Heat transfer in porous media has been investigated extensively with the motivation of enhancing heat removal in electronics cooling applications. Many investigations have been conducted on heat transfer in a channel filled with porous media. However, steady flow through a porous channel still yield a higher temperature difference along the flow direction. It is conceivable that oscillating flow through a porous channel will produce a more uniform temperature distribution due to the two thermal entrance regions of oscillating flow. As compared to a porous channel packed with metal particles, spheres or woven-screens, the highly porous open-cell metal foam possesses a different configuration. The polyhedral pore and reticulated ligament structures provide the extremely large fluid-to-solid contact surface area and tortuous coolant flow path inside the metal foam, which could increase dramatically the overall heat transfer rate. A survey of the literature shows that heat transfer in open-cell metal foam were mostly investigated under steady flow condition. Published literature on heat transfer in metal foams subjected to oscillating flow is scarce. This paper presents both experimental and numerical investigations on the heat transfer characteristics for oscillating flow through highly porous medium. Experiments were carried out to study the effect of the oscillatory frequency on the heat transfer in metal foams with various pore densities. The results show that the local Nusselt number increases with the kinetic Reynolds number. Higher total heat transfer rates for oscillating flow can be obtained by using high pore density metal foam. The numerical simulation is focused on the study of the variations of the transient temperature and Nusselt number at different locations in the porous channel during a complete cycle. The numerical results show that the profile of the transient temperature decreases with the increase of the distance along the vertical direction and the variation of the instantaneous Nusselt number at entrance region is more significant than that at the location close to the center of the porous channel. It is also found that the two-dimensional temperature distributions in the numerical domain are symmetric about the center of the channel at the cycle-steady state. The comparison shows that the results obtained by the simulation are in reasonably good agreement with the experimental data.
Thermal Transport Analysis of Injected Flow through Combined Rib and Metal Foam in Converging Channels with Application in Electronics Hotspot Removal
