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Using Finite Element Analysis to Design a New Guarded Hot Plate Apparatus for Measuring the Thermal Conductivity of Insulating Materials.


pdf icon Using Finite Element Analysis to Design a New Guarded Hot Plate Apparatus for Measuring the Thermal Conductivity of Insulating Materials. (675 K)
Healy, W. M.

ANSYS Users Group Conference Proceedings. October 2, 2001, College Park, MD, 1-9 pp, 2001.

Keywords:

insulating materials; thermal conductivity; equipment; guarded hot plate

Abstract:

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.