Importance In Many Industrial Processes Research Articles

New Progress on London Dispersive Energy, Polar Surface Interactions, and Lewis's Acid-Base Properties of Solid Surfaces.

The determination of the polar surface free energy, polar properties, and Lewis's acid base of solid materials is of capital importance in many industrial processes, such as adhesion, coatings, two-dimensional films, and adsorption phenomena. (1) Background: The physicochemical properties of many solid particles were characterized during the last forty years by using the retention time of injected well-known molecules into chromatographic columns containing the solid substrates to be characterized. The obtained net retention time of the solvents adsorbed on the solid, allowing the determination of the net retention volume directly correlated to the specific surface variables, dispersive, polar, and acid-base properties. (2) Methods: Many chromatographic methods were used to quantify the values of the different specific surface variables of the solids. However, one found a large deviation between the different results. In this paper, one proposed a new method based on the London dispersion equation that allowed the quantification of the polar free energy of adsorption, as well as the Lewis's acid-base constants of many solid surfaces. (3) Results: The newly applied method allowed us to obtain the polar enthalpy and entropy of adsorption of polar model organic molecules on several solid substrates, such as silica, alumina, MgO, ZnO, Zn, TiO2, and carbon fibers. (4) Conclusions: our new method based on the separation between the dispersive and polar free surface energy allowed us to better characterize the solid materials.

Influence of the molecular weight and physical properties of a thermoplastic polymer on its dynamic wetting behavior

The wetting dynamics of molten thermoplastic polymers, which are known to influence the force balance of the triple line, are not understood properly despite their importance in many industrial processes. In particular, the influence of the molecular weight Mn on the polymer dynamic wetting behavior is still unclear. In this work, we investigate how the dynamic equilibrium of the moving contact line between poly(ethylene glycol) and cellulosic substrates is influenced by Mn. After a careful assessment of the relevant material properties, dynamic wetting experiments are conducted using the Wilhelmy method. Our investigations reveal an influence of Mn on the evolution of all of the measured quantities. The dynamic wetting behavior is shown to relate to the polymer chain size, and to display a transition at the critical weight of entanglement Mc . This study should help defining guidelines for formulating and choosing polymers for various processes, such as composites manufacturing.

Asymmetric Jetting during the Impact of Liquid Drops on Superhydrophobic Concave Surfaces.

The impact of liquid drops on superhydrophobic solid surfaces is ubiquitous and of practical importance in many industrial processes. Here, we study the impingement of droplets on superhydrophobic surfaces with a macroscopic dimple structure, during which the droplet exhibits asymmetric jetting. Systematic experimental investigations and numerical simulations provide insight into the dynamics and underlying mechanisms of the observed phenomenon. The observation is a result of the interaction between the spreading droplet and the dimple. An upward internal flow is induced by the dimple, which is then superimposed on the horizontal flow inside the spreading droplet. As such, an inclined jet is issued asymmetrically into the air. This work would be conducive to the development of an open-space microfluidic platform for droplet manipulation and generation.

Experimental Investigation of Heat Transfer by Forced and Natural Convection in a Pin Fin for Different Materials

Abstract: In the modern generation heat exchange equipment has become of great importance in many industrial processes and internal combustion engines because it increases the use of energy resources as well as conversion and reuse of thermal energy. In recycling thermal energy, the minimization of temperature differences is more important. High-specific output engines can be developed by developing finned surfaces. Thus fins play an important role in energy. Our investigation deals with the problem of finding the optimum configuration of the fin with the maximum heat dissipation rate. This experimental study focuses on the analysis of the effectof forced convection and natural convection on the characteristics of heat transfer within the pin fin. Keywords: Heat transfer, forced convection, natural convection, pin-fin, Aluminium, Brass

Controlling the Interaction Forces between an Air Bubble and Oil with Divalent Cations and Sodium Citrate

Manipulating the interaction forces between an air bubble and oil is of great importance in many industrial processes, such as oil sands extraction. Recently, sodium citrate has been applied in the...

Motion of Nanofluid Droplets through Immiscible Quiescent Liquid: An Experimental Study

Motion of droplets in liquid –liquid extraction column is of importance for many industrial processes. This study aims at evaluation of hydrodynamic behavior of a nanofluid particle moving through an immiscible liquid. Toluene based nanofluids were used as referral systems in this study. Nanoparticles of ZnO, Al2O3, SiO2 and TiO2 have been used to synthesize stable nanofluids. The experiments were carried out using different concentrations of nanoparticles to study the variation in terminal velocity, drag coefficient and eccentricity of the nanofluid droplet. Observations show enhancement in terminal velocity and reduction in drag coefficient of the droplets, for all nanofluids up to optimum concentration of nanoparticles. With increase in concentration of nanofluid beyond the optimum concentration, the droplet terminal velocity decreases and drag coefficient increases due to deformation in shape and an increase in oscillation that could be due to nanoparticle aggregation in nanofluid. The eccentricity of...

