. The prediction of the dynamic spreading of water/ethanol mixture droplets on chemically heterogeneous surfaces can be improved significantly by using local properties to modify the molecular kinetic theory.

A Novel LiNO3-Based Eutectic Salt Mixture for Industrial Heat Treatment

Abstract A potassium nitrate–lithium nitrate–sodium nitrate (KNO3-LiNO3-NaNO3) eutectic mixture having a low melting point has been proposed as an alternative high-temperature quench medium. Inconel and steel probes were used to compare the quench performance of a conventional sodium nitrite (NaNO2) eutectic mixture and the proposed alternative medium at different bath temperatures. For the Inconel probe, the heat extraction rate was higher in the eutectic LiNO3 mixture maintained at 150°C. At elevated bath temperatures of 200°C, 250°C, and 300°C, the heat extraction rate was higher in the eutectic NaNO2 mixture. AISI 52100 steel probes quenched in eutectic LiNO3 quench medium at 150°C and 200°C showed higher hardness. At bath temperatures of 250°C and 300°C, the hardness of AISI 4140 steel probes quenched in both media was comparable. Wettability studies on Inconel and steel surfaces revealed the occurrence of nonuniform dilation of a LiNO3 eutectic mixture droplet. On the steel surface, the phenomenon occurred at lower temperatures, which resulted in an extended boiling stage and increased hardness.

Self-Induced Solutal Marangoni Flows Realize Coffee-Ring-Less Quantum Dot Microarrays with Extensive Geometric Tunability and Scalability.

Currently, quantum dot light‐emitting diodes (QD‐LEDs) are receiving extensive attention. To maximize their luminous performance, the uniformity of the QD‐LEDs is crucial. Although the spontaneously self‐induced solutal Marangoni flow of an evaporating binary mixture droplet has been widely investigated and used to suppress coffee‐ring patterns in ink‐jet printing technology, unfortunately, ring shapes are still present at the edges, and the Marangoni flow generated by the selective evaporation of volatile liquid components cannot be controlled due to its nonlinear instabilities. In this work, polygonal coffee‐ring‐less QD microarrays are created using two spontaneous and sequential solutal Marangoni flows. During the initial evaporation, internal circulating flows are controlled by polygonal‐shaped droplets. After that, sequential interfacial flows are generated by the captured volatile vapors. A theoretical model and scaling analysis are provided to explain the working mechanisms. It is expected that the newly designed printing system can be applied to the mass production of QD‐LEDs.

Effects of dispersed multiwalled carbon nanotubes on the micro-explosion and combustion characteristics of 2-methylfuran – diesel mixture droplets

Isolated droplet combustion experiments have been carried out on neat diesel, a 15 vol% 2-methylfuran – 85 vol% diesel mixture (MF15), and nanofuels made from MF15 base fuel with addition of multiwalled carbon nanotubes (MWCNTs) at 25 ppm, 50 ppm, and 100 ppm concentrations (referred to as MF15C25, MF15C50, and MF15C100). Compared to MF15, the nanofuels displayed increased micro-explosion intensity and reduced micro-explosion occurrences, both effects being more pronounced at higher MWCNTs loadings. This behavior is attributed to the higher surface tension and viscosity of the nanofuels compared to that of MF15. The ignition delay decreased from 2.33 s to 1.71 s, the combustion rate constant increased from 0.82 mm2 s−1 to 1.01 mm2 s−1, and the combustion period reduced from 5.31 s to 4.54 s when going from pure MF15 to MF15C50. The improved combustion characteristics can be related to the superior thermal conductivity and large specific surface area of the dispersed MWCNTs in the nanofuels. The combustion characteristics of the nanofuel deteriorate at the highest MWCNTs dosing investigated here, possibly due to nanoparticle agglomeration. Overall, the present results suggest that dosing of MWCNTs at optimum levels improves the thermal efficiency and reduces the NOx emissions upon combustion of MF-diesel blends.

