WO2009156649A1

WO2009156649A1 - Computer bay comprising an adaptive cooling device

Info

Publication number: WO2009156649A1
Application number: PCT/FR2009/051000
Authority: WO
Inventors: Audrey Julien-Roux; Lionel Coutancier; Thierry Fromont
Original assignee: Bull Sas
Priority date: 2008-06-02
Filing date: 2009-05-28
Publication date: 2009-12-30
Also published as: FR2931962B1; FR2931962A1

Abstract

The invention relates to a computer bay (10) that comprises an adaptive cooling device (20) including a means (22, 24) for cooling the air that has flowed over electric power components (18₁,..., 18_i,..., 18_n) arranged inside said computer bay (10), and a regulator (36, 38, 44, 46, 50, 52, 54, 56) for said air cooling means. The air cooling means (22, 24) are located at an interface between the inner space and the outside of the computer bay, and include a ventilation system (24) as well as an air/water heat exchanger (22) connected to a cold water supply (30) and to a hot water discharge (34). The regulator (36, 38, 44, 46, 50, 52, 54, 56) is furthermore adapted for adjusting the ventilation system (24) on the basis of a measured pressure (P1), and for adjusting the cold water supply (30) and/or the hot water discharge (34) of the air/water heat exchanger (22) on the basis of a temperature (Ts) measured at the outlet of the air cooling means (22, 24).

Description

COMPUTER BAY HAVING AN ADAPTIVE COOLING DEVICE

The present invention relates to a computer rack having an adaptive cooling device.

A computer bay is a physical structure in which are disposed computer equipment (computers, storage devices, etc.), generally identified by their vertical positioning in the bay. A standard U-unit has thus been defined by the EIA-310-D standard to define this identification universally: 1 U = 44.45 mm.

The computer equipment of a rack includes electrical power components whose operation generates heat dissipation that must be evacuated. Although the emergence of CMOS technologies has made it possible to reduce the dissipated power of the components and to increase their integration capacity on the same chip, the applications require at the same time ever more computing power (database management, decision-making applications , intensive computing, Internet access, etc.).

Thus, symmetric multiprocessor architecture (SMP) architecture design techniques and computer cluster clustering techniques make it possible to meet this need for power. It is then possible to design HPC type computers (high performance computing), which can integrate up to ten thousand elementary processors at very high clock rates, divided into a large number of computing servers arranged in several bays, themselves installed and interconnected in a closed and air-conditioned computer room in which we always try to incorporate a maximum of servers in three dimensions. The goal is to reach a maximum of Giga Flops per m ² and / or the maximum of Internet connections per m ² . At the same time, the use of increasingly fine technologies for the production of transistors and the high frequency travel have led to the increase of the leakage currents of the transistors and to an explosion of power dissipated by each processor. can reach today 185 Watts. For example, filling a computer room necessarily comes up against the first limit among the following three: its volume capacity, its power supply capacity and its ability to evacuate the calories generated.

With regard to this last capacity of the room, a cooling solution is based on the fact that the computer equipment arranged in the bay are self ventilated and cooled as well, thanks to the air conditioning of the computer room. The cooling circuit is thus the following: the fresh air supplied by the air conditioning of the room enters the bay via a front door having a certain percentage of opening, heats up while passing through the computer equipment and is rejected by the bay via a back door into the room with a higher outlet temperature, sometimes several tens of degrees depending on the devices. Since each piece of computer equipment can only operate in an input air temperature range, the air conditioning in the room must regulate the ambient temperature sufficiently to remain in that range.

The evacuation of the calories generated by the computer equipment using only an air conditioning of the computer room however poses significant cost problems: costs related to the electrical consumption of the air conditioning system, but also those related to its installation and to its maintenance. It also raises problems of cooling efficiency. Indeed, the heat transfer capacity of the air, compared to that of water, is not very high and the air conditioning system will also have to take care of the lack of homogeneity of the ambient temperature of the room if the equipment is mixed.

