Note: Descriptions are shown in the official language in which they were submitted.
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Cooling Apparatus and Methods for Cooling
This invention relates to methods and apparatus for cooling. Particularly, but
not
exclusively, aspects of this invention relate to the cooling apparatus and
methods in the
fpeld of information technology. Preferred examples of aspects of the
invention relate to
the cooling of information technology apparatus, in particular computer
equipment such
as personal computers and/or servers and has particular (but not exclusive)
relevance to
the cooling of computers and/or servers which are located in the region of
workstations.
It is common, for example in office environments, for personal computers to be
stored at
workstations or desks; in an office, each worker's computer equipment is often
stored
underneath their desk. In some office environments, several items of computer
equipment may be stored under each desk or workstation. For example in a bank
trading floor environment, it is not uncommon for each workstation to house
several
computers.. Such computer equipment generates heat when operational and such
heat
can be concentrated under the workstation where the equipment is mounted.
In a typical office environment, an air conditioning system supplies cool air
from an
overhead distribution system. The distribution system typically employs air or
water that
is either ducted or piped to the room that is the location for the
workstations.
However, by locating the heat-generating equipment under workstations, the
equipment
is often not exposed directly to the cool air supplied by the air conditioning
system. The
workstation itself can impede the supply of cool air to the equipment. This
problem can
be compounded due to heat generated by the equipment which may currently be up
to
1.5 kW or even 5 kW per workstation, for example desk, which may become
trapped
under the workstation to create a hot chamber.
Under floor air systems have been used in an attempt to provide an adequate
supply of
cool air to equipment. In such an arrangement, rather than air being supplied
from
above, it is supplied to the equipment from grilles in a false floor. For
example, the office
cooling system may comprise a combination air/water system: water being the
primary
coolant and air being the secondary coolant. Cooled air is pumped by fans into
the floor
void beneath the equipment and released into the room through grilles sited
appropriately around the floor. Air is electrically benign and inherently
safe, which makes
it a highly attractive coolant for use in such systems.
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However, as transistors have become smaller, and chip capacity has grown, the
power
dissipation requirements of IT or computing equipment has grown. Modern
equipment
can require a large volume of air to achieve the desired cooling. Thus a
disadvantage of
these systems is that in order to provide the desired cooling, the systems can
create
excessive air velocities at floor and ankle level. This can make the
environment
unpleasant to work in. Raised floor voids may also need to be increased to
accept the
large supply air through the floor in the form of a pressurized floor plenum.
In view of the
high heat outputs of some equipment it may be that air cooling is not adequate
to provide
sufficient cooling of the equipment, which might lead to malfunction and/or
issues of
safety of electronic components in the equipment.
Aspects of the present invention seek to provide cooling apparatus which
mitigates one
or more of the above-mentioned disadvantages.
According to a first aspect of the invention, there is provided a workstation
cooling unit,
the unit comprising: a heat transfer path adapted to contain a heat transfer
fluid, the
heat transfer path being adapted for connection to a condenser to form a heat
transfer
circuit, and a heat exchanger for cooling the workstation.
According to this aspect of the present invention, direct cooling of a
workstation can be
achieved.
In particular preferred examples of aspects of the invention referred to
herein, a
workstation comprises equipment, in particular heat-generating equipment, for
example
computer equipment for a user located at a desk or other work area. Where
reference is
made to the term workstation herein, preferably the term is to be interpreted
as including
(unless clear from the context to the contrary) a desk or other work area, in
particular
where that desk or work area includes heat-generating equipment. In particular
arrangements, the workstation is arranged such that the equipment is for use
by a single
user or small number of users at that desk or work area. This is to be
contrasted, for
example, from computer equipment located in a specialist work room, for
exampie a
server room. It is noted that, in contrast to most workstations, such rooms
are rarely
inhabited by users, except for during maintenance.
Particular reference is made herein to IT and computer equipment, and in
particular
personal computers, but it will be understood that aspects of the invention
are applicable
to the cooling of other equipment. Particular preferred examples relate to the
cooling of
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office equipment.
Thus arrangements according to aspects of the present invention can be used to
provide
cooling to individual user work areas. Preferred examples described in more
detail below
comprise cooling systems arranged to cool a plurality of separate workstations
or groups
of workstations.
In some such arrangement, each cooling unit may be arranged to cool a separate
workstation, for example with a separate heat exchanger being provided for
each
workstation. In other arrangements, each unit may be arranged to provide
cooling for
several workstations.
Where reference is made herein to cooling a workstation, preferably that
reference
includes (unless it is clear from the context to the contrary) cooling a part
of the
workstation and/or cooling equipment mounted at or in a part of the
workstation.
Preferably the heat transfer fluid comprises a volatile fluid. Localised
cooling systems
utilising chilled water can be employed in accordance with aspects of this
invention to
provide enhanced cooling. In such an arrangement, chilled water is piped to a
heat
exchanger at the relevant location by the workstation (optionally a fan can be
used to
blow air over cold pipe work to enhance cooling). Such arrangements can have
an
advantage over air-based solutions since the size of the distribution pipe
work can be
less when compared with air ducts required to achieve equivalent cooling with
an air-
based system. However, the use of chilled water as a coolant within an office
environment, in particular when local to electrical equipment, is considered
disadvantageous in some respects. Water presents a risk or perceived risk to
the
equipment as a result of water leakage since water is a conductor of
electricity.
Furthermore, by using a volatile fluid as the heat transfer fluid, more
efficient cooling of
the workstation can be obtained: greater cooling can be obtained from
exploiting the
evaporation of a volatile fluid compared with the use of a non-volatile fluid.
Preferably the heat transfer fluid comprises carbon dioxide. The use of carbon
dioxide
as a coolant fluid is known. Use of carbon dioxide as a secondary coolant
fluid is known,
being described in UK Patent Application No. 2 258 298. However, it has not
previously
been considered in the application of workstation cooling.
