Preparation and Characterization of CPCM for Thermal Energy Storage Unit

The efficiency and economy of an ASHP (air source heat pump) can be significantly improved in a cold area by combining it with a TESU (thermal energy storage unit). The work of looking for a phase change material with a suitable temperature range, a large thermal capacity, and high conductivity has been always on the road. This paper prepared 10 CPCMs (composites of a phase change material) by using the vacuum adsorption method, which consists of LA (lauric acid) as the phase change material and EG (expanded graphite) as the skeleton matrix for its high thermal conductivity and porous characteristics. By characterizing and analyzing their basic properties, surface morp\hology, and stability, a suitable CPCM for the TESU coupled with the ASHP heating system is found. The leakage experiment results show that the maximum effective content of LA absorbed in 100-mesh EG of a CPCM is 80%, and that in 200-mesh EG, it is 90%. Among 10 CPCMs, CPCM3, with a mass ratio of LA:EG/8:2, is considered the more satisfactory one for the TESU proposed by this paper, because its performance shows good stability, its phase transition temperature is 40.98–41.94 °C, its latent heat is 164.34–168.28 kJ/kg, and especially, its thermal conductivity is 8.15–8.33 W/(m·K). This paper will be followed by performance research on TESUs coupled with ASHP heating systems.