WO2011033270A2

WO2011033270A2 - Equipment cabinet

Info

Publication number: WO2011033270A2
Application number: PCT/GB2010/001757
Authority: WO
Inventors: Stuart Peter Redshaw
Original assignee: 4Energy Limited
Priority date: 2009-09-21
Filing date: 2010-09-20
Publication date: 2011-03-24
Also published as: EP2481272A2; CN102656960A; GB2473647A; WO2011033270A3; GB0916472D0; CN102656960B; GB2473647B

Abstract

An equipment cabinet (100) having an air cooling system comprising: an air inlet (101) extending across an outer wall (102) of the cabinet; an air inlet filter (103) disposed between opposing first and second side panels (104, 105) forming the outer wall of the cabinet; and a fan (106) arranged to draw air through the filter and into an internal volume (107) of the cabinet for cooling equipment (108) contained therein.

Description

EQUIPMENT CABINET

The invention relates to an equipment cabinet having an air cooling system for cooling of equipment within an internal volume of the cabinet.

To ensure proper operation and security of electronic equipment, particularly those installed in outdoor environments, such equipment is typically held inside cabinets. Such cabinets are generally used in telecommunications applications, for example cellular base stations and switchgear, as well as in other outdoor applications such as traffic signal control boxes and other street furniture applications where electronic equipment needs to be operated outdoors. The design of such equipment cabinets needs to be appropriate for the environment where the equipment is to be installed.

Since electronic equipment will inevitably generate heat when in operation, a way of extracting this heat from the cabinet is required. This is conventionally done by means of an air flow being directed through the cabinet to cool the equipment. Cooling may be achieved either directly, by air flow passing in and out of the cabinet and around the equipment, or indirectly, for example via a heat exchanger. Air conditioning may also be used, but this adds significantly to the bulk and the overall expense and running costs of an equipment cabinet and is therefore ideally avoided where possible.

GB2333185 discloses various kinds of base station arrangements in which cellular telephone equipment is contained within a cabinet in the form of an item of street furniture. Cooling is achieved by drawing air into the cabinet through inlet grilles and blowing hot air out of the cabinet through exit grilles or other openings.

GB2354066 discloses a cabinet for units which dissipate heat, comprising a rack for mounting electronic equipment and a fan unit for drawing air past the equipment through to an exhaust from a plenum chamber. A filter is provided on a door of the cabinet, through which air is drawn into the cabinet.

The above described systems concern forced air cooling of equipment within an equipment cabinet. A particular problem associated with existing systems is that of drawing airborne particulate matter such as dirt and dust into the cabinet, which could affect operation of the equipment inside. An air filter is therefore typically used, the filter being arranged to extract at least a proportion of any airborne particulate matter before it reaches the equipment inside the cabinet. The use of an air filter, however, inevitably raises the potential problem of clogging, which will cause the air flow through the cabinet to reduce, with a consequential effect of a reduced cooling efficiency and a rise in the operating temperature of the equipment. In extreme cases, a clogged filter will cause equipment to exceed a safe operating temperature, which may cause the equipment to automatically shut down to prevent any damage or malfunctioning. This results in a loss of service and the need for an engineer to be called out to service the equipment and replace any clogged filters. It is therefore important to be able to maintain cooling efficiency for as long as possible, and over as wide a range of operating conditions as possible, in order to reduce the possibility of equipment malfunction or failure.

US 2001/0052412 A1 seeks to address the problem of filter clogging by using an air-to-air heat exchanger that allows an internal volume in which equipment is installed to be isolated from the external environment. In extreme cases, where the heat exchanger does not provide sufficient cooling, a second cooling system operates to force air directly through the internal volume, the second cooling system having a filter on an air inlet to prevent airborne matter being drawn in. This solution, however, only partially addresses the problem of clogging, as a filter that will eventually clog is still required. In addition, the cooling a heat exchanger is able to provide is limited by the temperature differential required.

WO 2009/090405 discloses an air filter comprising a duct forming a passageway extending between an inlet and an outlet of the air filter, the duct comprising bristles extending from a wall of the duct across at least a portion of the passageway so as to remove entrained particles from air passing through the duct. This type of filter, incorporating bristles instead of a conventional foam filter element, can result in a reduction and, in some cases, an elimination of filter clogging. This is particularly useful in hot and dusty environments, where the cooling air flow cannot be allowed to be compromised by airborne particulates. For such a filter to work effectively, however, a large inlet cross-section is required, to allow the inlet air flow speed to be reduced to a level where entrained particles are trapped by the filter bristles. For applications where equipment cabinets are in the form of street furniture, additional bulky external filter units may not be an option, as the footprint of the cabinet may be very restricted, for example by local planning requirements.

