Computer Codes Used in Building Envelope Research










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 interval).

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.

Building Envelope Research
Oak Ridge National Laboratory

For more information, contact the program manager for Building Envelope Research:

André O. Desjarlais
Oak Ridge National Laboratory
P. O. Box 2008, MS 6070
Oak Ridge, TN 37831-6070
E-mail Andre Desjarlais

Revised: May 26, 2004 by Juanita Denton