Effects of various types of nanomaterials on PCM melting process in a thermal energy storage system for solar cooling application using CFD and MCMC methods

Abstract

• A vertical shell and tube LHTES unit where D-mannitol was utilized as the PCM on the shell side was numerically analyzed. • Ag, Cu, Al 2 O 3 , CuO, TiO 2 , GNP, MWCNT, and SWCNT were added to PCM to enhance its thermophysical properties. • CFD and, a method based on Bayesian inference, was adopted by coding the Bayesian MCMC simulation for predicting the melting time. • Adding carbon-based nanomaterials to pure PCM reduced the melting time by about 50%, while metal nanoparticles impaired the melting performance. • Adding metal oxide nanoparticles did not add any essential advantage to the LHTES system. Latent heat thermal energy storage (LHTES) systems are attractive for bridging the energy supply and demand gap. In such systems, reducing storage time is critical, especially for solar applications. Accordingly, this study mainly aims to employ various nano-additives, including metal (Ag and Cu) and metal-oxide (Al 2 O 3 , CuO, and TiO 2 ) nanoparticles and carbon-based nanomaterials (GNP, MWCNT, SWCNT), to improve the thermophysical properties of pure phase change materials (PCM) to accelerate the melting process. For this purpose, the energy storage performance was numerically analyzed in a vertical shell and tube LHTES unit where D-mannitol was utilized as the PCM on the shell side. Dynalene-ht was employed as a heat transfer fluid (HTF) in the tube. Using computational fluid dynamics (CFD) modeling, transient variations in liquid fraction, PCM temperature, and total melting time were investigated under the impact of the following parameters: the thermophysical properties and volume fraction of nanomaterials, Re and the inlet temperature of HTF. In addition, a methodology based on Bayesian inference was adopted by coding the Bayesian MCMC simulation to create proper models for predicting the melting time. The numerical results showed that adding carbon-based nanomaterials to pure PCM reduced the melting time by about 50%, while metal nanoparticles impaired the melting performance. It was also observed that adding metal oxide nanoparticles did not add any essential advantage to the LHTES system. This research will help design TES applications in the operating temperature range of 160–200 °C, especially in solar cooling systems.