Metal foam heat exchangers for heat transfer augmentation from a tube bank

A numerical study has been conducted to examine the heat transfer from a metal foam-wrapped tube bundle. Effects of key parameters, including the free stream velocity, longitudinal and transversal tube pitch, metal foam thickness and characteristics of the foam (such as porosity, permeability, and form drag coefficient) on heat and fluid flow are examined. It can be observed that the performance of the metal foam heat exchangers, measured in terms of area goodness factor, can noticeably be better than that of the conventional design of finned-tube heat exchangers. It is also found that even a very thin layer of metal foam, when wrapped around a bare tube bundle, can significantly improve the area goodness factor. Finally, it is shown that while friction factor is more sensitive to the metal foam permeability than its porosity, the converse is true when it comes to the Colburn factor. (C) 2011 Elsevier Ltd. All rights reserved.