Solidification enhancement of PCM in a triplex-tube thermal energy storage system with nanoparticles and fins

This study is on the application of nanoparticles and fins for improved phase change material (PCM) solidification in a heat exchanger. A major challenge in using PCMs is their poor thermal conductivities which consequently prolongs phase change processes giving rise to very slow charging/discharging rates. This seriously affects energy storage and recovery times, signifying the need for heat transfer enhancement in these systems. A model that considers heat conduction in the fins, natural convection in the liquid PCM, and Brownian motion of nanoparticles in the PCM was developed and validated with experimental data in this study. The influence of different dimensions of fins and volume concentrations of nanoparticles on PCM solidification evolution was studied. The effect of using fins alone, nanoparticles alone and combination of both on the solidification was investigated. Because of the extra added volume which limits available volume for PCM storage, the fin, nanoparticle and total volume fractions were used to evaluate volume usage associated with each technique. Results from the study show remarkable findings including substantial reduction in the PCM solidification time. It was also found that the application of fins alone shows better enhancement than using either nanoparticles alone or combination of fins and nanoparticles.