Thermal properties enhancement and application of a novel sodium acetate trihydrate-formamide/expanded graphite shape-stabilized composite phase change material for electric radiant floor heating

Abstract

Electric radiant floor heating system (ERFHS) with hydrate salt phase change material (PCM) as thermal storage medium owns the advantages of improving indoor comfort with high energy efficiency and favorable economic applicability. In this paper, based on sodium acetate trihydrate (SAT)-formamide (FA) eutectic mixture as PCM and expanded graphite (EG) as supporting carrier, a novel SAT-FA/EG composite PCM (CPCM) for ERFHS was prepared by physical blending method. The shape stability, thermal properties and thermal reliability of the SAT-FA eutectic mixture under EG were emphatically discussed. The heat storage and release performances of a simulation room established by ERFHS integrated with such CPCM were investigated. Experimental results showed that the SAT-FA/EG composite containing 8% EG displayed high phase change enthalpy (187.6 kJ/kg), suitable phase change temperature (38.54 °C), negligible supercooling degree (0.83 °C) and eminent thermal conductivity (3.11 W/m·K), along with the excellent shape stability and thermal reliability. The simulation showed that the ERFHS with CPCM layer presented smaller indoor operative temperature fluctuation in vertical orientation and longer total thermal comfort time (12.65 h), which greatly exceeds that of the one without CPCM layer (1.836 h). All the superior characters make the obtained SAT-FA/EG composite a promising candidate for ERFHS.