I don't see mentioned too often the use of grate-type perforated tiles such as Tate's GrateAire that offers a 58% open area as opposed to the typical 25% perforated tile open area in raised-floor data center designs.. Is the grate-type tile finding a place in computer rooms?
The grate-type tiles are a godsend -- but only if they're used correctly and the parameters are well understood. Unless you really know what your under-floor air flow is doing, installing grate-type tiles can deprive other parts of your floor of the air they should be getting. Remember, you can't get more air out of the floor than the CRAC has put in it. Since most data centers lose a significant percentage of their air in uncontrolled leaks and the under-floor air flow and pressures are uneven to begin with, it's highly unlikely that you have all the air your CRACs are delivering actually available at the tiles you install.
So you not only need to be concerned about how much air goes through which tiles, but you also need to be very knowledgeable about exactly where you install grate-type tiles. If you put them in a place where air volume and pressure are already low, they're going to do little for you and will probably make things worse somewhere else. Other then trial and error, the best way to make these determinations is through CFD modeling.
Also keep in mind that, while the GrateAire tile offers 58% open area, this is only if the tile does not have a damper. Dampered tiles allow you to control the air flow at each location so that you don't waste air in places where less cooling is needed. However, the dampered GrateAire tile has a maximum open area of only about 33%. This is not a whole lot better than a fully open standard perforated tile, so we don't specify it very much. But since the 58% open tiles affect under-floor air volume and pressure, we use them very carefully and only after performing a thorough CFD analysis.