Another cooling solution is to reduce the thermal problem to the bay space, that is to say to provide cooling means in the computer bay itself. These cooling means advantageously comprise an air / water heat exchanger. Since the heat-carrying power of water is four thousand times greater than that of air, the efficiency of such cooling is much greater. Power consumption and cooling costs are therefore reduced. In addition, the location of the cooling to the space of the bay improves the thermal transparency thereof in the computer room and at least partially solves the problems of homogeneity due to the mix of equipment.

In this solution, the cooling circuit is thus the following: fresh air, provided by the air conditioning of the room and / or by the cooling means of the bay, heats up while passing through the computer equipment and is cooled by the air / water heat exchanger installed in the bay, the latter allowing transfer the calories from the air to the water of the exchanger which is fed back into a hydraulic circuit of the room and is cooled at the level of cold groups.

Such a device is for example described in the document published under the number US 2006/0232945. In this document, the computer bay cooling means comprise an air / water heat exchanger integrated into the thickness of a rear door of this computer bay. Air circulation is provided by the self-ventilation of the computer equipment bay, the air / water heat exchanger with a low pressure drop in terms of this air flow. The rear door therefore remains relatively transparent in terms of pressure drop for self ventilated computer equipment.

Cold water arrives at a certain temperature in the heat exchanger, but no regulation or control is ensured on the air temperature at the input and / or output of the computer bay to verify the proper operation of the computer equipment integrated into the bay. The back door only partially cools the air that passes through it. Thus, the temperature of the air leaving the bay is much lower than that of air after passing through the computer equipment but it remains variable depending on the thermal load of the bay. There is therefore an impact on the temperature of the room and the bay is not thermally transparent. Therefore, this mode of cooling just allows to treat a local thermal overload in the computer room, but requires an air conditioning of the room almost as effective as in the case of a room cooled only in the air. So there is no reduction in electricity consumption for air conditioning and therefore no real cost reduction. To improve the efficiency of the cooling means, the heat exchanger air / water may be associated with a ventilation system, also disposed in the rear door for example or elsewhere in the computer bay, whose function is to attract the air circulating through the computer equipment to the outside of the bay or in an internal fresh air supply circuit. Such a device is for example described in the document published under number US 6,819,563 or in the document published under number US 2004/0100770.

However, in this case, the computer bay is no longer transparent in terms of pressure drop for the self-ventilated computer equipment that it contains and the clean ventilation of the cooling device of the bay is likely to negatively impact the ability of self-ventilating computer equipment to self-cool.

More specifically, when the fans are integrated in the rear door, if they have a higher flow than the fans of the self-ventilated computer equipment, this does not have a negative impact on the hardware: the rear area of the computer bay is then in depression and therefore the fans of the equipment integrated into the bay have an improved operating point and their pressure drop is reduced. On the other hand, when the flow rate of the fans of the rear door is lower than that of the fans of the self-ventilated computer equipment, an overpressure zone is created between the equipment and the rear door, which increases the pressure drop of the fans of the equipment. and lowers their operating point: they then have a lower flow so that the equipment is less well ventilated and does not work optimally.

One solution is to set the speed of the ventilation system of the computer rack to a value far greater than the sum of the maximum values of the flow rates of the ventilators of the self ventilated equipment. The rear area of the computer bay is still in depression and the equipment works optimally.

However, the flow rate of the ventilation system is not optimized with respect to the actual operation of equipment whose thermal curve varies with time and applications. It is set at a value far in excess of what is needed most of the time, which results in unnecessary electrical consumption and a source of energy waste.

In fact, it appears that the best solution is to have efficient and adaptive cooling means, solicited in a fair enough way without energy waste.

The invention therefore applies more particularly to a computer bay whose adaptive cooling device comprises air cooling means having circulated on electrical power components disposed within the computer bay and a regulator of these means air cooling.

