11 research outputs found
The liquid-vapor interface of an ionic fluid
We investigate the liquid-vapor interface of the restricted primitive model
(RPM) for an ionic fluid using a density-functional approximation based on
correlation functions of the homogeneous fluid as obtained from the
mean-spherical approximation (MSA). In the limit of a homogeneous fluid our
approach yields the well-known MSA (energy) equation of state. The ionic
interfacial density profiles, which for the RPM are identical for both species,
have a shape similar to those of simple atomic fluids in that the decay towards
the bulk values is more rapid on the vapor side than on the liquid side. This
is the opposite asymmetry of the decay to that found in earlier calculations
for the RPM based on a square-gradient theory. The width of the interface is,
for a wide range of temperatures, approximately four times the second moment
correlation length of the liquid phase. We discuss the magnitude and
temperature dependence of the surface tension, and argue that for temperatures
near the triple point the ratio of the dimensionless surface tension and
critical temperature is much smaller for the RPM than for simple atomic fluids.Comment: 6 postscript figures, submitted to Phys. Rev.
Physically Similar Systems - A History of the Concept
PreprintThe concept of similar systems arose in physics, and appears to have originated with Newton in the
seventeenth century. This chapter provides a critical history of the concept of physically similar
systems, the twentieth century concept into which it developed. The concept was used in the
nineteenth century in various fields of engineering (Froude, Bertrand, Reech), theoretical physics (van
der Waals, Onnes, Lorentz, Maxwell, Boltzmann) and theoretical and experimental hydrodynamics
(Stokes, Helmholtz, Reynolds, Prandtl, Rayleigh). In 1914, it was articulated in terms of ideas
developed in the eighteenth century and used in nineteenth century mathematics and mechanics:
equations, functions and dimensional analysis. The terminology physically similar systems was
proposed for this new characterization of similar systems by the physicist Edgar Buckingham.
Related work by Vaschy, Bertrand, and Riabouchinsky had appeared by then. The concept is very
powerful in studying physical phenomena both theoretically and experimentally. As it is not currently
part of the core curricula of STEM disciplines or philosophy of science, it is not as well known as it
ought to be
Recommended from our members
Thermodynamic properties of a geothermal working fluid; 90% isobutane-10% isopentane: Final report
We present tables of thermodynamic properties, and dew and bubble properties, of a mixture of 90 mol % isobutane and 10 mol % isopentane, a working fluid in a binary geothermal power cycle. The tables are generated by a formulation of the Helmholtz free energy, in which the mixture properties are mapped onto the known properties of pure isobutane by means of the principle of generalized corresponding states. The data base for the Helmholtz free energy formulation is new. We report data obtained in three different apparatus: critical-line and isopentane vapor pressure data obtained in a visual cell; vapor-liquid equilibria data obtained in a mercury-operated variable-volume cell; and pressure-volume-temperature data for the 90 mol %-10 mol % mixture obtained in a semi-automated Burnett-isochoric apparatus. The principles of the methods, and estimates of the reliability, are discussed and all experimental data are compared with the surface. The results are tables of specific volume, enthalpy, entropy, specific heat and density and temperature derivatives of the pressure at 10 K temperature increments from 240 to 600 K along isobars from 0.01 to 20 MPa. Separate tables are prepared from the dew and bubble properties of the 90-10 mixture. Estimates of the effects of isomeric impurity of isobutane are given in graphical form
Recommended from our members
Thermophysical properties of working fluids for binary geothermal cycles. Final report
The following are presented: thermodynamic properties of isobutane and isobutane-isopentane mixtures; a scaled fundamental equation for mixtures of isobutane and isopentane near gas-liquid critical line; and viscosities of hydrocarbons and their mixtures. (MHR