Topological optimization of flow-shifting microchannel heat sinks

Abstract

Efficient thermal management is required for electronic devices that generate multiple different spatially nonuniform thermal workloads during operation. Conventional heat sinks route coolant to all potential heat-generating regions of an electronic component which may result in unnecessarily broad dispersion of the coolant to regions that are sometimes inactive. To fully utilize flow for multiple potential thermal workloads, a “flow-shifting” design approach is proposed. A flow-shifting heat sink has multiple inlets, where the flow path from each inlet is optimized for cooling of a specific workload or heat map. Only the inlet corresponding to the active operating workload is open at a given time, while the rest of the inlets are kept closed until the operating workload changes, allowing a majority of the flow to be properly utilized for cooling the active heat map. This has the potential to allow many different optimal heat sinks to be simultaneously encoded into a single structure but brings forth a complex design problem to optimize the internal fluid flow pathways. A multi-objective topology optimization algorithm is implemented in this work for flow-shifting heat sink design generation. Microchannel heat sink designs are generated for a demonstration case involving two workloads. Designs optimized for flow-shifting between two inlets are compared to a benchmark that is optimized with only a single inlet. Pareto optimality curves, as well as the associated heat sink designs, are created that weigh between the thermal resistances of the two workloads. The flow-shifting designs are predicted to have lower thermal resistance under both workloads compared with every benchmark heat sink design generated along the Pareto optimality curve. Investigation of two designs selected from the Pareto curve showed that the flow-shifting heat sink achieved 10.7% and 6.8% lower thermal resistance at the two workloads relative to the benchmark. The flow-shifting approach is superior as it utilizes more flow rate for cooling the active heated region. The flow-shifting approach thereby allows for fixed heat sink structures that can be topologically optimized for many different possible heat maps and actively respond to changes in workload.