WO2011080168A2

WO2011080168A2 - Direct air cooling

Info

Publication number: WO2011080168A2
Application number: PCT/EP2010/070440
Authority: WO
Inventors: Jeffrey John Hunter
Original assignee: Sir Robert Mcalpine Ltd
Priority date: 2009-12-21
Filing date: 2010-12-21
Publication date: 2011-07-07
Also published as: WO2011080168A3; GB0922271D0

Abstract

A repository comprising: a first passage for supplying conditioned air; a second passage for withdrawing relatively warm air; and a cabinet having walls defining an interior volume which is substantially sealed except for an inlet opening and an outlet opening passing through the walls, the inlet opening being connected to the first duct and the outlet being connected to the second passage.

Description

DIRECT AIR COOLING

This invention relates to air handling, and specifically but not exclusively to air cooling mechanisms for use in data centres or other spaces.

Modern data centres typically house many thousands of computer servers. Normally, multiple servers are housed one above the other in rack-mount cabinets, and the data centre contains many rows of cabinets. As an illustration, a data hall might contain 17 rows of cabinets, with 26 cabinets in each row and an average of 42 servers in each cabinet. Each server might generate around 150W of waste heat, so the total heat generated in the data hall might be of the order of 2.8MW. Extracting this waste heat from the data centre is a major task. The plant needed to cool the servers has a major impact on the overall energy efficiency of the data centre. In conventional data centres, the cooling of the data centre might consume upwards of 120% as much energy as the servers themselves.

Figure 1 illustrates one way in which data centres are cooled. Figure 1 is a cross- section through the hall that houses the servers. The top and bottom of the hall are bounded by concrete slabs 1 and 2. A suspended floor 3 is supported by pedestals 4 which rise from the floor slab 2. A suspended ceiling 5 is supported by ties 6 which suspend from the ceiling slab 1. Cabinets 7 stand on the floor and contain servers 8. Conditioned air is pumped into the hall through a cold plenum which is the floor void 10. Alternate ones of the aisles between the cabinets are designated as cold aisles. In the cold aisles there are floor grilles 11 in the floor. The floor grilles allow air flow from the floor plenum into the room space 12 in which the cabinets are located. The remaining aisles are designated as hot aisles. In the hot aisles there are ceiling grilles 13 in the ceiling, which allow air flow from the room space 12 into ceiling return plenums 14 which from the ceiling void 15. Air is extracted from the ceiling plenum by computer room air-conditioning units (CRAC) and returned to the floor plenum once conditioned. By passing conditioned air into alternate aisles and extracting hot air from the remaining aisles, chilled air is encouraged to flow through the cabinets as illustrated at 16, where it can cool the servers and then be extracted through the space and the ceiling air plenum. This flow pattern is assisted by convection and may also be helped by fans in the cabinets and/or in the servers. However, this arrangement is highly inefficient. High volumes of air flow are needed because much of the air flow does not contribute effectively to cooling the servers, hotspots are produced which can only be eliminated by increasing the conditioned air into the data hall.

Another problem with conventional cooling is that the floor is typically formed of multiple tiles which rest on the pedestals 4, it is difficult to keep the gaps in the whole floor air-tight even when all the tiles are down; and the air flow is especially prejudiced whenever a floor tile is lifted to access the cabling that normally runs in the floor void. Also, the task of replacing floor tiles must be completed in sequence or the floor grilles can end up being located in the wrong position, further reducing the efficiency and increasing the chances of hot spots.

Another approach is to provide water cooling in each cabinet by passing chilled water through water coils in each cabinet. This approach has the problem that the water would cause considerable damage if it were to leak into the servers. This approach also requires cabinets that are complicated and expensive.

There is a need for a more efficient way of cooling spaces such data halls.

According to the present invention there is provided a repository comprising a first passage for supplying conditioned air; a second passage for withdrawing relatively warm air and a cabinet having walls defining an interior volume which is substantially sealed except for an inlet port and an outlet port passing through the walls, the inlet port being connected to the first passage and the outlet port being connected to the second passage. Other aspects and preferred features of the present invention are set out in the accompanying claims.

The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

Figure 1 is a vertical cross-section of a data hall, illustrating a conventional cooling mechanism.