A comprehensive model for stability of dispersed oil-water flow in horizontal and inclined pipes

Prediction of dispersed flow regimes in liquid-liquid pipe flow is of great importance for many industrial processes. This work proposes a mechanistic model to determine the stability bounds of dispersed liquid-liquid flow patterns that presents significant improvements compared to other classical criteria. The model accounts for turbulent break-up of dispersed phase droplets, sedimentation, dispersion, and accumulation of droplets. In addition, droplet coalescence and segregation are considered by means of attaining critical concentrations that can be associated with the phase inversion point of the liquid-liquid mixture. Modeled bounds are compared with available experimental data, showing good agreement in flows of mineral oil and water, as well as flows of crude oil and water. Moreover, the model is more accurate and descriptive than other predictions from commonly used criteria. The effect of fluid properties, flow rates, and pipe geometry are discussed. Limitations and possible refinements of the suggested model are also treated.

Molecular Dynamics Gives New Insights into the Glucose Tolerance and Inhibition Mechanisms on β-Glucosidases.

β-Glucosidases are enzymes with high importance for many industrial processes, catalyzing the last and limiting step of the conversion of lignocellulosic material into fermentable sugars for biofuel production. However, β-glucosidases are inhibited by high concentrations of the product (glucose), which limits the biofuel production on an industrial scale. For this reason, the structural mechanisms of tolerance to product inhibition have been the target of several studies. In this study, we performed in silico experiments, such as molecular dynamics (MD) simulations, free energy landscape (FEL) estimate, Poisson–Boltzmann surface area (PBSA), and grid inhomogeneous solvation theory (GIST) seeking a better understanding of the glucose tolerance and inhibition mechanisms of a representative GH1 β-glucosidase and a GH3 one. Our results suggest that the hydrophobic residues Y180, W350, and F349, as well the polar one D238 act in a mechanism for glucose releasing, herein called “slingshot mechanism”, dependent also on an allosteric channel (AC). In addition, water activity modulation and the protein loop motions suggest that GH1 β-Glucosidases present an active site more adapted to glucose withdrawal than GH3, in consonance with the GH1s lower product inhibition. The results presented here provide directions on the understanding of the molecular mechanisms governing inhibition and tolerance to the product in β-glucosidases and can be useful for the rational design of optimized enzymes for industrial interests.

Wetting transition on heated microstructrured superhydrophobic surface

Superhydrophobic surface has attracted significant attention since their potentiality to industrial and academic applications. Moreover, superhydrophobic surface wettability at non-ambient temperature, especially at high temperature (but not boiling) was of great importance in many industrial processes. In this paper, we designed and fabricated 4 series superhydrophobic micro-pillar surfaces on the Silicon wafers to investigate wettability at different temperatures. These micro-pillar surfaces were fabricated by photolithography and ICP etching technologies. The temperature-dependent wettability of DI water droplets was characterized using contact angle measurements. The wetting behavior was observed to be different on the surfaces, and the wetting transition occurred at a specific temperature.

Enhanced photocatalysis and biomolecular sensing with field-activated nanotube-nanoparticle templates

The development of new catalysts for oxidation reactions is of central importance for many industrial processes. Plasmonic catalysis involves photoexcitation of templates/chips to drive and enhance oxidation of target molecules. Raman-based sensing of target molecules can also be enhanced by these templates. This provides motivation for the rational design, characterization, and experimental demonstration of effective template nanostructures. In this paper, we report on a template comprising silver nanoparticles on aligned peptide nanotubes, contacted with a microfabricated chip in a dry environment. Efficient plasmonic catalysis for oxidation of molecules such as p-aminothiophenol results from facile trans-template charge transfer, activated and controlled by application of an electric field. Raman detection of biomolecules such as glucose and nucleobases are also dramatically enhanced by the template. A reduced quantum mechanical model is formulated, comprising a minimum description of key components. Calculated nanotube-metal-molecule charge transfer is used to understand the catalytic mechanism and shows this system is well-optimized.

