Combined Use Of Direct Or Duct Blowing And Underfloor Ventilation; Figure 4.3 Underfloor Ventilation Setup - Fujitsu M10 Series Installation Planning Manual

This setup features the ability to keep operators less chilled because this lessens direct
exposure to drafts of air blown out of the air conditioner. Because underfloor
ventilation blows air directly against equipment, the air must be filtered for dust by
the air conditioner beforehand. The lower the air temperature is, the greater the
chance for dew condensation becomes because of increased humidity. Hence, the air
requires regulation of both its temperature and humidity. A special underfloor-
ventilation air conditioner dedicated to computer room use, which permits
temperature and humidity regulation, is usually used. An air handling unit that uses a
water-based cooling coil must be controlled to maintain the humidity, as well as the
temperature, within a prescribed range. Regulation of the temperature and humidity in
this setup is generally accomplished by cooling and dehumidifying the room air to a
temperature lower than the target temperature and then heating and humidifying it to
some degree to attain the target temperature and humidity. The cooling capacity of an
air conditioner installed in this setup will be lower than its rating because of the
internal heating process involved.
In the winter time, heating to a predetermined temperature is required.
Figure 4.3
4.2.4 Combined use of direct or duct blowing and underfloor
ventilation
If direct blowing or duct blowing is combined with underfloor ventilation, the server
system is cooled down by the air blown from under the floor, while the air in the room
is conditioned to a temperature suitable for the operator by room air conditioning.
The underfloor-ventilation air conditioner dehumidifies the air by overcooling before
regulating the temperature and humidity by heating and humidifying.
C120-H007-08EN
shows a schematic view of the underfloor ventilation setup.

Figure 4.3 Underfloor ventilation setup

4.2 Styles of Air Conditioner
37