Conductance and viscosity of n-alkylamine hydrobromides in water at 25 °C: influence of hydrophobic hydration

1969 ◽  
Vol 47 (4) ◽  
pp. 547-553 ◽  
Author(s):  
Jacques E. Desnoyers ◽  
Marcel Arel ◽  
Paul-André Leduc
Keyword(s):  
Hydrophobic Hydration ◽  
Micelle Formation ◽  
Effective Size ◽  
Organic Ions ◽  
Empirical Relations ◽  
Semi Empirical

The equivalent conductivities and viscosities of the homologous salts RNH3Br, where R varies from H to n-octyl, have been measured in water at 25 °C. The data in the submicellar region can be represented adequately by the semi-empirical relations[Formula: see text]The parameters Bη+ and λ0+ are both functions of the effective size of the organic ions in solutions, while the parameters Dη and BΛ can be interpreted through structural salting-in of the hydrophobic cations. Viscosities and conductivities can be used equally well to study the micelle formation of n-octylamine hydrobromide.

Surface tensions and densities of solutions of large organic ions in molten pyridinium chloride

1968 ◽  
Vol 21 (6) ◽  
pp. 1525 ◽  
Author(s):  
. Bloom.H ◽  
VC Reinsborough
Keyword(s):  
Surface Tension ◽  
Aqueous Solutions ◽  
Hydrophobic Hydration ◽  
Micelle Formation ◽  
Pyridinium Chloride ◽  
Surface Tensions ◽  
Density Data ◽  
Organic Ions ◽  
Critical Micelle Concentrations

Surface tension and density data obtained with cetyl and myristyl cationic soaps dissolved in molten pyridinium chloride at 155� are interpreted in terms of micelle formation. The critical micelle concentrations determined by each method are in agreement at 0.060 molal for the solute cetyldimethylbenzylammonium chloride. Partial molar volumas for this same solute are calculated and discussed in concepts similar to the "hydrophobic hydration" theory of aqueous solutions.

Interaction Between Two Closely Spaced Azimuthing Thrusters

1998 ◽  
Vol 42 (01) ◽  
pp. 15-32 ◽  
Author(s):  
Paul Brandner ◽  
Martin Renilson
Keyword(s):  
Mathematical Model ◽  
Satisfactory Agreement ◽  
Vehicle Dynamics ◽  
Operating Conditions ◽  
Towing Tank ◽  
Empirical Relations ◽  
Series Of Experiments ◽  
Flow Effects ◽  
Semi Empirical

To assist in predicting the performance of omni-directional propelled vehicles a series of experiments has been conducted to measure the interaction between two closely spaced ductedazimuthing thrusters. The thrusters were tested below a shallow draft ground board in a towing tank at a spacing of approximately 2 propeller diameters. Measurements were made of forces acting on a single thruster for a range of operating conditions and similarly on two thrusters for a range of relative positions. The results show that forces from the trailing thruster are heavily affected by interaction, particularly due to impingement of the race from the leading thruster, where as forces from the leading thruster remain essentially unaffected despite its proximity to the trailing thruster. A semi-empirical mathematical model suitable for simulation of omni-directional vehicle dynamics is presented. The model is based on the trajectory of the race from the leading thruster derived from momentum considerations with additional empirical relations to account for other more minor flow effects. Comparison of the predicted and measured results show satisfactory agreement.

An Experimental Data Based Correction Method of Biomass Gasification Equilibrium Modeling

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
L. Damiani ◽  
A. Trucco
Keyword(s):  
Experimental Data ◽  
Gas Flow ◽  
Biomass Gasification ◽  
Correction Method ◽  
Solid Product ◽  
Gasification Process ◽  
Empirical Relations ◽  
Semi Empirical ◽  
Main Operating ◽  
Equilibrium Simulation

This paper presents a modified equilibrium simulation model for biomass gasification performance prediction. The model, implemented in the MATLAB-SIMULINK® environment, is able to calculate the reactor main operating parameters such as reaction temperature, gas composition, gas flow rate and solid product (typically charcoal). The comparison of model output with experimental data puts in evidence the insufficient precision of equilibrium models due to their incapability of taking into account the nonequilibrium effects always present in the gasification process. To obtain a better prediction of measured values, the pure equilibrium model has been modified on the basis of literature experimental data, introducing semi-empirical relations with the aim to consider the most meaningful effects of nonequilibrium. The results demonstrate that this modification leads to an increased precision of the model in reproducing experimental data.

