Thermal performance and optimal temperature design of cascade LHTES systems with different configurations

초록

Rapid electrification and the growing share of renewable energy increased the demand for compact and controllable latent heat thermal energy storage (LHTES) systems. This study presented an experimental and numerical comparison of three phase change material (PCM) configurations, namely single, axial series, and lateral parallel, under identical inlet conditions. A dedicated closed loop test facility was developed, and a three-dimensional enthalpy porosity model was established and validated against temperature histories and total melting times. The validated model was then used to examine the effects of mass flow rate and a sequential temperature design procedure consisting of cascade temperature level design (CTLD) and cascade temperature distribution optimization (CTDO). In CTLD, the melting temperature span and the relative position of the intermediate-stage temperature (phi) were varied systematically to identify the optimal span, the appropriate position range, and their effects on melting performance. In CTDO, the optimal span obtained from CTLD was fixed, and the detailed cascade temperature configuration was refined by varying the top layer temperature. Compared with the single configuration, the axial series and lateral parallel configurations reduced the total melting time by about 33% and 14%, respectively. For the series configuration, 3 L/min was the most practical operating condition. The CTLD and CTDO analyses showed that a small melting temperature span and an appropriate stage wise temperature distribution promoted earlier natural convection and faster overall melting. These findings provide practical design guidance for configuration selection, operating flow rate, and cascade temperature arrangement in LHTES systems.

키워드