Cooling system analysis for a data center using liquid immersed servers

Data centers are large consumers of power, of which a large proportion is spent on removing the heat generated by the semiconductors inside IT servers. This paper develops a full analysis of the cooling system when servers are immersed in a dielectric liquid and water is used to transport the heat outside of the data center. The analysis combines empirical curve fits and flow analysis with computational fluid dynamics (CFD) simulations of liquid immersed servers placed in parallel in a rack of a data center. The liquid immersed server concept is based on a dielectric liquid that is in direct contact with the semiconductor components to improve heat rejection. The heat generated from the microelectronics is naturally convected, via buoyancy, in the dielectric liquid to a cold plate on the opposing side. The cooling system of the data center in this study consists of a dry air cooler and a liquid-to-liquid buffer heat exchanger. It was found that the power usage effectiveness (PUE) is as low as 1.08 for the cooling system. The results also show that the PUE is affected by the server-rack occupancy and can increase by 26% as occupancy drops by 80%, thus the better the server-rack occupancy, the better the PUE.