WO2011141503A1

WO2011141503A1 - Device for cooling and computer racks

Info

Publication number: WO2011141503A1
Application number: PCT/EP2011/057598
Authority: WO
Inventors: Holger Sedlak; Oliver Kniffler
Original assignee: Efficient Energy Gmbh
Priority date: 2010-05-12
Filing date: 2011-05-11
Publication date: 2011-11-17
Also published as: DE102010028950B4; DE102010028950A1

Abstract

A device for cooling an object to be cooled, such as a computer in a computer rack of a computing center, includes a pump (12) for moving a cooling liquid in a cooling section and a negative pressure generator (14) configured to generate, in the cooling section, a pressure which is less than the atmospheric pressure. The device furthermore comprises an evaporator of a heat pump, wherein the pressure in the cooling section is at least partially influenced by a negative pressure in the evaporator, wherein the evaporator can be associated with a compressor adapted to compress and transport evaporated liquid to a liquefier. In addition, a pressure detector (16) may further be disposed in a cooling circuit to take an alarm measure upon a pressure rise. Due to the negative pressure, a leak does not result in the working liquid leaking out, so that water can be used as the working liquid.

Description

Device for Cooling and Computer Racks

Description

The present invention relates to the cooling of objects to be cooled, and in particular to cooling electronic components such as are found, for example, in computers which are disposed in computer racks.

In computing centers, but also in other fields of application, objects to be cooled such as computers are cooled by fans. However, if the cooling performance provided by fans is insufficient, or if mounting fans is unacceptable for reasons of noise generation or for other reasons, liquid cooling systems are also employed.

Based on its properties as a coolant, water would be favorable as a cooling liquid. Water has the further advantage of being easy to control, available at low cost and, moreover, harmless to the environment. One substantial disadvantage of using water as a cooling liquid for cooling objects and, in particular, objects that are sensitive to water, such as electronic components which are shorted by water, is the problems occurring if the cooling system becomes leaky. In that case, water leaks out, typically at high pressure, because a high pressure is maintained in the cooling circuits. The leaking water then runs uncontrolled over the object to be cooled and will, if that object is electronic components and in particular computers, result in short circuits and ultimately in a system breakdown. For that reason, water is avoided in liquid cooling systems of computing centers or, generally speaking, of computers in computer racks. Alternatively, liquids containing CFC are used. While they do not have as good a cooling effect as water, there is no risk of system breakdown if CFC liquids leak out. That is because they evaporate as soon as they leak out, and there is no risk of a short circuit. However, if evaporation occurs too strongly, there may be problems involving a fire alarm, so that a sprinkler system is turned on in the computing center, which again is unfavorable in the case of a false alarm, i.e. if there is no fire, but only a leaky cooling system. Evaporation of CFC liquids as they leak out of the cooling system occurs because the CFC liquids in the cooling system are kept at a high pressure, which in terms of the boiling temperature is chosen such that no evaporation occurs even at the temperatures to be expected during cooling. However, if the coolant leaks from the highly pressurized line and thus enters the atmosphere, which is at a lower pressure compared to the coolant, evaporation occurs due to the low pressure and the temperature of the cooling liquid, the evaporation ensuring, however, that there are no short circuits on sensitive electronic circuits. Besides the fact that piping for such cooling systems under high pressure is expensive and elaborate, the environmental problems occurring in case of a leak are also particularly substantial.

The object of the present invention is to provide an efficient and secure cooling concept.

This object is achieved by a device for cooling according to claim 1, a computer rack according to claim 10, or a method for cooling according to claim 13.

In contrast to the prior art, in which the cooling circuit was run at high pressure, the present invention uses a low pressure, which is so low that it is below the atmospheric pressure in which the object to be cooled is disposed. Using the example of a computer rack in which computers are disposed which are in the normal atmosphere, the pressure in the cooling system is less than the atmospheric pressure. Thus, the cooling system is run at negative pressure, which is generated by a negative pressure generator such as an evacuating means. The coolant under less pressure than the atmosphere, which coolant is preferably water, is moved past the object to be cooled by a pump in the cooling circuit.

If a leak occurs in the inventive cooling system, no coolant will leak out at least initially, but instead air from the atmosphere will enter the cooling system. Thus, a leak in the cooling system cannot damage the object to be cooled, but only the cooling effect will be reduced, because air in the coolant line cools less than the coolant. When the negative pressure ceases, i.e. when the pressure in the coolant line rises, a detector, which is preferably provided, will detect this pressure rise and initiate an alarm measure, such as a notification by optical or acoustic signals, or activating an emergency cooling circuit, or reducing the power dissipation of the computer system, such as by reducing the clock frequency of the computers or, in the extreme case, shutting down completely a computer to be cooled and/or the computers to be cooled which are disposed in a computer rack.

Preferably, the pressure in the cooling system is kept at 0.8 times the atmospheric pressure or at a pressure less than 0.8 times the atmospheric pressure in which the object to be cooled is disposed. More preferably, the pressure is even lowered to 0.5 times the atmospheric pressure or to even lower pressures, which are, however, so great that there is no evaporation in the cooling circuit just because of the heat of the object to be cooled. In that respect, as a security measure, the negative pressure in the cooling circuit should be at least 10% higher than the "critical pressure" at which the coolant in the cooling circuit would evaporate during operation. Preferred embodiments of the present invention will be discussed in detail below with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic diagram of a device for cooling according to one embodiment of the present invention;

Fig. 2 shows a preferred embodiment of the present invention with direct coupling to an evaporator of a heat pump; and

Fig. 3 shows a more detailed illustration of an evaporator of a heat pump.

