The effects of the thermal capacity of a heat source on the accuracy of thermal conductivity measurement were investigated numerically and analytically.
It was found that the accuracy is greatly affected by the thermal capacity ratio of the media to the heat source. It was also found that there exists a critical thermal capacity ratio at which the error becomes zero at a finite time. The relationship between measured and true thermal conductivities at sufficiently large times critically depends upon the capacity ratio, i.e. when the capacity ratio is smaller than the critical thermal capacity ratio, the measured thermal conductivity is always smaller than the true value and vice versa. A closed form formula defining the measurement errors for a given thermal capacity ratio and time was derived analytically.
