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Figure 1 - Forced Ventilation
FLOTHERM can predict the air movement and temperature distribution in
the environment around electronic equipment, as well as inside it. This
is often important when the equipment is to be located in a restricted
environment such as a cupboard, dashboard-mounted electronics in vehicles,
sealed units, or where one item of equipment may interfere with another.
"Using these techniques, BT has identified cost reductions
of more than 50% of the whole life cost for future cooling systems as
applied to Telecommunications switching installations" says BT's
Equipment Environment and Cooling Systems Manager.
An unexpected, but important discovery was to find that meeting the
conventional criteria as identified by the European Telecommunications
Standards Institute (ETSI) in terms of room environment was no guarantee
that the equipment cabinets would perform as designed. Relatively low
air velocities passing in front of the cabinets would upset the natural
convection through them. It became very clear that the thermal performance
of a cabinet could be adversely affected by room conditions that actually
met the ETSI standard.
The figures show the path of fresh air provided by forced (Fig.1) or,
alternatively, natural ventilation (Fig. 2). For natural ventilation as
shown in Fig 2., the heated air from the equipment cabinets creates a
deep recirculation in the side gangways. This results in much higher temperatures
at ¾ cabinet height 400mm for its face (the ETSI standard) than for
forced air cooling.
Figure 2 - Natural Ventilation
HOWEVER, for the forced ventilation case (Fig. 1), the high velocities
passing the air inlets to the cabinets reduced the ventilation rate for
the cabinets hence causing higher temperatures within the equipment itself.
At BT, analysis of a sample switching installation predicted specific
features of airflow were verified by actual measurements on site. The
simulations predicted not only the separations but also that they occurred
at different positions in each of the gangways.
BT is a world leader in energy efficiency for network operations and
these simulations allowed the company to identify a new ventilation strategy
which can be applied to up to 80% of their switching room installations
and is expected to reduce the whole life costs by at least half. For this
work, Flomerics was nominated for BT's annual Network Product Quality
award.
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