Droplet Growth Research Articles

Self-stabilization of droplet clusters levitating over heated salt water

When the water surface is heated locally, a self-ordered regular cluster of levitating droplets is formed above it. A condensational growth of water droplets leads to coalescence of the cluster with water layer. At the same time, the intended use of water droplets as biochemical microreactors is possible only when the cluster is stable. A method of self-stabilization of a droplet cluster levitating over the locally heated water surface is proposed for the first time. The physical analysis of the problem shows that the desired result can be reached by dissolving a small amount of sodium chloride in a layer of water. This is explained by simultaneous action of two processes with opposite effects on evaporation. On the one hand, when water evaporates, a thin layer of increased salt concentration that prevents evaporation is formed at its surface. On the contrary, diffusion of salt in water decreases the surface concentration of salt. Different combinations of water heating intensity and average salt concentration are expected to result in the stable size of nearly identical levitating droplets, when there is a balance between the droplet evaporation and the condensation of vapor from the ascending vapor-air flow. The predicted phenomenon has been observed experimentally. In a series of laboratory experiments, a range of parameters has been obtained for which self-stabilization of the droplet cluster takes place. The theoretical analysis of necessary conditions for spontaneous stabilization of a droplet cluster uses a steady-state solution for temperature and salt concentration in the water layer. The localization of a small cluster makes it sufficient to derive a solution to the one-dimensional problem. The obtained analytical solution to this problem takes into account the temperature dependence of the salt diffusion coefficient. The resulting threshold values of salt concentration agree well with the experimental data.

Two-phase Flow Dynamics at the Interface Between GDL and Gas Distributor Channel Using a Pore-Network Model

For improved operating conditions of a polymer electrolyte membrane (PEM) fuel cell, a sophisticated water management is crucial. Therefore, it is necessary to understand the transport mechanisms of water throughout the cell constituents especially on the cathode side, where the excess water has to be removed. Pore-scale modeling of diffusion layers and gas distributor has been established as a favorable technique to investigate the ongoing processes. Investigating the interface between the cathode layers, a particular challenge is the combination and interaction of the multi-phase flow in the porous material of the gas diffusion layer (GDL) with the free flow in the gas distributor channels. The formation, growth and detachment of water droplets on the hydrophobic, porous surface of the GDL have a major influence on the mass, momentum and energy exchange between the layers. A dynamic pore-network model is used to describe the flow through the porous GDL on the pore-scale. To capture the droplet occurrence and its influence on the flow, this dynamic two-phase pore-network model is extended to capture droplet formation and growth at the surface of the GDL as well as droplet detachment due to the gas flow in the gas distributor channels. In this article, the developed model is applied to single- and multi-tube systems to investigate the general drop behavior. These rather simple test-cases are compared to experimental and numerical data available in the literature. Finally, the model is applied to a GDL unit cell to analyze the interaction between two-phase flow through the GDL and drop formation at the interface between GDL and gas distributor channel.

Distinct condensation droplet distribution patterns under low- and high-frequency electrowetting-on-dielectric (EWOD) effect

Distinct droplet distribution patterns of open-plate grid-wire-patterned EWOD devices under low (1 Hz, 5 Hz) and high (500 Hz, 1000 Hz) frequencies of AC-EWOD were discussed in this paper. Under low frequencies, droplets stayed inside the grid; under high frequencies, droplets adhered to the grid wires. Single droplet (1 μL) dynamics were studied with a discovery of contact-angle-fully-recover and contact-angle-partially-recover oscillation modes. These two modes induced distinct droplet coalescence mechanisms and distribution patterns. The natural response frequency was introduced to validate these two modes. Visualization experiments of droplet distribution were carried out on 0.5 mm, 1 mm, and 2 mm grid samples under 2 Hz, 50 Hz, 100 Hz, and 200 Hz. Condensate was collected to investigate the grid size (0.5 mm, 1 mm, 2 mm) and frequency effect (1 Hz, 100 Hz, 200 Hz) on condensation rate. Higher frequency demonstrated a larger condensation rate than the lower ones; the 1 mm grid samples showed more inspiring results compared with the 0.5 mm and 2 mm grid samples. EWOD provided an active and reversible way to interfere with droplet dynamics, and promote droplet growth and coalescence, which demonstrated great potential for future applications in droplet control and condensation enhancement.