The volatile fluid, for example carbon dioxide, is electrically benign and may
be used
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relatively safely in applications for cooling workstations, despite the high
pressures
required. For carbon dioxide, in examples described herein, the fluid pressure
required
is of the order of 50 Bar; this can provide a fluid circulating temperature of
about 14
degrees C. By this arrangement, the system runs "dry" in normal operating
conditions in
that the temperature of the fluid is such that there is little formation of
condensation on
the pipe work. In some other applications, a lower operating temperature may
be chosen
to improve cooling efficiency, but measures will need to be taken to deal with
resulting
condensation, if necessary. For example, a drip tray and associated drain and
pump
may be provided.
The use of carbon dioxide as the volatile fluid can provide very energy
efficient cooling.
Also, the pipe diameters of the cooling system and the heat exchange surface
areas can
be reduced in size in comparison to systems using other coolant, for example
air or
water. Arrangements described herein can achieve loads of up to about 5 kW per
workstation.
Other volatile fluids may be used. For example, the volatile fluid may
comprise ammonia
or HFC-134a.
Preferably the heat exchanger is adapted to be mounted at the workstation. In
some
examples, the unit comprises a heat exchanger located at the workstation.
Preferably
the heat exchanger is arranged such that direct cooling of the workstation is
obtainable.
In some arrangements the heat exchanger is adapted to be mounted at the
workstation,
for example close to heat-generating equipment of the workstation.
By mounting the heat exchanger at the workstation itself, various improvements
may be
made. For example, direct removal of heat from the equipment at the
workstation can be
achieved.
In some arrangements, the heat exchanger is mounted local to the workstation;
in other
arrangements, the heat exchanger is mounted in the workstation.
The heat exchanger may be positioned to any of the sides, above or below a
workstation.
The heat exchanger may be positioned to more than one, or indeed all sides of
the
workstation.
In some arrangements, the heat exchanger is adapted to be mounted at least
partly in
the workstation. In this way, a compact arrangement can be achieved, together
with
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effective cooling of the workstation. The heat exchanger may be substantially
wholly
mountable within the workstation.
The cooling unit may be mounted local to the workstation, in the workstation,
or adjacent
the workstation, for example in the floor (above or below the floor) in the
ceiling above or
below the ceiling, or elsewhere.
The heat exchanger may be adapted to be mounted local to the workstation.
In some preferred arrangements, the heat exchanger may be mounted away from
the
workstation itself. In some preferred arrangements, the heat exchanger will be
mounted
in the floor beneath the workstation or in the ceiling above the workstation.
In most
practical arrangements, as discussed in further detail below, it will be
necessary for a fan
or other means for moving air across the heat exchanger to be provided. It is
envisaged,
however, that some arrangements may not include a fan or fans.
The cooling unit may be constructed having a suitable casing so that it may be
installed
in one or more possible locations, for example beneath a desk, floor mounted
or ceiling
mounted. The casing may include attachment portions for assisting with the
installation
or the cooling unit. Where the cooling unit is to be used as a floor-mounted
unit, the
cooling unit may be adapted so that it can replace a floor tile or multiples
of floor tiles
when installed, and can preferably be designed to withstand normal office
floor loadings.
Preferably the heat exchanger includes a finned coil. A suitable construction
for the heat
exchanger will be chosen in accordance with, for example, the desired
operating
pressure of the heat exchanger. In some arrangements a copper pipe having
aluminium
fins will be used; in arrangements where the pressure of fluid in the coil is
to be higher, a
stainless steel pipe having aluminium fins or an aluminium ribbon extrusion
having
aluminium fins might be used. The coil may be pressure tested at or above 100
Bar for
an arrangement intended to run at an operating pressure of 50 Bar. For an
arrangement
intended to run at a higher operating pressure, for example 100 Bar, the coil
may be
pressure tested to about 200 Bar. The evaporator may comprise interlaced coiis
with
dual pipe work.
Although carbon dioxide is a relatively safe substance, at high concentrations
it can be
dangerous.
Preferably the cooling unit further includes leak detection apparatus for
detecting leak of
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heat transfer fluid. Preferably the leak detection apparatus includes a gas
detection
monitoring chamber, and preferably the chamber is arranged such that the
integrity of
the heat exchanger and/or pipe work and/or other parts of the unit can be
monitored.
Preferably the system is provided with an automatic shut off safety device to
isolate the
supply of carbon dioxide to the unit, and/or take appropriate action with
regard to the
computer equipment, for example effecting shut down of the equipment and/or
sending a
warning message.
Preferably the cooling unit further includes a fan adapted to move air over
the heat
exchanger. Generally, the preferred option is for a fan to be included,
although it is
envisaged that some arrangements might not include a fan.
By arranging a fan to move air over the heat exchanger, greater cooling can be
obtained.
Furthermore, it is possible to obtain cooling of equipment where the equipment
is not
arranged directly adjacent the heat exchanger.
Preferably the heat exchanger is arranged in an air channel. Preferably the
heat
exchanger is arranged to be at an angle to the direction of air flow in the
channel. In this
way, air can be arranged to pass through the heat exchanger, for example
through the
coils of a heat exchanger, thereby achieving more efficient cooling.
Preferably the fan is arranged to move air along the channel, preferably to
blow warm air
along the channel.
In some arrangements, a fan is mounted in the air channel; by this method, the
air may
be moved efficiently through the air channel. However, in other arrangements,
the fan
may be mounted outside of the channel.
The unit may include a plurality of air channels. This feature can give
greater flexibility in
directing the air within the apparatus and thus can lead to more efficient
cooling. In
preferred arrangements, a heat exchanger may extend through several air
channels.
In some arrangements, the heat exchanger is mounted in an air chamber, the
apparatus
further comprising a dividing member for dividing the air chamber to form a
plurality of air
channels. The dividing member conveniently comprises a plate used to section
off part
of the air chamber to form air channels.
In some arrangements, the unit further includes a housing having an air inlet
and an air
outlet, the fan being arranged for moving air from the inlet to the outlet.
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Preferably the unit further includes an air directing formation. Preferably
the air directing
formation extends from the heat exchanger towards the heat-generating
equipment. In
preferred arrangements, the air directing formation terminates adjacent to,
but preferably
not fixed to, the heat source. In this way, the hot air from the heat-
generating equipment
may be more efficiently directed to the heat exchanger. Where the heat
exchanger is
arranged in a channel or housing, preferably the air directing formation is
adapted to
direct air from the equipment to an inlet region of the channel or housing.
