Metal Foams for Enhanced Heat Transfer. State of the Art and XRayMicrotomography Characterization

Metal foams have a great potential for enhancing the thermal performances of heat transfer devices, while allowing the use of smaller and lighter equipments. From a practical standpoint, it is necessary to compromise between the improved heat transfer rate and the higher pressure drop induced by the tortuous flow passages. In order to investigate the structure and properties of metal foams, and to provide adequate information for design purposes, the prediction of the permeability and thermal conductivity as a function of the structural characteristics would be desirable. From this perspective, computational fluid dynamics (CFD) computations at the pore scale are becoming a challenging approach in addition to classical transport models. To investigate the microstructure of metal foams, a three-dimensional approach by using X-ray computed microtomography (μ-CT) can be adopted. μ-CT is a nondestructive characterization technique representing a powerful investigation tool in many different applications. It consists in recording a number of projections of the sample at different angles, and reconstructing a 3D image with the help of a suitable algorithm. The reconstructed 3D dataset can be employed, after adequate geometric manipulation, to perform a CFD simulation on a realistic medium. In this work, a review of the recent experimental and numerical advances in the characterization of metal foams transport properties will be illustrated. Moreover, we will present the results of a high resolution 3D μ-CT imaging of three Aluminum foam samples, with different pore per inch values, performed at the TomoLab station, located at the Elettra Synchrotron Radiation Facility in Trieste.