Measurements of the Thermal Conductivity of Molten Lead Using a New Transient Hot-Wire Sensor

Bilek, J.; Atkinson, J.K.; Wakeham, W. A.

doi:10.1007/s10765-007-0182-2

Cited by 13 publications

(5 citation statements)

References 11 publications

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“…To overcome the former limitation, faster sampling rates would be preferred over a thicker annulus of liquid around the probe, as the thickness of the annulus needs to be limited to prevent the development of convective currents. To overcome the latter limitation and realistically solve the system in multiple dimensions, a finite element analysis software would need to be employed to provide model data to be used in the fitting process, similar to what was done with Billek et al [48]. This also has the benefit of more accurately modeling the separate materials within the probe, instead of the current method of lumping their properties.…”

Section: Limitations Of the Methodsmentioning

confidence: 99%

“…Most THW designs requires that the bare wire be in direct contact with the sample being measured, but unfortunately due to the electrical conductivity and the corrosivity of the molten salts this version of the method cannot be used. To overcome this, a thin insulating layer is often placed around the wire, such as sandwiching the wire between two alumina plates [48] or more commonly to anodize a tantalum wire and electrical leads [49][50][51]. This latter approach has performed well but is limited to temperatures below 550 K because of the breakdown of the tantalum oxide.…”

Section: Basis For Measurements With the Needle Probe Approachmentioning

confidence: 99%

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Use of a Needle Probe to Measure the Thermal Conductivity of Electrically Conductive Liquids at High Temperatures

Ruth,

Merritt,

Munro

2024

Preprint

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This paper considers the necessary conditions for using a derivative of a transient hot wire (termed a needle probe) approach to measure electrically conducting fluids at high temperatures, especially molten halide salts. The focus is on the development of a new theory based on a multi-layer system necessary to ensure electrical isolation of electrical wires from the surrounding fluid. This includes the use of a thin annulus of fluid to minimize convective heat transfer modes within the fluid of interest, which was inspired by the concentric cylinder method. Good measurements require the following considerations: concentricity of the probe and surrounding crucible to ensure a consistent fluid gap, accounting for corrections for deviation of the model at early times, and modeling radiation heat transfer through transparent fluids. Uncertainties are larger than transient hot wire methods because of the deviations from experimental conditions that can easily match an analytical approximation. An appropriate estimation of the measurement uncertainty can be obtained through careful design of the instrumentation, thorough uncertainty analysis, and limiting the measurements to only the applicable thermal property ranges of the approach. The 1D model used to interpret measured temperature data has been shown to be reliable for thermal conductivity measurements ranging from at least 0.39 W/mK to 0.92 W/mK and for temperatures from 293-1023 K. The approach is used to present thermal conductivity data of the molten salts NaCl-KCl (51-49 mol%) and LiCl-NaCl (28-72 mol%).

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Section: Limitations Of the Methodsmentioning

confidence: 99%

Section: Basis For Measurements With the Needle Probe Approachmentioning

confidence: 99%

Use of a Needle Probe to Measure the Thermal Conductivity of Electrically Conductive Liquids at High Temperatures

Ruth,

Merritt,

Munro

2024

Preprint

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“…A constant electrical current in the wire results in a nearly constant line source of a heat flux. The theoretical solution of the non-stationary heat transfer problem is known [27][28][29][30][31][32][33]36] for the ideal infinitely long wire. Assuming that the physical properties do not vary during a measurement and heat is generated from a wire of zero radius, the temperature rise T (t) at the extremity of the wire can be represented by…”

Section: Transient Hot-wire Methodsmentioning

confidence: 99%

“…The transient hot-wire method (THW) [27][28][29][30] is used for this purpose in order to avoid the problem related with the influence of the contact resistance on the measurement procedure. This method is well adapted for measurements in liquids [31][32][33][34][35], but the possibility of its application for characterization of porous solid media is an open question. For justification of THW measurements in porous media and estimation of possible errors related with the contact resistance, samples with different thicknesses have been tested.…”