Such adaptive cooling devices are known. In general, these devices include an air / water heat exchanger and a ventilation system integrated into the rear door. They also include a temperature sensor disposed upstream of the computer equipment in the direction of air flow. This temperature sensor is used to verify that the computer bay is working always within a set temperature range of the equipment it contains.

Thus, if the measured temperature is greater than a predetermined maximum set point temperature, the regulator acts to solve this problem by starting with regular cold water supply of the air / water heat exchanger. In a second step, if despite a maximum flow rate of the cold water supply of the air / water heat exchanger the predetermined maximum set temperature is still exceeded, the regulator acts to solve this problem by increasing the flow rate of the system ventilation. The regulator first acts on the air / water heat exchanger because it is the most efficient cooling system. But if the regulation of the air / water heat exchanger is sufficient to pass under the predetermined maximum set temperature, then the ventilation system will not be regulated and will operate at minimum flow. It can therefore again be in a situation of overpressure (between the equipment and the rear door) if the air flow of the ventilation system of the computer bay is less than the sum of the fan flows of the self ventilated equipment. This solution is not totally satisfactory.

It may be desired to provide an adaptive computer bay cooling device that allows to overcome at least some of the aforementioned problems and constraints.

The invention therefore relates to a computer bay adapted to receive electrical power components heat sink and further comprising an adaptive cooling device comprising air cooling means having circulated on electrical power components arranged at the interior of this computer bay and a regulator of these air cooling means, characterized in that:

the air cooling means are located at an interface between the interior space and the outside of the computer bay and comprise, on the one hand, a ventilation system and, on the other hand, an air heat exchanger. / water connected to a cold water supply and a hot water outlet, and

- the regulator is designed to regulate the ventilation system according to a measured pressure and to regulate the cold water supply and / or hot water discharge of the air / water heat exchanger according to a temperature measured at the outlet of the air cooling means. Thus, the combination of an adjustable ventilation system according to a measured pressure and an air / water heat exchanger adjustable according to a measured temperature makes it possible to obtain a complete transparency of the computer bay in the environment in which it is placed, both in temperature and in terms of pressure drop.

Optionally, the regulator comprises means for measuring a pressure in a predetermined cooling zone in which the air circulates, this zone being situated upstream of the air cooling means and downstream of the electrical power components in the direction of air circulation. It is indeed in this cooling zone that an overpressure problem is likely to generate an increase in the pressure drop.

Also optionally, the regulator comprises means for measuring another pressure in an area located downstream of the air cooling means in the direction of air flow and is designed to regulate the cooling means of the air. air based on the result of a comparison between the measured pressures.

This other pressure is for example the atmospheric pressure in the computer room, since the air cooling means are located at the interface between the interior space of the computer bay and the outside of this computer bay.

Optionally also, the regulator comprises a multi-way valve arranged in a cutoff between the air / water heat exchanger, on the one hand, and the cold water supply and the hot water discharge, on the other hand part, and electrical control means of this valve. Also optionally, the regulator comprises a plurality of temperature sensors disposed at the outlet of the air cooling means.

Also optionally, the regulator further comprises at least one temperature sensor disposed upstream of the electrical power components in the direction of air flow. Optionally also, the regulator is designed to:

- Send a set point for reducing the flow rate of the ventilation system when a comparison between the pressure or a pressure difference measured with a first predetermined reference value indicates that a limit depression is reached, and - Send an instruction to increase the flow rate of the ventilation system when a comparison between the pressure or a pressure difference measured with a second predetermined reference value (P-Sup) indicates that a limit overpressure is reached. Also optionally, the controller is adapted to trigger an alarm when a comparison of the measured pressure or pressure difference with a third predetermined reference value indicates that an abnormal depression is reached or when a comparison between the pressure or a measured pressure difference with a fourth predetermined reference value indicates that abnormal overpressure is reached.

