Metal foam regenerators; heat transfer and storage in porous metals

Open pore metal foams may be of interest as regenerators because of their large specific surface area and their high porosity. In this experiment, three aluminum foam samples (pore size 2–2.36 mm and around 65% porosity) were manufactured by the replication process. The volumetric heat transfer coefficient and number of transfer units (NTU) of the foams and a packed bed of steel ball bearings (2 mm diameter) were determined using a single-blow transient technique over the range 500 < Rem< 1400. The NTU values of the foams and ball bearings both reduced with increasing Reynolds number (flow velocity). The pressure drop across the matrices increased with the velocity, though the values for the metal foams were much lower than that of the ball bearings, indicating that they may have potential for this type of application.