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Thermal Modeling of Multiple-Line-Heat-Source Guarded Hot Plate Apparatus



William M. Healy, D R. Flynn


The National Institute of Standards and Technology is building an advanced-design guarded hot plate apparatus of advanced design to provide very accurate thermal transmission properties for specimens of thermal insulation 500 mm in diameter, with thicknesses up to 110 mm, at mean temperatures from 90 K to 900 K. This paper documents some of the extensive thermal modeling and analyses that were carried out in the course of designing this apparatus and characterizing potential errors and uncertainties. In an idealized guarded hot plate apparatus, the effective thermal conductivity is simply computed from the measured power input to the meter plate heater, the effective area of the meter plate, the temperature of the hot plate and the two cold plates, and the specimen thickness. In an actual apparatus, there may be (a) temperature variations in the hot plate and cold plates, (b) radial heat flow within the specimen, and (c) transient temperature fluctuations that add uncertainty to the measured thermal conductivity. For the new 500 mm apparatus, both analytical solutions and finite element analyses were used to model temperature distributions in critical thermal components, heat flows that might affect the measured thermal conductivity values, and the effects of departures from ideal steady-state conditions on test results. This paper focuses on the results of these analyses and computations.
Proceedings Title
The Fourth Symposium on Insulation Materials: Testing and Applications ASTM STP 1426
STP 1426
Conference Dates
October 21-22, 2002
Conference Title
American Society for Testing and Materials


finite element analysis, guarded hot plate, heat conduction, heat transfer, insulation, R-value, thermal analysis, thermal conductivity, thermal resistance


Healy, W. and Flynn, D. (2002), Thermal Modeling of Multiple-Line-Heat-Source Guarded Hot Plate Apparatus, The Fourth Symposium on Insulation Materials: Testing and Applications ASTM STP 1426, [online], (Accessed April 19, 2024)
Created October 1, 2002, Updated February 19, 2017