Figure 5 shows a schematic of an HDHC system using the rack enclosure concept described previously.
Figure 6 shows a picture of the HDHC racks installed in the high-density section of the data center.
The off-the-shelf components of a HDHC rack enclosure include: a) solid side panels; b) solid rear door with gasket; c) solid bottom panel with brush strip; d) high airflow, low power, variable speed supplemental fan system; e) fan airflow control; and f) exhaust duct.
The difference between the actual airflow and the design airflow, 240 cfm (113 L/s), is bypassing or short-circuiting the HDHC system.
Nearly 500 HDHC return duct fans are in operation today, and many have been in operation for more than 24 months.
A higher supply air temperature that is possible with HDHC system offers additional savings by improving the energy efficiency of the rest of the mechanical system.
A HDHC rack system has been successfully implemented to physically separate the hot and cold airstreams, eliminating excess airflow and providing the ability to raise the supply air temperature to the IT racks.
A HDHC system provides the necessary environmental conditions for high-density IT equipment loads while laying the foundation of significant energy efficiency improvement.