Axial Thrust Prediction for a Multi-Stage Centrifugal Pump

2017 ◽  
Author(s):  
K. A. J. Bruurs ◽  
B. P. M. van Esch ◽  
M. S. van der Schoot ◽  
E. J. J. van der Zijden
Keyword(s):  
Hybrid Method ◽  
Setup Time ◽  
Correct Selection ◽  
Centrifugal Pumps ◽  
Axial Thrust ◽  
Multi Stage ◽  
Empirical Relations ◽  
Cfd Method ◽  
Semi Empirical ◽  
Computer Resources

The prediction of axial thrust for centrifugal pumps has been an important topic for many years. This is especially the case for multi-stage pumps with opposed or inline impellers, as the correct selection of balancing device(s) and bearings depends highly on the accuracy of the calculated thrust. Up till now, many investigations regarding axial thrust have focused on fully analytical or (semi-)empirical relations while others have tried to predict the axial thrust using CFD simulations. Full analytical or empirical methods tend to give poor results or need tuning for each specific pump, while the full CFD methods are costly in both setup time and computer resources. This paper presents a hybrid method to calculate the axial thrust of a multi-stage pump with an inline impeller design. The hybrid method combines analytical methods and CFD to reduce the required setup time and computation costs. The CFD calculation of the main flow is used as a boundary condition for the semi-empirical models for the side chambers and the inter-stage seals, such that these tight regions can be excluded from the CFD calculation. To verify and validate the hybrid method, results are compared with measurements and with full CFD calculations that include the side chambers and seals. These results show that the hybrid method and the full CFD method give comparable results, but there is still some difference with the measurements.

scholarly journals Stress Concentration Factor of Expanded Aluminum Tubes Using Finite Element Modeling

2013 ◽  
Vol 10 (1) ◽  
pp. 88
Author(s):  
L Mhamdi ◽  
AC Seibi ◽  
A Karrech ◽  
S El-Borgi ◽  
I Barsoum
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Plastic Material ◽  
Structural Response ◽  
Perfectly Plastic ◽  
Empirical Relations ◽  
Aluminum Tubes ◽  
Semi Empirical

 This paper discusses the development of semi-empirical relations for the maximum stress concentration factor (SCF) around circular holes embedded in aluminum tubes under various expansion ratios and mandrel angles. Finite element models were developed to study the expansion of a typical aluminum tube with embedded holes of various sizes. An elastic perfectly-plastic material behaviour was used to describe the structural response of the tubes under expansion. Various hole-diameter-to-tubewall- thickness ratios, tube expansion ratios, and mandrel angles were considered to determine the stress state around the hole at zero and 90 degree locations from which the maximum SCF was determined. Semi-empirical relations for the maximum SCF using the Lagrange interpolation formulation were developed. The developed relations were found to predict the SCFs accurately. 

scholarly journals Development of a formalism for computing in situ transits of Earth-directed CMEs. Towards a forecasting tool II

2020 ◽  
Author(s):  
Pedro Corona-Romero ◽  
Pete Riley
Keyword(s):  
Space Weather ◽  
Weather Forecasting ◽  
Geomagnetic Storms ◽  
Average Error ◽  
Space Weather Forecasting ◽  
Empirical Relations ◽  
Halo Cmes ◽  
Semi Empirical ◽  
Analytic Models

