Hybrid lattice Boltzmann-TVD simulation of melting of Cu-water in a square cavity using Buongiorno’s model

The primary objective of the present article is to investigate the effect of nanoparticle migration on the melting process of Cu-water as nano-enhanced phase change material (NePCM) based on Buongiorno’s model. The NePCM is enclosed in a square cavity subjected to a high temperature at the left side wall. The hybrid Lattice Boltzmann method (LBM) and total variation diminishing (TVD) scheme are utilized to simulate the phase change process of NePCM. For the melting process of NePCM, the considered parameters include the nanoparticle volume fraction (ϕ = 0, 2, 4, and 6 vol%), nanoparticle size (d_s = 25, 50, 75, and 100 nm), Rayleigh number (Ra = 10³, 10⁴, and 10⁵), and Lewis number (Le = 4,000, 6,000, 8,000, and 10,000). The results show that, when the two-phase model is adopted, the melting behavior is optimal around ϕ = 0.04 in the present work, while the melting performance of the single-phase model enhances with higher ϕ. Similarly, the growth in d_s facilitates the melting process, yet it also leads to nanoparticle agglomeration, whereas the melting process of the single-phase model is minimally affected. Later, an increase in Ra enhances the convective melting performance, aligning with the single-phase model. Further, the increase of Le can also accelerate the melting rate, where the thermal diffusion capability is enhanced.