It is shown that a “nanofluid” consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity.

Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles

Oxide nanofluids were produced and their thermal conductivities were measured by a transient hot-wire method. The experimental results show that these nanofluids, containing a small amount of nanoparticles, have substantially higher thermal conductivities than the same liquids without nanoparticles. Comparisons between experiments and the Hamilton and Crosser model show that the model can predict the thermal conductivity of nanofluids containing large agglomerated Al{sub 2}O{sub 3} particles. However, the model appears to be inadequate for nanofluids containing CuO particles. This suggests that not only particle shape but size is considered to be dominant in enhancing the thermal conductivity of nanofluids.

Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles

We have produced nanotube-in-oil suspensions and measured their effective thermal conductivity. The measured thermal conductivity is anomalously greater than theoretical predictions and is nonlinear with nanotube loadings. The anomalous phenomena show the fundamental limits of conventional heat conduction models for solid/liquid suspensions. We have suggested physical concepts for understanding the anomalous thermal behavior of nanotube suspensions. In comparison with other nanostructured materials dispersed in fluids, the nanotubes provide the highest thermal conductivity enhancement, opening the door to a wide range of nanotube applications.

Anomalous thermal conductivity enhancement in nanotube suspensions

Heat transfer characteristics of nanofluids: a review

Pore fluids strongly influence the seismic properties of rocks. The densities, bulk moduli, velocities, and viscosities of common pore fluids are usually oversimplified in geophysics. We use a combination of thermodynamic relationships, empirical trends, and new and published data to examine the effects of pressure, temperature, and composition on these important seismic properties of hydrocarbon gases and oils and of brines. Estimates of in-situ conditions and pore fluid composition yield more accurate values of these fluid properties than are typically assumed. Simplified expressions are developed to facilitate the use of realistic fluid properties in rock models. Pore fluids have properties that vary substantially, but systematically, with composition, pressure, and temperature. Gas and oil density and modulus, as well as oil viscosity, increase with molecular weight and pressure, and decrease with temperature. Gas viscosity has a similar behavior, except at higher temperatures and lower pressures, where the viscosity will increase slightly with increasing temperature. Large amounts of gas can go into solution in lighter oils and substantially lower the modulus and viscosity. Brine modulus, density, and viscosities increase with increasing salt content and pressure. Brine is peculiar because the modulus reaches a maximum at a temperature from 40 to 80°C. Far less gas can be absorbed by brines than by light oils. As a result, gas in solution in oils can drive their modulus so far below that of brines that seismic reflection bright spots may develop from the interface between oil saturated and brine saturated rocks.

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Seismic properties of pore fluids

The paper reports the results of new measurements of the thermal conductivity of CH 4 -CO mixtures at 27.5°C and up to a pressure of 12 MPa. This further contribution to a growing body of data on the thermal conductivity of binary mixtures of polyatomic gases is analyzed in the same way as was done by the present group in several earlier publications with essentially identical conclusions.

Thermal conductivity of methane with carbon monoxide

In this paper, the results are reported of two separate tests on the validity of three mixing rules that are commonly employed in determining the force parameters for unlike molecular collisions from those for like‐molecular collisions where the interaction may be described by means of a two‐parameterforcepotential. Both tests utilize the equations for the viscosity of dilute gases based on the Chapman–Enskog solution to the Boltzmann equation, together with highly precise experimental data on the viscosity of pure gases and binary gas mixtures. Both tests indicated that the experimental data are incompatible with the simple combination rules; that is, the arithmetic average for the distance parameter and the geometric mean for the energy parameter. The results of the second test show that the combination rule eijσij6 = (eiiσii6ejjσjj6)1 / 2 is not contradicted by the experimental data. All possible binary combinations of the gases He, Ne, Ar, N2, and CO2 were analyzed for this report.

Combination Rules for Binary Gaseous Mixtures Deduced from Viscosity

The paper presents a simple, semitheoretical expression for the initial density dependence of the viscosity and thermal conductivity of gaseous mixtures in terms of the appropriate properties of the pure components and of their interaction quantities. The derivation is based on Enskog's theory of dense gases and provides us with an equation in which the composition dependence of the linear factor in the density expansion is explicit. The interaction quantities are directly related to those of the mixture extrapolated to zero density and to a universal function valid for all gases. The reliability of the formulation is assessed with respect to the viscosity of several binary mixtures. It is found that the calculated viscosities of binary mixtures agree with the experimental data with a precision which is comparable to that of the most precise measurements. The method developed in the paper allows us to calculate the viscosity and thermal conductivity of moderately dense binary and multicomponent mixtures of gases. The evaluation of the respective properties in the limit of zero density has been made possible by the law of corresponding states developed by Kestin, Ro, and Wakeham.

Viscosity and Thermal Conductivity of Moderately Dense Gas Mixtures

The paper gives an outline of a thermodynamic theory of metal plasticity reduced to its simplest terms. The theory is based on classical thermostatics as it applies to elastic deformations and argues that a system which undergoes plastic deformation traverses a densely spaced, alternating sequence of stable and unstable unconstrained equilibrium states. These occur on a scale which is not easily observed during macroscopic experiments and are confined to a microscale of the order of the size of a crystallite. The transition from a stable state to an unstable state can be treated as a reversible process but the further transition from an unstable to a stable state occurs through an intrinsically dissipative, irreversible “jump”.

Joseph Kestin

Papers

Thermal conductivity of methane with carbon monoxide

Combination Rules for Binary Gaseous Mixtures Deduced from Viscosity

Viscosity and Thermal Conductivity of Moderately Dense Gas Mixtures

Thermodynamics of Plastic Deformation

Hybrid fossil-geothermal power plants.