A new method for the evaluation of thermal conductivity and thermal diffusivity from transient hot strip measurements

Sabuga, Wladimir; Hammerschmidt, U.

doi:10.1007/bf01441921

Cited by 18 publications

(11 citation statements)

References 8 publications

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“…Initially, the first measurements using the circular heater (disc) form indicated that the thermal conductivity of the material was of the order of 20% greater than that obtained by all other methods. This factor confirmed that the material was anisotropic and, as discussed earlier, the SP and NPL data were subsequently analyzed (Sabuga and Hammerschmidt, 1995) to provide the values in the table for the specific direction perpendicular to the specimen surface.…”

Section: Transient Methodsmentioning

confidence: 95%

An inter-comparison of a steady-state and transient methods for measuring the thermal conductivity of thin specimens of masonry materials

Salmon

Tye

2010

Journal of Building Physics

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Recent standardization developments within the European Union relating to masonry and block systems now allow calculation of thermal performance to be undertaken based on the block configuration and reliable values of the material thermal conductivity. In general, to attain the optimum thermal resistance of a block a minimum amount of material is used such that the webs and faces bounding the air spaces are usually of the order of 6-8 mm. However, the current standard measurement methods are not suitable or precise enough for direct measurement on thin specimens cut from blocks. As a result the masonry industry requested that CEN TC89 investigate and recommend candidate alternative methods suitable for standardization.A working group was established and following consideration of the issues involved, including, in particular, the thermal conductivity range, simplicity, small size, and short operating times, two methods were proposed for further investigation. The first was the steady-state guarded heat flow meter and the second the transient hot strip in both its linear and disc configurations. In order to verify their applicability both methods were used in an initial inter-comparison involving a total of nine organizations. Measurements were made at or close to room temperature on uniform thin test specimens fabricated from a batch of one typical masonry material.This article contains details of the distinctive features and suitability of each method for the task, the participants, the material and test criteria, and includes a summary and discussion of the results that includes unexpected effects due to anisotropy in the particular material. Overall, the results were very promising such that a further Downloaded from series of intercomparison measurements is now underway on some typical materials within the total conductivity range for masonry type products.

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Section: Transient Methodsmentioning

confidence: 95%

An inter-comparison of a steady-state and transient methods for measuring the thermal conductivity of thin specimens of masonry materials

Salmon

Tye

2010

Journal of Building Physics

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“…Die Probentemperatur θ -∞ im eingeschwungenen Zustand stellt den arithmetischen Mittelwert der Temperaturdifferenzen (θ -E -θ 0 ) und (θ -A -θ 0 ) dar; θ 0 bezeichnet die Anfangstemperatur der Probe. Die Bestimmung der Zeitkonstanten τ q erfolgt aus der Antwortfunktion (14) indem für t = τ q gesetzt wird. Im Weiteren wird in gleicher Weise wie bei der Ermittlung von τ q vorgegangen.…”

Section: Thermische Anregung Durch Sprungfunktionunclassified

“…Letzteres trifft auch für eine Vielzahl von Verfahren mit instationärer Zustandsbeschreibung zu, bei denen die Bestimmung der Parameter λ, a oder ρc aus Lösungen der Wärmetransportgleichung abgeleitet wird, z. B. durch eine Anpassung von numerischen Ergebnissen und Meßwerten [13], [14], nach der Heizdraht-oder Laser-Flash-Methode [15], [16], [17], mittels heizbarer Sonden [18], [19] oder nach speziellen Auswertealgorithmen für extrem kleine Bauteile [20]. In [21] wird eine Methodik beschrieben, bei der die Temperaturleitfähigkeit einer dün-nen, instationär angeregten Materialprobe aus der Phasenverschiebung zweier Temperaturen bestimmt werden kann.…”

Section: Introductionunclassified

Bestimmung thermophysikalischer Parameter von Baustoffen

Rudolph

Grodde

2005

Bauphysik

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“…= P(AX)Z/4rr(£xt) (1) a, = 7r(AX)Z/Pln2( 02/0, ) (2) where aL--thermal diffusivity due to the phase lag, m2/s; a,--thermal diffusivity due to amplitude decrement, m2/s; P--the period of the wave of axial heat flow, s; AX--axial distance between the thermocouples, m; At--the phase time lag, s; 0~, 02--amplitude at thermocouplel,2, °C.…”

mentioning

confidence: 99%

“…1 Angstroms method for measuring thermal conductivity Angstroms method is an axial periodic heat flow technique Ejal . A long cylindrical specimen was rested at one end on a heater which generated periodic heat flow, and two temperatures were taken by thermocouples mounted at different height of the cylinder.…”

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confidence: 99%

Determination of thermal conductivity of magnesium-alloys

Zhou

Yang

Lamvik³

et al. 2001

J Cent. South Univ. Technol.

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An indirect method, Angstroms method was adopted and an instrument was designed to determine the thermal conductivity of magnesium metal and alloys. Angstroms method is an axial periodic heat flow technique by which the thermal diffusivity can be measured directly. Then thermal conductivity can be obtained with relation to thermal diffusivity. Compared with the recommended data from the literature the fitted values of the thermal diffiusivity correspond with 3%, and the credible probability of the thermal conductivity in the range of 0-450 °C is about 95 %. The method is applicable in the given temperature range. Document code: AThermal conductivity and thermal diffusivity are crucial to metallic materials as they affect the heat transfer rote in the processing process and therefore, influence the thermophysieal performance of the metal products. Therefore, it is of importance for metallurgical industry to determine them precisely. In this research, magnesium metal and alloys were measured to investigate the relationship between the alloying component and the thermal conductivity, and find the dependence of thermal conductivity on temperature.1 Experimental principle and instrument 1.1Angstroms method for measuring thermal conductivity Angstroms method is an axial periodic heat flow technique Ejal . A long cylindrical specimen was rested at one end on a heater which generated periodic heat flow, and two temperatures were taken by thermocouples mounted at different height of the cylinder. The thermal diffusivity of the specimen could be calculated by measuring the decreasing amplitude or increasing phase lag between the thermocouples as the heat wave propagated through the specimens in its axial direction. The following i n [33 express o s are used in the calculation: at. = P(AX)Z/4rr(£xt) (1) a, = 7r(AX)Z/Pln2( 02/0, )where aL--thermal diffusivity due to the phase lag, m2/s; a,--thermal diffusivity due to amplitude decrement, m2/s; P--the period of the wave of axial heat flow, s; AX--axial distance between the thermocouples, m; At--the phase time lag, s; 0~, 02--amplitude at thermocouplel,2, °C.The value of the diffusivity, calculated from the expression, may differ from each other, due to radial heat transfer between the specimen and the surroundings. This can be taken into account by a correction factor, 2rr(Ax) F~ = I Pln(02/0~ ) tand F~ = 1/F~where FL, F~--the correction factors of aL, aa •

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A new method for the evaluation of thermal conductivity and thermal diffusivity from transient hot strip measurements

Cited by 18 publications

References 8 publications

An inter-comparison of a steady-state and transient methods for measuring the thermal conductivity of thin specimens of masonry materials

An inter-comparison of a steady-state and transient methods for measuring the thermal conductivity of thin specimens of masonry materials

Bestimmung thermophysikalischer Parameter von Baustoffen

Determination of thermal conductivity of magnesium-alloys

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