Plastic Crystal Neopentyl Glycol/Multiwall Carbon Nanotubes Composites for Highly Efficient Barocaloric Refrigeration System

Plastic crystal neopentyl glycol (NPG) exhibits colossal barocaloric effect with high entropy changes. However, their application is restricted in several aspects, such as low thermal conductivity, substantial supercooling effect, and poor springback properties. In this work, multi-walled carbon nanotubes (MWCNTs) with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG. The optimal mixing ratio was determined to be NPG with 3 wt% MWCNTs composites, which showed a 6 K reduction in supercooling without affecting the phase change enthalpy. Subsequently, comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG. At 40 MPa, 390 J center dot K-1 center dot kg-1 change in entropy and 9.9 K change in temperature were observed. Furthermore, the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%. In addition, the thermal conductivity of the composite was increased by approximately 28%, significantly reducing the heat exchange time during a barocaloric refrigeration cycle. More importantly, ultra-high pressure release rate resulted in a 73.7% reduction in the springback time of the composites, offering new opportunities for the recovery of expansion work.