Thermal Diffusivity Determination of High-Temperature Levitated Oblate Spheroidal Specimen by a Flash Method

1998 ◽  
Vol 120 (3) ◽  
pp. 777-781 ◽  
Author(s):  
F. Shen ◽  
J. M. Khodadadi
Keyword(s):  
Thermal Diffusivity ◽  
Transfer Problem ◽  
Oblate Spheroid ◽  
Single Step ◽  
Flash Method ◽  
Conduction Heat Transfer ◽  
Oblate Spheroidal ◽  
Flash Technique ◽  
Transient Conduction

In extending the range of applicability of a recently developed method, a single-step containerless flash technique for determining the thermal diffusivity of levitated oblate spheroidal oblate spheroidal samples is proposed. The flash method is modeled as an axisymmetric transient conduction heat transfer problem within the oblate spheroid. It is shown that by knowing the sample geometric parameters and recording the temperature rise history at least at two different points on the surface simultaneously, the thermal diffusivity can be determined without knowing needed for determining the thermal diffusivity of oblate spheroidal samples are provided.

Containerless Thermal Diffusivity Determination of High-Temperature Levitated Spherical Specimen by Extended Flash Methods: Theory and Experimental Validation

1997 ◽  
Vol 119 (2) ◽  
pp. 210-219 ◽  
Author(s):  
F. Shen ◽  
J. M. Khodadadi ◽  
M. C. Woods ◽  
J. K. R. Weber ◽  
B. Q. Li
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Transfer Problem ◽  
Single Step ◽  
Temperature History ◽  
Step Method ◽  
Measured Time ◽  
Analytic Expressions

In order to determine the thermal diffusivity of materials, especially solids and liquids at high temperatures, two extended containerless flash techniques that are applicable to levitated spherical specimen are proposed. The extended flash methods are modeled as an axisymmetric transient conduction heat transfer problem within the sphere. For the “single-step” method, analytic expressions for the temperature history on the surface of the sphere are obtained that are independent of the incident energy and the absorption layer thickness. It is shown that by knowing the sample diameter and recording the temperature transient history at least at two different points on the surface simultaneously, the thermal diffusivity can be determined. A detailed discussion of the effects of the various parameters is presented. For the “two-step” analysis the problem of nonlinearity of the radiative heat transfer boundary condition is overcome by replacing it with the measured time-dependent surface temperature data. Upon obtaining the temperature field the determination of the thermal diffusivity turns into a minimization problem. In performing the proposed two-step procedure there is a need to undertake a cool-down experiment. Results of an experimental study directed at determining the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloy near their melting temperatures using the single-step method are discussed. Based on close agreement with reliable data available in the literature, it is concluded that the proposed techniques can provide reliable thermal diffusivity data for high-temperature materials.

Determination of thermal diffusivity in diathermic materials by the laser-flash technique

1997 ◽  
Vol 29 (6) ◽  
pp. 703-710 ◽  
Author(s):  
Rainer Hofmann ◽  
Oliver Hahn ◽  
Friedrich Raether ◽  
Harald Mehling ◽  
Jochen Fricke
Keyword(s):  
Thermal Diffusivity ◽  
Laser Flash ◽  
Laser Flash Technique ◽  
Flash Technique
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