Measurement of the macroscopic heat transfer coefficient in heterogeneous media by infrared thermography. A two temperature model application.

In this paper, a two equation model is used to describe macroscopic heat tr ansfer in heterogeneous media (porous media, composite materials, etc.) whe n there is local thermal non-equilibrium between the two constitutive phase s. Such macroscopic models involve a heat exchange coefficient between the phases. The objective of this study is to propose an experimental methodolo gy to measure this heat transfer coefficient. The experimental technique pr oposed here is based on the analysis of infrared images obtained from 2D, p eriodic, two-phase materials submitted to an instantaneous heat pulse. An i ntegral transformation of the macroscopic transfer equations, taking into a ccount the parietal heat exchange with the surroundings leads to a simple a nalytical expression between the macroscopic temperatures relative to each phase. From the temporal experimental evolution of these macroscopic temper atures, it is possible to estimate three Independent parameters, and to sep arate the parietal exchange from the exchange between the two phases. This approach has been validated by the comparison of experimental results and t heoretical values. (C) Elsevier, Paris.