Modeling of Corrugated Graphite Foam Heat Exchangers

A new manufacturing process was recently developed by the Oak Ridge National Laboratory for the production of graphite foam. The high thermal conductivity and heat transfer area of the foam make it desirable for thermal management applications such as compact heat exchangers. The heat transfer capabilities of the foam are especially useful in internal forced convection applications. However, due to the very low permeability of graphite foam, pressure-drop is very high compared to other porous media, and pressuredrop reduction schemes are necessary to ensure its practical application. Pressure-drop reduction can be achieved through the strategic machining of graphite foam into complex geometries. In this study, a corrugated configuration is analyzed. Computational methods are employed to determine optimal geometric parameters of corrugated graphite foam heat exchangers that result in a significant reduction in pressure-drop without severely affecting heat transfer performance. The results indicate that pressure-drop in optimal corrugated configurations is reduced by nearly two orders of magnitude when compared to a full graphite foam block of the same overall size. These optimal cases are characterized by relatively uniform flow in the transverse direction across the foam, and this uniformity is reduced by slot widths that are too long and narrow and by flowrates that are too high. These optimal configurations decrease the heat transfer coefficients by nearly fifty percent when compared to a full block, but the reduction of pressure-drop is much more significant. Therefore, corrugating the foam is shown to be an effective method to significantly reduce the pressure-drop without severely affecting the heat transfer performance of graphite foam heat exchangers.