Analysis of the effect of cooling rate on the solidification characteristics of solar salts

Abstract

The scale and interface effects of nanomaterials lead to their unique thermophysical properties, distinct from bulk materials, thereby significantly affecting the phase-transition behaviour of mesoporous nanomaterials. Studies on solidification characteristics of phase-change materials with different pore sizes or those adsorbed by different skeletons are of great significance for improving the efficiency of energy storage and developing composite phase-change materials (CPCMs). The variations in the solidification temperature, degree of subcooling, and solidification enthalpy of mesoporous skeleton/solar salt CPCMs under different cooling rates were analysed based on the self-diffusion coefficient and potential-energy–temperature curve, along with experimental methods. As the cooling rate increased, the above-mentioned phase-transition parameters varied with changes in the size of the mesoporous core. In particular, for the same core size, the degree of subcooling of the solar salt increased, whereas the solidification temperature decreased with increasing cooling rate, latent heat increased with increasing cooling rate. Moreover, an increase in the cooling rate significantly promoted the surface nucleation and heterogeneous nucleation processes, resulting in the influence of interface change on the phase-transition parameters.