Abstract:
Rapid thermal conductivity measurement of porous solids and composites remains a challenge. A
modified steady state technique has been proposed which uses two heat
flux sensors instead of one. The
parameter estimation is achieved through the deconvolution of these signals and the identification of the
system impulse response. A detailed derivation of the theoretically expected behaviour has been done,
which provides a basis for
fitting the measured impulse response. A six term expansion is required for the
theoretical model to achieve full convergence. The unit requires a calibration step to measure the
convective boundary condition. A signal validity check has been built into the approach through the use
of the energy balance which detects any drift due to ambient losses or other factors. Through suitable
choice of the mathematical algorithm rapid convergence of the non-linear
fitting procedure is achieved.
The parameter estimates of the standard test samples are excellent, with average errors of 2.3% for brass
and 6.3% for aluminium. The system has several advantages in addition to the short measurement time,
including low cost and no guard furnace or insulation requirement for room temperature measurements.
The approach is suitable for measuring the overall behaviour of practical, composite systems.
