Short-hot-wire method for the measurement of the thermal conductivity of a fine fibre

Abstract

A new method to measure the thermal conductivity of a single fine fibre is proposed. The method is based on the heat transfer phenomena of a pin fin attached to a short hot wire. The short hot wire is supplied with a constant direct current to generate a uniform heat flux and both its ends are connected to lead wires and maintained at the initial temperature. The test fibre is attached as a pin fin to the centre position of the hot wire at one end and the other end is connected to a heat sink. One-dimensional steady-state heat conduction along the hot wire and the test fibre is analytically solved. From the solutions, the relationships among the average temperature rise of the hot wire, the heat generation rate, the temperature at the attached end of the fibre, and heat flux from the hot wire to the fibre are accurately obtained. Based on the relationships, the thermal conductivity of the single test fibre can easily be estimated when the average temperature rise and the heat generation rate are measured for the same system as above. We have obtained analytical solutions for various measurement conditions and clarified quantitatively the applicability and accuracy of this method. It is found that the thermal conductivity can be measured within an error of 1% in the range up to 1000 W m -1 K -1 for a fibre of 10-30 μm in diameter. Furthermore, preliminary experiments have been carried out with samples of platinum wire (100.8 μm diameter) and copper wire (41.7 μm diameter), and confirmed the validity of the present method.