The performance of the lineup of equipment - CRAH
units [right arrow] chilled water pumps [right arrow] chillers [right arrow] condenser water pumps [right arrow] cooling towers - has been calculated for the worst case condition in the year in a climate similar to Washington, DC and corresponds to a peak system PUE of 1.
Total facility power consists of the power required to run the IT equipment and all other equipment, such as chiller compressor, cooling tower and CRAH
fans, pumps, lighting, and UPS losses (Belady et al.
In addition, because all of the CRAH
units are able to operate together in parallel with such low loads, the fans are all operating at their minimum speeds at a fraction of the energy of the same fans at full speed.
unit has a controllable flow valve associated with it, which, along with the heat exchanger, can be represented as a flow resistance.
The energy performance was typical for a legacy facility, with a large proportion of the energy used for cooling by the data hall CRAH
unit fans and in chilled-water production and distribution.
The chilled water CRAH
units (Figure 1) operate as 100% air recirculation units with no economizers.
Using weighted average temperatures to and from the CRAH
units and IT equipment, and applying mass flow balance equations, the average bypass and recirculation air, and the resulting efficiencies of air supply and demand can be determined.
10) LARGE SMALL COMPANIES COMPANIES COLD-AISLE/HOT-AISLE CONTAINMENT 78% 62% RAISING INLET AIR TEMPERATURES 75% 42% DETAILED POWER MONITORING, 55% 43% BENCHMARKING POWER MANAGEMENT FEATURES ON 44% 43% SERVERS VFDS ON CHILLERS, CRAH
, OR 62% 21% PUMPS MODULAR DATA CENTER DESIGN 33% 24% AIR-SIDE ECONOMIZATION 36% 19% WATER-SIDE ECONOMIZATION 31% 10% LIQUID COOLING 19% 11% DIRECT CURRENT POWER 8% 5%
and CRAC have become the popular nomenclature.
In the model, the electrical infrastructure load is being cooled by an independent branch line with CRAH
units, while the mechanical infrastructure load (mostly fan heat) is cooled by the rear door heat exchangers.
Economizers offer huge energy savings over traditional CRAC or CRAH
Eight of the ten CRAH
are capable of providing the required cooling in the computer room.