Enhanced thermal performance of the solidification process of nanopowder-phase change material-based latent thermal unit: Heat management

Abstract

In a cylindrical shell and multi-tube heat exchanger (of large configuration), the incorporation of four distinct nanoparticles (Al2O3, MgO, SiO2, and SnO2) at various concentrations (0%–5%, v/v) into PCM (RT82) was investigated during the solidification process. A numerical model was developed and validated through experimental and theoretical findings found in literature. Whatever the metal oxides’ concentration, a clear enhancement of the freezing rate of PCM was observed over its solidification period, where this improvement was boosted proportionally with the rise of metal oxides concentration. However, the worst performance of the nano-PCM system was obtained using SnO2 nanoparticles, where a total solidification of PCM is observed after 26000 s for 5% (v/v) SnO2. In contrast, the best performance was resulted using SiO2, for which a total hardening of PCM was reached after 21000 s for 5% (v/v) silicon dioxide. This means that a reduction of 19.23% of the freezing period was obtained using SiO2 compared to SnO2 system at the same volume fraction (5%). It was found that in presence of nanoparticles (nano-PCM system), the solidification rate of PCM is in the order: SiO2>MgO > Al2O3>SnO2. According to the thermo-physical properties of metal oxides, it was found that the enhancing role of nanoparticles (toward PCM solidification) is density-dependent. Therefore, the effect of heat capacity may be overlooked.