Determining the uncertainty in measurements of thermal conductivity (λ) of gypsum composites modified by PCM using the hot-wire technique

The article presents a method of estimating the uncertainty for measurement of thermal conductivity (λ) using hot-wire technique. An originally designed and developed measuring system for determining thermal conductivity of solid bodies using hot-wire technique (HWT) was applied. Thanks to low costs, high accuracy, and short measurement time, it is a common dynamic technique, effectively used in a transitional states. The experiments were conducted for PCM-gypsum composites in different temperatures of samples, to estimate the uncertainty in solid, liquid and transitional states of PCM. The experimental value of the thermal conductivity of the tested composite and values of relative components of standard uncertainties of this parameter were determined. A satisfactory, low value of complex relative extended uncertainty (below 4 %) of thermal conductivity U(λ)/λ was obtained. It was confirmed that the uncertainty does not depend on the sample temperature and physical state of PCM.