Characterization of the gas-liquid interfacial waves in vertical upward co-current annular flows

For more than fifty years, hundreds of research works have focused on the study of annular flow because of its huge importance in many industrial processes, for instance, chemical, petroleum, etc., being of particular interest in nuclear industry. Specifically, interfacial waves play a vital role in the mass, momentum and energy transference processes between gas and liquid phases. This paper describes the new experimental measurements of vertical upward co-current two-phase gas-liquid flow carried out in a tube with an inner diameter of 44 mm. The liquid film thickness and the major characteristics of the interfacial waves have been measured using a non-intrusive instrument, a conductance probe. The physical phenomenon in which this device is based is the change in the electrical conductivity between air and water, i.e., the electrical signal collected in the sensor receiver depends on the thickness of the liquid film layer. The experimental measurements range from 2000 to 3500 l/min for the gas volumetric flow rate, and from 4 to 10 l/min for the liquid volumetric flow rate. Correlation of the experimental measurements of liquid film thickness and the major properties of the interfacial waves have been analyzed using non-dimensional numbers. An important part of the document focuses on the comparison of the experimental data and the fitting correlations against several of the most widely used expressions. Throughout this paper, in addition to present all the available correlations, the existing scattering found when comparing against other expressions have been also confirmed, underlining the existence of gaps of knowledge even today. Emphasize that the proposed correlations are the ones that better fit the data of all experimental series carried out under the present study for the analyzed variables, with almost all the experimental points covered by the ±10% error bands of the new correlations.

Profile Characterization and Temperature Effect on the Wettability of Microstructured Surfaces

Wetting is one of the omnipresent phenomena governed via natural laws. Moreover, surface wettability at non-ambient temperature especially at high temperature (30°C to 90°C) is of great importance in many industrial processes. In this study, Si wafers with various structures were fabricated to investigate wettability at different temperatures. Three shapes with micro-pillar structured surfaces were designed and fabricated. Pillar-structured surfaces were fabricated by photolithography and ICP etching. The temperature-dependent wettability of single-phase regime droplets was characterized using contact angle measurements. The wetting behavior of a water droplet was observed.

Comparison of colloidal stability of montmorillonite dispersion in aqueous NaCl solution with in alcohol-water mixture

The colloidal stability of montmorillonite (MMT) dispersions in aqueous NaCl solution and in alcohol-water mixture has been studied in this work. The study was performed through the measurements of particle size, zeta potential, surface tension and swelling capacity. The experimental results have shown that the stability of colloidal MMT dispersion is distinct in the two cases, although the zeta potential has the same change trend. This observation might be attributed to the different behavior of surface tension in aqueous NaCl solution with alcohol-water mixture. The former would increase the surface tension of the media that deteriorate the wettability and swelling capacity of MMT, while the latter would decrease the surface tension. It is demonstrated that the surface tension of the media would affect strongly the colloidal stability of aqueous MMT dispersions, which is of great importance in many industrial processes as well as in soil chemistry and environmental science.

Symmetry breaking in drop bouncing on curved surfaces

The impact of liquid drops on solid surfaces is ubiquitous in nature, and of practical importance in many industrial processes. A drop hitting a flat surface retains a circular symmetry throughout the impact process. Here we show that a drop impinging on Echevaria leaves exhibits asymmetric bouncing dynamics with distinct spreading and retraction along two perpendicular directions. This is a direct consequence of the cylindrical leaves that have a convex/concave architecture of size comparable to the drop. Systematic experimental investigations on mimetic surfaces and lattice Boltzmann simulations reveal that this novel phenomenon results from an asymmetric momentum and mass distribution that allows for preferential fluid pumping around the drop rim. The asymmetry of the bouncing leads to ∼40% reduction in contact time.

Competition between Redlich–Kister and adapted Herráez equations of correlation conductivities in isobutyric acid + water binary mixtures near and far away from the critical temperature

Electrical conductivity deviation Δσ has been investigated by using electrical conductivity (σ) measurements for isobutyric acid + water (IBA + W) mixtures over the entire range of mole fractions at six different temperatures, both near and close to the critical temperature (0.055 < (T − T c)/K < 16.055). Knowledge of the conductivity of binary mixtures is of great importance in many industrial processes. Rarely can the conductivity of mixtures be obtained from the sum of the conductivities of the pure components. The theoretical study of the conductivity of mixtures is generally complicated. Numerous empirical correlation models have been proposed. The present study proposes a new empirical correlation equation, based on lineal behaviour. The results were also fitted with the Redlich–Kister polynomial equations and the recently proposed Herráez equation for viscosity correlation which is adapted for electrical conductivity in this work. The investigation of the Herráez equation shows that it exhibits a universal exponent as a physical magnitude feature. Competition between the two models at different temperatures and parameter numbers is discussed.

