Analysis of radiation effect on thermal conductivity measurement of semitransparent materials based on transient plane source method

The transient plane source (TPS) method has been extensively applied as a high-accuracy and short-duration technique for determining the thermal conductivities of materials. TPS method is not reliable when measuring semi-transparent materials where radiation occurs. The governing equations of the heat transfer process coupled with conduction and radiation are deduced and further nondimensionalized to comprehensively analyze the influence factors of measurement error. This study presents four dimensionless parameters determining temperature variation and measurement error. A numerical solution of the coupled heat transfer is established to quantitatively study the effects of the dimensionless parameters on measurement accuracy. Computed results show that the scattering effect can reduce the overestimate of the measured thermal conductivity; the deviation of the measured conductivity linearly depends on the sensor emissivity; the dimensionless power has a weak effect on measurement error; the decrease in the sensor optical radius and the increase in the conduction radiation parameter lead to a decrease in measurement error. The dimensionless parameters can be used to estimate the deviation of the measured conductivity. The measurement accuracy can be improved by using a sensor with low emissivity and minor radius when applying TPS method on semi-transparent materials.