Optionally also, the regulator is designed to:

- Send a cold water supply rate reduction instruction when a comparison between the temperature or a measured temperature difference with a first predetermined reference value indicates that a lowering temperature limit is reached, and

- Send an instruction to increase the flow rate of cold water supply when a comparison between the temperature or a measured temperature difference with a second predetermined reference value indicates that a rise in temperature limit is reached. Also optionally, the controller is designed to trigger an alarm when a comparison between the temperature or a measured temperature difference with a third predetermined reference value indicates that an abnormal temperature drop is reached or when a comparison between the temperature or a temperature difference measured with a fourth predetermined reference value indicates that an abnormal rise in temperature is reached.

The invention will be better understood from the following description, given solely by way of example and with reference to the accompanying drawings, in which: FIG. 1 schematically represents a side view of a computer bay; according to an embodiment of the invention, in which a part of the elements is represented outside the bay for the sake of clarity, FIG. 2 graphically illustrates a temporal variation of pressure values measured and used by a controller of the computer array of FIG. 1, and

FIG. 3 graphically illustrates a temporal variation of temperature values measured and used by the controller of the computer array of FIG. 1.

The computer rack 10 shown in Figure 1 comprises a front face 12 and a rear face 14. The front face 12 comprises for example a front door (not shown) having a certain percentage of opening. The rear face 14 has a discharge zone 16, towards the outside of the computer rack 10, a quantity of air circulated through computerized equipment self ventilated 18 ₁₃ ..., 18 ,, ... , 18 _n arranged vertically inside the rack 10 and located in position according to the standard unit U. The self ventilated computer equipment 18 ₁₅ ..., 18 ,, ..., 18 _n comprise electrical power components consumers of electrical energy and heat emitters, so that the air heats up through them.

The computer rack 10 comprises support means (not shown) on the floor of a computer room comprising slabs in false floor.

It further comprises an adaptive cooling device positioned against its rear face 14. This cooling device 20 may be independent of the bay 10, or even include its own ground support means, or conversely be an integral part of this computer rack 10. It comprises means 22, 24 for cooling air. These cooling means can be integrated in a rear door of the computer rack 10 which can be closed, in current use, or opened, for maintenance. The cooling means 22, 24 are positioned against the air evacuation zone 16 so that the entire amount of air passing through this exhaust zone 16 is caused to be cooled by them. The cooling circuit of the air is therefore the following, marked by the arrows A: the fresh air of the room enters the computer bay 10 via the front face 12, warms up by passing through the computer equipment self ventilated 18i, ..., 18 ,, ..., 18 _n , passes through a wiring space 26 located between the back of the computer equipment 18 ₁₃ ..., 18 ,, ..., 18 _n and the zone discharge 16, and is rejected out of the bay 10 via the cooling device 20 into the room with an outlet temperature to be equal to the inlet temperature in the bay 10, which makes the latter thermally transparent. The saving in air conditioning of the computer room is therefore very sensitive.

Note that the cabling space 26 can also extend to volumes left free by equipment not present in the computer rack. The means 22, 24 for cooling the air provided in the cooling device 20 comprise, for example, an air / water heat exchanger 22 and a ventilation system 24 comprising a plurality of fans distributed in relation to the zone d. evacuation 16 to attract the amount of air circulated on the electrical power components of the computer rack 10 to the outside thereof.

For the proper functioning of these air cooling means, the cooling device 20 further comprises first means 28 for connecting the air / water heat exchanger 22 to an external supply 30 in cold water and second means 32 connecting the air / water heat exchanger 22 to an external discharge 34 of hot water having circulated in this exchanger. The external power supply 30 and the external discharge 34 are connected to the floor of the computer room.

In the cooling device 20, between the air / water heat exchanger 22, on the one hand, and the cold water supply 30 and the hot water outlet 34, on the other hand, a motorized valve 36 is interposed in cut. This multi-lane motorized valve, for example three-way, is used for the regulation of the cold water supply and / or the hot water discharge and therefore for the regulation of the air / water heat exchanger 22.

