Expanded graphite intersperse reliable binary eutectic phase change material for low temperature thermal regulation systems

Abstract

Inorganic phase change materials (PCMs) frequently stuck by ineffaceable thermal conductivity and degree of supercooling for thermal energy storage (TES) accomplishment. The present research work is dedicated to resolve this problem by developing a unique inorganic salt hydrate based binary eutectic PCM employing sodium sulphate decahydrate (SSD) and sodium phosphate dibasic dodecahydrate (SPDD) in eutectic mixture ratio 62:38 mass percentage. The peculiar eutectic composition of SSD/SPDD developed with melting and bath sonication technique manifests eutectic latent heat of 207.4 J/g and eutectic melting point of 27.8 °C. Furthermore, to elevate thermal performance and to descent degree of supercooling three dimension expanded graphite (EG) is interspersed as nanoparticle. Optical absorbance of composite PCM elevated from 0.16 for SSD/SPDD to 0.92 with SSD/SPDD + EG nanoparticles; inversely transmissibility of the composite reduced by 82.13 %. Heat flow curves ensures the melting temperature (26.9 °C–28.7 °C) of EG dispersed composite to be within the operating condition with latent heat of 220.4 J/g at 2.0 % of EG owing to the intermolecular binding force of attraction increases as nano-sized sheets effectively disperse with the base PCM. Subsequently, thermal conductance of nano composite eutectic PCM upraised from 0.453 to 0.855 W/m⋅K. After 200 thermal cycle's chemical optical and thermal stability of the PCM composite was degraded insubstantially due to the presence of impurities with longer service; this affirmed the stability thermal perks of nanocomposite PCM. Numerical analysis on heat transfer propagation of heat source within SSD/SPDD PCM layer with and without EG nanoparticle provides inference on the importance of thermal conductivity.