Asymmetric Condensation Characteristics during Dropwise Condensation in the Presence of Non-condensable Gas: A Lattice Boltzmann Study.

In this work, the condensation characteristics of droplets considering the non-condensable gas with different interaction effects are numerically studied utilizing a multicomponent multiphase thermal lattice Boltzmann (LB) model, with a special focus on the asymmetric nature induced by the interaction effect. The results demonstrate that for isolated-like growth with negligible interactions, the condensation characteristics, that is, the concentration profile, the temperature distribution, and the flow pattern, are typically symmetric in nature. For the growth regime in a pattern, the droplet has to compete with its neighbors for catching vapor, which leads to an overlapping concentration profile (namely the interaction effect). The distribution of the condensation flux on the droplet surface is consequently modified, which contributes to the asymmetric flow pattern and temperature profile. The condensation characteristics for droplet growth in a pattern present an asymmetric nature. Significantly, the asymmetric condensation flux resulting from the interaction effect can induce droplet motion. The results further demonstrate that the interaction strongly depends on the droplet's spatial and size distribution, including two crucial parameters, namely the inter-distance and relative size of droplets. The asymmetric condensation characteristics are consequently dependent on the difference in the interaction intensities on both sides of the droplet. Finally, we demonstrate numerically and theoretically that the evolution of the droplet radius versus time can be suitably described by a power law; the corresponding exponent is kept at a constant of 0.50 for isolated-like growth and is strongly sensitive to the interaction effect for the growth in a pattern.

Experimental study on droplet breakup and droplet particles diffusion of a pressure nozzle based on PIV

• The turbulence of dust fall spray field are studied for the first time. • The I in the axial direction has an exponential relationship with the distance. • Droplet breakup mainly occurs in the range of 0–4 mm area near strong turbulence. • The droplet size and turbulence intensity change linearly in the range of 300 mm. • When the I reaches 3.35 or more, the droplets are broken more completely. The x-swirl nozzles has been widely used in the field of spray technology for dust reduction. In this study, experimental studies on the droplet breakup and droplet particles diffusion of X-swirl nozzles by particle image velocimetry (PIV). Based on the experimental results, the velocity fields at five different water supply pressures were compared, and 6 MPa was chosen as the water supply pressure to study droplet breakup and droplet particles diffusion. The results show that, turbulence can change the trajectory of droplets and have an important impact on the atomization process. The variation law of turbulence intensity in axial and radial directions is revealed. The turbulence intensity ( I ) in the spray field axial direction continuously decreased as the distance increased and had an overall exponential relationship. I within 2.5 mm in the radial direction of the spray field’s center rapidly decreased, but the downward trend slightly decelerated in the area exceeding 2.5 mm. Combined with the parameters of strain rate ( S ) and vorticity ( Ω ), the comparative analysis is carried out. When the gas and liquid are fully mixed, the turbulence intensity increases rapidly. This promotes the growth, deformation and breakup of droplets, and affects the diffusion of droplets. Through the probability density function, it is revealed that droplet breakup mainly occurs in the range of 0–4 mm near strong turbulence. The droplet size at different locations was measured by Phase Doppler Interferometer (PDI), which revealed the mechanism of turbulent flow on the droplet size. In the range of 0–300 mm, the droplets with larger initial particle size and velocity gradually evolve into droplets with small particle size, small velocity and large number over time. But in the 300–450 mm range, the turbulent flow’s effect on the breakup gradually decreased with the droplet movement time. Most of the droplets have finished breaking. Due to coalescence between small droplets, the particle sizes tended to slowly increase.

