High-Temperature Guarded Hot Plate Apparatus: Optimal Locations of Circular Heaters.
High-Temperature Guarded Hot Plate Apparatus: Optimal
Locations of Circular Heaters.
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.
guarded-hot-plate apparatus; high temperature; heaters;
temperature distribution; heat sources; equations;
finite element method
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.