Experimental investigations on the effect of perforated tile air jet velocity on server air distribution in a high density data center

High density racks are becoming increasingly common in modern datacenters. The cold air distribution to high density racks has been a major challenge in the data center thermal design. Generally, the cold air is supplied through perforated tiles placed in front of the racks. Previous literature has focused more on large scale air distribution with in the data center rather than detailed air distribution to individual servers placed in the rack. This paper investigates the effect of tile air flow rate on the server air distribution at various locations in the rack. A series of experiments are performed using a 22.8 kW server simulator placed in a raised floor data center environment. The tile air flow rate is varied in the range of 0 m³/s to 1.224 m³/s (~2594 CFM) by adjusting the fan speed of computer room air conditioning (CRAC) unit. Particle Image Velocimetry (PIV) technique is used to capture the air flow pattern at the server inlet. The PIV images are recorded at various locations and later combined to get the complete air distribution across the rack inlet. A significant change in the air distribution pattern is observed for various cases of tile air flow rates. Undesirable effects such as recirculation and cold air entrainment are observed at higher tile air flow rates.