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International Heat Transfer Conference 8

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

THERMAL DIFFUSIVITY MEASUREMENTS OF INSULATORS BY A STEP FUNCTION HEAT FLUX METHOD

J. S. Goodling
Auburn University, Auburn, Alabama, U.S.A. 36849

D. G. Swann, Jr.
SMI Steel Incorporated, Birmingham, AL

DOI: 10.1615/IHTC8.280
pages 633-638

Abstract

A technique for the measurement of thermal diffusivity of soft materials is offered. It is simple, inexpensive, quick and reasonably accurate for insulators which cannot readily be held rigid or cannot be easily formed into a Cartesian geometry as required by many known methods. A small cylindrical test specimen is formed by surrounding it with a rigid electrical heater. With one thermometer mounted at the outer periphery and another at the centerline of the cylinder, the heater is activated for a short span (tens of seconds). By monitoring these two temperatures at large times, thermal diffusivity of the specimen is found as an explicit function of the measured temperatures at these two points, and three fixed quantities; the radius of the specimen, the time from onset of the heat input and the initial uniform temperature of the sample. Standard laboratory equipment is used for the test. Results indicate a modest degree of reproducibility and accuracy for a test sample of uncured rubber, the new technique yielding values of thermal diffusivity differing by less than 2% from those measured using transient heat flow methods in a one dimensional Cartesian and cylindrical geometry.

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