A pressure sensor 38 is also provided in the computer bay 10. For the sake of clarity, it is shown outside the bay in Figure 1, but it may in fact be disposed within the cooling device 20 .

It is designed and mounted to measure, with the aid of a first pipe, a first pressure P1 in a predetermined cooling zone in which the air circulates, this zone being situated upstream of the cooling means 22, 24. air and downstream electrical power components of computer equipment 18i, ..., 18 ,, ..., 18 _n in the direction of air flow. This zone corresponds in fact to the wiring space 26. For a reliable measurement of this pressure P1, but also to ensure that all the air in this cooling zone is the one that has passed through the computer equipment 18i , ..., 18 ,, ..., 18 _n , this zone 26 is sealed. This sealing is for example ensured by:

- a bay 40 bottom not letting the air outside the computer room,

modules 42 for caulking zones left free by the absence of computer equipment in bay 10,

at the locations of cable and pipe passages, conventional brush-sealing devices (not shown).

The pressure sensor 38 is also designed and mounted to measure, with the aid of a second pipe, a second pressure P2 in an area located downstream of the air cooling means 22, 24 in the direction of circulation of the 'air. In the embodiment illustrated in FIG. 1, this zone is the space outside the bay

10. The pressure P2 is the pressure of the computer room.

Temperature sensors 44 are also provided on the computer rack 10, disposed at the outlet of the air cooling means 22, 24. For example, it is advantageous to have four regularly spaced at the output of the ventilation system 24. They measure several temperature values which, averaged, can give an average value of outlet temperature Ts.

Optionally, at least one additional temperature sensor 46 may be arranged upstream of the electrical power components in the direction of air flow, for example on the front face 12 of the computer rack 10, to give a value of inlet temperature Te.

The motorized valve 36, the pressure sensor 38 and the temperature sensors 44, 46 are elements of a regulator, designed to regulate the air cooling means 22, 24, which further comprises a regulation module 50 by example made using a microprocessor card.

This control module 50 is shown outside the bay in FIG. 1 for the sake of clarity, but it can in fact be disposed inside the cooling device 20.

Its hardware structure will not be detailed, but it comprises, for example, an OPMA (Open Platform Management Architecture) type card connected to different interfaces, via possible analog / digital converters, for connection to the aforementioned elements of the controller, an Ethernet type connector for transmitting information to an external management server, light-emitting diodes for generating alarms, one or more autonomous power supplies, etc. The regulation module 50 comprises first means 52 for regulating the ventilation system 24 as a function of the measured pressures P1 and P2, or more exactly as a function of the pressure difference (P1-P2). In a simpler variant, these first means 52 could regulate the ventilation system only as a function of the measured pressure P1.

The regulation module 50 further comprises second means 54 for regulating the air / water heat exchanger 22 as a function of the temperatures measured using the sensors 44 and possibly 46. These second means 54 can regulate the heat exchanger. air / water heat 22 as a function of the temperature difference (Ts - Te), or only as a function of Ts.

These second means 54 are provided with means 56 for electrically controlling a motor M of the motorized valve 36.

The operation of the first regulating means 52 of the ventilation system 24 will now be detailed using the graphical representation of FIG. 2.

In one embodiment of the invention, the pressure difference (P1-P2) is calculated at each instant and is denoted by P. It is compared with predetermined values P-Min, P-lnf, P-Ref, P- Sup and P-Max.

P-Ref is for example the value of a slight depression which is considered as ideal in the wiring space 26, giving a configuration close to the flow equilibrium between the ventilators of the self ventilated equipment 18 ₁₃ ... , 18 ,, ..., 18 _n and the fans of the ventilation system 24, stable configuration, without loss of load and not affecting the proper functioning of the hardware integrated in the bay 10. P-lnf is for example the value a limiting depression below which it is considered unnecessary to consume energy in excessive ventilation. When this limiting depression P-lnf is reached, for example at a time t1, the first regulation means 52 send a flow reduction instruction of the ventilation system 24. P-Min is for example the value of an abnormal depression which reveals a malfunction of the regulator. When this abnormal depression P-Min is reached, the first regulating means 52 trigger an alarm.