Transient multiphysics coupled model for multiscale droplet condensation out of moist air

As a key physical process, water vapor condensation has attracted significant attention because of its potential in engineering applications. The non-condensable gas in the surrounding vapor has a significant influence on condensation heat transfer. Considering as a crucial aspect, this work developed a transient multiphysics coupled solver to investigate droplet condensation in a moist air environment (considering dry air as the non-condensable gas). The current solver couples the time-dependent vapor-liquid phase-change heat transfer, mass transport of water vapor, and two-phase fluid flow. In contrast to the classical thermal resistance theory model, this solver can capture the dynamic and strong coupling characteristics during condensation comprehensively. The results demonstrate that for small-scale droplets, vapor condensation is driven by the coupled internal conduction-dominated heat transfer and external vapor diffusion. As the droplet grows and the contact angle increases, internal convection driven by the Marangoni effect becomes increasingly important. The enhanced fluid mixing inside the droplet can affect both the internal heat transfer and the external vapor diffusion. Because of the significant diffusion resistance, the droplet growth rates in a moist air environment are reduced up to 1-2 orders of magnitude compared with the case of pure steam. For large-scale droplets, the internal convection can increase the droplet growth rate up to 18.7%. Furthermore, the contact angle, the subcooling temperature, and the relative humidity have significant influences on droplet condensation in a moist air environment. This work not only promotes the mechanistic understanding of condensation heat transfer in a moist air ambient but also provides a flexible solver for vapor-liquid phase change problems.

Stomatin modulates adipogenesis through the ERK pathway and regulates fatty acid uptake and lipid droplet growth

Regulation of fatty acid uptake, lipid production and storage, and metabolism of lipid droplets (LDs), is closely related to lipid homeostasis, adipocyte hypertrophy and obesity. We report here that stomatin, a major constituent of lipid raft, participates in adipogenesis and adipocyte maturation by modulating related signaling pathways. In adipocyte-like cells, increased stomatin promotes LD growth or enlargements by facilitating LD-LD fusion. It also promotes fatty acid uptake from extracellular environment by recruiting effector molecules, such as FAT/CD36 translocase, to lipid rafts to promote internalization of fatty acids. Stomatin transgenic mice fed with high-fat diet exhibit obesity, insulin resistance and hepatic impairments; however, such phenotypes are not seen in transgenic animals fed with regular diet. Inhibitions of stomatin by gene knockdown or OB-1 inhibit adipogenic differentiation and LD growth through downregulation of PPARγ pathway. Effects of stomatin on PPARγ involves ERK signaling; however, an alternate pathway may also exist.

Dropwise condensation heat transfer of the surface with micro columns

Condensation is the process of changing a substance from a gaseous state into a liquid state, which is a phase-change process and has been widely applied in many fields. Dropwise condensation occurs on hydrophobic and superhydrophobic surfaces, and thus, has a much higher heat-transfer coefficient than film condensation. In this study, four types of micro-structured surfaces including cylinder, cube, cone and pyramid with the same height of 6μm were made on silicon surfaces. Due to the different surface morphology, the micro-structured surfaces with cylinders and cubes had superhydrophobic properties with the contact angle of 158.4° and 155.5°, respectively; while the micro-structured surfaces with cones and pyramids had hydrophilic properties with the contact angle of 86.4° and 44.4°, respectively. Through the experimentally study of the heat transfer and dynamic characteristics of droplets on the micro-structured surfaces, the results showed that under the same conditions (steam pressure is 0.1MPa, saturated steam temperature is 100 °C and steam flow rate is 0.298 ± 0.02 m3/h), the heat flux increased linearly with the increase of the cooling water temperature difference and the subcooling, respectively. Moreover, condensation heat transfer coefficient decreased as the increase of the subcooling. Because of less sharp edges and bigger contact angles, the cylindrical micro-structured surface had more excellent droplet mobility leading to faster condensation process and heat transfer. Through the comparison of the droplet growth in the horizontal and vertical directions, it was found that the micro-structured surface with more sharp edges had a larger droplets density. However, the sharp edges prevent the coalescence and shedding which slowed down the heat transfer. Therefore, the cylindrical micro-structured surface spent the shortest time in the whole growth process and thus had the best heat transfer performance.

