112 IBM System x3850 X6 and x3950 X6 Planning and Implementation Guide
The doors have no moving parts; the fans in the equipment move air though the heat
exchanger as easily as a standard rack door.
In the event of a disruption in water flow, the rack reverts to standard air cooling.
Each door is capable of removing 100% of the heat generated by servers consuming
30 kW of power; and 90% of the heat generated by servers consuming 40 kW, using 18° C
(64° F) water at a 27° C (81° F) server inlet air temperature.
Figure 4-1 shows additional information about the capability of this rear door heat
exchanger.
Figure 4-1 Heat removal performance with a 30 kW load
While it is possible to extract even more heat if the water is cooler; the water temperature
cannot be below the dew point in the server room, or condensation will form on the rear
door.
Some standard computer room air conditioning is usually provisioned, to control humidity
and enable doors to be disconnected for maintenance or other requirements.
The reduced air conditioning requirement typically saves about 1 KW per rack that would
be used to compress refrigerant and move air.
The reduction in air conditioner noise coupled with the acoustic dampening effect of the
heat exchangers, plus the decrease in high velocity cold air, has the additional benefit of
making the data center environment less hostile.
The ordering information for the rear door heat exchanger is listed in Table 4-3.
Table 4-3 Part number for the Rear Door Heat eXchanger for the IBM 42U 1100m rack
For more information, see the Rear Door Heat eXchanger V2 Type 1756 Installation and
Maintenance Guide, available at:
http://www.ibm.com/support/entry/portal/docdisplay?lndocid=migr-5089575
Part number Description
175642X Rear Door Heat eXchanger for IBM 42U 1100 mm Enterprise V2 Dynamic Racks
140
130
120
110
100
90
80
70
60
50
% heat removal as function of water temperature and flow rate for
given rack power, rack inlet temperature, and rack air flow rate
4101214
% heat removal
Water flow rate (gpm)
Water
temperature
12°C *
14°C *
16°C *
18°C *
20°C *
6 8
22°C *
24°C *
Airflow
(cfm) = 2500
Rack Power
(W) = 30000
Tinlet, air
(C) = 27
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