Liquid Cooled Racks - Compaq BL10e - HP ProLiant - 512 MB RAM Introduction Manual

In addition, any gaps between the cold and hot isles allow hot exhaust air to re-circulate and mix with
cold air, making a "short circuit". This situation can occur when hot aisle exhaust air flows straight
through a rack with open "U" spaces as shown in Figure 5. Gaskets or blanking panels must be
installed in any open spaces in the front of the rack to support the front-to-back airflow design and
prevent these negative effects. All rack space must be filled by equipment or enclosed by blanking
panels so that the cool air is routed exclusively through the equipment and cannot bypass through or
around the rack.
Figure 5. Airflow in rack without blanking panels (top) and with blanking panels (bottom)
Heat loads generated by blade servers in given rack configurations can be calculated by using the
HP BladeSystem Power Sizer found at:
Proper cable management practices:
• Segregate power and data cables. Cables in close proximity to each other, especially those
oriented in parallel or in loops, can create electromagnetic interference (EMI) through induction.
• Use cable routing and retention products. Cable rings, trays, and trunking products will reduce
problems associated with cooling, EMI, and cable damage.
• Employ new cable trays to allow routing of cables above the racks rather than in plenum sub
flooring, remove obstructions to airflow in the data center.
• Use CAT5 KVM cabling. The smaller, more flexible form factor of CAT5 cabling facilitates routing
through the rack and its customizable lengths eliminate coils of cabling in the rear of the rack. The
Interface Adapter (IA) that connects from the CAT5 cable to the server KVM port also provides
keep-alive and naming functionality. Keep-alive means that even if the CAT5 cable is disconnected
from the switch the IA will still respond as if the keyboard, mouse and video were present, allowing
a server reboot to occur without errors.

Liquid cooled racks

The rack itself is not the limiting factor in high density rack configurations. Instead, the maximum heat
load for air cooled racks is determined by the air volume and the air temperature being delivered to
the rack. The average maximum load for air cooled racks is about 10kW/rack. The actual maximum
load is dependant on the optimization of variables like data center design, placement of high density
racks, the use of closely coupled cooling techniques, and the other best practices addressed in this
document. When some or all of these techniques are optimized in concert, the actual load can go
beyond 10 kW/rack. Liquid-cooled racks embody the concept of "closely coupled" cooling where the
cooling mechanism is in close proximity to the servers to be cooled and is aware of the specific
www.hp.com/go/bladesystem/powercalculator.
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