Design of combinational fins for a vertical shell-tube latent heat thermal energy storage unit

The employment of annular fins and longitudinal fins in latent heat thermal energy storage unit can significantly improve its thermal performance. However, the annular fins can greatly suppress the convection and longitudinal fins lead to severe non-uniform melting. To address this issue, three different types of combinational fins were proposed and applied in a vertical shell-tube storage unit in this study. The numerical model was first built with the adoption of enthalpy-porosity method. The simulation results were then verified with experimental data. Results showed that combinational fins leads to faster melting thorough enhancing both natural convection and conduction compared with only longitudinal or annular fins. This advantage in melting enhancement is even greater with the increase of fin volume. Moreover, the enhancement effect of combinational fins is better with the same longitudinal and annular fins volume and a higher longitudinal fin at the same longitudinal fin volume. The optimum combinational fins in present work has a melting time reduction of 31.0% and 21.2% compared with only longitudinal and annular fins, respectively. The results can provide important reference for the fins design in vertical shell-tube thermal energy storage units.