Effect of radiative heat loss on thermal diffusivity evaluated using normalized logarithmic method in laser flash technique

Tsuyoshi Nishi,Hiromichi Ohta,Naoyoshi Azuma

doi:10.1515/htmp-2020-0079

Abstract

AbstractThe laser flash technique is a standard method to measure the thermal diffusivity of solid samples especially at high temperatures. To understand the reliability of thermal diffusivity evaluation at high temperature for solid samples with low-thermal-diffusivity values, we analyzed the effect of radiative heat loss using the logarithmic method. The results revealed that when the Biot number was 0.1, the deviation from the input thermal diffusivity value was approximately −1.6%. In addition, when an aluminum silicate (AS) sample was heated to 1,273 K, the maximum deviation was approximately −0.35%. In contrast, the difference between the input value and the thermal diffusivity evaluated by the halftime method when AS was heated to 1,273 K was approximately 2.38%. Thus, since the effect of radiative heat loss was found to be negligible, it is concluded that the normalized logarithmic method should be very useful for the thermal diffusivity analysis of low-thermal-diffusivity solid samples at high temperature.

Highlights

The laser flash technique is a standard method to measure the thermal diffusivity of solid samples especially at high temperatures
The difference between the input value (1.047 × 10−6 m2 s−1) and the thermal diffusivity evaluated by the halftime method (1.068 × 10−6 m2 s−1) when aluminum silicate (AS) was heated to
We utilized the logarithmic method to evaluate the thermal diffusivity of low-thermal-diffusivity solid samples

Summary

Introduction

Abstract: The laser flash technique is a standard method to measure the thermal diffusivity of solid samples especially at high temperatures. To understand the reliability of thermal diffusivity evaluation at high temperature for solid samples with low-thermal-diffusivity values, we analyzed the effect of radiative heat loss using the logarithmic method. Since the effect of radiative heat loss was found to be negligible, it is concluded that the normalized logarithmic method should be very useful for the thermal diffusivity analysis of low-thermaldiffusivity solid samples at high temperature. Effect of radiative heat loss on thermal diffusivity evaluated using normalized logarithmic method 391 order of seconds. Owing to this long analysis time, the measured thermal diffusivity could be influenced by external factors other than the radiative heat loss, such as the signal stability of the temperature-response curve. Compared to the situation under adiabatic conditions, the theoretical temperature with radiative heat loss reaches the maximum value of T/TM′ earlier and decreases after reaching the maximum value

Theoretical temperature-response curves with radiative heat loss

Conclusions