Analysis of transient thermal measurements on fibrous insulations obtained with an unguarded flat tester

The unguarded screen tester is a useful apparatus for measuring both steady-state and transient thermal properties. Agreement between calculated and measured time-temperature curves obtained, for example, with a constant physical property analytical model however is not satisfactory. The agreement between calculated and measured values is not improved by the introduction of a shine-through radiative term that is independent of the conductive transport. Numerically-derived time-temperature curves that use measured k/sub a/(T) and C(T) and no adjustable parameters differ as much as 1K during the first 600 seconds of a transient. Agreement between measured and calculated transient screen temperatures to better than + or - 0.25 K is achieved by treating the C of the screen heater as an adjustable parameter. The analysis of transient data for the two reference materials is complicated by the presence of a heat of transition in the temperature range of interest. The effects of coupled conduction-radiation transport have not been included in the present analysis and this may be the reason for difficulties in describing the initial segment of the time-temperature curves. The results and analyses presented identify a need for chemical characterization of thermal reference materials.