Apparent Thermal Conductivity Measurements by an Unguarded Technique

  • R. S. Graves
  • D. W. Yarbrough
  • D. L. McElroy


An unguarded longitudinal heat flow apparatus for measuring the apparent thermal conductivity (λa) of insulations was tested with mean specimen temperatures from 300 to 330°K on samples up to 0.91 m wide, 1.52 m long, and 0.15 m thick. Heat flow is provided by a horizontal electrically heated Nichrome screen that is sandwiched between test samples that are bounded by temperature controlled copper plates and 9 cm of mineral fiber insulation. A determinate error analysis shows λa measurement uncertainty to be less than ±1.7% for insulating materials as thin as 3 cm. Three-dimensional thermal modeling indicates negligible error in λa due to edge loss for insulations up to 7.62 cm thick when the temperature difference across the sample is measured at the screen center. System repeatability and reproducibility were determined to be ±0.2%.


Heat Flow Copper Plate Apparent Thermal Conductivity ASTM Special Technical Publication Density Thickness 
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  1. 1.
    S. H. Jury, D. L. McElroy, and J. P. Moore, “Pipe Insulation Testers,” Thermal Transmission Measurements of Insulation ASTM STP 660, R. P. Tye, Ed., American Society for Testing and Materials, pp. 310–326 (1978).CrossRefGoogle Scholar
  2. 2.
    J. P. Moore, D. L. McElroy and S. H. Jury, A Technique for Measuring the Apparent Thermal Conductivity of Flat Insulations, ORNL/TM-6494, Oak Ridge National Laboratory, Oak Ridge, TN (October 1974).Google Scholar
  3. 3.
    J. P. Moore, D. L. McElroy and S. H. Jury, “A Technique for Measuring the Apparent Thermal Conductivity of Flat Insulations”, Thermal Conductivity 17, J. G. Hust, Ed., Plenum Publishing Corporation, pp. 727–735 (1983).Google Scholar
  4. 4.
    C. Niven and A. E. M. Geddes, “On a Method for Finding the Conductivity for Heat,” Proc. Roy. Soc. (London) A87, 535–539 (1912).CrossRefGoogle Scholar
  5. 5.
    C. F. Gilbo, “Experiments with a Guarded Hot Plate Thermal Conductivity Set,” ASTM Special Technical Publication No. 119, 45, (1951).Google Scholar
  6. 6.
    N. E. Hager, Jr., “Thin Heater Thermal Conductivity Apparatus”, Rev. Sci. Instrum. 31 (2), 177–185, (Feb. 1960).CrossRefGoogle Scholar
  7. 7.
    N. E. Hager, Jr., U.S. Patent No. 3,045,473 (July 24, 1962 ).Google Scholar
  8. 8.
    N. E. Hager, Jr., “Miniature Thin-Heater Thermal Conductivity Apparatus,” ISA Transactions 8 (2), 104–109 (1969).Google Scholar
  9. 9.
    W. D. Turner, D. C. Elrod and I. I. Siman-Tov, HEATING5 — An IBM 360 Heat Conduction Program, ORNL/CSD/TM-15, Oak Ridge National Laboratory, Oak Ridge, TN (March 1977).Google Scholar
  10. 10.
    Report of Test on Thermal Resistance of Glass-Fiber Insulation, U.S. Department of Commerce, National Bureau of Standards, F. J. Powell to D. L. McElroy, Purchase Order i 21X-48695, May, 10, 1983.Google Scholar
  11. 11.
    Excerpt from Ref. 10, “The uncertainty in the thermal i resistance values is estimated to be not more than ±0.5 percent and includes apparatus systematic error and apparatus repeatability.”Google Scholar
  12. 12.
    Phoenix Wire Cloth, Inc., 40x40 Per Inch Nichrome V Wire, 0.010 Inch, P. 0. Box 610, Troy, Michigan 48084.Google Scholar
  13. 13.
    Leeds and Northrup, Philadelphia, PA, 0.01Q Standard Resistor. Model No. 4361, 100 amps dc current rating.Google Scholar
  14. 14.
    Hewlett Packard DC Power Supply Model 6260B (10V, 100A).Google Scholar
  15. 15.
    Leeds and Northrup K-5 Potentiometer with 1.6 Volt Accuracy of ±(0.001%+2μ,V).Google Scholar
  16. 16.
    Astrodyne, Inc., Thermal Bond 312, Burlington, MA.Google Scholar
  17. 17.
    B. Braun Instruments, Thermomix 1480 and Frigomix 1495, San Mateo, CA.Google Scholar
  18. 18.
    Fisher and Porter Company, Warminister, PA 18974, Flowrator Meter Model 10A1755XZ.Google Scholar
  19. 19.
    D. L. McElroy, R. S. Graves, D. W. Yarbrough, and J. P. Moore, “A Flat Insulation Tester that Uses an Unguarded Nichrome Screen Wire Heater,” Forum on the Guarded Hot Box Plate and Heat Flow Meter State-of-the-Art, Quebec City, Quebec, Canada, (October 7–8, 1982 ).Google Scholar
  20. 20.
    J. P. Moore, R. K. Williams, and R. S. Graves, “Precision Measurements of the Thermal Conductivity, Electrical Resistivity, and Seebeck Coefficient from 80 to 400 K and. Their Application to Pure Molybdenum,” Rev. Sci. Instrum. 45 (1), 87–95 (1974).CrossRefGoogle Scholar
  21. 21.
    R. P. Tye, A. O. Desjarlais, D. W. Yarbough and D. L. McElroy, An Experimental Study of Thermal Resistance Values (R-Values) of Low-Density Mineral-Fiber Building Insulation Batts Commercially Available in 1977, ORNL/tM-7266 (April 1980).Google Scholar
  22. 22.
    Y. S. Touloukian, P. E. Li ley, and S. C. Saxena, Thermophysical Properties of Matter 3, Plenum Publishing Corp., New York, p. 512 (1970).Google Scholar

Copyright information

© Purdue Research Foundation 1985

Authors and Affiliations

  • R. S. Graves
    • 1
  • D. W. Yarbrough
    • 1
  • D. L. McElroy
    • 1
  1. 1.Martin Marietta Energy Systems, Inc. Metals and Ceramics DivisionOak Ridge National LaboratoryOak RidgeUSA

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