STP660

    Drift Measurement Technique Applied to Poor Conductors

    Published: Jan 1978


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    Abstract

    Many applications require knowledge of thermal properties, over a wide range of temperature, to within 5 percent. The speedy and economical acquisition of the data is often a prime concern. We are investigating the potential of the very simplest system (an unguarded plate system), used in a drift mode rather than in a steady-state mode, to fulfill this need.

    When heat flows across a specimen whose mean temperature is drifting slowly and linearly with time, a term of the form CF(dT/dt) must be added to the steadystate equation. Data are taken over a given temperature range with the temperature both increasing and decreasing; the value of CF is then adjusted until the two sets of data produce the same value of conductivity. Since CF is a function of the density of the specimen and its specific heat at constant pressure, an approximate value of the thermal diffusivity is obtained as a by-product in this drift mode of operation.

    The successful application of the technique is illustrated by both drift technique and steady-state measurements on microconcrete over the temperature range -20 to +60°C. Corrections for heat losses and nonlinear heat flow have been appraised by finite-element analysis and by comparisons with data from adiabatic linear heat flow systems. Our objective is to develop the apparatus for use up to 500°C.

    Keywords:

    thermal conductivity, thermal diffusivity, drift measurement technique, microconcrete


    Author Information:

    Ashworth, T
    Professor of physics, graduate research assistant, and assistant professor of mining engineering, South Dakota School of Mines and Technology, Rapid City, S. Dak.

    Lacey, WG
    Professor of physics, graduate research assistant, and assistant professor of mining engineering, South Dakota School of Mines and Technology, Rapid City, S. Dak.

    Ashworth, E
    Professor of physics, graduate research assistant, and assistant professor of mining engineering, South Dakota School of Mines and Technology, Rapid City, S. Dak.


    Paper ID: STP35757S

    Committee/Subcommittee: C16.30

    DOI: 10.1520/STP35757S


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