Study of thermo-physical properties and cycling stability of d-Mannitol-copper oxide nanocomposites as phase change materials

Abstract

Sugar alcohols (SA) are emerging as one of better energy storage materials for thermal energy storage (TES) application due to its phase change temperature ranges (−15 to 245°C) and considerable phase change enthalpies of 100–430kJ/kg. However, the main challenges include the low thermal response of the phase change materials (PCM) owing to its very low thermal conductivity values. In this study, d-Mannitol (DM)-copper oxide (CuO) nanocomposites (DM-CuON) were prepared using dispersion technique to form high thermal conductive nanocomposites. In this view, copper oxide (CuO) nanoparticles were mixed in DM in various mass fraction of 0.1, 0.2 and 0.5wt.% using high-speed ball mill. Structural analysis was done by SEM and crystallography by XRD diffraction techniques. The XRD data reveal that the pure DM exhibited the polymorphic form of beta (β) phase. By varying the weight percentage from 0.1 to 0.5wt.% the rate of relative crystallization increased as compared to pure DM. Thermal conductivity enhancement of 25.2% was observed for DM-CuON with 0.5wt.%. It was observed that the interaction between CuO nanoparticles and DM were only physical in nature which confirmed its high chemical stability. After repeated heating/cooling cycles the heat of fusion decreased yet it showed high latent heat value of 256.20kJ/kg, 252.48kJ/kg, 246.85kJ/kg and 240.78kJ/kg after 50 cycles and 241.16kJ/kg, 237.49kJ/kg, 229.86kJ/kg and 205.48kJ/kg after 100 cycles for DM and DM-CuON. Mass changes observed were less than 3% after thermal cycling for a temperature range up to 250°C. Overall CuO helps to achieve improved thermo-physical and heat storage characteristics for DM-CuON which suggest their potential candidate of usage in the medium temperature thermal energy storage system.