Experimental investigation of the cooling performance of 3-D printed hybrid water-cooled heat sinks

An experimental characterization of hybrid water-cooled heat sinks for multi-core CPUs was conducted. The hybrid heat sinks consist of a water block containing fractal channel manifolds ending in an array of jet nozzles attached to a copper plate. Advanced additive manufacturing techniques were required for the fabrication of the heat sinks due to the manifolds complexity. The effects of the jet nozzles number and distribution, depth of the flood chamber, and surface enhancing features were investigated in terms of hydraulic and thermal performance. A minimum pressure drop variation was observed for different number of jet nozzles (16, 32, and 64 jets), which is consistent with previous simulation results. Alternatively, the pressure drop associated with a 3-mm size reduction of the flood chamber generated a two-fold increase in the pressure drop difference, but under 5% of the total pressure drop. A sharp temperature increase (~30 °C) was observed from idle operation within 10 s after applying a full load on the CPU and the system reached steady state in ~74 s. The highest core temperature was observed using the heat sink with 32 jets, while the heat sinks with 16 and 64 jets had similar thermal performance. Area enhancing features added to the copper plate produced negligible effects on the hydraulic performance, while average core temperature reductions up to 3 °C were measured using circular pin fins. To further analyze the thermo-hydraulic performance, the thermal resistance and the pumping power were calculated. The overall performance assessment was conducted using a metric formed by the combination of the thermal resistance and pumping power. This metric helped to identify the best heat sink based on the thermo-fluid characteristics, i.e., the lowest core temperature with the least pumping power.