This study focused on observing the melting phenomena and investigated a principle factor of enhanced heat transfer in phase change material when the ultrasonic vibrations were applied during the melting process. For visualization, particle image velocimetry and thermal-vision camera for observing the flow phenomenon was used. Also, experiments were performed to obtain the experimental results such as melting time and temperature distribution. Besides, structural vibration simulator which is applying a coupled finite element-boundary element method (Coupled FE-BEM) was used for calculation of acoustic pressure occurred by ultrasonic vibrations in liquid region. The results of experimental and numerical observations show that acoustic streaming induced by ultrasonic vibrations is one of the prime effects acoustically enhanced phase change heat transfer and help to accelerate the melting of phase change material. Also, the application technique of visualization and computational simulation introduced in this study is very useful and important to analyze the mechanical behavior of material in a fast fluid dynamic or acoustic field.