Study on thermal properties of phase change material by an optical DSC system

Abstract

An optical differential scanning calorimeter (DSC) system was used in studying the thermal properties of phase change material (PCM). In this study, several typical PCMs were studied on its thermal properties by the optical DSC system. These PCMs are sodium sulfate (Na2SO4·10H2O), paraffin, n-octadecane, and the paraffin/n-octadecane composites at different mass ratios. The thermal properties and micro-structure change of these PCMs were mainly investigated. The results showed that for Na2SO4·10H2O, paraffin and n-octadecane, the measured phase change temperatures and enthalpies appeared no large relative deviation (<5%) from the theoretic values. A high measurement accuracy of the optical DSC system has been obtained and concluded from the experimental results. For the paraffin/n-octadecane composites, the measured phase change temperatures appeared to be lower than that of paraffin, and could be adjusted from 24.2 °C to 49.6 °C by changing the mass fractions of n-octadecane. The lowest eutectic temperature was obtained at the mass fraction 40% of n-octadecane. The measured phase change enthalpies, however, appeared no large variation between 186.4 J/g (paraffin) and 230.5 J/g (n-octadecane). And according to the micro-photos before and after phase change, n-octadecane existed as crystal particles which disappeared with increasing temperature and finally combined with the paraffin matrix.