Melting of a Phase Change Material Filled in a Metal Foam: A Visualized Study at the Pore-Scale Using Infrared Imaging

The thermal imaging technique was applied in this work to measure the transient temperature fields during melting of a phase change material (PCM) in a metal foam. A paraffin wax was used as the PCM that was filled in an open-celled copper foam. Melting of a paraffin wax in the presence of copper foam was studied in a rectangular cavity that was heated from one lateral side wall, while the top surface was exposed to an infrared (IR) camera. A thermocouple (TC) was also employed to validate the accuracy of temperature measurements by IR thermal imaging. The relative deviation of measured temperature by the TC and IR camera was found to be under 2% in steady state and under 4% during the entire course of melting. The resolution of IR thermal imaging with the aid of a macro lens allowed for temperature measurements at pore-scale of the copper foam. Local thermal imaging was captured through a minor window on the top plate of the container. Three points (Sp1–3) inside a selected individual pore were marked to quantify the temperature variations of melting process within metal foam/PCM at pore-scale. The average temperature differences between Sp1 and Sp2, Sp3 were found to be about 1 °C over the entire course of melting, and the maximum value was up to nearly 10 °C around the melting point. These preliminary results clearly highlighted the effect of metal ligaments on the temperature distributions at pore-scale.