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Abstract

This report provides the information necessary to choose the appropriate appara tus size for a measurement of thermal resistance of a specimen of insulation material of a particular thickness. This information consists of the order of magnitude of ap paratus edge error as a function of specimen thickness. The report defines the edge effect, derives a model for its calculation for both circular and square geometries, and it indicates graphically the sensitivity of the edge-effect curves (as a function of thickness) with respect to the following parameters: the ratio of the guard to metered sizes, the metered size itself, the ratio of the surface heat, transfer coefficient to the specimen apparent conductivity, and the apparent-thermal-conductivity anisotropy. The results of the square metered area are compared with those of the circular metered area, and the theoretical results are compared with experimental results for a circular geometry (using a 1-m guarded hot plate). A detailed discussion of the er ror analysis is presented, and curves are presented to enable the user of a guarded-hot-plate or heat-flow-meter apparatus to determine the maximum thick ness of operation for typical apparatus sizes.

Keywords

Apparent thermal conductivity edge effect guarded hot plate heat flow meter thermal insulation thermal resistance.

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References

1984 Annual Book of ASTM Standards, Vol. 04.06, ANSI/ASTM C-177-76e,

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1984 Annual Book of ASTM Standards, Vol. 04.06, ANSI/ASTM C-518-76,

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Circular and Square Edge Effect Study for Guarded-Hot-Plate and Heat-Flow-Meter Apparatuses

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