Abstract. Earth-directed coronal mass ejections (CMEs) are of an important interest for space weather purposes, because they are precursors of the major geomagnetic storms. The geoeffectiveness of a CME mostly relies on its physical properties like magnetic field and speed. There are multiple efforts in the literature to estimate in situ transit profiles of CMEs, most of them based on numerical codes. In this work we present a semi-empirical formalism to compute in situ transit profiles of Earth-directed fast halo CMEs. Our formalism combines analytic models and empirical relations to approximate CME properties as would be seen by a spacecraft near the Earth's orbit. We use our formalism to calculate synthetic transit profiles for 10 events, including the Bastille day event and three varSITI Campaign events. Our results showed qualitative agreement with in situ measurements. Synthetic profiles of speed, magnetic intensity, density and temperature of protons had average errors of 10 %, 27 %, 46 % and 83 %, respectively. Additionally, we also computed the travel time of CME centers, with an average error of 9 %. We found that compression of CMEs by the surrounding solar wind significantly increased our uncertainties. We also outline a possible path to apply this formalism into a space weather forecasting tool.

Oil and water do not mix—hydrophobic hydration

Surfactants ◽  
2019 ◽  
pp. 17-24
Author(s):  
Bob Aveyard
Keyword(s):  
Free Energy ◽  
Water Structure ◽  
Hydrophobic Hydration ◽  
Micelle Formation ◽  
Aqueous Environment ◽  
Thermodynamic Quantities ◽  
Positive Contribution ◽  
Energy Of Hydration ◽  
Free Energy Of Hydration ◽  
Nonpolar Molecules

Many surfactants contain hydrocarbon moieties that are removed from their aqueous environment (‘dehydrated’) in, for example, adsorption and micelle formation. Hydrophobic hydration relates to the interactions between individual nonpolar solute molecules and water, and can be probed using thermodynamic quantities for the dissolution of dilute hydrocarbon vapours to form dilute aqueous solutions. Contrary to the simple expectation that the entropy of hydration of a nonpolar moiety should be positive (due to disruption of water structure), it is large and negative, giving a large positive contribution to the free energy of hydration. The hydration of nonpolar molecules in water leads to an attraction between the molecules in close proximity, which is termed hydrophobic bonding. Although the free energy of hydration of nonpolar groups in bulk aqueous solution is positive, the interaction free energy of nonpolar molecules/groups with interfacial water at an air/water interface is negative.

A non-Bornian analysis of the Gibbs energy of hydration for organic ions

RSC Advances ◽  
2014 ◽  
Vol 4 (53) ◽  
pp. 27634-27641 ◽  
Author(s):  
Wataru Murakami ◽  
Masahiro Yamamoto ◽  
Kazuo Eda ◽  
Toshiyuki Osakai
Keyword(s):  
Field Strength ◽  
Gibbs Energy ◽  
Empirical Equation ◽  
Hydration Energy ◽  
Organic Ions ◽  
Surface Field ◽  
Energy Of Hydration ◽  
Semi Empirical

The hydration energy of organic ions can be well evaluated from the distribution of surface field strength, by using a simple semi-empirical equation.

scholarly journals Synthesis and properties of some α-D-alkyl glucosides and mannosides: apparent molal volumes and solubilization of nitrobenzene in water at 25 °C

1970 ◽  
Vol 48 (16) ◽  
pp. 2525-2531 ◽  
Author(s):  
G. M. Brown ◽  
P. Dubreuil ◽  
F. M. Ichhaporia ◽  
J. E. Desnoyers
Keyword(s):  
Hydrophobic Interactions ◽  
Hydrophobic Hydration ◽  
Micelle Formation ◽  
Apparent Molal Volume ◽  
Molal Volume ◽  
Step Procedure ◽  
Octyl Glucoside ◽  
Alkyl Glucosides ◽  
Sugar Unit ◽  
One Step

Normal and cyclic α-D-alkyl glucosides and mannosides have been synthesized in a one-step procedure from the corresponding sugar. The apparent molal volume and the influence on the solubility of nitrobenzene of some of these glycosides have been measured in water at 25 °C. Evidence for micelle formation is presented for α-D-n-hexyl glucoside, -n-octyl glucoside, and -cyclohexyl mannoside. Comparison of the physical properties of the aqueous solutions shows that the stereochemistry of the sugar unit plays an important role in the hydrophobic hydration and hydrophobic interactions of the glycosides.

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