Figure 2 is a vertical cross-section of a data hall, illustrating an alternative cooling mechanism.

Figure 3 is a plan view of the data hall of figure 2, showing the ducting for feeding air to the cabinets.

Figure 4 is an oblique cut-away view of the data hall of figure 2, showing a conditioned air passage.

Figure 5 is a cross-section of a rack-mount cabinet.

The data hall of figure 2 comprises a series of cabinets of which one is shown at 20 in figure 2. Supply ducting 21 supplies conditioned air and extract plenums 22 removes warm air that has been heated by flowing through the equipment. In the data hall of figure 2, the cabinets are connected directly into the ducting. The cabinets are substantially air-tight except for upper and lower ports 23, 24 by means of which the cabinets are coupled to the ducting. In this way, the air flowing through the system is used more efficiently, because it is passed specifically through the cabinets.

In more detail, the data hall of figure 2 comprises a floor slab 25 and a ceiling slab 26. The slabs are conventionally made of concrete, but they could be made of any other suitable building materials. A suspended floor is made up of rigid floor tiles. These may be of any size, but are typically 600 x 600mm. The tiles are supported by pedestals 28. The pedestals 28 stand on the floor slab. A floor void 29 is defined between the floor and the floor slab. A suspended ceiling 30 depends on ties 31 from the ceiling slab. A ceiling plenum 32 is defined between the suspended ceiling and the ceiling slab. The ducting 21 for supplying conditioned air runs in the floor void. A plenum 22 for removing warm air is defined by the ceiling void.

The base of the cabinet 20 stands on the floor 27. Typically the top of the cabinet 20 will be spaced from the ceiling 30. In the base of the cabinet is the inlet port 24 for allowing conditioned air to enter the cabinet. In the lid of the cabinet is the outlet port 23 for allowing warm air to exit the cabinet. A supply branch duct 33 connects the inlet port to the main supply duct 36. To allow the supply branch duct to pass through the floor, a floor tile under the cabinet has a cut-out 37 through which the branch duct runs. A warm branch duct 38 connects the outlet port 23 to the main extract plenum 22. To allow the warm branch duct to pass through the ceiling, the ceiling over the cabinet has a cut-out 35 through which the warm branch duct runs. The supply and exit connections may be of any suitable size, length or cross-section. Circular, square or rectangular cross-sections are convenient. A top hat connector (not shown in figure 2) could be used to couple the warm branch duct 38 into the ceiling into an air-tight manner. Preferably the warm branch duct runs vertically, with the cut-out 35 being directly over the outlet 23. The warm branch duct can conveniently be solid, but could be flexible.

The branch ducts 33, 38 communicate with the main ducts 36, and plenum 32 respectively and are sealed to them in a substantially air-tight fashion. The branch ducts also communicate with the interior of the cabinet and are sealed to the cabinet in a substantially air-tight fashion. The cabinet itself is substantially air-tight. As a result, the cabinet is directly connected into the conditioned air circuit. When the system is in operation there is a positive or negative pressure in the main conditioned duct relative to the main warm duct applied by fans in the supply leg of the system, which together with extract fans in the extract leg of the system causes air to circulate from the main conditioned duct 36, through the conditioned branch duct 33, the cabinet 20 and the warm branch duct 38 and back to the extract plenum 22. By virtue of the sealing of the cabinet, of the cabinet to the branch ducts and of the ducting itself, that circulation is substantially leak-free and hermetically sealed for noise containment and cleanliness.

The cabinet may be a conventional server rack-mount cabinet that is capable of airtight sealing. Such cabinets are currently available for anechoic applications when sound emissions from the cabinet are to be kept to a low level. Alternatively, the cabinet may be a conventional non-sealed rack-mount cabinet that has been modified by the addition of seals, or it may be a purpose-built cabinet. Typically, the cabinet will be of generally cuboid shape, having a lid, a floor and four orthogonal walls extending between the top and the bottom of the cabinet but other shapes are possible. The cabinet may be of any suitable dimensions. Typically the cabinet will be a rack-mount cabinet - that is a cabinet having provision for rack-mounting servers or other equipment. However, other arrangements for supporting the equipment are possible, for example simple shelving or manufacturer-specific mounting mechanisms. The cabinet may have one or more doors that can be opened to give access to the equipment therein, or each door can be shut in a substantially air-tight manner, for example by virtue of sealing strips around its periphery.