An Equation for the Correlation of Viscosities of Binary Mixtures

Knowledge of the viscosity of binary mixtures is of great importance in many industrial processes. Rarely can the viscosity of mixtures be obtained from the sum of the viscosities of the pure components.

Scaling factors in granular flow—analysis of experimental and simulations results

The relationship between the design of powder mixers and their performance is of crucial importance for many industrial processes and yet is not well understood. Here the flow patterns generated by an agitator carrying a long flat blade were compared to those generated by a single ploughshare using positron emission particle tracking and DEM. The performances of these agitators were also assessed against those of multi-blade and multi-plough agitators. The powder flows created by the different designs had some qualitative similarities. Indeed, all the agitators were shown to generate a loop of circulation below the free surface of the bed. The radial support of each mixing element was also observed to act as a separatrix for the axial flow, leading to the formation of a loop of circulation on each side of the mixing elements, thus inhibiting axial convection of material. The single-blade agitators, be the flat blade or the plough, were found to induce a pulsing regime, this feature being also observe with the multi-blade agitators but with a lesser amplitude. For moderate agitator frequencies of rotation where inertial effects are negligible, fundamental characteristics of the flow patterns extracted from power spectra of axial displacements could be scaled with the number of blade passes.

On the Scaling of the Visible Lengths of Jet Diffusion Flames

Length of jet diffusion flames is of direct importance in many industrial processes and is analyzed by applying scaling method directly to the governing partial differential equations. It is shown that for jet-momentum-dominated diffusion flames, when the buoyancy effects are neglected, the flame length normalized by the burner exit diameter increases linearly with the Reynolds number at the burner exit in the laminar burning regime and decreases in inverse proportion to the Reynolds number in the transitional regime. For turbulent diffusion flames, the normalized flame lengths are independent of the burner exit flow conditions. It is further found that for vertical upward flames, the buoyancy effect increases the flame length in the laminar and transitional regime and reduces the length in the turbulent regime; while for vertical downward flames, the buoyancy effect decreases the flame length in the laminar and transitional regime and increases the length in the turbulent regime, provided that jet momentum is dominated, and there is no flame spreading out and then burning upward like a downward-facing pool fire. Hence, for turbulent flames the flame lengths depend on the Froude number, Fr, and increase (or decrease) slightly as Fr increases for upward (or downward) flames. By comparison, it is found that the foregoing theoretical results are in good agreement with the experimental observations reported in literature.

Some surface tension and contact angle problems in industry

Contact angle, surface tension and wetting properties are of fundamental importance in many industrial processes, e.g. coating of television screens and fluorescent lights. In addition, different stages of many processes may involve immersion cleansing and subsequent drying. We consider two different problems: one being very practical and involving cleansing and drying of silicon substrates in the semiconductor industry, and the other being theoretical whereby the problem of the shape of scssile and pendant drops is addressed with a possible practical application for making contact angle and surface tension measurements. In the case of cleansing of silicon substrates, we model a process whereby dirt particles are removed as a result of the surface tension forces exerted on a particle passing through a water/air interface and give a possible explanation as to why the efficiency of the process is vclocity dependent. For the case of small liquid drops, a new formulation of the governing equation yields solutions for multiple pendant and extended sessile drops.

Genotoxicity of 1,3-dichloro-2-propanol in the SOS chromotest and in the Ames test. Elucidation of the genotoxic mechanism

1,3-Dichloro-2-propanol (1,3-DCP-OH, glycerol dichlorohydrin) is of great importance in many industrial processes and has been detected in foodstuffs, in particular in soup spices and instant soups. It has been shown to be carcinogenic, genotoxic and mutagenic. Its genotoxic mechanisms are, however, not yet entirely understood. We have investigated whether alcohol dehydrogenase (ADH) catalysed activation to the highly mutagenic and carcinogenic 1,3-dichloroacetone or formation of epichlorohydrin or other genotoxic compounds play a role for mutagenicity and genotoxicity. In our studies, no indications of ADH catalysed formation of 1,3-dichloropropane could be found, although we could demonstrate a clear activation by ADH in the case of 2-chloropropenol. Formation of allyl chloride could also be excluded. We found, however, clear evidence that epichlorohydrin formed chemically in the buffer and medium used in the test is responsible for genotoxicity. No indication was found that enzymatic formation of epichlorohydrin plays a role. Additional mutagenicity and genotoxicity studies with epichlorohydrin also confirmed the hypothesis that genotoxic effects of 1,3-DCP-OH depend on the chemical formation of epichlorohydrin.