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Data and communication intensive firms, such as telecom, banks and security organizations, are facing a
thermal crisis. Their data centers are being driven to deliver ever increasing performance, which, in
turn, is increasing power demands. Over recent years, power consumption per rack has risen dramatically,
frequently 4-5 times. A rack that used to draw 2-3 KW, now commonly consumes 8-10 KW, and in extreme
cases, may reach 30 KW per rack.
When one of the largest telecommunications companies in the world, France Telecom (Orange),
wanted to boost performance in two data
centers in Israel, the company enlisted the help of thermal design experts, CAS, Ltd to perform a CFD analysis and
make recommendations. The data centers had been built to handle low power density racks (2-3 KW/rack), and
previous performance enhancements had pushed temperatures to borderline conditions. Each data center
contained 80 racks cooled by four CRACs mounted in pairs at opposite ends of the room. Cold air passed
through the perforated tile floor, entered the racks and then returned to the CRACs. The front of some
racks reached 30C, even though the recommended limits were no more than 27C. As a result, the racks were
populated only up to 2/3 their height because the tops were too hot.
CAS started the process from modeling existing conditions and verified the model by comparing
calculated temperatures and airflows to actual measurements. The CoolitDC predictions proved accurate to
within 5%. CAS engineers then proposed a redesign, with a "cold aisle" created by enclosing the two
center rack-rows and placing additional cooling units inside. The enclosure bounded the cooling air
flow and prevented uncontrolled mixing of hot and cold air.
CoolitDC analysis of this configuration showed that it would significantly decrease temperatures
throughout the entire room, and that the center rows would not exceed 25C - well below the
recommended equipment limits. Mission accomplished!
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