A diagrammatic formulation of the kinetic theory of fluctuations in equilibrium classical fluids. VI. Binary collision approximations for the memory function for self correlation functions

We use computer simulation results for a dense Lennard-Jones fluid for a range of temperatures to test the accuracy of various binary collision approximations for the memory function for density fluctuations in liquids. The approximations tested include the moderate density approximation of the generalized Boltzmann-Enskog memory function (MGBE) of Mazenko and Yip, the binary collision approximation (BCA) and the short time approximation (STA) of Ranganathan and Andersen, and various other approximations derived by us using diagrammatic methods. The tests are of twotypes. The first is a comparison of the correlation functions predicted by each approximate memory function with the simulation results, especially for the self longitudinal current correlation function (SLCC). The second is a direct comparison of each approximate memory function with a memory function numerically extracted from the correlation function data. The MGBE memory function is accurate at short times but decays to zero too slowly and gives a poor description of the correlation function at intermediate times. The BCA is exact at zero time, but it predicts a correlation function that diverges at long times. The STA gives a reasonable description of the SLCC but does not predict the correct temperature dependence of the negative dip in the function that is associated with caging at low temperatures. None of the other binary collision approximations is a systematic improvement upon the STA. The extracted memory functions have a rapidly decaying short time part, much like the STA, and a much smaller, more slowly decaying part of the type predicted by mode coupling theory. Theories that use mode coupling commonly include a binary collision term in the memory function but do not discuss in detail the nature of that term. ...Comment: 18 pages, 10 figure

Monte Carlo study of the Widom-Rowlinson fluid using cluster methods

The Widom-Rowlinson model of a fluid mixture is studied using a new cluster algorithm that is a generalization of the invaded cluster algorithm previously applied to Potts models. Our estimate of the critical exponents for the two-component fluid are consistent with the Ising universality class in two and three dimensions. We also present results for the three-component fluid.Comment: 13 pages RevTex and 2 Postscript figure

Transport properties of dense fluid argon

We calculate using molecular dynamics simulations the transport properties of realistically modeled fluid argon at pressures up to $\simeq 50GPa$ and temperatures up to $3000K$. In this context we provide a critique of some newer theoretical predictions for the diffusion coefficients of liquids and a discussion of the Enskog theory relevance under two different adaptations: modified Enskog theory (MET) and effective diameter Enskog theory. We also analyze a number of experimental data for the thermal conductivity of monoatomic and small diatomic dense fluids.Comment: 8 pages, 6 figure

Radius of curvature approach to the Kolmogorov-Sinai entropy of dilute hard particles in equilibrium

We consider the Kolmogorov-Sinai entropy for dilute gases of $N$ hard disks or spheres. This can be expanded in density as $h_{\mathrm{KS}} \propto n N [\ln n a^d+ B + O(n a^d)+O(1/N)]$, with $a$ the diameter of the sphere or disk, $n$ the density, and $d$ the dimensionality of the system. We estimate the constant $B$ by solving a linear differential equation for the approximate distribution of eigenvalues of the inverse radius of curvature tensor. We compare the resulting values of $B$ both to previous estimates and to existing simulation results, finding very good agreement with the latter. Also, we compare the distribution of eigenvalues of the inverse radius of curvature tensor resulting from our calculations to new simulation results. For most of the spectrum the agreement between our calculations and the simulations again is very good.Comment: 12 pages, 4 figure

Technical and Economic Feasibility of U. S. District Heating Systems using Waste Heat from Fusion Reactors

In this study district heating systems are shown to be economically attractive for large-scale implementation in the U.S., provided suitable sources of waste heat are available. Fusion reactors appear to be very desirable as sources of waste heat for district heating systems. Since fusion reactors appear to be more environmentally acceptable than fission reactors or coal steam electric plants, they could possibly be located closer to district heat load centers, which should result in substantial cost savings due to lower transmission costs. In this study, CTR distances on the order of 20 miles from urban areas are acceptable in terms of transmission cost. Model district heating systems are designed for nine regions in the U.S. (New York City, Paterson, N.J., Chicago, Philadelphia, Los Angeles, Baton Rouge, New Orleans, Jersey City, and Newark). Estimates are also made as to the implementation and costs to be expected for district heating systems in the U.S. as a whole. The study evaluates the impact of the CRT-district heat option on the U.S. energy system; this was carried out using the BNL BESOM program. It is concluded that two additional markets exist for district heating, those of process heat and air conditioning. (MCW

Nonequilibrium temperature and bulk viscosity for a dense fluid of square-well molecules

A recently proposed nonlinear kinetic theory for a dense fluid of square-well molecules reveals the existence of two temperature scales, one associated with kinetic energy and the other with potential energy. The scales are coupled through conservation of energy and, for nonequilibrium states, the temperature scales are not identical. The distinction between the temperature scales affects the value of the bulk viscosity

Planning analyses for geothermal district heating

Methodology and data bases are described which can provide a comprehensive planning assessment of the potential for geothermal district heating in any US market. This economic systems model encompasses life-cycle costing over a period of rising competitive fuel prices, it addresses the expansion and financing of a district system over time, and it includes an overall optimization of system design. The elemental area for all analyses is the census tract, for which published data allow estimation of residential and commercial heating demands, building retrofit requirements, and competitive fuel consumption and cost. A system type design, an appropriate hot water district piping system, and costing of heat supply is performed for groups of contiguous tracts in any urban market. Groups are aggregated, in decreasing benefit to cost order, to achieve optimal systems. A specific application for Salt Lake City, Utah, is also described

MICROSCOPIC THEORY OF INTRINSIC SHEAR AND BULK VISCOSITIES

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Kinetic mean field theories: Results of energy constraint in maximizing entropy

Structure of liquids and solids; crystallography Classical, semiclassical, and quantum theories of liquid structure Statistical theories of liquid structure - Kinetic and transport theory of fluids; physical properties of gases Kinetic and transport theor