Section: Introductionmentioning

confidence: 99%

Thermal-Conductivity Characterization of Gas Diffusion Layer in Proton Exchange Membrane Fuel Cells and Electrolyzers Under Mechanical Loading

et al. 2011

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Accurate information on the temperature field and associated heat transfer rates is particularly important for proton exchange membrane fuel cells (PEMFC) and PEM electrolyzers. An important parameter in fuel cell and electrolyzer performance analysis is the effective thermal conductivity of the gas diffusion layer (GDL) which is a solid porous medium. Usually, this parameter is introduced in modeling and performance analysis without taking into account the dependence of the GDL thermal conductivity λ (in W · m −1 · K −1 ) on mechanical compression. Nevertheless, mechanical stresses arising in an operating system can change significantly the thermal conductivity and heat exchange. Metrology allowing the characterization of the GDL thermal conductivity as a function of the applied mechanical compression has been developed in this study using the transient hot-wire technique (THW). This method is the best for obtaining standard reference data in fluids, but it is rarely used for thermalconductivity measurements in solids. The experiments provided with Quintech carbon cloth indicate a strong dependence (up to 300 %) of the thermal conductivity λ on the applied mechanical load. The experiments have been provided in the pressure range 0 < p < 8 MPa which corresponds to stresses arising in fuel cells. All obtained experimental results have been fitted by the equation λ = 0.9log(12 p + 17)(1 − 0.4e −50 p ) with 9 % uncertainty. The obtained experimental dependence can be used for correct modeling of coupled thermo/electro-mechanical phenomena in fuel cells and 123 1026 Int J Thermophys (2011) 32:1025-1037 electrolyzers. Special attention has been devoted to justification of the main hypotheses of the THW method and for estimation of the possible influence of the contact resistances. For this purpose, measurements with a different number of carbon cloth layers have been provided. The conducted experiments indicate the independence of the measured thermal conductivity on the number of GDL layers and, thus, justify the robustness of the developed method and apparatus for this type of application.

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“…Accordingly, the wires were maintained under stable tension while their temperature changed over time. This design was modified to suit other applications and used to measure many fluids and molten metals [94][95][96]. A similar portable instrument was also built to meet in-situ measurements [97].…”

Section: Recent Developments In Hot-wire Instrumentsmentioning

confidence: 99%

Thermal conductivity measurements using the transient hot-wire method: a review

Salim

2022

Meas. Sci. Technol.

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The accurate determination of the thermal conductivity of any material is a key element in understanding its actual thermal performance, thus assigning its suitability for a particular application. This, of course, includes its efficiency while being used, lifetime, probability of failure or breakdown, and most importantly, user safety. Several methods are used to measure the thermal conductivity of materials. However, the transient hot-wire method has many practical advantages over other methods due to its relative simplicity and suitability for different materials. The hot-wire method can deliver accurate measurements of gases, liquids, and some solids over a relatively-wide thermal conductivity range. Furthermore, with careful design of the hot-wire instrument, it can be used to measure the thermal conductivity at elevated temperature and under high pressure, which is essential for many industrial applications. In turn, this has made the method one of the most frequently used. This review paper explains the theory of the hot-wire method and demonstrates the technical developments of hot-wire instruments. The paper also presents the advances of electric circuits used to measure the resistance of the hot wire, thus its temperature, during the transient experiment. In addition, it shows the calibration of the hot wire together with the calculation of thermal conductivity.

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Measurements of the Thermal Conductivity of Molten Lead Using a New Transient Hot-Wire Sensor

Cited by 13 publications

References 11 publications

Use of a Needle Probe to Measure the Thermal Conductivity of Electrically Conductive Liquids at High Temperatures

Use of a Needle Probe to Measure the Thermal Conductivity of Electrically Conductive Liquids at High Temperatures

Thermal-Conductivity Characterization of Gas Diffusion Layer in Proton Exchange Membrane Fuel Cells and Electrolyzers Under Mechanical Loading

Thermal conductivity measurements using the transient hot-wire method: a review

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