Preferably the air directing formation includes a duct for directing the air.
The air
directing formation, for example duct or hose, may be associated with and/or
mounted
adjacent an air outlet of the heat-generating equipment and be arranged to
direct air
towards the heat exchanger. Preferably the duct further includes an inlet
formation,
wherein the inlet formation is adapted to enclose an outlet of the equipment.
In this way,
efficient collection of warm air exiting the equipment into the duct can be
achieved. The
inlet formation may include a funnel for directing the air. The hose end or
funnel is
preferably shaped so that it cannot effect a seal with the heat source; this
enables
additional air to flow into the device when required, for example when the air
flow
associated with the heat source is less than the suction fan duty.
Alternatively, or in
addition, orifices or air holes may be included in a part of the duct and/or
inlet formation
to allow air into the duct. In such an arrangement, the inlet formation may or
may not be
sealed to the heat source. The duct may include a plurality of inlet
formations for
enclosing a plurality of outlet regions of the equipment.
The duct may comprise a flexible hose. In this way, the duct can be arranged
so that the
inlet formation or formations can more easily enclose outlet regions of
equipment, and a
range of different equipment designs can be accommodated.
The fan may be arranged in the duct. It should be understood that the fan may
comprise a plurality of fan elements. The fan may be arranged to direct air
into the
region where the heat exchanger is mounted so that the warm air from the
equipment is
directed across the heat exchanger.
Once the air has passed over the heat exchanger, it may be recirculated past
the
equipment and/or it may be vented to the atmosphere. A further air directing
formation
or duct may be used to direct the cooled air which has passed over the heat
exchanger.
In some arrangements, further air directing formations or ducts may be
arranged to direct
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air, preferably cool air (from the atmosphere or from a cooling system) to the
equipment,
for example to the air inlet of the equipment.
The fan may direct air into a cavity in the workstation or into a floor
cavity, and/or may
direct the air into the atmosphere.
Preferably the heat exchanger is adapted to be mounted beneath the
workstation. In
preferred arrangements, the heat exchanger is mounted in or adjacent a floor
cavity
underneath the workstation.
By arranging the heat exchanger under the workstation, efficient use of space
can be
achieved. Preferably the heat exchanger unit comprises a floor tile
replacement unit.
The heat exchanger may be adapted to be mounted at or directly above floor
level. In a
workstation environment, the area under the floor tiles is often utilised for
cables and
other services being supplied to the workstations. It is thought that in some
situations,
there will be insufficient available space in the underfloor area for the heat
exchangers to
be mounted. By mounting the heat exchanger at or directly on the floor level,
less space
under the floor is utilised. In a preferred arrangement, the fluid supply is
mounted under
the floor, and the heat exchangers are mounted immediately above the floor
level,
directly under the workstations.
Preferably the heat exchanger unit is adapted to be mountable in a space
intended for a
standard floor tile. Thus individual floor tiles can be replaced with heat
exchanger units
where workstations are to be sited on the floors. Where several workstations
are
arranged, for exampie in a row, a corresponding row of floor tiles can be
replaced by
heat exchanger units arranged under the workstations.
In further examples, the heat exchanger unit is adapted to be mounted above
the
workstation. In this arrangement, the heat exchanger units are preferably
adapted to be
mountable in a space intended for a standard ceiling tile. Preferably the heat
exchanger
units are mounted in the space directly above a false ceiling. Ducts may be
provided to
direct air from the equipment to the heat exchangers.
The cooling unit may further comprise cable management formations. Such
formations
can be used to direct electrical or other cables in the workstation
environment. The
cooling unit may incorporate pre-formed cable channels such that it can easily
be
integrated into a heavily cabled desk or other workstation area while still
allowing
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successful cable co-ordination.
The heat exchanger may be adapted to provide cooling for a plurality of
workstations. In
some arrangements, each heat exchanger may provide cooling for a plurality of
items of
equipment. Preferably the heat exchanger will extend so as to be local a
plurality of
workstations. In some arrangements, an array of air directing formations
and/or ducts is
provided to effect cooling of several workstation environments. One or more
heat
exchanger units may be provided for each array.
Preferably the cooling unit is adapted for use in a secondary heat transfer
circuit of a
cooling system. Preferably, the primary circuit includes an evaporator, an
expansion
device, a condenser and a compressor. Preferably the secondary circuit
includes a heat
exchanger, a pump, a condenser and an expansion device.
The invention also provides a cooling apparatus comprising a cooling unit as
described
herein and a condenser connected to the heat transfer path to form a secondary
heat
transfer circuit, the condenser being adapted to be cooled by a primary heat
transfer
circuit. The secondary heat transfer circuit contains, in use, a secondary
heat transfer
fluid which preferably comprises a volatile fluid, preferably carbon dioxide.
The secondary circuit may be operable at more than 25 Bar. Conveniently the
secondary circuit is operable at about 50 Bar. In some arrangements, it will
be preferred
that the secondary circuit is operable at up to 100 Bar. Where the system
comprises a
primary-only circuit, the circuit may be operable at about 100 Bar.
Preferably the volatile fluid is carbon dioxide. The temperature of the carbon
dioxide
received at the secondary heat exchanger may be in the region of 0 C to 30 C
and
conveniently is in the region of 12 C to 16 C, preferably being substantially
14 C where
the secondary circuit is arranged to run "dry" under normal operating
conditions with the
formation of condensation on the coil being discouraged. In some other
applications, a
lower operating temperature may be chosen to improve cooling efficiency, but
measures
will need to be taken to deal with resulting condensation, if necessary. For
example, a
drip tray and associated drain and pump may beprovided.
The secondary heat transfer circuit may further include a pump, or may be
gravity fed.
The unit may accept integrated carbon dioxide flow and return distribution
pipe work or
such pipe work may be located outside the housing or casing of the unit.
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A further aspect of the invention provides a workstation cooling system
comprising: a
primary heat transfer circuit; a secondary heat transfer circuit for
containing a secondary
heat transfer fluid, a secondary condenser adapted to be cooled by the primary
heat
transfer circuit and a secondary heat exchanger for cooling the workstation.
Preferably, the secondary heat transfer fluid comprises a volatile fluid.
