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Fluid radiation effects in the transient hot-wire technique

Measurement of thermal conductivity of propane

Journal of Thermal Analysis and Calorimetry
Authors: Y. Shi, L. Sun, F. Tian, J. Venart, and R. Prasad

Abstract  

The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity of fluids. Refinement of this method has resulted in a capability for accurate and simultaneous measurement of both thermal conductivity and thermal diffusivity together with a determination of the specific heat. However, these measurements, especially those for the thermal diffusivity, may be significantly influenced by fluid radiation. The present work investigates the effect of fluid radiation on the measurements of the thermal conductivity of propane. Recently developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. Measurements at 372 K with a hot-wire instrument demonstrate the presence of radiation effects in both the liquid and vapor phase. The influence is much more pronounced in liquid propane at 15.5 MPa than in the vapor phase at 881.5 kPa. The technique employed to obtain radiation-free thermal conductivity measurements is described.

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Radiation effects in the transient hot-wire technique

Measurement of the thermal conductivity of n -pentane

Journal of Thermal Analysis and Calorimetry
Authors: Y. Shi, L. Sun, J. Venart, and R. Prasad

Abstract  

The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity and thermal diffusivity of fluids. It is well established that fluid radiation effects significantly influence these measurements, especially those for the thermal diffusivity. Corrections for radiation effects are based on the models developed and deviations of the measured data from the ideal line source model. In this paper, the effect of fluid radiation on the measurements of the thermal conductivity of n-pentane is presented. For comparison, the influence of thermal radiation effect on measurement of transparent fluids, such as argon is also shown. The difference between the influence of natural convection and thermal radiation is also demonstrated.

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and the ideal line source technique In the transient hot-wire technique, a thin wire is immersed in the test fluid and connected to the electrical circuit. The thin wire is used simultaneously as a heat source and a resistance temperature

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Abstract  

The paper describes a new transient hot wire instrument which employs 25.4 μm diameter tantalum wire with an insulating tantalum pentoxide coating. This hot-wire cell with a thin insulating layer is suitable for measurement of the thermal conductivity and the thermal diffusivity of electrically conducting and polar liquids. This instrument has been used for experimental measurement of the thermal conductivity and the thermal diffusivity of poly(acrylic acid) solution (50 mass%) in the temperature range of 299 to 368 K at atmospheric pressure. The thermal conductivity data is estimated to be accurate within ±4%. Thermal diffusivity measurements have a much higher uncertainty (±30%) and need further refinement.

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Abstract  

Various techniques and methodologies of thermal conductivity measurement have been based on the determination of the rate of directional heat flow through a material having a unit temperature differential between its opposing faces. The constancy of the rate depends on the material density, its thermal resistance and the heat flow path itself. The last of these variables contributes most significantly to the true value of steady-state axial and radial heat dissipation depending on the magnitude of transient thermal diffusivity along these directions. The transient hot-wire technique is broadly used for absolute measurements of the thermal conductivity of fluids. Refinement of this method has resulted in a capability for accurate and simultaneous measurement of both thermal conductivity and thermal diffusivity together with the determination of the specific heat. However, these measurements, especially those for the thermal diffusivity, may be significantly influenced by fluid radiation. Recently developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. A thermal conductivity cell for measurement of the thermal properties of electrically conducting fluids has been developed and discussed.

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Progress in Agricultural Engineering Sciences
Authors: Monika Božiková, Peter Hlaváč, Vlasta Vozárová, Zuzana Hlaváčová, Ľubomír Kubík, Peter Kotoulek, and Ján Brindza

properties of liquids and gases using a transient hot-wire technique . Review of Scientific Instruments , 49 ( 10 ): 1460 – 1463 . Pereira , F. M. , Freitas , B. M. , Vieira Neto , J

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diffusivity of poly(acrylic acid) by transient hot wire technique . J Therm Anal Calorim. 2009 ; 96 ( 1 ): 67 – 71 http://dx.doi.org/10.1007/s10973-008-9840-2 . 11. Borca-Tasciuc T

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. Tian , F , Sun , L , Mojumdar , SC , Venart , JES , Prasad , RC 2011 Absolute measurement of thermal conductivity of poly (acrylic acid) by transient hot wire technique . J Therm Anal Calorim. 104 : 823 – 829 10.1007/s10973

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-007-8518-5 . 9. Tian , F , Sun , L , Mojumdar , SC , Venart , JES , Prasad , RC 2011 Absolute measurement of thermal conductivity of poly (acrylic acid) by transient hot wire technique . J Therm Anal Calorim. 104 : 823 – 829

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. 33. Tian F , Sun L , Mojumdar SC , Venart JES , Prasad RC . Absolute measurement of thermal conductivity of poly (acrylic acid) by transient hot wire technique . J Therm Anal Calorim . 2011

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