Heat Transfer Through a Still Air Layer

    Published: Jan 1987

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    One question is at the origin of this study—Could a still air layer be used as a reference material in interlaboratory measurements by the guarded hot plate or heat flow meter method? Such a “material,” which is easy to get, has indeed been recommended by the International Organization for Standardization (ISO) Technical Committee 163 in a round-robin test, but very few measurement results have been reported from the participating laboratories.

    The authors have investigated this configuration of particular interest using a one-specimen guarded hot plate apparatus with a thermal gradient directed downwards. By studying the variation of thermal conductance as a function of air layer thickness, we have been able to determine the thermal conductivity of still air, λg, and the total hemispherical emissivity, ε, of the measurement surfaces and to compare the experimental data with the numerical results derived from a simple model, taking into account simultaneous radiative and conductive heat transfers and giving the values of λg and ε.

    This study allows us to answer the initial question positively and to show the possible sources of misunderstanding in comparing and analyzing the thermal conductivity measurements from different laboratories.


    air layer, conductance, conductive heat transfer, emissivity, guarded hot plate, heat transfer, radiative heat transfer, reference material, round-robin test, thermal conductivity, thermal insulation

    Author Information:

    Jaouen, J-L
    Physicist and research engineer, Centre de Recherches Industrielles de Rantigny, Rantigny,

    Klarsfeld, S
    Physicist and research engineer, Centre de Recherches Industrielles de Rantigny, Rantigny,

    Committee/Subcommittee: C16.30

    DOI: 10.1520/STP18486S

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