Experimental visualization on thermal energy storage enhancement through metal foam filled annuli

Intensified heat transfer research was carried out for the heat exchange basic unit-heat exchange tube in the tube-and-tube phase change regenerator. The metal foam was added on the side of the phase change material to enhance the heat storage. Phase interface was recorded by a high-definition camera during the charging process. T-type thermocouples were attached separately on the radial and axial sides of the PCM. Charging processes of smooth tube and metal foam tube were quantified under the flow rate of 0.15 m•s^-1. The results demonstrated that the involvement of metal foam can significantly enhance the efficiency of thermal energy storage under the same charging condition (initial temperature, inlet temperature and flow rate). It took over 2.9 more times for the melting time of pure paraffin than that of metal foam under the same condition. The temperature response rate of metal foam tube was much higher and the temperature distribution was more uniform, in comparison with that of smooth tube.