Molecular dynamics simulation of the transport properties and condensation mechanism of carbon dioxide

The application of supersonic gas separation technology to remove carbon dioxide (CO2) from natural gas is an emerging concept; however, the microscopic mechanisms of CO2 condensation remain unknown. The accuracy of various CO2 flexible force field models is evaluated in this study, and the CO2 nucleation and growth processes are elucidated using molecular dynamics simulations. The results show that the ZHU model predicts CO2 density, self-diffusion coefficient, shear viscosity, and vapor–liquid phase interface thickness with high accuracy. At low temperatures, CO2 molecules can spontaneously nucleate. The subsequent droplet growth is determined by the collision of monomer molecules with clusters as well as the merging of clusters. The mass transfer of the CO2 condensation process is aided by the droplet growth process. Furthermore, the lower the cooling temperature and the higher the initial pressure are, the shorter is the time required for CO2 nucleation, the higher is the nucleation rate, and the faster is the liquefaction. Furthermore, the temperature control method that directly controls the overall temperature of the system was discovered to force the removal of the heat transfer process from clusters to CO2 molecules, and the carrier gas temperature control method should be used in subsequent indepth research.

Numerical Research of Spontaneous Condensation of Boron Oxide Vapor in Flat Nozzles

A model of spontaneous condensation of boron oxide vapor in chemically reacting gas mixtures is proposed, based on the classical theory of nucleation and one-speed and one-temperature approximation for the equations of two-phase mixture flow. The model considers nucleation, condensational growth, coagulation, and gas-phase chemical reactions of molten boron oxide droplets. Numerical research of the spontaneous condensation of boron oxide in flat nozzles of different sizes and geometries was carried out using the model. The condensation shock wave is shown to occur immediately behind the nozzle throat. The highest nucleation rates (up to ) are characteristic of a zone adjacent to the sidewall of the nozzle, where the rate of expansion of combustion products is maximum. In nozzles with similar geometries, the position of the front of the condensation shock wave does not depend on the linear dimensions of the nozzle; and only the Mach number in front of the condensation shock wave determines its position. In flat nozzles with geometrically similar inlet regions, the front of the condensation shock wave position does not depend on the nozzle linear dimensions because the condensation shock wave is formed in the field that is independent of the expansion angle of the nozzle. The effect of gas-phase chemical reactions on the spontaneous condensation of boron oxide vapor development is estimated. This effect is weak and tangible only in large nozzles.

Hierarchical liquid marbles formed using floating hydrophobic powder and levitating water droplets

HypothesisLiquid marbles i.e. droplets coated by hydrophobic particles may be formed not only on the solid substrates but also on the floating layers of hydrophobic powders such as fluorinated fumed silica or polytetrafluoroethylene. ExperimentsFormation and growth of liquid marbles on fluorinated fumed silica or polytetrafluoroethylene powder floating on a heated water-vapor interface is reported. Marbles emerge from condensation of water droplets levitating above the powder layer. FindingsThe kinetics of the growth of droplets is reported. Growth of droplets results from three main mechanisms: water condensation, absorption of small droplets and merging of droplets with neighboring ones. Growing droplets are coated with the hydrophobic powder, eventually giving rise to the formation of stable liquid marbles. Formation of hierarchical liquid marbles is reported. Growth of liquid marbles emerging from water condensation follows the linear temporal dependence. A phenomenological model of the liquid marble growth is suggested.

