Phase behaviours and conductivity study of water/CPC/alkan-1-ol (C4 and C5)/1-hexane water/oil microemulsions with reference to their structure and related thermodynamics

2001 ◽  
Vol 79 (1) ◽  
pp. 1-12 ◽  
Author(s):  
S P Moulik ◽  
Wanda M Aylward ◽  
R Palepu
Keyword(s):  
Percolation Threshold ◽  
Phase Diagrams ◽  
Cetylpyridinium Chloride ◽  
Interfacial Area ◽  
Physicochemical Characteristics ◽  
Interfacial Region ◽  
Number Density ◽  
Thermodynamics Of Transfer ◽  
Water Contents

The microemulsion forming systems of water/cetylpyridinium chloride/butan-1-ol/n-hexane, and water/cetylpyridinium chloride/pentan-1-ol/n-hexane have been studied with respect to their phase behaviours and percolation of conductance to derive information on their droplet physicochemical characteristics (dimension, interfacial area and composition, and number density). This was carried out at different water contents at specific ratios of surfactant and cosurfactant and at various temperatures. From the information collected, the energetics of the transfer of the alkanol (butan-1-ol and pentan-1-ol) from the continuous oil-phase to the interfacial region (the interphase) have been estimated. At the conductance percolation threshold, the droplets cluster or associate, can be considered to form a pseudophase similar to surfactants forming micelles. Based on this concept, the energetics of the clustering process have been evaluated, and the results are discussed in comparison with other recently studied systems.Key words: energetics of clustering, percolation, phase diagrams, microemulsions and thermodynamics of transfer.

Progress in Modeling Injector Cavitating Flows With a Multi-Fluid Method

2006 ◽  
Author(s):  
De Ming Wang ◽  
David Greif
Keyword(s):  
Bubble Dynamics ◽  
Measurement Data ◽  
Interfacial Area ◽  
Number Density ◽  
Cavitating Flows ◽  
Set Up ◽  
Single Bubble Dynamics ◽  
Bubble Number ◽  
Bubble Number Density ◽  
Constricted Channel

A finite volume, pressure based semi-implicit algorithm is developed for solving a multi-fluid system of any number of phases with strong coupling between the phases in mass, momentum and energy transfer. The mass transfer from liquid to vapor due to cavitation is modeled based on a single bubble dynamics (Rayleigh-Plesset equation). In order to model the vapor phase of variable size distribution, or polydispersion, the transport equations of bubble number density and interfacial area are derived from taking the moments of the PDF equation in phase space. The modeling of the result equations are effected through consideration of breakup and coalescence. The k-zeta-f turbulence model is adopted which is found to be particularly effective for predicting near wall effects on the turbulence level. Validation efforts are presented in which comparison with available measurement data are made for a number of cases including constricted channel flow with sharp inlet (I-channel), with smooth inlet (Y-channel), a flash-boiling cavitation set-up, and an actual injector set-up.

scholarly journals Effects of Moisture Released during Forest Burning on Fog Formation and Implications for Visibility

2008 ◽  
Vol 47 (5) ◽  
pp. 1287-1296 ◽  
Author(s):  
Gary L. Achtemeier
Keyword(s):  
Ambient Air ◽  
The United States ◽  
Early Morning ◽  
Mixing Ratio ◽  
Number Density ◽  
Radiation Model ◽  
Extinction Coefficients ◽  
Dry Air ◽  
Humidity Measurements ◽  
Water Contents

Abstract Smoke from wildland burning in association with fog has been implicated as a visibility hazard over roadways in the United States. Visibilities at accident sites have been estimated in the range from 1 to 3 m (extinction coefficients between 1000 and 4000). Temperature and relative humidity measurements were taken from 29 “smokes” during 2002 and 2003. These data were converted to a measure of the mass of water vapor present to the mass of dry air containing the vapor (smoke mixing ratio). Smoke temperatures were processed through a simple radiation model before smokes were mixed with ambient air with temperature and moisture observed during the early morning on the days following the burns. Calculations show supersaturations implying liquid water contents (LWC) up to 17 times as large as LWC found in natural fog. Simple models combining fog droplet number density, droplet size, and LWC show that the supersaturation LWC of smokes is capable of reducing visibility to the ranges observed.

