Thermal Conductivity Measurements of Liquid Mercury and Gallium by a Transient Hot-Wire Method in a Static Magnetic Field

Fukuyama, Hidetoshi; Yoshimura, Takuya; Yasuda, Hideyuki; Ohta, Hiromichi

doi:10.1007/s10765-006-0089-3

Cited by 18 publications

(15 citation statements)

References 22 publications

(44 reference statements)

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“…The temperature dependence of viscosity for liquid metals can be described by ν = η 0 ρ expðE=RT ab Þ; [9] where η 0 = 4:36 × 10 −4 Pa · s and E = 4; 000 J/mol are constants specific to liquid gallium, R = 8:3144 J/(K · mol) is the gas constant, and T ab is the absolute temperature of the fluid in kelvins (41). The temperature dependence of the thermal conductivity of liquid gallium is, unfortunately, not very well constrained (42,43). For simplicity, we elect to use a single value of k such that Nu = 1 for our experiment with no convection (see Figs.…”

Section: Methodsmentioning

confidence: 99%

Turbulent convection in liquid metal with and without rotation

King

Aurnou

2013

Proc. Natl. Acad. Sci. U.S.A.

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The magnetic fields of Earth and other planets are generated by turbulent, rotating convection in liquid metal. Liquid metals are peculiar in that they diffuse heat more readily than momentum, quantified by their small Prandtl numbers, Pr = 1. Most analog models of planetary dynamos, however, use moderate Pr fluids, and the systematic influence of reducing Pr is not well understood. We perform rotating Rayleigh-Bénard convection experiments in the liquid metal gallium (Pr = 0:025) over a range of nondimensional buoyancy forcing (Ra) and rotation periods (E). Our primary diagnostic is the efficiency of convective heat transfer (Nu). In general, we find that the convective behavior of liquid metal differs substantially from that of moderate Pr fluids, such as water. In particular, a transition between rotationally constrained and weakly rotating turbulent states is identified, and this transition differs substantially from that observed in moderate Pr fluids. This difference, we hypothesize, may explain the different classes of magnetic fields observed on the Gas and Ice Giant planets, whose dynamo regions consist of Pr < 1 and Pr > 1 fluids, respectively.T he interiors of Earth and other terrestrial bodies, as well as the Gas Giant planets, contain vast oceans of flowing metals. Mixed by turbulent convection as these planets cool, the flowing conductors produce electric currents that maintain planetary magnetic fields. These bodies also rotate, and it is expected that the resulting Coriolis forces strongly influence convective dynamo processes. Beyond linear theory (1), however, not much is known about the dynamics of rotating convection in liquid metal that underlie planetary magnetic field generation.Theory and experiments often focus on a simplified analog of geophysical and astrophysical systems, Rayleigh-Bénard convection (RBC). The RBC system consists of a fluid layer contained between flat, horizontal plates separated by distance h, the bottom of which is warmer than the top by ΔT, and with downward pointing gravity, g. Near the bottom boundary, the fluid warms and expands by a volumetric factor α (per degree kelvin) and similarly cools and contracts near the top boundary, such that the fluid is unstably stratified.Rotating convection is explored by spinning the RBC system about a vertical axis at an angular rate Ω, which is adopted as the reference frame for the model. The fluid dynamics of the system are characterized by three dimensionless parameters. The Prandtl number, Pr ≡ ν=κ, defines the diffusive transport properties of the fluid, where ν and κ are its viscous and thermal diffusivities. The Rayleigh number, Ra ≡ αgΔTh 3 =ðνκÞ, prescribes the magnitude of the buoyancy force. Finally, the rotation period is specified by the Ekman number, E ≡ ν=ð2Ωh 2 Þ. The primary diagnostic used in many convection studies, including this one, is the Nusselt number, which characterizes the efficiency of heat transport by convection as Nu ≡ qh=ðkΔTÞ, where q is total heat flux and k is the fluid's thermal conductivi...

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Section: Methodsmentioning

confidence: 99%

Turbulent convection in liquid metal with and without rotation

King

Aurnou

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…4.2.1), the appearance of parasitic convective heat transfer around the wire can easily be experimentally detected (and therefore eliminated for λ determination); the appearance of free convection is clearly dependent on the liquid and wire heating (see Figs. [6][7][8][9][10][11][12][13]. In fact, for short hot wires like those used for the present experiments, the main error for λ determination is coming from the conductive heat transfer between the ends of the finite wire and the supporting prongs; a theoretical analysis of this error has been made in [27], with an upper limit of the relative value given by…”

Section: Uncertaintiesmentioning

confidence: 96%

“…For such liquids, the wire must then be electrically insulated by coating it with a thin insulation layer. A number of coating techniques have been employed for this purpose (polyester coating [3], silica coating [4], aluminum-oxidecoated wire [5,6], and tantalum-oxide-coated wire [7][8][9][10][11]. Each coating technique has to be adapted to the wire and liquid types, and to the working (pressure and temperature) conditions.…”

Section: Introductionmentioning

confidence: 99%

A New Transient Hot-Wire Instrument for Measuring the Thermal Conductivity of Electrically Conducting and Highly Corrosive Liquids using Small Samples

et al. 2008

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The transient hot-wire technique is widely used for measurements of the thermal conductivity of most fluids. However, for some particular liquids such as concentrated nitric acid solutions or similar nitric mixtures, for which the thermal properties are important for industrial or security applications, this technique can be difficult to use, which is essentially due to incompatibility between measurement probe materials and highly electrically conducting and corrosive liquids. Moreover, the possible highly energetic (explosive) character of these liquids requires minimum volume liquid samples, and safety measurement devices and processes. It is the purpose of this paper to report on a new patented instrument, based on tantalum short-hot-wire probe technology, which responds to the above requirements and allows safe automated thermal-conductivity measurements of concentrated acid nitric solutions and similar nitric mixtures for liquid samples less than 2 cm3, with uncertainties better than 5%

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“…In addition, the applied voltage of the electrophoresis was 100 V, and the electrodeposition time was 5 s. The sample was dried in air at room temperature for 24 h after the electrodeposition. The thickness of the alumina film formed by this procedure was approximately 40 µm [7,14]. …”

Section: Samplementioning

confidence: 99%

An application of thermal microscopes to the measurement of thermal effusivity of films

Hatori¹,

Suzuki

Fukuyama

et al. 2008

Heat Trans. Asian Res.

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The application of thermal microscopes to the measurement of local thermal properties has drawn considerable scientific interest. We report on the application of a thermal microscope to the measurement of thermal effusivity for films comprising alumina deposited on a substrate, which were fabricated by an electrophoretic deposition method. The measured data was analyzed to consider the undulations on the sample surface The thermal effusivity of these samples was approximately 1 × 10 ; this value is smaller than that for dense alumina because the alumina grain makes contact with a point.

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Thermal Conductivity Measurements of Liquid Mercury and Gallium by a Transient Hot-Wire Method in a Static Magnetic Field

Cited by 18 publications

References 22 publications

Turbulent convection in liquid metal with and without rotation

Turbulent convection in liquid metal with and without rotation

A New Transient Hot-Wire Instrument for Measuring the Thermal Conductivity of Electrically Conducting and Highly Corrosive Liquids using Small Samples

An application of thermal microscopes to the measurement of thermal effusivity of films

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