Automated Identification of Characteristic Droplet Size Distributions in Stratocumulus Clouds Utilizing a Data Clustering Algorithm

Abstract Droplet-level interactions in clouds are often parameterized by a modified gamma fitted to a “global” droplet size distribution. Do “local” droplet size distributions of relevance to microphysical processes look like these average distributions? This paper describes an algorithm to search and classify characteristic size distributions within a cloud. The approach combines hypothesis testing, specifically, the Kolmogorov–Smirnov (KS) test, and a widely used class of machine learning algorithms for identifying clusters of samples with similar properties: density-based spatial clustering of applications with noise (DBSCAN) is used as the specific example for illustration. The two-sample KS test does not presume any specific distribution, is parameter free, and avoids biases from binning. Importantly, the number of clusters is not an input parameter of the DBSCAN-type algorithms but is independently determined in an unsupervised fashion. As implemented, it works on an abstract space from the KS test results, and hence spatial correlation is not required for a cluster. The method is explored using data obtained from the Holographic Detector for Clouds (HOLODEC) deployed during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign. The algorithm identifies evidence of the existence of clusters of nearly identical local size distributions. It is found that cloud segments have as few as one and as many as seven characteristic size distributions. To validate the algorithm’s robustness, it is tested on a synthetic dataset and successfully identifies the predefined distributions at plausible noise levels. The algorithm is general and is expected to be useful in other applications, such as remote sensing of cloud and rain properties. Significance Statement A typical cloud can have billions of drops spread over tens or hundreds of kilometers in space. Keeping track of the sizes, positions, and interactions of all of these droplets is impractical, and, as such, information about the relative abundance of large and small drops is typically quantified with a “size distribution.” Droplets in a cloud interact locally, however, so this work is motivated by the question of whether the cloud droplet size distribution is different in different parts of a cloud. A new method, based on hypothesis testing and machine learning, determines how many different size distributions are contained in a given cloud. This is important because the size distribution describes processes such as cloud droplet growth and light transmission through clouds.

Enhancing Recurrent Droplet Jumping Phenomena on Heterogeneous Surface Designs

AbstractCoalescence‐induced droplet jumping phenomena on superhydrophobic surfaces can significantly enhance their heat transfer performances by effectively removing droplets from the surfaces. However, understanding the ideal design for condensing surfaces is still challenging due to the complex nature of droplet dynamics associated with their nucleation, coalescing, and jumping mechanisms. The intrinsic dynamic nature of droplet behaviors suggests the use of hierarchical concave morphology to account for the different length scales associated with each transport phenomenon. The hierarchical morphology thereby enables heterogeneous wetting characteristics by realizing both microscale droplets on superhydrophobic surfaces and nanoscale pinning regions beneath the droplets by arresting liquid residues after droplet jumping. Heat transfer performances are further examined by extracting physically meaningful descriptors, such as nucleation sites, droplet growth rates, and droplet jumping frequency, showing 44% enhancements when droplet nucleation sites are designed in selective locations.

Collision Fluctuations of Lucky Droplets with Superdroplets

Abstract It was previously shown that the superdroplet algorithm for modeling the collision–coalescence process can faithfully represent mean droplet growth in turbulent clouds. An open question is how accurately the superdroplet algorithm accounts for fluctuations in the collisional aggregation process. Such fluctuations are particularly important in dilute suspensions. Even in the absence of turbulence, Poisson fluctuations of collision times in dilute suspensions may result in substantial variations in the growth process, resulting in a broad distribution of growth times to reach a certain droplet size. We quantify the accuracy of the superdroplet algorithm in describing the fluctuating growth history of a larger droplet that settles under the effect of gravity in a quiescent fluid and collides with a dilute suspension of smaller droplets that were initially randomly distributed in space (“lucky droplet model”). We assess the effect of fluctuations upon the growth history of the lucky droplet and compute the distribution of cumulative collision times. The latter is shown to be sensitive enough to detect the subtle increase of fluctuations associated with collisions between multiple lucky droplets. The superdroplet algorithm incorporates fluctuations in two distinct ways: through the random spatial distribution of superdroplets and through the Monte Carlo collision algorithm involved. Using specifically designed numerical experiments, we show that both on their own give an accurate representation of fluctuations. We conclude that the superdroplet algorithm can faithfully represent fluctuations in the coagulation of droplets driven by gravity.

