Pulsed flash boiling for high heat flux electronics cooling

As demand for computing continues its rapid growth, the required digital processing capabilities necessitate more powerful devices and sophisticated thermal management techniques. Conventional electronic cooling technologies such as air and single-phase liquid cooling technologies are often inadequate for emerging applications due to their requirement of heat spreading to maximize the coolant contact area. We report a pressure-driven boiling approach, termed flash cooling, for thermal management of high-heat flux electronics. A significant innovation is that the operating fluid is flashed in pulses, facilitating higher pressure gradients within cycles. A closed-loop system is implemented, and methanol is used as the operating fluid. Experiments are reported with varying heat fluxes, flow rates and pulse cycle time until steady-periodic conditions were achieved. The heat flux varies from 0.2 W/mm² (125 W) to 1 W/mm² (625 W). The evaporator temperature is observed to be below 85 °C for heat fluxes up to 0.6 W/mm². The key findings suggest that pulse cycle time is the most important control parameter that influences the operative phase-change regime. The maximum oscillations in evaporator temperature and evaporator outlet pressure are observed to be ± 3.5 °C and ± 9 kPa for 1 W/mm² heat flux. A major advantage of the pulsed flash cooling system is that the flow rates can be dynamically and precisely controlled near the heat source by varying the pulse cycle time without requiring system-level modifications, unlike conventional continuous flow single or two-phase cooling. This feature of flash cooling technology enables it to control the operating boiling regime, and as shown in experiments here, to recover from dry-out conditions.