Abstract
In this paper, the influence of weak radiative heat transfer on measured thermal conductivity by the transient line source technique is discussed. Fundamental equations and non-dimensional parameters (emissivity, ε; Fourier modulus, t*=at/(r1)2 ; optical thickness, R=Kr1 ; non-dimensional radius, r*=r/r1), which determine the apparent thermal conductivity, λapp, are shown, and the relations between these parameters and radiative heat flux, temperature distribution and λapp are discussed using the results of numerical calculations. The optical condition, R=0.010.07, where the influence of radiation appears maximum for t*<600, is pointed out. This optical condition corresponds to the measurements of Ccl4 or toluene for the usual line radius, r1=12.5μ. As λapp increases rapidly in the range of small t* (t*<200), the extrapolation, t*→0, using λapp - t* curves (t*<200), doesn't give the real thermal conductivity, λ. A method to modify λapp is proposed.
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