The cabinet contains a number of items of equipment 40. The equipment could be computers, such as servers, ancillary equipment such as uninterruptable power supplies (UPSs) or user interface controllers or other equipment. Typically, the equipment will generate heat whilst it is running, and that heat needs to be dissipated from the cabinet. This is the objective of the cooling system. Each item of equipment may include a fan 41 for circulating air within the device.

.At the inlet 24 to the cabinet is an air control valve 42. The valve could be of any suitable type, but one preferred form of valve is an iris damper. An iris damper comprises a number of leaves 43 which can be moved by an actuator 44 between an open position in which they are withdrawn and do not obstruct the flow of air through the inlet 24 and a closed position in which they come together to block the flow of air through the inlet 24. An iris damper is preferred because it causes less friction than many other air valve designs, allowing the air to flow more efficiently. The iris damper allows the flow of air into the cabinet to be controlled to reflect the needs of the cabinet, rather than a predetermined design load. Thus the iris damper may be controlled manually or automatically after it has been installed so as to alter the resistance to air flow into the cabinet. The control may conveniently be directed to adapting the air flow through the cabinet to match current or anticipated requirements due to equipment in the cabinet. In this way, as those requirements change the air flow can be adjusted without changing the structure of the cabinet or the air feed and extraction system.

The cabinet includes a local control unit 45 which receives information on temperatures in the cabinet from one or more temperature sensors 46 located within the cabinet. The control unit comprises a processor 47 which executes program code stored in a memory 48 to analyse the inputs from the temperature sensors and control the valve actuator 44 accordingly. The control program is such as to cause increasing opening of the valve 42 with increasing temperature in the cabinet and vice versa. The control program may have a preset window within which the temperature in the cabinet is intended to be maintained. The window may be defined by upper and lower bounds, such as 18°C and 30°C. The control program may be such that if the measured temperature is at or below the lower bound the valve is fully closed; and if the measured temperature is at or above the upper bound the valve is fully open. If the lower bound is T|_, the upper bound is TH, the measured temperature is T_M, the maximum aperture size of the valve is A_max, the minimum aperture size of the valve is A_mi_n and the currently set aperture size is A then according to one example control scheme the valve may be controlled as follows:

If T_M≤ T_L then : A = 0

If T_L < TM < TH then : A = Amin ⁺ (A_max-A_mi_n) x (TM-TL)/(TH-TI_)

If T_M≥ T_H then : A = A_max

By means of a monotonic control scheme such as this it can be expected that once the data hall is operating in a steady state, the temperatures and flow rates in the cabinets will settle to a substantially constant level. This reduces wear on the air valves.

Other control schemes may be used, but it is preferred that the control scheme is such as to promote the maintenance of the temperature in the cabinet at an acceptable level without excessive usage of the available air flow. In a typical data hall there may be hundreds of cabinets, and it is desirable to avoid unnecessary circulation of air because that requires the flow speed and/or ducting sizes to be increased.

The control scheme can conveniently be implemented by PID loop control principles.

Each cabinet is preferably controlled independently of the others, for example in the ways discussed above.

Instead of the inlet valve being automatically controlled, as described above, it could be set manually to permit a flow rate that will be just sufficient to cool the cabinet to an acceptable level, bearing in mind the anticipated heat production in the cabinet. For this purpose, the cabinet could be provided with a dedicated manual valve, or with a valve that can be controlled both manually and automatically, alternatively a preformed orifice plate could be used for each cabinet, the opening size of the plate being selected so as to match the allowable, expected or current load within the cabinet. A set of orifice plates may be supplied, the orifice plates having variously sized orifices. The sizes of the orifices are conveniently calculated to allow an appropriate flow of air into the cabinet for cooling a certain load in the cabinet. For example, an installer could be supplied with a set of orifice plates corresponding to loads of 4, 5 and 6kW, or indeed loads of a megawatt or higher depending on the circumstances. The appropriate orifice plate for the current load in the cabinet could then be installed and if the load changes, for example if servers are added or removed, a different orifice plate could be installed instead. The plates could be colour coded to allow the appropriate plate to be readily identified. A further alternative is for the valve to be controlled mechanically, for example under the influence of a linkage control mechanism that is attached to a mechanical temperature sensor such as a bimetallic strip located in the cabinet.