Preferably the
secondary heat transfer fluid comprises carbon dioxide. In preferred examples,
the
primary heat transfer fluid for the primary heat transfer circuit is not
carbon dioxide; it
may be chilled water, air, or other coolant for example ammonia.
Each heat exchanger may be arranged to provide cooling for one or more
workstations.
In this way efficient cooling of a large number of workstations can be
achieved, even
where the workstations are spaced apart.
Preferably the workstation cooling system comprises a plurality of cooling
units as
described herein. A plurality of cooling units may be contained in a singie
secondary
heat transfer circuit or in a plurality of such circuits, or in a combination
of these
arrangements.
'By providing localised cooling to workstations using cooling units, efficient
cooling of the
workstations can be effected, in preferred arrangements, to achieve safe
working
temperature of the equipment while avoiding discomfort to users located at the
workstations, as might occur in an arrangement where high air flows were used
to effect
cooling.
According to a further aspect of the invention there is provided a cooling
unit for cooling a
workstation, the unit including an air inlet, an air outlet, an air duct and a
heat exchanger
for forming part of a secondary heat transfer circuit.
Preferably, in use a heat transfer fluid flowing in the heat transfer circuit
is a volatile fluid.
The invention also provides a workstation adapted to house a cooling unit as
described
herein. Preferably the workstation includes a compartment for housing the
cooling unit
such that at least a part of the cooling unit is mounted in the compartment.
In some arrangements it is preferred that at least the heat exchanger of the
unit can be
mounted in the compartment. Preferably the compartment is adapted to house
heat-
generating equipment.
Preferably the compartment is such that the equipment is at least partly
mounted in the
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compartment.
Preferably the workstation comprises heat-generating equipment, wherein the
heat-
generating equipment preferably comprises computer equipment.
The compartment may be adapted to be substantially sealed when the cooling
unit and
equipment are housed in the compartment. The compartment may provide some heat
sealing function. In this way, heat generated by the equipment can be to some
extent
contained within the compartment, and thus can be more efficiently removed by
use of
the cooling unit.
Preferably, in such an arrangement, the compartment is sealed but is not air
tight. The
heat load is thus contained within a notionally sealed unit such that the heat
may be
successfully absorbed by the liquid carbon dioxide.
In an alternative arrangement, the compartment is provided adjacent to the
workstation,
for example in a floor cavity.
The compartment may comprise heat insulation. Heat load insulation screens may
be
utilised to form such a compartment. The screens may be formed from, for
example,
open or closed cell foam, faced mineral wool panels, plasterboard or other
suitable
panelling.
By mounting the unit in the compartment, the equipment can also be protected
from
physical damage.
Also provided by an aspect of the invention is a workstation comprising
equipment to be
cooled and a cooling unit for cooling the equipment, the unit comprising: a
heat transfer
path adapted to contain a heat transfer fluid, the heat transfer path being
adapted for
connection to a condenser to form a heat transfer circuit, and a heat
exchanger for
cooling the equipment.
Preferably the heat transfer fluid is a volatile fluid.
The heat exchanger may be mounted beneath the workstation.
The equipment may comprise computer equipment.
A further aspect of the invention provides a floor unit for mounting beneath a
workstation
area, the floor unit comprising a a heat transfer path adapted to contain a
heat transfer
fluid, the heat transfer path being adapted for connection to a condenser to
form a heat
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transfer circuit, and a heat exchanger for cooling the workstation area.
Also provided by the invention is the use of a volatile fluid at a heat
transfer fluid in an
apparatus for cooling a workstation. Preferably the heat transfer fluid
comprises carbon
dioxide.
The invention also provides a method of cooling a workstation, the method
comprising:
circulating fluid through a heat transfer circuit to a heat exchanger disposed
adjacent or
in the workstation.
Also provided is a method of cooling a workstation, the method comprising:
circulating
fluid through a heat transfer circuit to a heat exchanger disposed such that
the heat
exchanger effects removal of heat from the workstation.
Where reference is made to cooling a workstation, preferably that reference is
to include
cooling equipment located in a workstation environment.
Preferably the heat transfer circuit comprises a secondary heat transfer
circuit
comprising a secondary condenser, and the method further comprises circulating
fluid
through a primary heat transfer circuit to effect cooling at the secondary
condenser.
Also provided by the invention is a cooling unit, cooling apparatus, cooling
system, or
workstation being substantially as herein described having reference to any
one or more
of the accompanying drawings.
The invention also provides a cooling method, optionally for cooling a
workstation or
computer equipment, the method being substantially as herein described.
Any feature in one aspect of the invention may be applied to other aspects of
the
invention, in any appropriate combination. In particular, method aspects may
be applied
to apparatus aspects, and vice versa.
Preferred features of the present invention will now be described, purely by
way of
example, with reference to the accompanying drawings, in which:
Figure 1 shows schematically a flow diagram of an example of a primary - only
cooling system;
Figure 2 shows schematically a flow diagram of an example of a primary and
secondary cooling system;
Figure 3 shows a perspective view of a workstation;
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Figure 4 shows a schematic cross-sectional view of a workstation of a type
illustrated in Figure 3;
Figure 5 shows an alternative arrangement of the workstation cooling unit;
Figures 6a, b and c show an example of a workstation arrangement having an
under-
floor mounted heat exchanger;
Figure 7 shows an alternative heat exchanger unit arrangement;
Figure 8 shows a further example of a heat exchanger unit;
Figure 9 shows an arrangement where the heat exchanger is mounted in a ceiling
void;
Figures 10a, b and c show three examples of arrangements for the flow of
carbon
dioxide to a plurality of heat exchanger coils;
Figures 11 a, b and c show a further alternative cooling unit arrangement to
that of
Figures 6a b and c
Figures 12a and b show a cooling arrangement for cooling an array of computer
equipment; and
Figures 13a to d show a further cooling arrangement for cooling an array of
computer equipment.
