At the IDF (Israel Defense Forces) Data Centers, exceptionally high reliability is an absolute must.
The critical and often mobile nature of the applications demand that the Data Centers run cool even under
harsh conditions, and often it impossible to incorporate spare capacity for backup. To boost reliability,
as well as efficiency and capability, Israeli consulting and thermal simulation firm, CAS relies on
A typical site consisted of a 16 x 12 m room containing 8 rows of racks cooled by 4 CRACs. This
configuration did not provide uniform cooling, and the tops of some racks were exceeding allowable
First CAS built a model of the data center and then calibrated it against actual flows and
temperatures. If, say, an unexpected disturbance below the raised floor was found to be disturbing
airflow, the model was modified to reflect it. Typically actual and calculated measurements matched within
a few percent.
Once the model was calibrated, CAS investigated the impact of a mix of cold and hot aisles, reducing
the air leakage and replacing missing blanking panels which were affecting the cold aisle efficiency due
to a mixing of hot and cold air. In some instances, cold aisles that were not well-sealed, were resealed
to insure that no uncontrolled mixing of hot-cold air took place. Many other potential solutions were
evaluated in a brief time span: concentrating high power dissipating racks in one place, trying different
perforated tiles to increase the airflow, checking different tiles arrangements, etc. All this required
computing dozens of different cases in order to arrive at the optimal solution. Speed of modeling, both in
making model changes and in actual computing of cases was of the essence.
A solution developed for one IDF data center required completely sealed cold aisles which eliminated
all hot spots without any additional cooling equipment. In fact, the simulation showed that CRAC supply
temperatures could be increased from 12 deg C to 15 deg. C. while still keeping inlet temperatures under
25 deg C. The design change resulted in over 12% energy savings which more than paid for the consulting