A review on thermal application of metal foam

Heat exchangers embedded with metal foam are drawing increasing attention in the thermal application field, due to the performance of low density, large ratio of surface area to volume as well as high thermal conductivity. In these applications, compact heat exchanger, solar thermal facilities and thermal energy storage are the three core components. This paper focuses on the lasted advances in thermal applications, presenting a review of theoretical and experimental progress over metal foam in thermal application. The empirical and theoretical models for pressure drop, heat transfer coefficient and performance evaluation criteria of compact heat exchangers with metal foam are reviewed and discussed, especially different optimized configurations. There is a trade-off between heat transfer enhancement and increase of pressure drop. Some exploratory work performed by present authors are also introduced. The manufacturing, heat transfer and flow characteristics of tube bundle wrapped with metal foam are taken into account for optimization of heat exchanger. It is confirmed that the conversion mechanism of heat transfer is carried out that heat conduction is the dominative term at high dimension permeability. The correlations of heat transfer rate and pressure drop for staggered and single row tube bundle wrapped with metal foam are concluded, respectively. The effects of different bonding methods are revealed for point-contact in metal foam and base tube. The powder-sintering method can provide a stable and minimum-thickness bonding layer. Various types of solar thermal facilities utilized metal foam to improve the energy conversion efficiency from solar radiant energy to thermal energy are also reviewed and discussed, including solar collector for intermediate-low temperature utilization and solar receiver for high temperature utilization. The Last but not least, existing and future metal foam thermal application stations are overviewed.