TRANSIENT COUPLED CONDUCTIVE RADIATIVE HEAT-TRANSFER IN ABSORBING, EMITTING AND SCATTERING MEDIA - APPLICATION TO LASER-FLASH MEASUREMENTS ON CERAMIC MATERIALS/

A model is presented for the calculation of transient combined radiati ve/conductive heat transfer in heterogeneous semitransparent materials at elevated temperatures. It is based on optical material properties (scattering, absorption) that can be determined experimentally at room temperature. This model is applied to the simulation of laser-flash m easurements on ceramic powder compacts. We demonstrate that the releva nce of the radiative contributions for the determination of the therma l diffusivity from laser-flash measurements depends on the sample thic kness, which is confirmed by corresponding experiments. It is shown th at the thermal diffusivity of 1-2 mm thick alumina powder compacts may be overestimated by about 10-20% at 850 degrees C. Copyright (C) 1996 Elsevier Science Ltd.