The arrangement described above allows for particularly efficient usage of conditioned air because the air is directed specifically into the space defined by the cabinet, rather than into the general room space of the data hall, and because the flow to each cabinet is controlled by an individual valve. Only the air necessary for conditioning the individual cabinet will be consumed by that cabinet. The arrangement also avoids the need for ducting running through each cabinet, or individual cooling for each server, which increases cost. Simulations suggest that by means of the arrangement described herein a data centre might achieve a power usage efficiency (PUE) of less than 1.2, whereas current data centres that are viewed as being highly efficient have PUEs of around 1 .6. One reason for this is that the system described herein readily conforms to the requirements of data halls that are only partially utilized, e.g. because they are only partially full of equipment or because some of the equipment is switched off. If a cabinet in the data hall is lightly utilised then the system described herein can supply a relatively low amount of air to that cabinet, and if there is no equipment running in the cabinet then it would be expected that reduced air would be supplied. Thus the system need only condition as much air as is needed for servicing the equipment that is actually installed and switched on.

When the inlet 24 and the outlet 23 are located in the top and bottom of the cabinet respectively, they are preferably spaced apart from each other in the horizontal plane, so as to promote air flow through and around the equipment in the cabinet. Preferably the inlet 24 is located near the front of the cabinet, for example in the front half of the bottom, and the outlet 23 is located near the rear of the cabinet, for example in the rear half of the top. (The front and rear of the cabinet may be defined by reference to the mounting orientation of equipment in the cabinet). This helps to promote air flow through equipment whose fans 40 draw air from front to rear, To assist the effective circulation of air in the cabinet it may be fitted with baffles such as baffle 49 or with an air management box. Baffle 49 extends over the top and rear of the inlet 24 so as to throw inlet air towards the front of the cabinet. Air circulation within the cabinet may be assisted by fans if necessary. The inlet and/or the outlet could be located in the sides of the cabinet. There could be multiple inlets and/or outlets. There could be a valve at the outlet instead of or in addition to the inlet. There could be a VC damper in the outlet from the cabinet. However, it is preferred that there is a valve at the inlet and no valve at the outlet since this can allow flow of air in the event of a failure, in the manner described below. There could be multiple inlets and/or outlets between the cabinet and the conditioned ducting and warm plenum respectively, any one or more of which could be equipped with manual valves or orifice plate, or valves that are controlled automatically in the manner described above.

One particularly convenient design of cabinet is shown in cross-section in figure 5. The cabinet comprises a front side wall 90 and a rear side wall 91. The cabinet also has lateral side walls which extend between the front and rear side walls. There is a top wall 92 at the top of the cabinet and a floor 93 at the bottom of the cabinet. In the basal region of the cabinet is a compartment which houses features intended for managing the air that is inlet into the cabinet. The compartment comprises a vertical wall 94, a horizontal wall 95, a baffle 96 and a damper 97. The horizontal and vertical walls both extend between the lateral side walls and are attached in an air-tight manner to the lateral side walls; for example by welding along the entire adjoining surfaces of the respective walls. The vertical wall 94 is also joined to the horizontal wall 95 and to the base wall 93 in an air-tight manner along the axes where they meet. The horizontal wall 95 extends forwards in the cabinet from the vertical wall to an axis spaced rearwardly from the front wall 90, leaving a slot 98 between the horizontal wall 95 and the front wall 90. The horizontal and vertical walls define a chamber in the basal region of the cabinet which is air-tight apart from the slot 98 and the air inlet 100. The damper 97 is fitted in the inlet. When conditioned air enters the cabinet through the inlet, the air enters the chamber and exits through slot 98. Since the slot 98 is at the front of the cabinet, the action of the chamber is such as to encourage the air to circulate through equipment installed on racks 101 and then out of the outlet 100 which is rearward of the slot 98. To reduce the resistance of the air to such a flow path, the baffle 96 curves forwardly from near the intersection of the vertical wall 94 and the floor 93 and an axis more forward of that on the horizontal wall 95. The baffle is concave facing the inlet 99.

