Abstract
In air-cooled data centres, hot aisle containment is used to separate hot and cold air from mixing to improve cooling effectiveness. However, this creates a significant pressure imbalance between the cold and hot aisles, with the latter being high. The hot aisle high pressure creates back pressure that pushes against the server-unit fan system, which subsequently results in hot air recirculation and insufficient server-unit cooling.
This study examines the application of series-configured server fans with the intention of increasing the system pressure head to overcome hot aisle containment back pressure and eliminate server hot air recirculation. A detailed computational fluid dynamics model for the Dell 2950 2U server is calibrated and validated using existing experimental test results. Furthermore, the impact of changing the server fan system to a series configuration by adding four or more server fans is investigated under different hot aisle pressure conditions.
It was found that changing the server fan system configuration from parallel to series arrangement positively improved the available system static pressure but did not result in the elimination of hot air recirculation. The server with the series-configured fan system experienced an average inlet air temperature increase of 9% when compared to the original server under similar conditions. The series configured fan system CFD results have shown altered velocity streamlines and high magnitude, which can be one of the reasons why the net system positive pressure did not result in the elimination of hot air recirculation. High velocity region experiences low static pressure which will subsequently experience a venturi effect.
This research paper serves as a base for integrating liquid and air-cooling systems to form hybrid cooling systems for high-density racks in legacy data centres.