Closed loop liquid cooling of high-powered CPUs: A case study on cooling performance and energy optimization

This case study presents an experimental investigation of closed loop liquid cooling of CPUs. The cooling system implements a pumped liquid supplying a cold plate fixed to the emulated CPU heat source and a remote Air-Cooled Heat Exchanger (ACHE). The Hybrid Liquid-Air (HLA) system employs 25% v/v Arteco-Freecor with distilled water solution as the primary coolant, and air as the secondary coolant. The thermal-hydraulic performance of the system is characterized over a range of operating conditions, including CPU heat loads (12–72 W/cm2), water volumetric flow rates (0.5–8 L/min), and air velocities (1–3 m/s). In order to provide a performance frame of reference, evaluations were also conducted with a conventional air-based fan-fin CPU cooling system. The results indicate that the HLA system significantly outperforms the traditional air-cooled fan-fin system, with much lower CPU temperatures and feasible power levels exceeding 300 W. Additionally, the study highlights the importance of the liquid flow rate and fan speed on the overall cooling performance. Finally, an optimal combination of liquid and air flow rates is identified for minimum energy consumption. Overall, these findings support the conclusion that conventional air-cooling is reaching its theoretical limit and closed loop liquid cooling has the potential keep pace with the escalating power levels of modern CPUs. However, the additional energy cost of the cooling system should be carefully managed in order to maximize overall system Coefficient of Performance.