Simultaneous measurements of the thermal conductivity, thermal capacity and thermal diffusivity of an individual carbon fibre

摘要

An experimental system of a four-pad 3 omega-method with noise cancellation circuit was designed to measure simultaneously thermal conductivity, thermal diffusivity and heat capacity of an individually suspended wire. The closed solution of temperature oscillation, in which the heat transport in the wire is modelled as one-dimensional diffusion in vacuum, was developed in the frequency domain for fitting the experimental results. Both the closed solution and the series solution were used to determine the thermal properties. The measurements on an individual polyacrylonitrile-based carbon fibre 7 mu m in diameter were performed using both the closed solution and the series solution, which yielded the thermal conductivity of 84.4 W m(-1) K-1, the heat capacity of 1.23 MJ m(-3) K-1 and the thermal diffusivity of 7.16 x 10(-5) m(2) s(-1) at room temperature. The relative uncertainties of the measurements were analysed.