Figure 1 shows schematically the general operation of a primary-only cooling
system and
in particular shows fluid flow around a heat transfer circuit 20. The heat
transfer circuit
comprises a condenser 30, which is cooled by any appropriate method, a pump
32,
which circulates fluid, an expansion device 34 which reduces the heat transfer
fluid to a
design evaporating pressure and a heat exchanger 36, and a fan or fans 38
contained in
a workstation cooling unit 12, which provides cooling to the equipment 10 at
the
workstation as described in more detail below. The circulating fluid picks up
heat from its
surroundings in the heat exchanger and returns to the condenser 30, thereby
completing
the circuit. Instead of a pump 32, the circuit may be gravity fed.
Figure 2 shows schematically the general operation of a secondary cooling
system and
in particular shows fluid flow around a primary heat transfer circuit 18 and a
secondary
heat transfer circuit 20. The primary heat transfer circuit 18 comprises a
compressor 22,
a primary condenser 24, an primary expansion device 26 and an evaporator 28.
The
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heat transfer fluid used in the primary circuit is a volatile primary
refrigerant of
conventional composition. For example chilled water, refrigerant (for example
ammonia)
or other cooling medium may be used as the primary refrigerant.
The secondary heat transfer circuit 20 comprises a secondary condenser 30,
which is
cooled by the evaporator 28, a pump 32, which circulates fluid, a secondary
expansion
device 34 which reduces the heat transfer fluid to a design evaporating
pressure and a
heat exchanger 36, and optionally a fan or fans 38 contained in a workstation
cooling unit
12, which provides cooling to the equipment 10 at the workstation as described
in more
detail below. The circulating fluid picks up heat from its surroundings in the
heat
exchanger and returns to the secondary condenser 30, thereby completing the
circuit.
Instead of a pump 32, the secondary circuit may be gravity fed.
In this example, the heat transfer fluid circulating in the heat transfer
circuit 20 is carbon
dioxide under pressure. The advantages of using carbon dioxide are that it is
readily
available, inexpensive, and relatively non-toxic and non-polluting. Most
importantly,
however, when compared to systems which use non-volatile secondary heat
transfer
liquids, such as air, the mass flow of carbon dioxide required to produce the
same
cooling effect is substantially lower due to the high latent heat of carbon
dioxide, when
compared to the relatively low specific heat capacities of conventional non-
volatile
cooling media such as air.
The carbon dioxide arrives at the heat exchanger in a volatile state at
temperatures
suitable to cool a surface area sufficiently below the local temperature to
ensure that
heat exchange takes place. Preferably the temperature is in the region of 14 C
in order
to avoid condensation on the pipes and coil, in an environment having a
temperature of
20 C dry bulb, with a relative humidity of 45 to 55% (a typical office
environment). In
some applications, it is desirable to avoid such condensation because of the
risk that
water will drip, for example in the vicinity of electrical equipment.
Advantages of carbon dioxide as the volatile fluid are that it is readily
available,
inexpensive, relatively non-toxic and non-polluting. An important property of
carbon
dioxide is that compared with non-volatile media such as air and water, the
mass flow
rate of carbon dioxide required to produce the same cooling effect is
substantially lower
due to the high latent heat of carbon dioxide when compared with the
relatively low
specific heat capacities of non-volatile media.
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In preferred examples, the working pressure of the system is in the region of
50 Bar,
although it may be higher or lower depending on the design of the system and
the
cooling capacity required.
The use of carbon dioxide as a secondary coolant fluid is known, being
described in UK
Patent No. 2 258 298. However, it has not been previously considered suitable
for
providing local cooling of IT workstations where air cooling has dominated
ever since the
field begun, as it is both electrically benign and intrinsically safe. Carbon
dioxide is
electrically benign but is not intrinsically safe. Carbon dioxide can present
a health and
safety issue, if adequate precautions are not taken. Whilst the quantities of
carbon
dioxide are small in the arrangements described, it is volatile, used at high
pressure, and
often in confined or small spaces. The main hazards associated with the use of
carbon
dioxide at high pressure are: (a) its asphyxiation properties; and (b) the
very low local
temperature associated with the escaped fluid (which may affect people or
equipment in
the vicinity).
Also, the monitoring of degradation or failure of cooling systems is, in some
cases,
important for averting damage to the equipment due to over-heating, in the
event of a
local failure in a cooling system and implementing strategies for maintaining
operations
and recovery actions. The apparatus may, for example include gas detection
device
similar to that described in co-pending UK Patent Application No. 0515399.4,
for
detecting leakages. As it is generally used at high pressures for effective
cooling (50 Bar
or above) leakage could be a problem. The cooling media system incorporates
leak
detection and shut-off life safety measures, aiong with a rejection system to
deal safely
with any leaked substance.
The cooling unit may be arranged under or above a workstation, for example
below the
floor (within a raised floor construction or within a floor void) or above the
ceiling, for
example within a ceiling void.
Figure 3 is a perspective view of features of a workstation 40. The
workstation shown
comprises two desk work surfaces 42, 44 and two foot wells 46, 48 such that a
worker
can sit at each of the work surfaces 42, 44 facing each other. Between the
foot wells 46,
48 is a computer equipment compartment 50 having front and back walls 52, 54
facing
the foot wells 46, 48 and side walls 56, 58. The front, back and side walls
define a
compartment for the computer equipment. The walls may be insulated as
described in
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further detail below.
Figure 4 shows a schematic cross-sectional view of a workstation of a type
illustrated in
Figure 3. In the compartment is mounted a personal computer 60. A workstation
cooling
unit 12 is mounted above the personal computer 60 at the top of the
compartment under
the work surfaces 42, 44.
As shown schematically in Figure 4, the workstation cooling unit comprises a
heat
exchanger 36 and a fan arrangement 38 which here is shown including one fan,
but
could include several fans. When in use, the computer 60 emits heat which is
generally
contained in the compartment 50. Pipes (not shown in Figure 4) supply CO2 to
and from
the heat exchanger 36. The cooling unit 12 includes an air inlet 62 and air
outlet 64 and
the fan arrangement 38 acts to draw air across the heat exchanger 36 and the
cold C02
acts to remove heat from the compartment 50. In this arrangement, air
circulates within
the compartment.
Figure 5 shows an alternative arrangement of the workstation cooling unit 12.
