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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

MEASUREMENT OF A THERMAL EXCHANGE COEFFICIENT IN POROUS MEDIA BY INFRARED THERMOGRAPHY - TWO-TEMPERATURE MODEL APPLICATION

Get access (open in a dialog) DOI: 10.1615/IHTC11.3080
pages 155-160

Resumo

In this paper, a two-equation model is used to describe macroscopically heat transfer in porous media when the constitutive phases are not in local thermal equilibrium (initially Vortmeyer et al., 1974 and Schlunder, 1975, see review in Quintard et al., 1997). Here the words "porous media" may refer to real porous media, or the concept can be extended to systems like composite materials, some heat exchangers, etc. Such macroscopic models involve a heat exchange coefficient between the phases. The objective of this study is to propose an experimental methodology to measure this exchange coefficient. The idea is to gather sufficient information in terms of temperature fields in order to calculate macroscopic temperature evolutions, and derive the relevant effective transport properties. To solve this problem, the infrared thermography is a tool of choice.
The experimental technique proposed here is based on the analysis of infrared images obtained from 2D, periodic, two-phase materials submitted to an instantaneous heat impulse. An integral transformation (Laplace transform) of the macroscopic transfer equations taking into account the heat exchange with the surrounding atmosphere, later referred to as parietal exchange, leads to a simple analytical expression between the macroscopic temperatures relative to each distinct phase. From the temporal experimental evolution of these macroscopic temperatures, it is possible to estimate three independent parameters and to separate the parietal exchange from the exchange between the two phases. This approach has been validated by the comparison of experimental results and theoretical values, and a very good agreement was found.