Physics

Composite material

Volumetric flow rate

Thermal energy storage

Materials science

Thermal

Phase-change material

Heat transfer fluid

Environmental science

Heat transfer

Natural convection

Mechanics

Latent heat

Thermodynamics

Renewable Energy

The popular application of latent heat storage (LHS) units using phase change materials is limited in converting and utilizing renewable energy due to their poor thermal efficiency. To address this deficiency, a tree-shaped fin inspired by nature is employed for the thermal enhancement of vertical LHS units. A three-dimensional mathematical model using the enthalpy-porosity method is developed to comprehensively evaluate the heat charging/discharging process of the new and traditional LHS units, focusing on the role of heat transfer fluid (HTF) direction. The results indicate that tree-shaped fins improve the temperature uniformity and facilitate the melting/solidification rate, which exhibits a preferable advantage that the full melting/solidification duration shortens by 34.5% and 49.2%, and the time-averaged heat storage/release rate augments by 49.4% and 96.4%. Interestingly, natural convection significantly improves the heat charging performance, while the role of natural convection can be considered negligible during discharging processes. Moreover, the HTF temperature seriously affects the performance of LHS units, while the role of HTF flow rate is less prominent. It is found that the upward flow of HTF is beneficial to the heat charging improvement while a downward flow mode facilitates the discharging performance, providing useful advice for practical applications of vertical LHS units.

Charging and discharging enhancement of a vertical latent heat storage unit by fractal tree-shaped fins