Air forced convection through metal foams: Experimental results and modeling

Metal foams are a class of cellular structured materials with open cells randomly oriented and mostly homogeneous in size and shape. In the last decade, several authors have discussed the interesting heat transfer capabilities of these materials as enhanced surfaces for air conditioning, refrigeration, and electronic cooling applications. This paper experimentally characterizes twenty-one aluminum and copper foam samples with different number of pores per linear inch (PPI), which vary between 5 and 40 and with porosity ranging between 0.896 and 0.956; samples of different heights (20 and 40 mm) have been studied. The most important parameters both geometrical (porosity, pore density, and foam core height) and operative (air mass flow rate, imposed heat flux) affecting the heat transfer and fluid flow behavior of these enhanced surfaces are analyzed and discussed. The results are presented with reference to different performance parameters: overall and interstitial heat transfer coefficients, foam finned surface efficiency, normalized mean wall temperature, pumping power per area density, and pressure gradient. From the experimental measurements two correlations for the heat transfer coefficient and pressure drop calculations have been developed, validated and here proposed. These models can be successfully used to optimize different foam heat exchangers for any given application.