Wally Phelps, product marketing manager for AdaptivCool (www.adaptivcool.com), says:

With IT equipment becoming both denser and more capable; many Data Centers while they face serious power and cooling challenges are finding space is becoming much less of an issue than in the past. The result for many is unused space in the Data Center. The other challenge many face is Data Centers being fit into existing office buildings into available space. Let’s address some of the issues these factors can cause.

How does a data center room’s shape and size impact data center cooling?

Since air is the predominant cooling medium, its properties and characteristics must be understood to solve any significant cooling challenge. Data Centers move a lot of air so it’s usually turbulent; tumbling and swirling throughout the room which makes it hard to predict without the help of some tools like CFD. Laminar airflow by comparison is easy to predict but has limited application in studying Data Center Airflow.

Being a fluid, air will always take the path of least resistance. We like to say “Air is Lazy”. Room size and shape plays a big part in where this “Lazy” air chooses to go. Like herding cats it doesn’t always go where you would like, without a little help.

Before the consolidation takes place however there needs to be an assessment of the cooling available in the consolidated area and a study both supply and return paths. For the supply path Downflow CRAC units have a maximum underfloor throw of roughly 30-40 feet, (less if there are many perforated tiles in this path). This needs to be used as a guideline. Thus if you are trying to place IT equipment farther than 30- 40 feet from a CRAC there will usually be a problem. For the return side there needs to be a low resistance path for the warm air to return directly to the CRACs. If this air has to follow a circuitous path it will promote mixing and poor efficiency. Hot Aisle/ Cold Aisle configurations are of course recommended with CRACs at the ends of the rows. Often times there may be corners of the Data Center that have CRACs at right angles. Caution needs to be applied since these right angle CRACs can cause vortexes under the floor and reduce available flow from a few tile locations. To detect this, lift the tiles in the locations where perforated tiles are planned to insure there are no “dead spots” where cool air does not billow out of the open tile hole. If there is a dead spot, there are active underfloor air mover products that can solve this.

If consolidation is not possible then look for lower density portions of the room that can be targeted to reduce cooling air flow, so this capacity and energy can be used elsewhere. Of course

Factors to consider how COOLABLE a specific data center may be:

Rack layout – Hot/Cold aisle is best with long unbroken rows. Pay attention to maximum row length based on how far the CRAC units can throw air. A random or non hot/cold aisle layout will always compromise efficiency and capacity by allowing mixing.
Racks should be placed at least 6 feet from CRACs.

CRAC orientation – The CRACs should be at the ends of the rows to allow cooling and heat to flow easily in and out of the rows with the minimum amount of mixing.

Raised floor height – As a general rule a 10K sq ft data center should have a minimum of 2 feet. Smaller sites can get by with less, Larger sites need more.

Underfloor obstructions – Obstructions close to CRAC units cause the most problems. As you get farther away from the CRACs they become less intrusive. Cable trays and other large obstructions should be limited to the hot aisles if possible.

Shape – Square or rectangular rooms will usually be easier to cool.

Floor cutouts – These should be sufficiently small that excess air is not leaking out to spaces that don’t need cooling.

Ceiling height – Below 9 ft it is often difficult to get good return air paths.

Ducted ceiling returns or containment – Properly engineered these always improve the cool ability of a data center. Special attention must be paid to local fire code enforcement which varies widely.

Blanking panels – These prevent recirculation of hot air from the back to front of a rack. If there in not enough CFM being delivered to the front of the racks however blanking panels won’t help

If your Data Center is sub optimal in any of the areas above there are solutions that can remedy most if not all issues. Air is relatively easier to move than Facilities or entire rows of IT racks.