A further problem for street furniture applications is that of vandalism, resulting in a conflict between, on the one hand, ensuring the equipment in the cabinet is sufficiently secure from damage (whether accidental or otherwise) and, on the other, ensuring that an adequate volume of cooling air flow through the cabinet. Large external grilles on such a cabinet for improving air flow can be a target for vandals, so the external appearance of the cabinet needs ideally to be as unobtrusive as possible.

To address the main problem of cooling, one solution would be to increase the volume of air flowing into the cabinet. The resulting increase in air flow speed into the cabinet could, however, draw in even more airborne particulate matter, thereby reducing the lifetime of any inlet filter. Although effective in the short term, such a solution would inevitably result in a filter needing to be replaced more frequently. It is consequently an object of the invention to address one or more of the above mentioned problems.

According to a first aspect of the invention there is provided an equipment cabinet having an air cooling system comprising:

an air inlet extending across an outer wall of the cabinet;

an air inlet filter disposed between opposing first and second side panels forming the outer wall of the cabinet; and

a fan arranged to draw air through the filter into an internal volume of the cabinet for cooling equipment contained therein.

The air inlet filter preferably comprises one or more panels having an array of bristles extending from one or both faces. Such panels may be of the type disclosed in, for example, WO 2009/090405, comprising a card on which a layer of filter material is applied.

The air inlet to the cabinet may be provided by a gap between the lower edges of the first and second side panels. In this form, the air inlet is made to be minimally obtrusive, and may not even be visible as an inlet under normal inspection. This form of inlet is therefore advantageous in reducing the risk of damage through vandalism.

The equipment cabinet may comprise a conduit that defines an air flow path between an outlet side of the air inlet filter and the base of the internal volume of the cabinet. Since the filter extends across the outer wall of the cabinet, it is advantageous to direct the air flow down to the base of the cabinet after leaving the filter to maximise the cooling effect on equipment held within the cabinet, since warm air from heat generated by the equipment will tend to rise and draw the cooler air through the internal volume.

The equipment cabinet may comprise a first and a second of said air inlets and air inlet filters extending across opposing outer walls of the cabinet. This is advantageous in extending the filter cross-sectional area while minimising the additional space taken up by the filter.

When using two air inlet filters on opposing outer walls, a conduit may define an air flow path between an outlet side of each air inlet filter and the base of the internal volume of the cabinet, in order to ensure that cooling air reaches the base of the internal volume of the cabinet, to improve cooling efficiency. To further improve cooling efficiency, particularly in the case where a fan drawing air through one of the inlet filters fails, the conduit may be divided into two portions by a partition dividing air flow from the outlet side of the first and second air inlet filters into a first portion extending between the outlet side of the first filter and the base of the internal volume and a second portion extending between the outlet side of the second filter and the base of the internal volume. If one fan fails, the partition ensures that air is still drawn towards the base of the internal volume, rather than out of the cabinet through the other filter, which could happen without the use of such a partition.

The conduit extending between the outlets of each filter and the base of the internal volume advantageously extends across an outer wall of the cabinet between the first and second filters, thereby minimising the space taken up by the conduit and maximising the volume available within the cabinet for equipment.

The invention will now be described by way of example, and with reference to the enclosed drawings in which:

figure 1 is a schematic drawing of a section through an exemplary equipment cabinet;

figure 2a is a schematic drawing of a elevation section across an alternative exemplary equipment cabinet; and

figure 2b is a schematic drawing of a plan section across the alternative exemplary equipment cabinet of figure 2a.

Figure 1 illustrates an exemplary equipment cabinet 100 in accordance with an embodiment of the invention. The cabinet 100 comprises an air cooling system that includes an air inlet 101 extending across an outer wall 102 of the cabinet 100, the air inlet 101 leading to an air inlet filter 103 disposed between opposing first 104 and second 105 side panels forming the outer wall 102 of the cabinet 100. A fan 106 is arranged to draw air through the filter 103 and into and internal volume 107 of the cabinet 100 for cooling equipment 108 contained therein.

The direction of air flow into, through, and out of the cabinet 100 is indicated in figure 1 by arrows 110, 111 , 112, 113, 114 and 115. Air first enters the cabinet (arrow 110) by flowing into the air inlet 101 , which is in the form of a gap between the lower edges 116, 117 of the first and second side panels 104, 105. A mesh 118 is disposed across the gap, in order to prevent larger objects (such as leaves and litter) being drawn into the filter 103 and to protect the filter 103 from accidental or deliberate damage. Air flows upwards (arrows 111) along the side wall 102 between the side panels 104, 105 and through the filter 103. Particulate material drawn in through the inlet 101 is trapped by the filter 103. The air flow speed is preferably low enough such that such particulate material eventually falls out of the air inlet rather than being trapped within the filter, thereby reducing the need for cleaning and replacement.

The mesh 118 is preferably a strong wire mesh, and is preferably oriented at around 45 degrees to the vertical, defined by the side walls 104, 105. A small gap between the lower edge 116 of the first side wall 104 and the mesh reduces the visibility of the mesh from normal view.