It is preferred that the air valve 42 is configured such as to adopt the open configuration in the event of a failure, so as to avoid overtemperatures in the cabinet. One way to achieve this for at least some modes of failure is to spring-load the valve to the open configuration. In addition, the cabinet might not be totally air-tight: for example it may include cable openings 50, which may be largely blocked by means such as flexible flaps or brushes but which may be capable of allowing a limited amount of air through.

When a data hall is being established, it is conventional for the cabinets to be filled progressively with equipment as demand for capacity increases. With the present arrangement, cabinets that are not in use will not typically reach a temperature at which cooling is required, and so will not consume any cool air. Alternatively, their controllers 45 may be turned off with their air valves closed manually. In cabinets that are partially occupied, or that are running at low power, the air flow will only be such as is needed to cool the equipment as it is running.

If there are vacant zones in the data hall where no cabinets have been installed yet, blanking plates or tiles could be installed to block the supply and extract ducts, until their use is required.

The control unit 45 may have a data link 52 by which it can communicate with a control centre and or building management system. The data link can transmit to the control centre information such as the measured temperature in the cabinet, the position of the valve, whether a fault has been detected, and information from other sensors such as pressure or relative humidity sensors that may be located in the cabinet. The data link can be used to control the control unit 45 remotely, for example to change its control program or the temperature limits that it employs. Figure 3 is a partial schematic plan view of a data hall to illustrate how the conditioned air can be supplied and the warm air extracted from the cabinets. Example cabinets in a data hall 59 are shown at 20. In this example, the cabinets are to be located in rows running parallel with the axis A-A'. An air handling unit (AHU) or mulitiple AHUs 63 generate(s) conditioned air for circulation within the cabinets. This may be done by drawing in outside air and filtering and/or drying and/or chilling/heating it as required. The AHU also processes extracted warm air by re-circulating it, using it in the drying process or emitting it to the atmosphere. The AHU provides the conditioned air at an outlet 65. Air from the outlet 65 first passes into a cross-passage or central plenum 62 which runs generally parallel to the axis A- A'. The conditioned air divides and flows towards the outer ends of the cross- passage 62. The ends of the cross-passage communicate with longitudinal passages or A & B plenums 61 providing dual redundancy, which run generally perpendicular to the axis A-A' and parallel with the axis B-B'. The conditioned air from the cross-passage enters the longitudinal passages and runs along the length of the data hall 59. At points along the length of the longitudinal passages 61 air is tapped off to pass along row supply ducts 36 which correspond to the main supply ducts 36 shown in figure 2. The row supply ducts run generally parallel with the axis A-A' and extend between the longitudinal passages 61. Air is tapped off the row supply ducts to feed individual cabinets, as illustrated in more detail in figure 2. Each row supply duct may feed air to the cabinets in only a single row, in which case it preferably runs under or adjacent to that row of cabinets. Alternatively it may supply multiple rows of cabinets. The row supply ducts 36 preferably run under the floor of the data hall, as shown in figure 2. These ducts can be of various shapes and sizes and positions. Warm air from the cabinets passes through ducts (which for clarity are not shown in figure 3) up to the ceiling of the data hall in to a main return plenum 66.

In a practical installation, a considerable flow rate of air might be required along the cross-passage 62 and down the longitudinal passages 61. For this reason, it is advantageous not to form those passages from conventional ductwork material, but instead to embed them between walls of the data hall. In the example shown in figure 4, the data hall is bounded by external walls 64. The data hall 59 is divided from the external walls 64 by partition walls 67 and 60. The cross-passage 62 and the longitudinal passages 61 are defined between the external walls 64 and the partition walls 67 and 60. In this way, substantially sealed floor-to-ceiling volumes can be provided for air flow along those passages. This allows passages of large dimensions to be provided in an especially efficient way. The partition walls 60 and 67 may be made of any suitable partitioning material, but materials such as white- walling, plasterboard, blockwork and brickwork are preferred since they are quick to construct and have good thermal insulating properties which limit the passage of heat between the conditioned air passages and the main volume of the data hall 59. Materials such as white-wall, which are faced with a sheet metal skin, allow air to flow freely across their face, which reduces the resistance through the system.

