Using Finite Element Analysis to Design a New Guarded Hot Plate Apparatus for Measuring the Thermal Conductivity of Insulating Materials.
Using Finite Element Analysis to Design a New Guarded
Hot Plate Apparatus for Measuring the Thermal
Conductivity of Insulating Materials.
Healy, W. M.
ANSYS Users Group Conference Proceedings. October 2,
2001, College Park, MD, 1-9 pp, 2001.
insulating materials; thermal conductivity; equipment;
guarded hot plate
The National Institute of Standards and Technology
(NIST) is developing an instrument to measure the
thermal conductivity of building insulation over a
temperature range from 90 K to 900 K. The apparatus will
create one-dimensional heat flow through a specimen by
placing it between two isothermal plates at different
temperatures. The temperatures of those plates, the heat
input to the hotter plate, and the thickness of the
specimen are measured, and the thermal conductivity is
then calculated from Fourier's Law. In order for this
apparatus to provide accurate results, however, each
plate must be maintained at a nearly uniform
temperature, and the edge of the specimen must be
guarded to prevent radial heat flows. Designing the
apparatus to meet these criteria over the desired
temperature range proved to be quite a challenge, and
the use of finite element analysis significantly helped
detect flaws in the design. Commercially available
software was used to estimate temperature profiles
throughout the instrument, unwanted heat gains or
losses, and the ability of fluid channels to provide
adequate cooling. With the help of finite element
analysis, NIST will build an instrument that will
provide the building industry with better measurement
capabilities to judge the effectiveness of thermal
insulation over a wide range of temperatures.