Numerical study on the condensation characteristics of natural gas in the throttle valve

Due to the cooling effect of natural gas throttling, spontaneous condensation will occur in the throttle valve, which may affect pipeline system efficiency. However, the condensation characteristics (such as nucleation rate and condensation rate) remain unclear, and the traditional method based on the isenthalpic hypothesis can hardly solve this non-equilibrium issue. Based on the geometry differences between the throttle valve and the Laval nozzle, this paper explored the condensation parameters of the CH4–C2H6 binary mixture in the throttle valve and the Laval nozzle using CFD techniques (solving non-equilibrium condensation at a lower cost). This paper discussed the influence of the inlet pressure and inlet temperature on the spontaneous condensation process in the throttle valve as well. The findings are that the nucleation and droplet growth regions in the throttle valve are closer to the throat but narrower than that of the Laval nozzle, and the liquid mass fraction decreases after reaching the peak value. The onset of droplet nucleation and droplet growth is closer to the throat when increases inlet pressure or decreases inlet temperature. The condensation rate of ethane in the throttle valve is lower than that in the Laval nozzle, and the sensitivity of the nucleation rate and the Wilson point to the inlet parameters is higher and lower than that in the Laval nozzle, respectively.. The main innovation of the paper lies in revealing the differences in the condensation between the throttle valve and the Laval nozzle using the non-equilibrium method.

Prediction of Newtonian Droplet Breaking Time from a Capillary at Low Weber Numbers.

Droplet formation and growth processes have numerous scientific and industrial applications. Experimental and numerical studies on the formation, growth, and breaking of droplet are carried out in present work. The numerical results are in good agreement with the experiment. This work focused on the effect of different Weber numbers (We) on the droplet breaking time. The results show when We < 0.05, the length and volume of the droplet increase, and the breaking time decreases rapidly. The resultant force acting on the main droplet suddenly drops around the critical breaking time. The difference rate between the time tn (when the resultant force is zero) and the breaking time tb is less than 8.49%. For the dimensional analysis of the numerical results, a prediction formula of breaking time on the Weber number is modeled as aWeb + c for We < 0.5.

Thermodynamic study on the natural gas condensation in the throttle valve for the efficiency of the natural gas transport system

The condensation of natural gas in the throttle valve may affect and even damage the downstream equipment, which threatens the safety and efficiency of the natural gas transport system. However, the mainly used method based on the isenthalpic hypothesis can hardly solve this problem. In this work, we developed a spontaneous condensation model of condensed natural gas with high temperature and pressure in the throttle valve using CFD modelling, which defined a hypothetical saturation line and introduced two empirical correction coefficients (α and β) into the nucleation and growth models. The scouring effect of natural gas on the valve was analysed, and the condensation characteristics and effect of latent heat of condensation on the flow were discussed in detail. The results show that the average absolute relative deviation (AARD) of the outlet temperature of the angle throttle valve (ATV) obtained by this model is 0.39% when α and β equal 10-10 and 10-2, respectively, while that without considering condensation is 1.13%. The inner wall near the throat of the straight-through throttle valve (STV) and ATV are susceptible to the scouring effect of natural gas. For STVs (type I, type II) and ATVs (type I, type II), after the droplet nucleation (1026 m−3·s−1) and growth (10-2 m/s) stage, the droplets are condensed and accumulated with a maximum liquid mass fractions of 3.12 %, 2.22 %, 3.42 %, and 3.24 %, respectively, then flow along the wall with a flow pattern of the annular flow and stratified flow. Compared to the case without condensation, the pressure and temperature at the condensation position increase slightly due to the latent heat of condensation, the condensation shock wave, while the velocity decreases slightly due to the momentum exchange between the natural gas and liquid phase.

Long-Term Stability of Pickering Nanoemulsions Prepared Using Diblock Copolymer Nanoparticles: Effect of Nanoparticle Core Crosslinking, Oil Type, and the Role Played by Excess Copolymers.

