A Code for Determination of Thermal Conductivity from In-Situ Data
The computer program PROPOR (Properties-Oak Ridge was
developed for ORNL by Dr. James Beck (Michigan State University) to compute
the thermal conductivity of insulation samples. The insulation is installed
in a test panel where sensor readings of temperature and heat flux are
automatically recorded at one-minute intervals and averaged into hourly values.
A test panel would typically be installed in the
Roof Thermal Research Apparatus (RTRA) where it is exposed to ambient
conditions over a long period of time. However, PROPOR can be used to
determine the thermal conductivity of materials with transient data
collected from any source (not just the RTRA). PROPOR is an application
of parameter estimation techniques. Using a time series
of boundary conditions and initial estimates of thermal properties, PROPOR
calculates the temperatures and heat fluxes at the sensor locations using
the conduction heat transfer equation for a homogeneous medium. PROPOR
assumes that heat flow is one-dimensional and involves heat conduction only.
Layered systems can be accomodated. The outputs are the apparent thermal
conductivity and the density-specific heat product, both as a function
of temperature if desired. PROPOR also estimates the expected
convergence of results (sensitivity coefficients), correctness of the
initial model (residual analysis), and precision of results (confidence
The procedure in PROPOR was added to ASTM C 1155 Standard Practice for
Determining Thermal Resistance of Building Envelope Components from In-Situ
Data in 1995.