Performance assessment of phase change material-based thermal energy storage

Phase change material (PCM) based thermal energy storage (TES) offers high energy density and better heat transfer performance by encapsulating PCM within a specifically designed container, i.e., shell and tube type TES. In this work, the PCM is packed in multiple cylindrical tubes, and heat transfer fluid (HTF) flows in the annulus. Such arrangement of PCM and HTF in the TES system is termed a cylindrical model, and the one opposite to the cylindrical model is called a pipe model. This work conducts the performance evaluation for PCM-based shell and tube TES using an experimentally validated numerical model. The 3D cyclic periodic model for TES has been developed based on hexagonal circle packing, and the effective energy storage ratio as a performance index under varying geometrical and operating parameters has been investigated. The variation in parameters includes tube length (0.5–7 m), diameter (10–50 mm), initial temperature (293.15–303.15 K), volumetric flow rate (10–500 l/min), inlet temperature (323.15–393.15 K). Using a conjugate heat transfer model, the influence of parameters was investigated, and the performance index was evaluated using the effectiveness-NTU theory. It was found that TES was effective for geometrical parameters diameter d≤ 30 mm and length L≥ 2 m. The performance index of 1.54 was optimum and achieved when the inlet temperature was 333.15 K. This optimum performance index value was compared with existing work and found to be performing comparatively well.