The bare wire thermal conductivity apparatus consisted of an
aluminum cylindrical sample tube of 104 mm length and
28.4 mm inner diameter, with a removable Teflon cover and with
a fixed bottom base cover. A chromel resistance heating wire of
33 gauge and a length of 200 mm stretched between copper
leads along the axis of cylindrical tube used as line heat source,
of which the effective length of heating element inside the test
cylinder is 104 mm and the remaining length (96 mm) is used
to connect the leads on either sides outside the test cylinder. A
constant DC Power supply was used for all the tests. A pre-calibrated
T-type 28 gauge iron-constantan thermocouple was
installed for measuring the core temperature of the sample in
the cylinder. The power input to the line heat source was sufficient
to give a measurable temperature difference between the
time t1 and t2.