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 re‐analyzes the results of earlier, very precise measurements of the viscosity of water at essentially atmospheric pressure. This is done in terms of a new, theoretically‐based equation for the operation of a capillary viscometer rather than in terms of semi‐empirical equations used by the original authors. The new analysis eliminates possible systematic errors and permits the establishment of realistic error bounds for water in its role as a standard reference substance for viscosity. The latter are smaller than those embodied in the most recent International Formulation. Standard values of the ratio of viscosity at a temperature T to its value at 20 °C have been derived from the re‐analyzed data because the uncertainty of this ratio is an order of magnitude smaller than that of the absolute values. The ratios are used to generate absolute values with the aid of the standard NBS datum μ=1002.0 μPa s at 20 °C. The viscosity ratios have been correlated with the aid of two empirical equations. The more accurate equation covers the range 0 °C?t ?40 °C with an uncertainty of ±0.05%. The less accurate equation covers the wider range −8 °C?t?150 °C with the more limited accuracy of ±0.2%. The two empirical equations are compatible with each other to 0.09%.

Viscosity of Liquid Water in the Range - 8 C to 150 C,

Tabulated values of the dynamic and kinematic viscosity of aqueous sodium chloride solutions are given. The tables cover the temperature range 20–150 °C, the pressure range 0.1–35 MPa and is the concentration range 0–6 molal. It is estimated that the accuracy of the tabulated values is ±0.5%. The correlating equations from which the tables were generated are given.

Tables of the Dynamic and Kinematic Viscosity of Aqueous KCl Solutions in the Temperature Range 25-150 C and the Pressure Range 0.1-35 MPa,

The report contains a set of easy‐to‐program expressions for the calculation of the thermodynamic and transport properties of the five noble gases (He, Ne, Ar, Kr, Xe) and of the 26 binary and multicomponent mixtures that can be formed with them. The properties in question are second virial coefficient B, viscosity η, thermal conductivity λ, self‐diffusion and binary diffusion coefficient D, and thermal diffusion factor αT. The calculation of properties is restricted to low densities ( ρ≪B/C) but covers the full range of compositions and a temperature interval extending from absolute zero to the onset of ionization. Owing to the careful theoretical basis on which the algorithm has been erected, all properties are thermodynamically consistent with each other. Reference to a selected set of critically evaluated measurements provides a basis for the estimation of uncertainties. The report contains 54 abbreviated tables of numerical data and 86 deviation plots. It is asserted that the results are comparable to the best measurements that could be performed at present.

Equilibrium and transport properties of the noble gases and their mixtures at low density

The paper contains a complete, modernized theory of the transient hot-wire method for measuring the thermal conductivity of fluids which can be employed in the form of an absolute instrument and which can be operated with a precision of 0.02% and an accuracy of 0.2%. It is a companion paper for ref. 1.

The analysis demonstrates that the instrument can be designed to imitate very closely the behaviour of a finite portion of an infinite line source of constant heat flux, q, which transfers the heat radially into an infinite fluid.

Expressions for the corrections are obtained by a general perturbation method which allows us to examine them one or several at a time. The principal corrections discussed in the form of nine subproblems are: finite inner cylinder, composite cylinders, Knudsen effects, radiation, outer cell circumference, compressibility and natural convection, finite cell dimensions, variable fluid properties and heating over a finite length.

The last section summarizes the most important corrections for a reader who is interested in using them rather than in following the analysis itself. The main text supplies all data required by the designer of an instrument of this type.

The theory of the transient hot-wire method for measuring thermal conductivity

The present publication contains data on the thermophysical properties of deuterium oxide (heavy water). It is a companion to the paper on the thermophysical properties of fluid H2O published earlier in this journal by the same authors. The properties are represented by equations which can be readily programed on a computer and incorporated in data banks. All data have been carefully and critically analyzed. The compendium represents the best available data for fluid D2O.

Joseph Kestin

Papers

Viscosity of Liquid Water in the Range - 8 C to 150 C,

Tables of the Dynamic and Kinematic Viscosity of Aqueous KCl Solutions in the Temperature Range 25-150 C and the Pressure Range 0.1-35 MPa,

Equilibrium and transport properties of the noble gases and their mixtures at low density

The theory of the transient hot-wire method for measuring thermal conductivity

Thermophysical properties of fluid D2O