A strategy for enhancing heat transfer in phase change material-based latent thermal energy storage unit via nano-oxides addition: A study applied to a shell-and-tube heat exchanger. Issue 6 (December 2021) - Chibani, Atef
Abstract: Due to the scarcity of data on the industrial use of energy storage technology based on material phase change (PCM), a complete computational assessment is done in this work, where a nano-PCM technique is used to enhance the thermal energy storage in a big-scale shell-and-tube heat exchanger. Four high thermal conductive nano-oxides (i.e., Al2 O3, MgO, SiO2, and SnO2 ) are added at various concentrations (1–5% v/v) into the PCM (i.e., paraffin RT82). A two-dimensional mathematical model is used to study the produced nano-PCM systems' heat transfer and melting rate. The model accurately predicted the PCM-melting data's observed behavior, showing that it is adequate for simulating PCM problems. The addition of nano-oxides, for up to 5%, in the PCM solid matrix dramatically enhances heat transmission and melting rate during the first melting stage. However, after a long melting period, the melting performance of the nano-PCMs decreased and became equivalent to that of the pure PCM. Furthermore, increasing the concentration of nanoparticles from 1 to 5% did not significantly improve the temperature and liquid fraction evolutions for the four studied nano-PCMs. Therefore, the use of nano-PCMs in the adopted LTES unit can effectively improve heat recuperation and melting rate, but only for a short charging time during which a part (up to 60%) of the PCM's latent heat is recovered. Consequently, the present paper's data is considered a guideline for increasing the efficacy of thermal energy storage in big-scale shell-and-tube heat exchangers using nano-PCM technology. Graphical Abstract: ga1 Highlights: The melting process of pure-PCM (paraffin) and various nano-PCMs was compared. Heat transfer and solid melting rate were analyzed for diverse cases of nano-PCMs dosage. Nano-PCMs accelerated the melting rate over the pure-PCM at the initial melting period. After a period of melting, the performance of the pure-PCM overlaps those of non-PCMs. Nanoparticles allow rapid recovering of up to 60% of the latent heat of the PCM at short time.