The double arrows in figures 3 and 4 illustrate the direction of air flow.

The so-called warm air could be at any suitable temperature for the circumstances of the installation. It is envisaged that in the most typical installations, temperatures of 15 to 45°C might be appropriate, but higher or lower temperatures could be chosen.

It could be advantageous to increase the velocity of the air to the final cabinet, or to maintain a constant velocity along the length of the passage, and for this reason, the longitudinal passages may be tapered to take account of the fact that air is progressively tapped off along their lengths. Preferably this is done by means of a sloping ceiling in the longitudinal passages. Figure 4 shows a cut-away view of one of the longitudinal passages. The passage 61 is defined between the walls 61 and 64, the floor 70 of the building and the sloping ceiling 71 which is suspended below the actual ceiling 72 of the building. Outlets 73 to the row supply ducts 36 are set into the partition wall 60 at a level below the floor level 74 of the suspended floor 27 of the data hall. The ceiling 71 is configured so that the height of the longitudinal passage progressively diminishes as the distance from the cross-passage 62 increases and the air flow falls due to the tapping of air through the openings 73. Alternatively, or in addition, the floor of the longitudinal passages could slope, or the walls 61 could be angled relative to the walls 64 so that the longitudinal passage tapers in the vertical and/or horizontal plane to similar effect.

The outlets 73 are built so as to seal the row supply ducts to the longitudinal ducts, preventing air from escaping into the sub-floor space of the data hall, these connections also may have balancing/MSFD dampers and can be of varying size and shape depending on location and density of cabinet.

The AHU contains fans which pump the conditioned air through the system. As the amount of air flowing through the cabinets changes the demand for air flow will change accordingly. Preferably, the ducting and plenums include one or more pressure sensors 80 (see figure 3) which sense the pressure in the ductwork and plenums. A fan controller 81 in the AHU receives pressure data from the pressure sensors and controls the fans 82 so as to maintain the required pressure within preset bounds.

Instead of the cabinets being fed from below the cabinets, the ducts for supplying conditioned air could run parallel to the rows of cabinets but between rows of cabinets. One or two such ducts could run in a "supply" aisle, and conditioned air could be piped from that duct or each of those ducts to adjacent rows of cabinets. Alternate aisles could be empty of conditioned air supply ducts.

The cabinets could be purpose-built computer cabinets, such as standard-sized data racks, or could be other forms of enclosure, such as cupboards or spaces defined by partition walls. Preferably, each cabinet has walls that are sufficiently impermeable that it defines a zone within it that is at least partially thermally isolated, and most preferably substantially thermally isolated, from the surrounding environment. Conveniently, the cabinets may contain equipment such as computer equipment.

As indicated above, each cabinet may be equipped with inlet ports, outlet ports, valves, dampers (including iris dampers), ducts, plugs and openings. Where any such apparatus is provided, there may be one or more for each cabinet. The conditioned air generated by the AHU may be drawn from outside the building. Alternatively or in addition it could be derived from recirculating air extracted from the cabinets. The incoming air could be conditioned by the AHU by one or more of the steps of filtering, cooling, heating, drying and humidifying it before it is passed out towards the servers. Typically, the air will be dried by the AHU to a pre-set humidity and heated or chilled as required to a pre-set temperature. If the external air is of satisfactory temperature and humidity then it could be circulated by the AHU without further processing.

Air could be fed to a system as shown in figure 2 by ductwork and plenums different from that of figure 3. For example, air from outside or from a chiller unit could pass to a simple manifold and/or central plenum from which the main supply ducts 36 branch off. Individual AHUs or simple chillers could be provided for sub-units of the data hall, for example for individual rows. This is useful if there is an especially high density of load in a particular place. The supply ducting of each row could be equipped with a fan for pushing air through the system.

The AHUs could conveniently have their outlets in line with the side passages 61 . This reduces air resistance in the system. The cross-passage 62 could be equipped with one or more dampers which allow it to be closed during normal operation and opened if, for example, one of the AHUs fails.

