Heat transfer in building thermal insulation: the thickness effect

(1) The measurement of the apparent thermal properties (i.e., conductivity, resistivity, and resistance) of insulation of the guarded hot-plate technique is modeled using a digital computer that solves the coupled conductive and radiative heat transfer problem for an absorbing and emitting single-phase gray medium contained between parallel black isothermal plates. The results of these calculations for the worst limiting case and the previously determined results for the best limiting case are used to bracket the effect of sample thickness on the apparent thermal properties of insulation and to develop an extrapolation equation that shows the relationship between the apparent thermal properties and the measurement conditions (e.g., hot- and cold-plate emissivities and temperatures and specimen thickness). 16 refs.