Experimental Data For Water Research Articles

The dielectric constant of water to high temperatures and pressures from the mean spherical model in the Wertheim solution

AbstractGeneral expressions for the static dielectric constant of a fluid of hard cores with embedded point dipoles have been presented by Wertheim [1], on the basis of a Mean Spherical Model (MSM) treatment. Numerical results are derived for water from these expressions, with the additional inclusion of polarizability effects, using only the dipole moment strength, polarizability coefficient and diameter of water‐molecules. These results are compared with new experimental data for water extending to 800 K and 5 kbar. The calculated values compare satisfactorily with measured data at temperatures between 500 and 800 K, for all densities up to 1 g/cm3. In the lower temperature region, at high densities, the predicted values are systematically too high.

Structural Relaxation and Ultrasonic Absorption in Aqueous Solutions of Alkali Halides

The ultrasonic absorption in aqueous solutions of a number of alkali halides has been measured in the frequency range 5–100 MHz. Lower as well as higher ultrasonic absorption than in pure water has been found depending on type and concentration of the ions present. A kinetic model of the structural relaxation processes in ionic solutions is presented with which the absolute values of the structural absorption as a function of ion concentration and temperature for different types of ions can be described quantitatively. The analysis of the ultrasonic absorption data of the alkali halide solutions with this model yields information concerning the kinetic properties as well as the number of solvent molecules at different distances from the ions. The relaxational parameters obtained are consistent with other experimental data of water and of the solutions.

Ultrasonic Absorption and Molecular Motion in Ionic solutions

AbstractA model of the structural relaxation processes in ionic solutions is presented with which the absolute values of the structural absorption as a function of ion concentration and temperature for different types of ions can be described quantitatively. An analysis of the ultrasonic absorption in aqueous solutions of alkali halides with this model yields information concerning the kinetic properties as well as the number of solvent molecules at various distances from the ions. The sets of relaxational parameters obtained are consistent with other available experimental data of water and of the solutions, such as total compressibility, molar volume, thermal expansion coefficient, specific heat, and radial distribution data.

Analysis of Combined Free and Forced Convection for Fully Developed Laminar Flow in Horizontal Tubes

This paper summarizes an analytical investigation of the effects of free convection on fully developed laminar flow in horizontal circular tubes with uniform heat flux. Solutions for heat transfer and pressure drop, with both heating and cooling, were obtained for water with two limiting tube-wall conditions. The infinite-conductivity tube exhibits higher Nu and f than the glass tube, with Nu being over five times the Poiseuille value at Gr ∼ 106. With the glass-tube boundary condition, significant circumferential wall temperature variations exist. A correlation for the difference between the wall temperatures at the top and bottom of the tube is presented. Design correlations for Nu and f are developed from the analytical solutions. The analytical predictions bracket recent experimental data for water.

Slow-Neutron Scattering by Liquids: a Hindered-Translator Model

A hindered-translator model including damping is constructed with the aim of accounting for the one-particle motions in a liquid, in connection with slow-neutron scattering. Liquids which exhibit the Arrhenius law for self-diffusion are considered and the activation energy ${U}_{0}$ is assumed to represent the energy barrier against translations for a single particle. In the absence of dissipation and for energies below the barrier, the hindered translator is allowed to carry out harmonic oscillations with frequency ${\ensuremath{\omega}}_{0}$ given by the mean field of force experienced by the particle in the liquid. Dissipation is taken into account using methods of non-equilibrium statistical mechanics. Dissipation is considered, first, on the weak-collision hypothesis, and it is assumed that no transitions between vibrational and translational states occur during the time the dynamic correlation persists. By looking into the phase space of the hindered translator at thermal equilibrium, its velocity autocorrelation function is shown to be a weighted superposition of the autocorrelation functions for vibrations and translations, respectively. Explicit expressions are found for their correlation times ${\ensuremath{\tau}}_{\mathrm{I}}$ and ${\ensuremath{\tau}}_{\mathrm{II}}$, in terms of the interatomic potential $\ensuremath{\phi}(r)$, the radial distribution function $g(r)$, the activation energy ${U}_{0}$, and the self-diffusion coefficient $D$. Next, the effect that hard collisions have on dissipation is included by simply superimposing hard on weak collisions; terms which contribute to Gaussian and non-Gaussian parts of Van Hove's ${G}_{s}(r,t)$ are considered. Finally, the expression for Van Hove's scattering function ${S}_{s}(\ensuremath{\kappa},\ensuremath{\epsilon})$ is given in terms of the physical quantities entering our model. The numerical computation concerns quantities related to the Gaussian part of ${G}_{s}(r,t)$. The width of the quasi-elastic peak at different scattering angles, the mean-square displacement versus time, the velocity autocorrelation function, and the Egelstaff $p(\ensuremath{\beta})$ are compared with the experimental data for water at 25\ifmmode^\circ\else\textdegree\fi{}C and 75\ifmmode^\circ\else\textdegree\fi{}C and for liquid argon. Fairly good agreement is obtained without using any adjustable parameter. A significant role is played by ${\ensuremath{\omega}}_{0}$ and ${U}_{0}$ in accounting for the different behavior that liquids with similar self-diffusion coefficient may exhibit with respect to slow-neutron scattering.

The spectral dynamics of laminar convection

The non-linear equations of the Bénard convection problem are transformed to the spectral domain. The spectral basis consists of the supercritical normal modes of the characteristic-value problem in which the exponential growth rates are characteristic values. The norm of the spectrum is the variance of an arbitrary finite-amplitude state of convection. The equations that govern the spectrum are solvable by linear methods when the spectrum is truncated by exclusion of all convective modes except those of lowest-order symmetric vertical structure. Numerical computations of heat flux for a spectrum that contains only one convective mode are in good agreement with experimental data for water in the laminar régime.

A theory of the dielectric polarization of polar substances

With the aid of classical statistical mechanics, a general expression for the static dielectric constant is derived. It is found, as in earlier work, that the dielectric constant is dependent upon the mean-square dipole moment of a macroscopic spherical sample of the substance. This mean-square moment is expanded as a series in powers of the mean molecular polarizability, and the terms proportional to the zero and first powers are evaluated in detail and in such a way that the long- and the short-range effects are separated. The former are determined with the aid of macroscopic arguments, so that a purely molecular theory remains. In the limit when short-range directional forces are zero, the formula reduces to the well-known Onsager equation. It is found that it is not in general legitimate to replace the surroundings of a macroscopic sample by a continuum having the bulk properties of the substance, and for this reason the approximate equation of Harris & Alder is found to lead to doubtful conclusions. The general equations are applied to the experimental data for water and other liquids, and the results are not unsatisfactory.