Numerical Simulation of Flow Boiling of Binary Mixtures Using Multi-Fluid Modeling Approach

2011 ◽  
Author(s):  
Vedanth Srinivasan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Interfacial Area ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Number Density ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper, the development of a new mass transfer model to simulate the thermal and phase change characteristics encountered by binary mixtures during flow boiling process is discussed. A new boiling mass transfer model based on detailed bubble dynamic effects, inclusive of local bubble shear, drag and buoyancy dynamics, has been developed and full implemented within the commercial CFD code AVL FIRE v2010. In the present study the phasic mass, momentum and energy equations are solved in a segregated fashion in conjunction with an interfacial area transport and a number density equation to study the heat and mass transfer characteristics of binary flow boiling inside a rectangular duct. Turbulence in the fluidic system and those generated by the bubbly flow are treated using an advanced k-ζ-f model. The simulation results comprising of flow variables such as volume fraction, fluidic velocities and temperature and the resultant heat flux generated on the heated wall section clearly monitors the suppression in heat transfer coefficients with enhancement in flow convection. Competing mechanisms such as phase change process and turbulent convection are identified to influence the heat transfer characteristics. In particular, the varying influence of the mass transfer effects on the heat flux characteristics with alteration in wall temperature is well demonstrated. Comparisons of the predicted heat transfer coefficients for varying wall superheat and varying fluidic velocity indicates a very good agreement with experimental data, wherever available. Description of the flow field inclusive of interfacial area and number density distribution is provided. The current model can be easily extended to simulate multiphase flow in complex systems such as a cooling water jacket for automotive applications.

scholarly journals Design of a novel tryptophan-rich membrane-active antimicrobial peptide from the membrane-proximal region of the HIV glycoprotein, gp41

2012 ◽  
Vol 8 ◽  
pp. 1172-1184 ◽  
Author(s):  
Evan F Haney ◽  
Leonard T Nguyen ◽  
David J Schibli ◽  
Hans J Vogel
Keyword(s):  
Antimicrobial Peptide ◽  
Positive Charge ◽  
Helical Structure ◽  
Physicochemical Characteristics ◽  
Proximal Region ◽  
Peptide Sequence ◽  
Interfacial Region ◽  
Cytotoxic Activities ◽  
Glycoprotein Gp41 ◽  
Membrane Proximal Region

A number of physicochemical characteristics have been described which contribute to the biological activity of antimicrobial peptides. This information was used to design a novel antimicrobial peptide sequence by using an intrinsically inactive membrane-associated peptide derived from the HIV glycoprotein, gp41, as a starting scaffold. This peptide corresponds to the tryptophan-rich membrane-proximal region of gp41, which is known to interact at the interfacial region of the viral membrane and adopts a helical structure in the presence of lipids. Three synthetic peptides were designed to increase the net positive charge and amphipathicity of this 19-residue peptide. Ultimately, the peptide with the greatest degree of amphipathicity and largest positive charge proved to be the most potent antimicrobial, and this peptide could be further modified to improve the antimicrobial activity. However, the other two peptides were relatively ineffective antimicrobials and instead proved to be extremely hemolytic. This work demonstrates a novel approach for the design of unexplored antimicrobial peptide sequences but it also reveals that the biological and cytotoxic activities of these polypeptides depend on a number of interrelated factors.