Equivalent
components are given the same reference numbers as in Figure 4. In this
arrangement,
the cooling unit 12 is mounted such that it extends from the computer
equipment
compartment 50 through the work surfaces to above the desk. Again, inlet and
outlet
pipes 66 pass through the chamber 50 from under the floor to the cooling unit
12 and
provide carbon dioxide to the heat exchanger 36. In this arrangement the fans
38 are
arranged to draw air from the compartment 50, through the air inlets 62, over
the heat
exchanger 36 and upwards through the air outlet 64. (Alternatively the fan is
arranged to
blow air downwards through the compartment towards the floor.) It is envisaged
that the
air outlet 64 could be connected to an air duct to transport the air away from
the
workstation, but in this example shown, the air is emitted into the space
above the desk
work surfaces 42, 44. The air outlet 64 in this arrangement is located
approximately 80
mm above the work surfaces.
In some arrangements, for example in view of the air discharge characteristics
of the
computer equipment, the cooling unit 12 may comprise air flow extract ducts.
Such
ducts will be associated with an air inlet 62 of the unit and/or air outlet of
the computer
equipment and assist the hot air exiting the equipment to be directed towards
the cooling
unit. The duct design will depend on the arrangement of the computer air
outlets. For
some arrangements, specific ducts can be designed for specific equipment.
However,
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preferably the design of the duct enables its dimensions to be alterable. For
example,
the duct may be able to extend from the vicinity of the air outlet of the
computer
equipment towards the cooling unit. The duct or snorkel may be constructed
from a rigid
material, or it may comprise flexible material, for example in the form of a
hose, in which
case the snorkel might be able to be manipulated to direct it towards the air
outlet of the
computer equipment. The snorkel may be of a fixed length, or it may be
extendable, for
example it may be telescopic. One end of the snorkel may be attachable to the
cooling
unit in the vicinity of the air inlet; the other end may be positioned in the
region of the air
outlet of the computer equipment.
The extracted air may be drawn from the cooling unit using fans, either a
single unit per
snorkel or multiples thereof to provide a back-up unit and/or build redundancy
into the fan
system. Multiple fans may be installed either in series or in parallel.
Parallel fan
assemblies may incorporate non-return valves to avoid short circuiting between
fan units.
The air may be either sucked or blown across the heat exchanger what is
supplied with
liquid carbon dioxide.
In preferred arrangements, the pressure of CO2 is 50 Bar which provides a
circulating
temperature of 14 degrees C. Some arrangements enable loads of up to 5kW per
workstation to be dealt with. It is also found that the air emitted at the air
outlet 64 in this
arrangement is close to room temperature. This can be achieved by, for example
choosing an appropriate carbon dioxide flow rate and/or pressure. In some
arrangements there may be benefit in providing a temperature sensor for
determining the
temperature of the emitted air; the output of this sensor may be used to
adjust the flow
rate and/or pressure to maintain a desired temperature.
In an alternative example, using the arrangement of Figure 5, air is blown
using the fan
arrangement 38 into the compartment 50 from above the workstation (ie
downwards in
the arrangement shown in Figure 5). Grilles (not shown) are provided in the
floor at the
base of the compartment for the discharge of the air to the local vicinity of
the computer
equipment beneath the workstation.
In the arrangement of Figure 5, it will be seen that the front and back walls
52, 54 include
insulation 68. In this case the insulation comprises closed cell foam, but
other materials
could be used. Insulation is also provided on the side walls (not shown here).
The walls
and the insulation extend from the floor to the lower surface of the desk work
surface and
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forms a sealed insulated compartment 50. The heat generated by the computer 60
is
therefore substantially retained in this compartment for removal by the
cooling unit 12.
The heat transfer capacities of the carbon dioxide can enable a smaller heat
exchanger
to be used and thus the cooling unit may have a smaller, slimmer construction
that'might
have been possible for a comparable unit using chilled water. Such reduced
unit size
may be beneficial where the unit is to be used in an office environment where
space is of
a premium and may normally be congested with wiring and cables.
In some arrangements, several units may be provided together. For example, a
continuous run of cooling units 12 may be mounted side-by-side. Where the unit
is
provided as a continuous run made up of sections, each section may be, for
example 5
metres long, although longer or shorter sections could be used, as
appropriate.
The unit may comprise a gas detection monitoring chamber. By monitoring for
gas in the
chamber, the presence of carbon dioxide can be detected and thus the integrity
of the
heat exchanger can be monitored. An automatic shut off safety device can be
provided
for isolating the supply of carbon dioxide to the unit. A notification device
may alert the
user to any problem with the gas flow.
The cooling unit may incorporate a connection chamber where connections may be
made to the carbon dioxide flow and return distribution pipe work. The chamber
may
incorporate some or all of the control valves and gas detection monitoring
equipment. By
providing the gas detection monitoring equipment, leaks associated with carbon
dioxide
pipe work connections and/or control valves can be efficiently detected.
Gas detection monitoring equipment is described in our co-pending UK Patent
Application No. 0515399.4, the contents of which are incorporated herein by
reference.
It will be seen that gas detection monitoring equipment similar to that
described therein
could be incorporated into any of the examples of cooling equipment described
herein.
Figures 6a, b and c show a further workstation arrangement. Figure 6a shows a
sectional side view of a desk including computer equipment 360 and an
associated
cooling unit. In this example, part of the cooling unit is mounted under a
raised floor 340.
The workstation comprises a desk including two work surfaces 342 and 344. Here
the
desk comprises a back-to-back arrangement for two users and a compartment is
arranged under the desk to house computer equipment 360 for both desks.
However, a
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similar arrangement could be used for a single desk.
The compartment comprises a roof 371 and walls 354, 356 shown. The walls
comprise
heat load screens which extend downwards from the roof 371 to a position above
the
floor 340. The gap between the walls and the floor provides a ventilation gap.
In the
raised floor 340 within the compartment are provided air grilles 370 providing
ventilation
between the compartment and the under floor cavity 362.
The computer equipment 360 stands on the raised floor and in the floor cavity
362 under
the raised floor is mounted a heat exchanger 336 which includes a coil for
carbon
dioxide. This arrangement is shown in more detail in the plan view of Figure
6b.
