Manifold microchannel heat sinks: Isothermal analysis

Numerical analyses of manifold microchannel (MMC) heat sinks were performed. The MMC differs from a traditional microchannel heat sink in that the flow length is greatly reduced to a small fraction of the total length of the heat sink. Alternating inlet and outlet channels guide the coolant to and from the microchannels. A silicon heat sink cooled by fluorocarbon liquid was studied. The repetitive nature of the manifold and microchannels results in many planes of symmetry. The thermal and fluid characteristics of a MMC assembly can modeled by a "unit cell" bounded by the centerlines of the manifold inlet and outlet channels and by those of the microchannels and heat sink walls. Three-dimensional (3-D) finite element models of single manifold microchannels were constructed and used to simulate fluid flow and heat transfer. Conjugate analysis suggested that an isothermal model would produce suitably accurate results. In addition to coolant flow rate, channel length, width, and depth were varied. Regions of high heat transfer were found near the inlet. At higher inlet velocities, secondary maxima in heat transfer were seen at the base of the microchannel below the inlet, and at the top of the microchannel near the exit. The flow was found to accelerate to a greater extent than predicted by rectangular duct analysis.