Importance of Perforated Raised Floor Tiles in a Raised Floor System
When cold air is pumped into a raised floor, it's expected to arrive at its destination, the server racks, but this cooled air usually ends up where it shouldn't, costing thousands in wasted energy costs every year. One study conducted by Innovative Research Inc. found that this air leakage has a great deal to do with the perforated tiles in raised floor systems, particularly how they are used.
Perforated raised floor tiles are one of the most essential yet improperly used components of an efficient raised floor system. All too often, raised floor owners add them haphazardly in areas that "feel warm," overuse these tiles or have too few in their design. Distributed air leakage usually represents a large percentage of the total airflow into the raised floor plenum, and air leakage may account for up to 15% of all the airflow leaving into the data center room. This not only wastes cooling, it also means more power is necessary to cool equipment.
The authors of the study by Innovative Research Inc. found that air leakage in raised floor systems is most apparent when the ratio of perforated data center floor tiles to total floor space is smaller, and fewer perforated tiles actually leads to greater air leakage. The company even set up a mini data center with a 12-inch raised floor system to further research this issue, analyzing air leakage with 4, 8, 12, 16 and 20 perforated tiles. They found that there was over twice as much leakage with four tiles as there was with 20 perforated tiles, and not all of the airflow is exiting through the tiles themselves.
Data centers may see a reduction in bypass airflow by increasing the amount of perforated tiles, provided they are directing cool air to the equipment and other areas for leakage are shut down.
Perforated raised floor tiles are dispersed among solid data center floor tiles to allow cold air flowing from air conditioners to rise through the floor to server racks to cool this hot equipment. Still, when raised floor systems aren't constructed properly, air may be pushed through other accidental openings in the floor where it doesn't help equipment.
Air may leak through loose cable cutouts under cabinets, between computer floor tiles and walls, between poorly aligned floor tiles, missing tiles or even unnecessary perforated raised floor tiles. This is why care should also be taken to properly seal any unintentional openings, such as using grommets and self-forming foam to seal cable cutouts and edges, and replace any missing or damaged floor tiles.
Of course, installing perforated computer floor tiles is not something that should be done simply because an area feels warm, and the best way to determine where these tiles should be placed is with Computer Fluid Dynamics (CFD) modeling. Too few perforated tiles will result in air recirculation, while too many will increase bypass air.
As the proper installation of perforated tiles can make a world of difference in the energy efficiency of raised floor systems, it's best to start with a thorough CFD analysis to map out air flow and hot spots and work from there.