P-Sup is for example the value of a limiting overpressure beyond which it is considered that the pressure drop generated is penalizing. When this P-Sup overpressure limit is reached, the first regulating means 52 send an instruction to increase the flow rate of the ventilation system 24.

P-Max is for example the value of an abnormal overpressure which reveals a malfunction of the regulator. When this abnormal P-Max overpressure is reached, the first regulation means 52 trigger an alarm.

Alternatively, in one embodiment of the invention where only the pressure P1 is measured, the predetermined values P-Min, P-1nf, P-Ref, P-Sup and P-Max are values of absolute pressures defined by example around a pressure P-Ref corresponding to a pressure slightly lower than the presumed pressure of the computer room, and it is the pressure P1 which is compared with these predetermined values.

The operation of the second means 54 for regulating the air / water heat exchanger 22 will now be detailed with the aid of the graphical representation of FIG. 3. In one embodiment of the invention, the difference in temperature ( ts

Te) is calculated at each instant and denoted T. It is compared with predetermined values T-Min, T-lnf, T-Ref, T-Sup and T-Max.

T-Ref is for example a value close to zero giving a configuration close to the thermal transparency of the computer rack 10. T-lnf is for example the value of a limit temperature drop below which it is considered that it is no need to consume excessive cooling energy. When this temperature limit drop T-lnf is reached, for example at a time t3, the second regulation means 54 send a cold water supply rate reduction instruction using the valve 36. T-Min is for example the value of an abnormal temperature drop which reveals a malfunction of the regulator. When this abnormal temperature drop T-Min is reached, the second regulation means 54 trigger an alarm.

T-Sup is for example the value of a temperature rise limit beyond which it is considered that warming of the bay 10 is penalizing. When this temperature limit increase T-Sup is reached, for example at a time t2, the second regulating means 54 send an instruction to increase the flow rate of cold water supply using the valve 36.

T-Max is for example the value of an abnormal rise in temperature which reveals a malfunction of the regulator. When this temperature rise abnormal T-Max is reached, the second regulating means 54 trigger an alarm.

Alternatively, in one embodiment of the invention where only the temperature Ts is measured, the predetermined values T-Min, T-lnf, T-Ref, T-Sup and T-Max are absolute temperature values defined by example around a temperature T-Ref corresponding to a temperature considered ideal at bay entrance 10.

It is clear that an adaptive cooling device of a computer rack 10 as described above makes it possible to achieve a thermal transparency, but also a transparency in terms of the loss of load of the computer rack 10, thanks to the measurement of at least one pressure P1.

In addition, this adaptive device optimizes energy consumption to achieve this transparency of the computer bay.

It will also be noted that the tightness of the zone in which the pressure P1 is measured makes it possible to improve the efficiency of the regulator.

Claims

Computer bay (10) adapted to receive electrical power components (18i, ..., 18 ,, ..., 18 _n ) heat sinks and further comprising an adaptive cooling device (20) comprising means (22, 24) having circulated on electric power components ( ^" I 8 ₁ , ..., 18 ,, ..., 18 _n ) arranged inside this computer rack (10) and a regulator (36, 38, 44, 46, 50, 52, 54, 56) of these air cooling means, characterized in that: - the air cooling means (22, 24) are located at an interface between the interior space and the outside of the computer bay (10) and comprise, on the one hand, a ventilation system (24) and, on the other hand, an air / water heat exchanger (22) connected to a cold water supply (30) and a hot water outlet (34), and - the regulator (36, 38, 44, 46, 50, 52, 54, 56) is adapted to regulate the heating system. ventilation (24) e n function of a measured pressure (P1) and for regulating the cold water supply (30) and / or the hot water discharge (34) of the air / water heat exchanger (22) as a function of a temperature (Ts) measured at the outlet of the air cooling means (22, 24).