Internet of things-based real-time monitoring of air quality in Sulaymaniyah, Iraq

Providing accurate measurements and monitoring of air quality is considered to be one of the most prominent features of modern cities. One component of air pollution is particles of diameter between 2.5 and 10 micrometres and less. They are mixtures of small solid particles and liquid droplets produced due to chemical reactions. Having said this, in this paper, an attempt is made to design and program a low-cost air detector accumulating data about the concentration of particulate matter of diameters 2.5 and 10 micrometres in two different places in the city of Sulaymaniyah and at two different times, (i) during the institution of quarantine regulations, due to COVID pandemic, and (ii) after quarantine is lifted. In addition, a website is created simultaneously to both demonstrate and save the data obtained by the air detector. Moreover, using the quantifying method developed by the United States Environmental Protection Agency (EPA), the accumulated data can be used for decision making. Lastly, it should be mentioned that all the millstones of this research were carried out practically on a small scale, and the created system was able to provide data with reasonable accuracy. It should be pointed out that the process of data recording was between 20th of February and 10th of May 2020, in two different places namely Sarchnar and Saholak, which was during quarantine. Thus, the concentration of both particulate matter of 2.5 and 10 micrometres till end of April was low with an average of 40 and 60 µg/m3 for 2.5 micrometre in Sarchnar and Saholaka, and 90 and 140 µg/m3 for 10 micrometres in Sarchnar and Saholaka since quarantine regulations were strict. However, from 20th of April till 10th of May as the quarantine regulations got less serious, the number increased to 75 and 70 µg/m3 for 2.5 micrometre in Sarchnar and Saholaka, respectively and 140 and 180 µg/m3 for 10 micrometres in Sarchnar and Saholaka, respectively.

Охлаждение парогазовой смеси испаряющимися каплями воды

A model of thermal relaxation in the flow of a hot vapor–gas mixture and cold water droplets is presented. Numerical modeling of vapor and gas cooling during heating and evaporation of droplets has been carried out. Approximation expressions are obtained for the cooling time of vapor and gas in a given temperature range depending on the initial radius of droplets, the mass fraction of droplets, and the initial composition of the vapor-gas mixture.

Refractive index and mole fraction field of the vapor evaporated from ethanol-water mixture droplet

Refractive index and mole fraction field of the vapor evaporated from ethanol-water mixture droplet

Research of air-drop mixture particles movement in passenger aircraft cabin

The paper examined the mechanism of propagation and deposition of potentially pathogenic particles in the field of turbulent air flow of the heating and air conditioning system of the closed cabin of a passenger aircraft. In pandemic conditions, when the disease is transmitted from person to person through the air, knowledge and understanding of the patterns of movement of particles of the airborne droplet mixture in a small confined space with a high population density allows assessing the risks of infection and the amount of post-flight processing required, as well as the level of passenger control. Simulation model of air-drop mixture distribution in passenger aircraft cabin is proposed, which is built on the basis of three-dimensional finite-element model of flow motion in non-stationary setting. Two-factor dispersion analysis was carried out to determine the significance of the effect of flight time and cabin area on particle deposition intensity. A regression model of the propagation density of precipitated viral particles of the air drop mixture was constructed and investigated depending on the temperature, ventilation method, layout and number of infected passengers. Based on the results of the studies, temporal and volumetric characteristics of the distribution of particles of the air-drop mixture were obtained, directions and meanings of the mutual influence of the selected main factors of the model on the mechanism of distribution and deposition of potentially pathogenic particles were determined, recommendations were developed on the organization of the process of disinfection measures in the passenger aircraft cabin.

Binary mixture droplet wetting on micro-structure decorated surfaces

Liquid surface tension as well as solid structure play a paramount role on the intimate wetting and non-wetting regimes and interactions between liquids droplets and solid substrates. We hypothesise that the coupling of these two variables, independently addressed in the past, eventually offer a wider range of understanding to the surface science and interfacial communities.In this work, intrinsically hydrophobic micro-pillared surfaces varying in the spacing between structures, and pure ethanol, pure water and their binary mixtures (as well as acetone–water and ethylene glycol–water mixtures) are utilised, accessing a wide range of substrate solid fractions and liquid surface tensions experimentally. Wettability measurements are carried out at different azimuthal directions to exemplify the wetting/non-wetting behaviour as well as the droplet asymmetry function of both liquid composition and structure spacing.Our findings reveal that high water concentration droplets, i.e., high surface tension fluids, sit in the Cassie-Baxter regime while partial non-wetting Wenzel or mixed-mode regimes with enhanced droplet asymmetry ensuing for medium and high ethanol concentrations, i.e., low surface tension fluids, below certain micropillar spacing. Beyond micropillar spacing s ≥ 40 µm, the impact of the surface structure on the droplet shape is negligible, and droplets adopt a similar contact angle and circular shape as on a flat smooth hydrophobic surface. Wetting and non-wetting regimes are then supported by classical wetting theories and equations. A wetting regime map for a wide range of surface tension fluids and/or their mixtures on a wide domain of solid fractions is then proposed.

