Influence of fluctuating heat sources and the subzone rotation strategy on the solid-liquid phase transition process: experimental and numerical studies

The application of the rotation mechanism promotes heat exchange in the phase-change energy storage (PCES) process and improves the temperature non-uniformity at the end. This research proposes a novel type of subzone rotation condition, where different rotational speeds and rotation directions are applied to distinct phase transition regions, and it is implemented in the triple-tube heat storage process. An experimental system is constructed to monitor the temperature of PCM inside the PCES unit connected to the motor for rotation. Cross-comparisons are made with numerical process of PCES under the application of rotation conditions to verify its accuracy. The effect of constant and fluctuating heat sources on this PCES under different subzone rotation conditions is also considered. The comparison results indicate that the fluctuating heat source on overall melting behavior can be ignored, while the subzone rotation condition can improve the negative effect of the difficult-to-melt area. After applying a subzone rotational speed of 0.2 rpm, compared with static energy storage process, the mean PCES rate increased by 299.43 %, while the required time for heat storage completion is reduced by 74.73 %. The novel active enhanced heat exchange method proposed in the research is conducive to the further development of PCES technology.