Interfacial Area and Number Density Transport Equations for Modeling Multiphase Flows With Cavitation

2005 ◽  
Author(s):  
De Ming Wang ◽  
Jaehoon Han ◽  
David Greif ◽  
Iztok Zun ◽  
Matjaz Perpar
Keyword(s):  
Cavitation Erosion ◽  
Volume Fraction ◽  
Interfacial Area ◽  
Physical Models ◽  
Number Density ◽  
Cavitating Flows ◽  
Bubble Distribution ◽  
Bubble Breakup ◽  
Bubble Number ◽  
Bubble Number Density

In this paper we report progress toward developing advanced cavitation models with Eulerian multifluid method. The bubble number density and the interfacial area equations are introduced into the general framework of multifluid method for multiphase cavitating flows in order to account for the variable size nature of the bubble distribution. The physical models for bubble breakup and coalescence are based on the work by Ishii group’s work in recent years. Simulation results of a cavitating flow are compared with the corresponding experimental data, which include the bubble size distribution, bubble volume fraction and bubble number density. The ability of predicting bubble distribution characteristics is particularly useful as an input for cavitation erosion analysis.

Chemical and structural analyses of the graphene nanosheet/alumina ceramic interfacial region in rapidly consolidated ceramic nanocomposites

2017 ◽  
Vol 52 (3) ◽  
pp. 417-428 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Mohammad Islam ◽  
Nabeel H Alharthi ◽  
Hussain Alawadhi ◽  
Tayyab Subhani ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Load Transfer ◽  
Chemical Interaction ◽  
Graphene Nanosheets ◽  
High Surface ◽  
Interfacial Area ◽  
Reduction Reaction ◽  
Interfacial Region ◽  
Graphene Nanosheet ◽  
Mechanical Attachment

Graphene nanosheets (GNS) reinforced Al2O3 nanocomposites were prepared by a rapid sintering route. The microhardness and fracture toughness values of the resulting nanocomposites simultaneously increased due to efficient graphene nanosheet incorporation and chemical interaction with the Al2O3 matrix grains. The properties enhancement is attributed to uniformly dispersed graphene nanosheet in the consolidated structure promoted by high surface roughness and ability of graphene nanosheet to decorate Al2O3 nanoparticles, strong GNS/Al2O3 chemical interaction during colloidal mixing and pullout/crack bridging toughening mechanisms during mechanical testing. The GNS/Al2O3 interaction during different processing stages was thoroughly examined by thermal and structural investigation of the interfacial area. We report formation of an intermediate aluminum oxycarbide phase via a confined carbothermal reduction reaction at the GNS/Al2O3 interface. The graphene nanosheet surface roughness improves GNS/Al2O3 mechanical attachment and chemical compatibility. The Al2O3/GNS interface phase facilitates efficient load transfer, thus delaying failure through impediment of crack propagation. The resulting nanocomposites, therefore, offer superior toughness.

scholarly journals Mango (Mangifera indica) and ambarella (Spondias cytherea) peel extracted pectins improve viscoelastic properties of derived jams

2012 ◽  
Vol 12 (51) ◽  
pp. 6200-6212
Author(s):  
BB Koubala ◽  
◽  
G Kansci ◽  
C Garnier ◽  
MC Ralet ◽  
...  
Keyword(s):  
Phase Diagrams ◽  
Sucrose Concentration ◽  
Mangifera Indica ◽  
Sol Gel ◽  
Ammonium Oxalate ◽  
Physicochemical Characteristics ◽  
Gelling Properties ◽  
Sol Gel Transition ◽  
Mechanical Spectra ◽  
Mango Pulp