A poly(N,N′-dimethylacrylamide) (PDMAC) precursor is chain-extended via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of diacetone acrylamide (PDAAM) to produce PDMAC77-PDAAM40 spherical nanoparticles. Post-polymerization core-crosslinking of such nanoparticles was performed at 20 °C, and the resulting covalently stabilized nanoparticles survive exposure to methanol. The linear and core-crosslinked nanoparticles were subjected to high-shear homogenization in turn in the presence of n-dodecane to form macroemulsions. Subsequent processing of these macroemulsions via high-pressure microfluidization produced nanoemulsions. When using the core crosslinked nanoparticles, the droplet diameter was strongly dependent on the copolymer concentration. This indicates that such nanoparticles remain intact under the processing conditions, leading to formation of genuine Pickering nanoemulsions with a z-average diameter of 244 ± 60 nm. In contrast, the linear nanoparticles undergo disassembly to afford molecularly dissolved diblock copolymer chains, which stabilize oil droplets of 170 ± 59 nm diameter. The long-term stability of these two types of n-dodecane-in-water nanoemulsions with respect to Ostwald ripening was examined using analytical centrifugation. When prepared at the same copolymer concentration, Pickering nanoemulsions stabilized by core-crosslinked nanoparticles proved to be significantly more stable than the nanoemulsion stabilized by the amphiphilic PDMAC77-PDAAM40 chains. Moreover, higher copolymer concentrations led to a significantly faster rate of droplet growth. This is attributed to excess copolymer facilitating the diffusion of n-dodecane through the aqueous phase. Finally, analytical centrifugation is used to assess the long-term stability of the analogous squalane-in-water nanoemulsions. These systems are much more stable than the corresponding n-dodecane-in-water nanoemulsions, regardless of whether the copolymer is adsorbed as sterically stabilized nanoparticles or surface-active chains.

Whey Protein Peptides Have Dual Functions: Bioactivity and Emulsifiers in Oil-In-Water Nanoemulsion.

Whey protein isolate (WPI)-derived bioactive peptide fractions (1–3, 3–5, 5–10, 1–10, and >10 kDa) were for the first time used as emulsifiers in nanoemulsions. The formation and storage stability of WPI bioactive peptide-stabilized nanoemulsions depended on the peptide size, enzyme type, peptide concentration, and storage temperature. The highly bioactive <10 kDa fractions were either poorly surface-active or weak stabilizers in nanoemulsions. The moderately bioactive >10 kDa fractions formed stable nanoemulsions (diameter = 174–196 nm); however, their performance was dependent on the peptide concentration (1–4%) and enzyme type. Overall, nanoemulsions exhibited better storage stability (less droplet growth and creaming) when stored at lower (4 °C) than at higher (25 °C) temperatures. This study has shown that by optimizing peptide size using ultrafiltration, enzyme type and emulsification conditions (emulsifier concentration and storage conditions), stable nanoemulsions can be produced using WPI-derived bioactive peptides, demonstrating the dual-functionality of WPI peptides.

Numerical Analysis of the Condensing Steam Flow by Means of ANSYS Fluent and in-House Academic Codes With Respect to the Capacity for Thermodynamic Assessment

In this paper numerical analysis of the condensing steam flow in a converging-diverging nozzle is investigated. The ANSYS Fluent results are compared with the results of the in-house academic Computational fluid dynamics code with respect to the capacity for thermodynamic assessment. The “local” real gas equation of state is used as a mathematical complement of flow governing equations in the in-house code. In the Fluent code, the thermodynamic functions as well as the steam and water physical properties are calculated based on the IAPWS formulation with the use of the UDF. The condensation model with the Fuchs and Sutigin correction of the droplet growth equation and nucleation rate with the Kantrowitz correction is implemented in both CFD codes. The CFD results are compared with the obtained experimental data. The experiment was carried out using an in-house steam facility with a transonic steam tunnel. The investigated geometry is a converging-diverging nozzle as adopted under the International Wet Steam Experimental Project with the diverging section expansion rate of 3,000 s−1 and the total throat height of 40 mm.