Study on a Thermal-diffusivity Standard for Laser Flash Method Measurements

Abstract

The National Metrology Institute of Japan (NMIJ) of AIST has been studying the laser flash method in order to establish an SI traceable thermaldiffusivity standard. Key technologies have been developed to reduce the uncertainty in laser flash measurements. In the present study, an uncertainty evaluation has been carried out on the laser flash measurement method in order to determine the thermal diffusivity value of IG-110, a grade of isotropic high-density graphite, as a candidate reference material. The thermal diffusivity measured by the laser flash method is derived from a specimen thickness and a heat diffusion time. And a laser flash measurement is carried out at a given temperature. The measurement system is composed of three sections corresponding to each measured quantity: length, time, and temperature. Therefore, we checked and calibrated our measurement system, and estimated the uncertainty of measurement results for the case of a grade of isotropic graphite.

Errors in Determining the Thermal Characteristics of Liquids by the Laser-Pulse Method

“…In [14][15][16][17] was found, that in determining thermal characteristics of solid materials by laser pulse method there is methodological errors caused adopted in formulating the problem [6,7] assumptions. The errors in determining the thermal characteristics of material can be defined [14][15][16] by comparison of the actual values of thermal diffusivity ( a ) with the material obtained by numerical simulation of the implementation conditions of experiments on determination of thermal characteristics materials by this method.…”

“…To investigate the thermal properties of such materials, it is best to use highly efficient procedures, for example, the laser pulse -laser flash (LFA) method [6,7]. It is based on the absorption of a pulse of radiant energy in a thin layer by the frontal "hot" surface of the sample and the approximate solution of the one-dimensional heat conduction problem for an infinite plate.…”

“…If thermal diffusivity is known, the specific heat capacity c, and the thermal conductivity λ of the material can be calculated by formulas from [6,7]. The practical interest is the use of LFA method to determine the thermal diffusivity of organic liquids.…”

Errors of optical vitreous silica heat diffusivity determination by pulse method

“…An iterative algorithm developed for solving the nonlinear problems of heat transfer in terms of the local intense heating [15,16] was used. The verification of difference schemes conservatism by the method [17], developed for testing the heat and mass transfer problems in terms of fast phase transformations processes was conducted to justify the validity of the numerical simulation results in the absence of experimental data on the material sample's temperature fields under conditions of the heat by radiation fluxes of high intensity (appropriate to methodology [1,2]). …”

“…A method of the laser impulse [1][2][3][4] which essence consists in absorption of a frontal ("hot") surface of a radiant energy impulse sample in a thin layer and its return ("cold") surface temperature measurement registration in time represents the greatest interest for researchers.…”