Dynamics of cold aisle air distribution in a raised floor data center

Server manufacturers test compute equipment under ideal conditions such as quiescent surroundings, with no adverse pressure gradients at the inlet, which, hardly exist in a real data center. The dynamics of cold air delivery to the server can significantly impact server cooling and performance, especially at higher rack densities. Presently, very little is known on the physics of cold air distribution in a rack in a high density data center environment. The experimental work reported in this paper provides an insight into the raised floor cold air delivery system currently adopted for rack cooling in a hot aisle/cold aisle data center. Air flow measurements using Particle Image Velocimetry (PIV) are performed in the cold aisle at the inlet of a single rack. Two cases of perforated tile air delivery rates are investigated. The first case with no discharge from the tile represents the ideal case under which the servers are typically tested by manufacturers. The second case represents a realistic high density data center environment, wherein 0.755 m³/s (~1600 CFM) of air is discharged through the perforated tile. The analysis of the flow dynamics at the perforated tile surface, rack inlet and cold aisle boundaries is reported for both cases. A distinct change in the cold aisle air velocities and flow pattern at the interrogation boundaries is observed for both the cases.