Review of the binary mixture droplet evaporation studies

Review of the binary mixture droplet evaporation studies

Investigation on the formic acid evaporation and ignition of formic acid/octanol blend at elevated temperature and pressure

With the growing advancements in new energy sources, formic acid has become a subject of interest as a hydrogen carrier. Apart from being a hydrogen carrier source, to explore the possibility of formic acid being used as a potential fuel in engines, the combustion of formic acid is yet to be explored fully. Few studies have been conducted to determine its laminar burning velocity. The study of droplet combustion and evaporation is also critical if formic acid is to be deployed as a potential fuel. Therefore, the evaporation of formic acid with a droplet diameter of ∼1.00 mm is investigated in a constant volume combustion chamber for pressures ranging from 5 bar to 20 bar at a wide temperature range (150–300 °C). A model was developed to get a fundamental understanding of the experimental results. The D2 plot from experimental data exhibited the presence of two zones for evaporation. Zone 1 showed a slower evaporation rate compared to zone 2. Due to a thin layer of formic acid remaining on the thermocouple, the surface area of the droplet increased in zone 2, resulting in faster evaporation of the droplet. The steeper decline in droplet evaporation occurred at the point of complete loss of sphericity of the droplet. Even so, the trend for total evaporation time from the model and experiments was consistent. Formic acid is a low reactive fuel, and it did not ignite at the ambient temperature and pressure of 300 °C and 20 bar, respectively. So, to determine the auto-ignition behavior of formic acid, a separate experimental setup that could exceed the ambient temperature higher than the auto-ignition temperature of formic acid was used. When pure formic acid did not ignite, it was mixed with octanol at different concentrations and further investigated. The mixture droplet’s ignition probability slightly decreased to 65 vol% of formic acid addition in the octanol. Further addition of formic acid in octanol significantly decreased the ignition probability of the mixture droplet. Lastly, a polynomial equation is proposed to extrapolate the auto-ignition time of pure formic acid droplets with a droplet diameter of ∼0.7 mm.

Phase Behavior and Crystal Structure of Binary Mixtures of Droplets and Four-Patch Colloids

We report simulation studies on the phase behavior and crystal structures of anisotropic colloid–droplet binary mixtures. The droplets interact with the colloids at the patches of different geometr...

Evaporation of Sessile Binary Mixture Droplets: Time Dependence of Droplet Shape and Concentration Profile from One-Dimensional Magnetic Resonance Microscopy.

Many technological applications like inkjet printing, coating, or cooling processes rely on the evaporation of sessile droplets. Regarding liquid mixtures, the understanding of the underlying physics is still incomplete and process optimization requires trial and error. Our main goal is to establish a novel method in this field, one-dimensional magnetic resonance microscopy, to investigate the evaporation of sessile binary mixture droplets in the microliter range. It allows us not only to determine the droplet volume and shape, including contact angle, but also to measure concentration profiles with a spatial resolution of a few micrometers. These capabilities are demonstrated for a mixture of 1-octanol (OCT) and pentadecafluoro-1-octanol (F-OCT) by combining spatially resolved 1H and 19F nuclear magnetic resonance measurements. We clearly observe three evaporation regimes for the OCT/F-OCT mixture. The first and second regimes are characterized by the predominant evaporation of F-OCT and are separated by a depinning event. The third regime starts when no F-OCT is left and, thus, features the evaporation of a pure OCT droplet. During all stages, concentration gradients perpendicular to the substrate are weak in the studied binary droplet.