Food industries in developing countries are faced with the problem of inadequate supply of additives which can be met by proper utilization of local pectin sources. Mango ( Mangifera indica ) and ambarella ( Spondias cytherea ) peels are most of the time thrown into nature or used for animal feeding . The y have been reported to be a potential source of pectins which could be used to process the fruits into various products. In order to assess their feasibility to be used in jam processing, ambarella and mango ( Mango variety) peel pectins were extracted using three different extraction conditions: HCl at 85 °C/1h, water at 70 °C/1h and oxalic acid/ammonium oxalate (OAAO) at 85 °C/1h. Compare to commercial lime pectin with degree of methoxylation (DM) 70%, phase diagrams presenting sol -gel transition of purified pectins established as sucrose concentration (40 -75 %, weight/weight) versus reduced pectin concentration (0.1 -1.8 %, weight/weight) were studied at pH 3. Mango and ambarella jams were prepared with and without highly methoxylated peels pectins (0.4 %; DM 60 -75% ) and the effect of pectins on jam firmness was studied. Prepared hot jams, with 64 % of dry matter, 60 % of sucrose and/or 0.4 % of pectin, were characterized for their gelation kinetics and mechanical spectra at 20 °C . Phase diagrams showed that at pH 3, the minimal sucrose concentration used to obtain the gel is 40 % for OAAO mango pectin, 45 % for HCl mango and OAAO ambarella pectin, and 50 % for HCl ambarella and commercial pectin . Only gelation of OAAO extracted pectins was possible at low polymer (0.2 %) and standard sucrose (60 %) concentrations. Jams prepared without pectins exhibited a week gel behaviour (G’ = 500- 1000 Pa at 10 Hz) with those of ambarella being stronger than those of mango. Because of its good physicochemical characteristics, ambarella pulp was more suitable than mango pulp for jam processing. Mango and ambarella jams exhibited very strong gels (G’= 2000- 5000 Pa at 10 Hz ) behaviour while using OAAO extracted pectins ; the viscoelastic strength of the processing fruits increases 3 -6 folds . Accordingly, OAAO extracted mango and ambarella peel pectins allow to obtain jams with excellent gelling properties

Interfacial area density, mean radius and number density measurements in bubbly two-phase flow

1993 ◽  
Vol 142 (2-3) ◽  
pp. 341-351 ◽  
Author(s):  
S. Kalkach-Navarro ◽  
R.T. Lahey ◽  
D.A. Drew ◽  
R. Meyder
Keyword(s):  
Two Phase Flow ◽  
Interfacial Area ◽  
Phase Flow ◽  
Number Density ◽  
Two Phase ◽  
Area Density ◽  
Density Measurements ◽  
Interfacial Area Density

scholarly journals Effect of Rotating Magnetic Field on Microstructure in AlCuSi Alloys

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1804
Author(s):  
Piotr Mikolajczak
Keyword(s):  
Magnetic Field ◽  
Fluid Flow ◽  
Temperature Gradient ◽  
Phase Diagrams ◽  
Forced Convection ◽  
Rotating Magnetic Field ◽  
Electromagnetic Stirring ◽  
Number Density ◽  
Calphad Technique ◽  
Almost All

The solidification of AlCuSi alloys with Mn and Fe was studied by rotating a magnetic field to understand the effect of melt flow. The specimens solidified with a forced convection, low cooling rate and low temperature gradient. Electromagnetic stirring generated by an electric coil around the specimens caused a transformation from equiaxed dendritic to rosette morphology, occasionally with spheroids and minor dendrites. The transformation was quantitatively observed with a specific surface Sv, that decreased for almost all alloys and marked the flow effect on α-Al. The computer coupling of phase diagrams and thermochemistry (CALPHAD) technique was applied for the calculation of phase diagrams and property diagrams. Forced convection decreased secondary dendrite arm spacing λ2 in almost all alloys, while it increased slightly in one studied alloy. The length of detrimental β-Al5FeSi phases decreased in the alloy, where β starts to precipitate in the presence of α-Al, while increasing in alloys where β starts as first and grows in the fully liquid melt. The average overall dimension of the Mn-rich phases increased in almost all alloys, and the number density decreased under flow. The modification of spacing for AlSi-eutectics and Al2Cu was analyzed. It was found that the occurrence of Al2Cu does not influence the fluid flow and vice versa.

Modeling of isothermal bubbly flow with ınterfacial area transport equation and bubble number density approach

2009 ◽  
Vol 36 (2) ◽  
pp. 222-232 ◽  
Author(s):  
Salih Sarı ◽  
Şule Ergün ◽  
Muhammet Barık ◽  
Cemil Kocar ◽  
Cemal Niyazi Sökmen
Keyword(s):  
Transport Equation ◽  
Bubbly Flow ◽  
Interfacial Area ◽  
Number Density ◽  
Interfacial Area Transport ◽  
Interfacial Area Transport Equation ◽  
Bubble Number ◽  
Bubble Number Density
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