A study of direct liquid cooling for high-density chips and accelerators

Liquid cooling provides a feasible thermal management solution in the case of high power density cooling, in addition, it offers several advantages for improving data center energy efficiency. For example, liquid cooling solution may eliminate the utilization of conventional chiller in a data center cooling infrastructure. Since a large portion of heat can be extracted directly to the liquid, the requirement of cooling airflow can is significantly decreased, especially in the cases of cooling high power density racks. A great amount of energy saving maybe achieved since chiller compressor and CRAH/CRAC consumes huge amount of electricity. With proper design and deployment, the direct liquid cooling solution may be a cost-effective alternative to many existing data center cooling technologies under some circumstances. This work focus on the direct liquid cooling technology using cold plates in the cases of cooling high density processor chips and GPU accelerators. The current paper summaries two parts of work: an experimental testing work and a CFD modeling study. In the modeling study, different methodologies using a commercial available CFD package are developed. Several compact liquid cooling cold plate models are developed and validated against experimental data. The results show good agreement. In the experimental work, a single phase pumped liquid system test setup is developed in the lab, and it is used for liquid cooling tests. The test setup enables to adjust the fluid supply temperature and fluid mass flow rate to the designed test conditions. An electrical heater is used in the system to generate high fluid supply temperatures to the cold plate, such as 45°C or even higher. In the current work, a thermal mock-up chip and an actual GPU accelerator are used for characterizing the cold plate liquid cooling performance.