At the air outlet 372 of the computer equipment 360 is arranged a snorkel
device 374
which contains a fan (or fans) 376. The snorkel device 374 extends from the
air outlet
372 to an inlet hole 380 in the floor grille 370. When the fan is activated,
air is drawn
from the air outlet 372 of the computer 360, through the snorkel device 374
(past the fan
376), through the inlet hole 380 into the floor cavity 362 where is passes
over the heat
exchanger 336 and then exits the floor cavity through the grille 370. The
snorkel device
shown could be adapted to have several inlets to collect air from several
outlet locations
on the equipment.
Figure 6c shows a rear view of the snorkel device 374 and computer 360
arrangement.
As can be seen in Figure 6b, the heat exchanger 336 extends under several
workstations
to provide cooling for several items of computer equipment. In this
arrangement there
may be two or more items of computer equipment under each desk; the heat
exchanger
336 provides cooling to both of these items. Furthermore, where several
workstations
are located together, the heat exchanger can extend across several
workstations,
providing cooling to several workstations.
A manifold chamber 390 is provided at the end of each coil and includes a gas
detection
device similar to that described in UK Patent Application No. 0515399.4,
Any of the examples which show integral fans could, alternatively or
additionally, be
connected to workstations through a ducted air system.
Figure 7 shows an alternative heat exchanger unit 410 arrangement in which the
heat
exchanger coil 400 is arranged at floor level (compared with under the floor
as in the
arrangement of Figure 6a).
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The heat exchanger unit 410 is formed so as to be a similar size as a standard
floor tile
412 so that it can easily be mounted within the floor on the floor pedestals
414. The
heat exchanger unit comprises a base 416, side walls 418, and a roof
comprising a
central solid portion 420 and two parallel grille sections 422 extending along
two sides of
the roof of the unit. The heat exchanger is mounted within the unit, under the
solid
portion 420. Carbon dioxide is provided to the coil by flow and return pipes
provided
within the floor void 426. Carbon dioxide supply pipes 428 are provided with a
steel
cover 430 for protection against damage.
The heat exchanger comprises a plane coil which is mounted having its plane at
an
angle to the base of the unit. In this way, when the unit is mounted under the
workstation
the snorkel and fan arrangement is arranged to blow warm air from the
equipment into
the unit through one of the grilles 422, over the tilted coil and out through
the other grille
422. In this way, the warm air from the equipment may be cooled.
Figure 8 shows a further example of a heat exchanger unit. This arrangement is
similar
to that of Figure 7; like parts are indicated by like numerals. In the
arrangement of
Figure 8, however, the carbon dioxide supply pipes 428 are arranged
immediately
beneath the base 416 of the unit 410. Thus the carbon dioxide supply pipes 424
are
shorter and the workings of the unit do not extend so far into the floor void
426. This is of
benefit in that there is less potential interference with services already
present in the floor
void, for example cables. It will be seen, however, that the height of the
unit of Figure 8
is greater than that of Figure 7; there may be some applications where the
arrangement
of Figure 7 is preferred.
Also in the arrangement of Figure 8, an inlet 432 specifically for the entry
of air from a
snorkel device (see for example Figure 6a) is provided in one of the grilles.
The flow of
air through the unit is shown by arrows.
Figure 9 shows an arrangement where the heat exchanger is mounted in a ceiling
void.
In this arrangement, the floor may still comprise a false floor 612 mounted on
floor
pedestals 614, but in this arrangement the floor void may be left clear of the
cooling
apparatus to allow more space for, for example, cables.
In this arrangement, the computer equipment 660 is located under a desk 600 at
the
workstation 610. A duct 612 extends from adjacent the computer equipment 660
under
the desk 600, through the desk top 614 and upwards to the ceiling 615. An
inlet
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formation 618 is provided at the lower end of the duct 612 for directing air
from an outlet
or outlets of the computer equipment 660 to the duct 612.
The ceiiing 615 comprises a false ceiling 616 below a ceiling void 620. Within
the ceiling
void 620 is mounted a heat exchanger coil 622. Flow and return pipes 624, 625
provide
carbon dioxide to the coil 622 in a manner similar to that described above.
The duct
extends upwards through the false ceiling 616 to the coil 622. A fan
arrangement 626 is
provided at the top of the duct 612 adjacent the coil 622. The fan arrangement
626 is
arranged to draw warm air upwards from the computer equipment 660, through the
duct
612 and over the coil 622 and into the ceiling void 620. The air is cooled as
it passes
over the coil 622.
Figures 10a, 10b and 10c show three different arrangements for the supply of
carbon
dioxide to and from a plurality of heat exchanger coils.
In the arrangements of Figures 10a, 10b and 10c, carbon dioxide flow and
return pipes
700, 702 supply carbon dioxide to a plurality of heat exchange coils 710.
Valves 720 and
721 are provided to control the flow of carbon dioxide in the system. In the
arrangement
of Figure 10a, the valve locations allow dual coil units to be arranged in
parallel; this
allows additional coils to be arranged in series. Figure 10b and 10c show
alternative
arrangements.
Figure 11a shows a further alternative cooling unit arrangement to that of
Figure 6a. In
the arrangement of Figure 11, the snorkel or duct 374' comprises a flexible
hose 500
extending from an inlet formation 502 for enclosing an outlet region 504 of
the
equipment, to the fan arrangement 376.
A cable path enclosure 506 is arranged under the workstation above the coil
and is
adapted to receive cables from the equipment, cooling unit and/or other
cables. A drain
point 508 may be provided beneath the heat exchanger, for the removal of any
water
which condenses on the coil.
In Figure 11 b, it will be seen that, compared with Figure 6b, further inlets
380 have been
provided in the grille 370 to allow for different snorkel positions and thus
to give flexibility
in arrangement of equipment at the workstations, and/or to provide for more
than one
snorkel or hose arrangement to be provided for each item of equipment, to
provide
additional cooling.
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Figures 12a and 12b show a cooiing arrangement for cooling an array of
computer
equipment.
Figurel2a shows a schematic plan view of an array of eight items of computer
equipment 800 arranged side-by-side beneath a desk (not shown). The width of
the
desk may be, for example 1600mm (A); the depth of the desk (B) may be 600 mm.
The cooling arrangement for cooling the computer equipment 800 in the
arrangement of
Figures 12a and b could for example be similar to that of Figure 6a to c.
