Phase-change heat transfer systems coupled with multi-transducer ultrasonic field: A visual experimental study

Driven by the rapid development of the artificial intelligence and cloud computing, the increasing thermal management demands and the need for energy optimization have become urgent challenges for data centers. Paraffin phase-change heat transfer has emerged as a promising thermal management strategy owing to its high energy density and favourable latent heat characteristics. In this study, a multi-transducer ultrasonic field is ​proposed to actively enhance and regulate phase-change processes, thereby mitigating the thermal hysteresis​ induced by the inherently low thermal conductivity of phase-change materials (PCMs). A visualization platform for ultrasonic-assisted phase-change heat transfer is developed to systematically investigate the effects of transducer positioning, array configurations, ultrasonic power, and thermal boundary conditions on the melting dynamics and heat transfer performance of PCMs. The results reveal that positioning a single transducer in the hot fluid inlet achieves the maximum heat transfer enhancement, which increases the average total heat absorption rate of PCM by 64.91%. The integration of the multi-transducer ultrasonic array and higher ultrasonic power significantly intensifies forced convection, with the strongest thermal enhancement observed in the central region. Notably, when the power increases to 240 W, the melting efficiency and average temperature response rate increase by 68.11% and 256.25%, respectively, exhibiting nonlinear enhancement characteristics dominated through the acoustic cavitation. Furthermore, the ultrasonic field exhibits a greater responsiveness under lower thermal boundary conditions. Finally, based on stage-specific energy efficiency ratios, the multi-transducer system combined with an intermittent pulsing strategy​ is proposed to optimize the full-cycle energy efficiency.