The number of vehicles in use is increasing from year to year.

Aluminum foams are favorable in modern thermal engineering applications because of the high thermal conductivity and the large specific surface area. The present study aims to investigate an application of porous aluminum foam by using the local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) heat transfer models. Three-dimensional simulations of laminar flow (porous foam zone), turbulent flow (open zone) and heat transfer are performed by a computational fluid dynamics approach. In addition, the Forchheimer extended Darcy's law is employed to evaluate the fluid characteristics. By comparing and analyzing the average and local Nusselt numbers, it is found that the LTNE and LTE models can reach the same Nusselt numbers inside the aluminum foam when the air velocity is high, meaning that the aluminum foam is in a thermal equilibrium state. Besides, a high interfacial heat transfer coefficient is required for the aluminum foam to reach a thermal equilibrium state as the height of the aluminum foam is reduced. This study suggests that the LTE model can be applied to predict the thermal performance at high fluid velocities or for the case with a large height.

Due to the increased power consumptions in equipment, the demand of effective cooling methods becomes crucial. Because of the small scale spherical pores, graphite foam has huge specific surface area. Furthermore, the thermal conductivity of graphite foam is four times that of copper. The density of graphite foam is only 20 % of that of aluminum. Thus, the graphite foam is considered as a novel highly -conductive porous material for high power equipment cooling applications. However, in the commercial market, aluminum and copper are still the preferred materials for thermal management nowadays. In order to promote the graphite foam as a thermal material for heat exchangers, an overall understanding of the graphite foam is needed. This paper describes the structure of the graphite foam. Based on the special structure, the thermal properties and the flowing characteristics of graphite foam are outlined and discussed. Furthermore, the application of graphite foam as a thermal material for heat exchangers is highlighted for electronic packages and vehicle cooling systems. The physical problems and other aspects, which might block the development of graphite foam heat exchangers, are pointed out. Finally, several useful conclusions and suggestions are given to promote the development of graphite foam heat exchangers.

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