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High-Temperature Guarded Hot Plate Apparatus: Optimal Locations of Circular Heaters.


pdf icon High-Temperature Guarded Hot Plate Apparatus: Optimal Locations of Circular Heaters. (1309 K)
Flynn, D. R.; Healy, W. M.; Zarr, R. R.

International Thermal Conductivity 28th Conference/International Thermal Expansion 16th Symposium. Proceedings. June 26-29, 2005, New Brunswick, Canada, DEStech Publications, Inc., Dinwiddie, R.; White, M. A.; McElroy, D. L., Editor(s)(s), 466-477 pp, 2005.

Keywords:

guarded-hot-plate apparatus; high temperature; heaters; temperature distribution; heat sources; equations; finite element method

Abstract:

The National Bureau of Standards (now the National Institute of Standards and Technology (NIST)) pioneered the use of circular line-heat-sources in guarded hot plate (GHP) apparatus, the most common type of absolute apparatus for measurement of the thermal transmission properties of insulation. The prototype 305 mm GHP apparatus used one circular line-heat-source in the meter plate and one in the guard plate. The later one-meter GHP apparatus used a single circular line-heat-source in the meter plate and had two heaters in the guard plate. NIST is now completing the fabrication of a 500 mm GHP apparatus, designed to cover a much broader temperature range than that achievable by the previous designs, that utilizes multiple line-heat-sources in the meter plate, the guard plate, and the cold plates. The purposes of the present paper are to (1) describe strategies for locating these heaters in order to obtain the desired (uniform) temperature distribution on the plates, (2) provide analytical solutions for computing the circular heater locations for the various strategies, (3) provide tabulated values for the desired circular heater locations, (4) compare computed temperature variations for a specific circular heater layout as obtained using both an analytical solution and a finite element method (FEM), and (5) provide a representative temperature variation, obtained using FEM, for a heater layout that is more complex than circular line-heat-sources.