Effects of mechanical vibration on melting behaviour of phase change material during charging process

Abstract

Mechanical vibration exists in many thermal energy storage systems and thermal management systems. It is well-known that mechanical vibration can enhance heat transfer of thermal systems. However, the open studies on the effects of mechanical vibration on the performance of thermal energy storage and/or thermal management systems are quite sparse. To bridge the knowledge gap, the effects of vibration frequency and orientation of vibration axis on melting processes are investigated numerically. Three findings are reported for the first time: (1) for low frequency mechanical vibration ( ω ≤ 10 ), the enhanced mixing of molten phase change materials (PCMs) will accelerate the melting processes critically; (2) a higher vibration frequency ( ω ≥ 100 ) can cause an obviously faster charging speed, but the acceleration effect will become weak against the increasing of vibration frequency; (3) when the vibration axis is parallel to the gravity, the thermal response rate is the fastest. Especially, the present study answers a very interesting question: how does low frequency vibration ( ω ≤ 10 ) accelerate the charging processes? It is observed that the time averaged heat transfer rate under the low frequency vibration condition is lower than its counterpart without mechanical vibration. The knowledge learnt from this work can provide guides for many practical applications. • Effect of vibration frequency on melting process is revealed for the first time. • Effect of orientation of vibration axis on melting process is revealed for the first time. • The contributions of low frequency vibration to melting process are analysed from a new viewpoint.