Air is drawn through the fan 106 and is then directed (arrow 112) down towards the base of the cabinet through a conduit 119 extending between the outlet 129 of the filter 103 and the base of the internal volume 107. Air then flows (arrow 113) along the base 130 of the cabinet, preferably beneath a false, air permeable, floor 120 before entering the internal volume 107 through the floor 120 (arrows 114). After passing through and around the equipment 108 contained within the internal volume 107 the air, now warmed by the heat generated by the equipment 108, passes into a roof space 121 of the cabinet 100 and out of the cabinet 100 (arrows 115) through exhaust openings 122, which are advantageously positioned along the edge of the roof 123 of the cabinet 100.

The filter 103 is in the form of a card having arrays of bristles provided on both faces. The filter 103 may alternatively be in the form of more than one card, with bristles provided on one or both faces of each card. The bristles are preferably provided by layers of artificial turf, which provides the necessary properties for allowing air flow while trapping larger particulates that may otherwise enter and remain within the internal volume 107. Very small, e.g. micron or sub-micron scale, particulate material may pass through the filter 103, but would be less likely to result in problems for the equipment 108 since such material would generally pass straight through the cabinet 100. In certain alternative embodiments, however, a finer scale filter may be provided to capture such smaller particles.

Figures 2a and 2b illustrate schematically an alternative exemplary embodiment of an equipment cabinet 200 according to the invention, in sectional elevation and plan views respectively. Figure 2b represents a plan view taken across the section indicated by A-A' in figure 2a.

As shown in figure 2a, the equipment cabinet 200 has a first air inlet 201a and second air inlet 201b, leading to respective first and second air inlet filters 203a, 203b extending across opposing side walls 202a, 202b of the cabinet 200, each filter 203a, 203b disposed between opposing first and second side panels forming opposing outer walls 202a, 202b of the cabinet 200. The filters 203a, 203b may alternatively be disposed along non-opposing walls of the cabinet in certain less-preferred arrangements.

As with the embodiment shown in figure 1 , air flows into the cabinet (arrows 210) through the air inlets 201a, 201b and through the filters 203a, 203b along the side walls 202a, 202b (arrows 211). After passing through fans 206a, 206b, air flows into a cavity

217. The cavity 217 is optionally divided into two sub-cavities 217a, _.217b by a partition

218, shown in figure 2b, the partition 218 extending down the conduit 219a, 219b through which the inlet air flows to reach the base of the cabinet 200. The air then enters the internal volume 207 through an air permeable floor 220 (arrows 214) and rises up through the internal volume before existing the cabinet, via an opening 222 at the upper portion of the internal volume 207, through exhaust ports in the roof 223 of the cabinet in a similar way to that shown in figure .

The fans 206a, 206b are preferably centrifugal-type fans, in which air is drawn up along a direction parallel to the rotation axis of the fan and expelled outwards in a direction orthogonal to the axis, indicated by arrows 212 in figure 2b.

The partition 218 prevents air flow from flowing directly from one fan 206a, 206b to the other fan 206b, 206a and out of the cabinet 200 through the opposing air inlet if one of the fans should fail. The partition therefore ensures that air continues to flow through the internal volume 207 which, providing a sufficient safety margin is accounted for, should enable sufficient cooling air flow to be provided until the failed fan can be replaced.

Other embodiments are intentionally within the scope of the invention as defined by the appended claims.

Claims

1. An equipment cabinet having an air cooling system comprising:

an air inlet extending across an outer wall of the cabinet;

a fan arranged to draw air through the filter and into an internal volume of the cabinet for cooling equipment contained therein.

2. The equipment cabinet of claim 1 wherein the air inlet filter comprises one or more panels having an array of bristles extending from one or both faces.

3. The equipment cabinet of claim 1 or claim 2 wherein the air inlet is provided by a gap between the lower edges of the first and second side panels.

4. The equipment cabinet of any preceding claim comprising a conduit defining an air flow path between an outlet side of the air inlet filter and the base of the internal volume of the cabinet.

5. The equipment cabinet of any one of claims 1 to 3 comprising a first and a second of said air inlets and air inlet filters extending across different outer walls of the cabinet.

6. The equipment cabinet of claim 5 wherein the first and second air inlets and air inlet filter extend across opposing outer walls of the cabinet.

7. The equipment cabinet of claim 5 or claim 6 comprising a conduit defining an air flow path between an outlet side of the first and second air inlet filters and the base of the internal volume of the cabinet.

8. The equipment cabinet of claim 7 wherein the conduit is divided into two portions by a partition dividing air flow from the outlet side of the first and second air inlet filters into a first portion extending between the outlet side of the first filter and the base of the internal volume and a second portion extending between the outlet side of the second filter and the base of the internal volume.

9. The equipment cabinet of claim 8 wherein the conduit extends across an outer wall of the cabinet between the first and second filters.

10. An equipment cabinet substantially as described herein, with reference to the accompanying drawings.