Performance of Graphite Foam Evaporator for Use in Thermal Management

This paper presents the results of an investigation of the thermal performance of a graphite foam thermosyphon evaporator and discusses the foam’s potential for use in the thermal management of electronics. The graphitized carbon foam used in this study is an open-cell porous material that consists of a network of interconnected graphite ligaments whose thermal conductivities are up to five times higher than copper. While the bulk graphite foam has a thermal conductivity similar to aluminum, it has one-fifth the density, making it an excellent thermal management material. Furthermore, using the graphite foam as the evaporator in a thermosyphon enables the transfer of large amounts of energy with relatively low temperature difference and without the need for external pumping. Performance of the system with FC-72 and FC-87 was examined, and the effects of liquid fill level, condenser temperature, and foam height, width, and density were studied. Performance with FC-72 and FC-87 was found to be similar, while the liquid fill level, condenser temperature, geometry, and density of the graphite foam were found to significantly affect the thermal performance. The boiling was found to be surface tension dominated, and a simple model based on heat transfer from the outer surface is proposed. As much as $149W$ were dissipated from a $1cm2$ heated area.