Improved phase change performance of ultrasonic-assisted melting: A visualized experimental study

To address the non-constant heat sources and fluctuating user heat loads of renewable energy utilization, ultrasonic-assisted solid-liquid phase change technology with a faster thermal response was proposed for balancing supply and demand. In this study, an ultrasonic field due to its sound flow and cavitation effect was introduced to enhance phase change heat transfer in pure paraffin. The effectiveness of ultrasonic-assisted melting in achieving faster thermal response was experimentally proved. A visual experimental system was established to test the solid-liquid phase change performance of a cavity under varying ultrasonic power and heat sources. Melting interfaces were shot and binarized, while temperature evolutions of paraffin were obtained and compared. Meanwhile, melting endothermicity was also assessed and performed. The experimental results demonstrated that higher ultrasonic power correlated with increased efficiency. The dumbbell-shaped phase interface observed with ultrasonic assistance reflected significant advantages in enhancing overall heat transfer, particularly in the severely underperforming bottom paraffin region. The provision of ultrasonic field decreased melting time by 59.72 % and increased temperature response rate by 161.70 % with a 60 W ultrasonic power compared to no initiating vibration. Ultrasonic-assisted melting also could achieve enhancement of 151.90 % on melting endothermic rate, offering valuable potentiality in notably short heat absorption/thermal storage processing.