The invention has been described above by way of example with reference to a data centre. The invention could be applied to other spaces that require temperature regulation. Examples include storage spaces for perishable goods and repositories for pharmaceutical or process engineering equipment. The invention is especially advantageous when applied to spaces storing temperature-sensitive equipment that emits a substantial amount of heat.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. A repository comprising:

a first passage for supplying conditioned air;

a second passage for withdrawing relatively warm air; and

a cabinet having walls defining an interior volume which is substantially sealed except for an inlet port and an outlet port passing through the walls, the inlet port being connected to the first passage and the outlet port being connected to the second passage.

2. A repository as claimed in claim 1 , comprising a valve which is set at one of the inlet and outlet ports, the valve being adjustable to vary its resistance to air flow through the said one of the ports.

3. An equipment repository as claimed in claim 2, wherein the valve is manually adjustable.

4. An equipment repository as claimed in any preceding claim, wherein the valve is automatically adjustable and the repository comprises:

a temperature sensor for sensing temperature in the cabinet; and

a controller configured to control the valve in dependence on the sensed temperature so as to cause the valve to open with increasing temperature.

5. A repository as claimed in claim 4, wherein the controller and the sensor are located in the cabinet.

6. A repository as claimed in claim 4 or 5, wherein the sensor is external to any equipment located in the cabinet.

7. A repository as claimed in any of claims 2 to 6, wherein the valve is an iris damper.

8. A repository as claimed in any of claims 2 to 7, wherein the valve is located at the inlet port.

9. A repository as claimed in any preceding claim, wherein the outlet port is substantially unobstructed by any valving.

10. A repository as claimed in any preceding claim, wherein the cabinet is a rack- mount cabinet.

1 1. A repository as claimed in any preceding claim, comprising one or more servers located in the cabinet.

12. A repository as claimed in any preceding claim, wherein the inlet is located lower than the outlet.

13. A repository as claimed in claim 12, wherein the inlet is located at the base of the cabinet.

14. A repository as claimed in any preceding claim, wherein the cabinet stands on a floor and the first duct extends under the floor.

15. A repository as claimed in any preceding claim, comprising an air handling unit coupled to the first duct for supplying the conditioned air.

16. A repository as claimed in claim 2, comprising two such cabinets, the valves of the cabinets being independently controllable.

17. A repository as claimed in claim 1 , comprising a set of orifice plugs, each orifice plug being sized to fixably obstruct one of the inlet and outlet ports, and each plug of the set having an orifice therethrough, each orifice plug of the set having an orifice of a different size from the others of the set.

18. A repository comprising:

a set of first upright walls bounding an internal space;

a hall located in the internal space and comprising a plurality of cabinets, the hall being bounded on at least one side by an upright partition wall;

a source of conditioned air;

a series of ducts coupled via an air supply path to the source and running through the hall for supplying the conditioned air to the cabinets; and

at least one plenum located in the air supply path between the source and the series of ducts, the plenum being bounded on one side by one of the set of first walls and on the other side by the partition wall.

19. A repository as claimed in claim 18, wherein each duct branches from the plenum, and the points at which the ducts branch from the plenum are spaced apart along a first horizontal axis.

20. A repository as claimed in claim 19, wherein the plenum extends along the first axis.

21. A repository as claimed in claim 19 or 20 wherein the plenum diminishes in cross-section with increasing distance from the source.

22. A repository as claimed in claim 21 , wherein the top of the plenum is bounded by a ceiling and the ceiling is lower with increasing distance from the source.

23. A repository as claimed in claim 22, wherein the ceiling is a suspended ceiling.

24. A repository as claimed in any of claims 19 to 23, wherein the ducts extend substantially perpendicular to the first axis.

25. A repository as claimed in any of claims 18 to 24, comprising a second plenum located in the air supply path between the source and the series of ducts, the second plenum being bounded on one side by another of the set of first walls and on the other side by a second partition wall that bounds the hall.

26. A repository as claimed in claim 25, wherein the first and second plenums are in parallel in the air supply path.

27. A repository as claimed in claim 26, wherein the first and second plenums are redundantly in parallel in the air supply path.

28. A repository as claimed in any of claims 18 to 27, wherein the or each plenum is composed of metal-faced walling material.

29. A repository as claimed in any preceding claim, wherein the repository is an equipment repository and each cabinet is an equipment cabinet.

30. A repository as claimed in claim 29, wherein the repository is a computer equipment repository and each cabinet is a computer equipment cabinet.