Verification of the slab model for pulse transient technique using laboratory reference material PMMA

Abstract

The primary objective of the paper was to verify validity of the slab model for Pulse Transient Technique (PTT) using the Thermophysical parameters data obtained from inter-comparison measurements on PMMA with other techniques. This paper proposed the results of an inter-comparison data of thermal diffusivity (k), thermal conductivity (λ) and specific heat capacity (c) measured at normal room atmosphere and pressure. Data were measured on Laboratory reference material Polymethyl Methacrylate (PMMA) with verified known Thermophysical parameters. The purpose of this investigation was to proof the reliability of mathematical model using PTT with data uncertainty less than 0.5 % for all basic Thermophysical parameters. Besides k and λ, the slab model also includes two additional parameters responsible for the delay in the response to the heat pulse. These two parameters, the heat transfer coefficient from the heat source to the sample and the heat capacity of the heat source influence the measurement especially in the case of the sample-set interfaces with air gaps. During measurement of PMMA the Thermophysical parameters were estimated for dry contact interface to ensure the presence of these two effects and to avoid any influence from thermal conductive paste in experiment. In previous measurements a thermal conductive paste containing silicone oil as was used to suppress the air gaps influence. Nevertheless, in some cases of porous samples measurements it was found that the paste penetrates into the porous stone material and thus causes irreversible changes of properties during the measurement. So we decided not to use it for this kind of materials. The theoretical Slab Model (SM) was successful in estimation these two additional parameters. Estimation of these parameters was important as it helps to attain the uncertainty of the parameters estimation below 0.5%.