by A thesis submitted to the University of Plymouth in ... - PEARL home

The early history of the thermal probe
Schleiermacher (1888) was a pioneer of measurements by a line source in the
late nineteenth century. The thermal conductivities of gases were measured
using a hot wire technique. A cylinder held the gas to be measured and a
heating wire was placed along its axis. The current, and temperature of the
wire, gas and cylinder, were measured and the thermal conductivity calculated.
By 1903 this technique had become known as the Schleiermacher
Method
(Schwarze, 1903).
Niven (1905) carried out experiments with a platinum wire acting as a line
source of heat along the central axis of solid cylindrical samples, including
various timbers and sands (Figure 6). Platinum wires or thermocouples were
used to take temperature readings at a choice of radii across the sample, which
had sufficient dimensions that were considered adequate to avoid the effects of
heat losses at the boundary during measurements. Thermal conductivity was
calculated from the temperature difference between the radii once a steady
state had been reached in the sample, which occurred after a number of hours.
Thermal diffusivity values were not reported but said to be available from the
calculations, based on the elapsed time taken to reach the steady state.
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