IBM NeXtScale System Planning And Implementation Manual page 141

In data centers that contain several power dense racks, extracting the used
warm air and providing enough chilled air to the equipment intakes can be
challenging.
In these environments, one of the primary considerations is preventing warm air
from recirculating directly from the equipment exhaust into the cold air intake. It is
important to use filler panels to block any unused rack space. Part numbers for
kits of five filler panels, which install quickly and without tools, are provided in
Table 5-5.
Table 5-5 Blank filler panel kits: Five panels per kit
Part number Description
25R5559 1U Quick Install Filler Panel Kit (quantity five)
25R5560 3U Quick Install Filler Panel Kit (quantity five)
The blank filler panel kits that are listed in Table 5-5 can be used next to the
NeXtScale n1200 Enclosure. However, next to switches mounted in the front of
the rack requires the use of the IBM 1U Pass Through Bracket (part number
00Y3011), as described in 5.4.3, "Rack options" on page 135. This bracket is
required if there is an empty 1U space above or below a front-mounted switch to
prevent air recirculation from the rear to the front of the switch. Front-mounted 1U
switches that are used with NeXtScale are recessed 75 mm behind the front rack
mounting brackets to provide sufficient room for cables. A standard filler panel
does not contact a switch that is recessed 75 mm; therefore, hot air recirculation
can occur.
The next areas to watch for air recirculation are above, below, and around the
sides of the racks. Avoiding recirculation above the racks can be difficult to
address because this is typically the return path to the air conditioner and there is
often overhead lighting, plumbing, cable trays, or other things with which to
contend.
Examples of the use of recirculation prevention plates or stabilizer brackets to
prevent under rack air return, and joining racks to restrict airflow around the sides
is described in 5.4.1, "The IBM 42U 1100mm Enterprise V2 Dynamic Rack" on
page 125. We also suggest covering any unused space in rack cable openings.
There are a number of approaches to addressing the cooling challenge. The use
of traditional computer room air conditioners with a raised floor and perforated
floor tiles requires numerous floor space that is dedicated to perforated tiles and
generous space for air return paths.
Chapter 5. Rack planning
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