With reference to Figure 6c, a coil unit extends under the full array of eight
items of
computer equipment 800; the computer equipment is mounted between air grilles.
Figure 12b shows a side view of the heat exchanger coil 810 mounted beneath
the
computer equipment 800 (in this arrangement, the coil is tilted to give more
efficient
cooling). As in the arrangement shown, for example in Figure 8, warm air from
the
computer equipment passes through one of the air grilles 820, over the coil
810 and exits
through the opposite air grille 840.
Whilst in many cases the air entry and exit are in the same direction for each
item of
computer equipment, in this arrangement, however, the air inlet and outlet
grilles are
interchangeable. Thus the arrangement may be such that the direction of air
flow may
be in either direction across the coil 810. This has the advantage that the
computer
equipment may be arranged in the most convenient orientation for the user:
with the air
outlet of the equipment facing grille 820 or grille 840.
Furthermore, as shown in the arrangement of Figures 12a and b, one or more
dividing
members can be provided so that air flow can be controlled with regard to a
particular
section of the coil 810.
In the arrangement of Figure 12a, a dividing plate 850 is provided between two
of the
items of computer equipment. The plate extends substantially vertically
through the
passage containing the heat exchanger coil 810, and also preferably through
the
compartment under the desk containing the computer equipment. In the
arrangement
shown in Figure 12b, the coil passes through the plate 850.
By isolating the air flow on the two sides of the dividing plate 850, the air
flow on the two
sides can be different. As shown in Figure 12a, the air flow on one side of
the dividing
plate can be opposite that on the other side. Thus on one side of the plate
850, the grille
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is an air inlet grille 820 for warm air from equipment El to E4, and on the
other side, the
grille is an air outlet grille 840' for equipment E5 to E8. Similarly, on one
side of the,
plate, the other grille is an air outlet grille 840 or warm air from equipment
El to E4, and
on the other side, the grille provides an air inlet grille 820' for equipment
E5 to E8.
Thus the dividing plate allows flow in opposing directions and thus avoid the
need for the
equipment to be positioned so that it all faces in the same direction. Since
the
equipment is usually arranged such that it faces its user, the use of the
dividing plate
allows the system to be more flexible with regard to different desk and
workstation layout
possibilities.
It will be appreciated that further dividing plates could be used to provide
further
variations in air flow and thus further flexibility in the arrangement of
equipment in relation
to the cooling unit.
Figures 13a to d show a further cooling arrangement for cooling an array of
computer
equipment. Figures 13a and b show, respectively, a perspective and a side
sectional
view of a workstation 900 including a desk 910 being arranged such that two
users can
work at the desk 910 facing each other. Under the work surface 912 of the desk
is an
insulated compartment 914 in which a plurality of items of computer equipment
916 is
mounted. The construction of the compartment 914 is similar to that of the
example
shown in Figure 4, described above. In this arrangement, a double-walled
construction is
used including heat load screens
From the perspective view of Figure 13a and the plan view of this arrangement
shown in
Figure 13c it can be seen that the compartment 914 extends across the width of
the desk
910 and houses eight items of computer equipment 916A to H.
The structure of the cooling apparatus is similar to that of Figures 6 and 11
except that
no air directing formation is mounted within the desk to direct the air. A
cooling unit 918
comprising plurality of floor tile-replacement units (600 mm square) is
provided beneath
the compartment 914. The cooling unit 918 extends across the width of the desk
910
(and, optionally, beyond) and includes an air channel 919 in which are
arranged a
vertically mounted heat exchanger coil 920 and a fan 922. Carbon dioxide
supply pipes
923 supply carbon dioxide to the coil 920. A manifold chamber is provided at
the ends
of the coils and includes a gas detection device.
The air channel of the cooling unit 918 is in air communication with the
inside of the
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compartment 914 via air inlet and outlet grilles 924, 926. The computer
equipment
stands on a raised perforated platform 928 mounted on the floor of the
compartment 914
and at least partially over the grilles 924, 926 so that air flow to the
grilles is not
substantially impeded by the computer equipment 916. The raised platform
allows air to
pass into the underfloor plenum.
With reference to Figure 13a, when the fan is activated, air circulates
between the
compartment 914 and the air channel 919. Specifically, warm air exiting the
air outlet
930 of the computer passes through the compartment 914 to the air inlet grille
924, is
drawn through the air channel 919 by the fan 922 and passes over the coil 920
where the
air is cooled. The cool air then enters the compartment via the air outlet
grille 926. In
preferred arrangements, the air inlet of the computer equipment is located
close to the
air outlet grille 926 so that cool air is drawn into the computer equipment
inlet 932.
In this way, effective cooling of the equipment can be achieved. For example,
in an
arrangement similar to that described, air exiting the outlet 930 may have a
temperature
of from 30 to 35 degrees C; cooled air entering the compartment 914 might have
a
temperature of about 15 degrees C. In some arrangements, further fans may be
provided in the air channel 919 upstream of the coil 920.
Considering Figure 13c, it will be seen that a dividing plate 932 is provided
in the air
channel such that opposite flow of air can be achieved in the portion of the
compartment
cooling equipment 916A to D compared with equipment 916E to H in a manner
similar to
that of the arrangement of Figure 12. Thus the dividing plate forms two air
channels
beneath the desk, the coil extending through both.
This arrangement is shown in Figure 13d which shows a simplified perspective
view of
parts of the cooling unit 918.
From Figures 13c and d it will be seen that a single coil is provided across
the array of
equipment, and one fan arrangement is provided for each pair of items of
computer
equipment. It will be appreciated that other arrangements are possible.
Further dividing
plates may be provided, for example to form further air channels (for example
so that
only one fan is provided in each channel) and/or to divide the compartment 914
to further
direct the air flow.
It will be seen that, in this arrangement, the two users sitting facing each
other at the
desk can each have a plurality of items of computer equipment facing them,
while
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efficiencies may be made by using a common cooling unit arrangement to effect
cooling
of all of the equipment at that workstation.
It will be understood that the present invention has been described above
purely by way
of example, and modification of detail can be made within the scope of the
invention.
Each feature disclosed in the description, and (where appropriate) the claims
and
drawings may be provided independently or in any appropriate combination.