2. Computer rack according to claim 1, wherein the regulator (36, 38, 44, 46, 50, 52, 54, 56) comprises means (38) for measuring a pressure (P1) in a cooling zone. (26) predetermined in which the air flows, this zone being located upstream of the means (22, 24) of air cooling and downstream of the electrical power components (18 ₁₃ ..., 18 ,, ... , 18 _n ) in the direction of air flow.

3. Computer bay according to claim 2, wherein the controller (36, 38, 44, 46, 50, 52, 54, 56) comprises means (38) for measuring another pressure (P2) in an area located downstream of the air cooling means (22, 24) in the direction of air flow and is adapted to regulate the air cooling means (22, 24) according to the result of a comparison between the air cooling means measured pressures (P1, P2).

Computer rack according to any one of claims 1 to 3, wherein the regulator (36, 38, 44, 46, 50, 52, 54, 56) comprises a multi-way valve (36) arranged in a cut-off between air / water heat exchanger (22), of a on the one hand, and the cold water supply (30) and the hot water outlet (34), on the other hand, and the electrical control means (54, 56) for this valve (36).

Computer rack according to any one of claims 1 to 4, wherein the controller (36, 38, 44, 46, 50, 52, 54, 56) comprises a plurality of temperature sensors (44) arranged at the output of means (20) for cooling air.

6. Computer rack according to claim 5, wherein the regulator (36, 38, 44, 46, 50, 52, 54, 56) further comprises at least one temperature sensor (46) arranged upstream of the electrical power components. (18 ₁₃ ..., 18 ,, ..., 18 _n ) in the direction of air flow.

Computer rack according to any one of claims 1 to 6, wherein the regulator (36, 38, 44, 46, 50, 52, 54, 56) is designed to:

- send a flow rate reduction instruction of the ventilation system (24) when a comparison between the pressure or a measured pressure difference (P1, P2) with a first predetermined reference value (P-lnf) indicates that a negative pressure limit is reached, and

- send a setpoint for increasing the flow rate of the ventilation system (24) when a comparison between the pressure or a measured pressure difference (P1, P2) with a second predetermined reference value (P-Sup) indicates that a Overpressure limit is reached.

A computer bay according to any one of claims 1 to 7, wherein the controller (36, 38, 44, 46, 50, 52, 54, 56) is adapted to trigger an alarm when a comparison between the pressure or a measured pressure difference (P1, P2) with a third predetermined reference value (P-Min) indicates that an abnormal depression is reached or when a comparison between the pressure or a measured pressure difference (P1, P2) with a fourth predetermined reference value (P-Max) indicates that abnormal overpressure is reached.

Computer rack according to any one of claims 1 to 8, wherein the controller (36, 38, 44, 46, 50, 52, 54, 56) is designed for:

- send a cold water supply flow reduction instruction when a comparison between the temperature or a measured temperature difference (Ts, Te) with a first value of predetermined reference (T-lnf) indicates that a limit temperature drop is reached, and

- send an instruction to increase the flow rate of cold water supply when a comparison between the temperature or a measured temperature difference (Ts, Te) with a second predetermined reference value (T-Sup) indicates that a rise limit temperature is reached.

A computer bay as claimed in any one of claims 1 to 9, wherein the controller (36, 38, 44, 46, 50, 52, 54, 56) is adapted to trigger an alarm when a comparison between temperature or a measured temperature difference (Ts, Te) with a third predetermined reference value (T-Min) indicates that an abnormal temperature drop is reached or when a comparison between the temperature or a measured temperature difference (Ts, Te ) with a fourth predetermined reference value (T-Max) indicates that an abnormal rise in temperature is reached.