Decreasing the Weight-Size Parameters of Gas-Steam Turbine Plant by Increasing the Efficiency of Thermodynamic Processes in the Condenser

The aim of this work is decreasing the weight-size parameters of the contact gas-steam turbine plant and contact condenser elements by increasing the efficiency of thermal-gas dynamic processes of condensation through rational irrigation of countercurrent gas-steam flow. To achieve the goal the total efficiency of water-return drops ranging from 0.1 to 1 mm at different initial velocities from 5 to 35 m/s emitted by the multi-nozzle sprinkler was determined by mathematical modeling of the liquid droplet movement processes, heat and mass transfer between the liquid droplet and gas-vapor mixture, and gas-vapor mixture pressure loss. The effect of increasing the gas-steam mixture velocity from 3.3 to 6 m/s on the overall efficiency of water return was determined. The novelty of the obtained results was defined by an increase in the water return into cycle from 12 to 13% with a droplet diameter of 0.3 -- 0.4 mm and the initial velocity from the sprinkler of 5--10 m/s. The velocity of the mixture was to 6 m/s at rational correlations of the initial velocity of the droplets’ escape, which increased the total amount of heat withdrawn to 11%. The positive effect conditions of irrigation processes on thermogasdynamic and weight-size parameters of the condenser elements for the contact gas and steam turbine plant at full pressure recovery coefficients of over 0.967 were substantiated. The most significant result was the reduction of the weight-size parameters of the marine infrastructure object power plant from 8 to 19%.

Molecular dynamics simulations on evaporation of a suspended binary mixture nanodroplet

Mixture working fluids have the advantages of active design and adjustable physical properties, therefore it has a promising future in many power and refrigeration applications. Studies on the evaporation process of mixture nanodroplets are helpful to reveal the mechanism of heat transfer at the interface of mixture working fluids. However, at present, there are few studies on the evaporation of mixture droplet, and the conclusions on the pure fluids evaporation cannot be directly applied to the mixture working fluids, thus it is necessary to carry out specific research on the evaporation of mixtures. In this study, molecular dynamics simulation was used to study the evaporation process of R32/R1234yf nanodroplets with different compositions (xR32=0, 0.2, 0.4, 0.6, 0.8, 1) in a large space. The dynamic changes of evaporation rates of droplets with different components were compared, and the evaporation characteristics of droplet with different concentrations were analyzed in combination with the density, temperature and concentration field distribution near the liquid-vapor interface during the evaporation process. The results show that the evaporation rate of the mixture nanodroplets is lower than the linear interpolation with those of the two components, which is similar to the heat transfer deterioration of the mixture working fluids in pool or flow boiling. The prediction deviation of R32/R1234yf mixture nanodroplet evaporation by the D2 law is around 80%. Considering the scale effect and the interfacial concentration gradient, the prediction accuracy of the D2 law can be improved.

Wave Dynamics of a Vapor–Droplet Mixture in an Acoustical Resonator

Wave Dynamics of a Vapor–Droplet Mixture in an Acoustical Resonator

Indoor Particulate Matter in Urban Households: Sources, Pathways, Characteristics, Health Effects, and Exposure Mitigation.

Particulate matter (PM) is a complex mixture of solid particles and liquid droplets suspended in the air with varying size, shape, and chemical composition which intensifies significant concern due to severe health effects. Based on the well-established human health effects of outdoor PM, health-based standards for outdoor air have been promoted (e.g., the National Ambient Air Quality Standards formulated by the U.S.). Due to the exchange of indoor and outdoor air, the chemical composition of indoor particulate matter is related to the sources and components of outdoor PM. However, PM in the indoor environment has the potential to exceed outdoor PM levels. Indoor PM includes particles of outdoor origin that drift indoors and particles that originate from indoor activities, which include cooking, fireplaces, smoking, fuel combustion for heating, human activities, and burning incense. Indoor PM can be enriched with inorganic and organic contaminants, including toxic heavy metals and carcinogenic volatile organic compounds. As a potential health hazard, indoor exposure to PM has received increased attention in recent years because people spend most of their time indoors. In addition, as the quantity, quality, and scope of the research have expanded, it is necessary to conduct a systematic review of indoor PM. This review discusses the sources, pathways, characteristics, health effects, and exposure mitigation of indoor PM. Practical solutions and steps to reduce exposure to indoor PM are also discussed.