The thermal conductivity and surface emissivity of a material may be determined by heating its bottom surface and exposing its top surface to quiescent air and large surroundings of equivalent temperatures, T∞ = Tsur = 25°C. The remaining surfaces of the sample/heater are well insulated.

Consider a sample of thickness L = 25 mm and a square plan form of width W = 250 mm. In an experiment performed under steady-state conditions, temperature measurements made at the lower and upper surface of the sample yield values of T1 = 150°C and T2 = 100°C, respectively, for a power input of P e1ec = 70W. What are the thermal conductivity and emissivity of the sample?

Tsur Ambient air, T Sample, k E, T2 www -W Pelec