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

Chapter 3 – quantum mechanics

The paper reports new, absolute measurements of the thermal conductivity of hydrogen and deuterium as well as of two binary mixtures of the two components at 27.5°C. The measurements have been carried out as a function of density in a transient hot-wire instrument and extend over the pressure ranges 2 13 MPa for the mixtures and 2 36 MPa for pure hydrogen. The uncertainty in the absolute thermal conductivity data is estimated as one of ±0.2%. The measurements have been arranged so as to yield the ratio of the thermal conductivities of the two pure gases with essentially the same uncertainty. The Eucken factors for the two pure hydrogen isotopes at zero density have been derived and differ from each other by as much as 1.8% which is well beyond experimental uncertainty. The existing kinetic theory expressions for the Eucken factor of a polyatomic gas are not able to account for this difference. On the other hand the first density coefficients for the thermal conductivity of the two hydrogen isotopes are found to be the same within the limits of experimental error.



Es wird uber neue, absolute Messungen den Warmeleitfahigkeit von Wasserstoff, Deuterium und binarer Gemische der beiden Komponenten bei 27,5°C berichtet. Die Messungen sind in einer nicht stationaren Heizdrahtanordnung ausgefuhrt worden und uberdecken den Bereich von 2 13 MPa fur die Gemische und 2 36 MPa fur reinen Wasserstoff. Die Ungenauigkeit der absoluten Warmeleitfahigkeitsdaten wurde auf 0,2% abgeschatzt. Die Messungen sind so ausgefuhrt worden, das die Warmeleitfahigkeiten der beiden reinen Gase mit dem gleichen Fehler behaftet sind. Fur die beiden reinen Isotope sind die Eucken-Faktoren abgeleitet worden. Sie unterscheiden sich um 1,8%, was deutlich auserhalb der Fehlergrenzen liegt. Mit den Ausdrucken fur die Eucken-Faktoren aus der kinetischen Theorie polyatomarer Gase kann dieser Unterschied nicht erklart werden. Andererseits sind die ersten Koeffizienten einer Entwicklung der Warmeleitfahigkeit nach Potenzen der Dichte fur die beiden Wasserstoffisotope innerhalb der Fehlergrenzen gleich.

The thermal conductivity of hydrogen, deuterium and their mixtures near room temperature within the pressure range 2-36 mpa

The paper uses a topologic-geometric method to analyze the flow patterns which can occur in very long vertical pipes. The study explores the consequences of the homogeneous diffusion model when coupled with the standard closure equation for shearing stress and the equation of state for water in the two-phase region. Two cases are analyzed: upward flow in which the gravity and shearing-stress vectors are codirectional, and downward flow when the two vectors are counter-directional.

Application of Geometric Methods to the Study of Two-Phase Flow and Choking in Vertical Pipes

The paper describes two sets of measurements of the viscosity of liquid mercury, essentially along the saturation line, performed in two different oscillating-cup viscometers.



An examination of our own and of other reliable data allows us to recommend the use of the empirical correlation η = 535.3 exp(314.42K/T) μPa s in the range 235 K < T < 600 K. In the wider range we recommend the equation 






The experience acquired during this investigation suggests that an oscillating-cup viscometer cannot be used to determine accurate values of the viscosity of a liquid by reducing the measurement to that of the period only. This is due to small and uncontrollable changes in the elastic properties of the suspension wire or quartz strand which are produced by overstressing or cold-working.



Zwei Reihen von Messungen der Viskositat von flussigem Quecksilber unter Gleichgewichts-Dampfdruck werden beschrieben. Zwei unterschiedliche Viskosimeter nach dem oszillierenden Hohlzylinder-Prinzip wurden benutzt. Kritischer Vergleich der eigenen, neuen Resultate mit Literaturdaten ergibt die empirische Korrelations-Gleichung η = 535.3 exp(314.42 K/T) μPa s fur den Bereich 235 K < T < 600 K. Fur den weiteren Bereich 90 K < T < 1520 K wird die folgende Gleichung vorgeschlagen: 






Die Erfahrungen der Arbeit scheinen zu zeigen, das Bestimmungen der Schwingungszeiten allein nicht ausreichen, um mit dem oszillierenden Hohlzylinder-Viskosimeter ausreichende Genauigkeit zu erhalten. Dies liegt wahrscheinlich an kleinen und unkontrollierbaren Veranderungen der elastischen Eigenschaften des Torsiondrahtes oder Quarzelementes.

The viscosity of liquid mercury from 20°c to 260°c along the saturation line

A method, based on the modified Enskog theory (MET), as extended to binary mixtures by H.H. Thorne, is presented which allows the computation of the thermal conductivity of binary mixtures of monatomic gases up to densities of about 200 amagat with an uncertainty no greater than 2 percent when compared with the best available measurements.

Joseph Kestin

Papers

Chapter 3 – quantum mechanics

The thermal conductivity of hydrogen, deuterium and their mixtures near room temperature within the pressure range 2-36 mpa

Application of Geometric Methods to the Study of Two-Phase Flow and Choking in Vertical Pipes

The viscosity of liquid mercury from 20°c to 260°c along the saturation line

A Theory for the Composition Dependence of the Thermal Conductivity of Dense Binary Mixtures of Monatomic Gases