The thermal storage performance and numerical simulation of organic-inorganic composite phase change materials based on nitrate-acetamide system

Compared with single phase change materials (PCMs), organic-inorganic composite PCMs exhibits superior properties. Such as enhanced chemical stability, maintaining high energy storage density during thermal cycles. In this paper, a novel inorganic-organic composite PCM is synthesized with lithium nitrate (LNH) and acetamide (AC), which thermophysical properties are investigated systematically. The impact of α-Al 2 O 3 , β-Al 2 O 3 , expanded vermiculite, expanded graphite, boron nitride and bentonite on the energy storage density and cycle stability of composite PCM is examined intensively. The energy storage density of the composite PCM augmented with 1 wt% bentonite exhibits an increase rather than a decrease. After 100 cycles, a comparison of the data reveals that the average melting enthalpy of the PCM with bentonite (149.2 J·g −1 ) is 14.1 % higher than that without bentonite (124.2 J·g −1 ). The average enthalpy of solidification (150.8 J·g −1 ) is 21.4 % higher than that (130.7 J·g −1 ). Furthermore, the fluctuation range of the melting point and the freezing point is significantly reduced from 381.6 K–402.8 K and 313.8 K–402.2 K to 402.5 K–404.3 K and 393.8 K–403.9 K, respectively. The deviation of the melting temperature and latent heat after 100 cycles is <0.2 % in comparison to the initial value. The heat storage and release process of composite PCM in macro quantity is studied by step cooling curve test and computational fluid dynamics numerical simulation. It is confirmed that the LNH-AC/bentonite composite PCM not only has excellent long-term cycle stability, but also has no supercooling. LNH-AC/bentonite system is one of excellent candidates for solar heat storage.