Simulation of Performance Optimization of a Latent Heat Thermal Energy Storage Device

Thermal energy storage (TES) provides a potential adjustable load for the new type of power system. The TES system not only reduces the cost of green power heating, but also realizes thermo-electrolytic coupling, and increases the flexibility of thermal power units. Phase change material (PCM) has been highly concerned in TES system due to the advantages of higher heat storage density and smaller temperature rise during chargedischarge processes. However, the low thermal conductivity of PCM leads to the difficulty in meeting the storage and release efficiency of the TES system for engineering applications. To improve the performance of heat transfer and energy storage of TES system, a two-dimensional computational fluid dynamics model is established and validated. A typical shell and multi-tube energy storage unit was selected to simulate the natural convection, temperature rise and liquid fraction distribution. To optimize thermal storage performance, the eccentricity distance, tube diameter and tube arrangement of the multi-tube energy storage unit were designed using Taguchi orthogonal method. The results show that the total melting time of the original case is 19000 s, of which the melting time of the PCM at the bottom accounts for about 38.4 % of the total time; The optimal case has an eccentricity of 30 mm, a tube diameter of 15 mm and uniform row of tubes. The melting time was 12443 s, which is 52.7 % less than the original case. At 120 min, the average heat storage rate is 882.26 W/m, which is 60 % higher than the original case, and the total heat storage energy reaches a maximum of 10978 kJ/m, which is a significant increase in the heat storage capacity.