Temperature field inversion and break-down at the interface of semi-transparent two-layer system in radiative heat transfer

The paper describes analysis of radiation heat transfer in a system of semi -trans parent two layers, with a diffuse or partially diffuse interface. Tw o cases are considered, of "optically closed" and "optically open" systems. In the former case, heater and cooler surfaces with angular-dependent emis sivities. enclose the two layers. In the latter case, the system is irradia ted by a collimated heat flux on one side and the two boundary surfaces rad iate to space. Two interesting phenomena have been found from the results o btained by the mathematical-numerical methods developed here: inversion and break-up of the temperature field. In some cases, depending on the radiati on properties of the heater and cooler surfaces and on the refraction indic es of the layers and the specular-diffuse shares of the interface: the temp erature decreases from the side facing the heater to the interface, exhibit s a sharp jump increase across It, and then decreases, again, in the second layer (facing the cooler). The whole temperature curve is sometimes higher in the second layer than in the first one. These phenomena occur due to co llimation of the radiative heat flux at the boundary surface facing the hea ter and "de-focusing" the flux at the diffuse (or partially diffuse) interf ace. The strength of these effects depends on the radiative properties ment ioned above and on the optical thickness. Another phenomenon is that of "he at trap" in the case of "optically open" one- or two-layer system, caused b y total internal reflection. (C) 2001 Editions scientifiques et medicales E lsevier SAS.