Fig. 1 shows a device for cooling an object 10 to be cooled in an atmosphere having an atmospheric pressure. Typically, the object 10 to be cooled will be in the normal atmosphere having the normal atmospheric pressure, although the inventive cooling device may also be employed in other atmospheres having other atmospheric pressures. The device for cooling includes a pump 12 for moving a cooling liquid in a cooling section 14, which extends on or in or under the object 10 to be cooled, for example in a serpentine or other manner, as indicated schematically in Fig. 1. The object to be cooled may, for example, be a device with electronic components. That device is, for example, a computer in a computer rack in a computing center, where a great amount of power loss occurs, which has to be dissipated.

The inventive system further includes a negative pressure generator 14 which is configured to generate a pressure in the cooling section which is less than the atmospheric pressure. Preferably, for example, the pressure is less than 0.8 times and/or, even more preferably, less than 0.5 times the atmospheric pressure in which the object 10 to be cooled is disposed. In a preferred embodiment, the cooling circuit further includes a pressure detector 16 which is configured to detect, in some known manner, a pressure rise that would occur if the cooling section 14 had a leak. For example, the pressure detector 16 is configured to monitor whether an actual pressure in the cooling section deviates from a target pressure in the cooling section and/or cooling circuit, the target pressure being less than the atmospheric pressure and it further being monitored whether the actual pressure deviates from the target pressure by more than a threshold. Alternatively or additionally, the pressure detector may also monitor whether a pressure rise in the cooling circuit occurs faster than a permissible pressure rise.

The pressure detector 16 is further configured to have an alarm generator, the alarm generator being configured to take an alarm measure such as outputting an optical or acoustic signal as indicated at 18a. An alternative alarm measure is to influence the object to be cooled via a line 18b, the influencing consisting in controlling the object so that less heat is generated. In the case of a computing center, the influencing of a computer might consist in decreasing the clock frequency to reduce the power loss, or even shutting down the computer system completely.

An alternative alarm measure might be to activate a backup cooling system such as a liquid cooling system with its own cooling circuit or a fan cooling system, or a combination of all of these measures.

In a preferred embodiment, the inventive cooling circuit system includes a heat sink 20 which is configured to extract heat from the hot cooling liquid, i.e. the cooling liquid carrying heat from the object to be cooled, in order to turn the hot cooling liquid back to a cold cooling liquid, it being noted that the expressions "hot" and "cold" are to be understood relative to one another, i.e., that "cold" means colder than hot and "hot" means hotter than cold.

As will be discussed later, the pump 12, the negative pressure generator 14 and the heat sink 20 may be implemented in a single component or in two different components, depending on the particular implementation. Thus, the heat sink 20 and the negative pressure generator 14 may collectively be implemented as an evaporator of a heat pump, as schematically indicated in Fig. 2, with Fig. 3 further showing a more detailed illustration of a preferred embodiment of such an evaporator or the connection of the cooling section or cooling circuit to that evaporator.

It should be noted that the object 10 to be cooled is preferably configured as a computer in a computer rack. The computer rack in this embodiment includes one or more computers which are mounted in the rack and which are disposed in an atmosphere having an atmospheric pressure. Further, the computer rack includes a pipe section, also referred to as a cooling section 14, which is mounted on the computer rack or on the one or more computers. In addition, the pump 12 is disposed for moving a cooling liquid through the pipe section. Further, the computer rack also includes a negative pressure generator for generating a pressure which is less than the atmospheric pressure. In the preferred embodiment, water is used as a cooling liquid, the cold liquid having temperatures between e.g. 8°C and 20°C, and the hot liquid having temperatures between e.g. 13°C and 30°C. Thus, the evaporator intake 20a in Fig. 2 carries water at the cold temperature, and the evaporator outlet 20b carries water at a hot temperature. The electronic components to be cooled, such as a computer in a computer rack, are shown at reference numeral 10 in Fig. 2. The elements 12, 16 are also not shown in Fig. 2. Shown in Fig. 2, however, is the fact that a negative pressure generator 14 of Fig. 1 and a heat sink 20 of Fig. 1 may collectively be configured as an evaporator 22. The evaporator 22 is part of a heat pump, which further includes a compressor 24 and a liquefier (condenser) 26, as well as a heat dissipator 28, which is coupled to the liquefier 26 via a dissipator intake 30a and a dissipator outlet 30b. In a closed system, the liquefier 26 is coupled to the evaporator 22 via a connection 32, shown as a dashed line. However, there are also open systems in which the evaporator is supplied with the working liquid and the liquefier discharges the working liquid from the system, so that it is not a closed system in the strict sense, because liquid is constantly supplied on the evaporator side. However, closed systems are preferred for their easier maintainability.

It should be noted that the heat pump in Fig. 2 may either be configured exclusively for cooling the electronic components to be cooled 10, or may at the same time function as an air conditioner for the room in which the computer rack is disposed. In that case, the evaporator 22 includes further intakes/outlets for air-cooling the room in which the computer rack is disposed. In other embodiments, the computer rack does not necessarily have to be in the same room which is climatized by the heat pump shown in Fig. 2, as the evaporator 22 can easily be used in multiple ways through appropriate piping, i.e. on the one hand for cooling the electronic components 10, and on the other hand to also be configured for an air conditioner. In that case, a ventilator (not shown in Fig. 2) might ventilate a cooled object 34 to cool the air generated by the ventilator through contact with the cooled object 34 in order to climatize a room with it. Thus, the evaporator 22 has multiple supply lines, i.e. connections 35a, 35b in addition to connections 20a, 20b.

In the preferred embodiment of the present invention, the evaporator is configured as shown in Fig. 3. The evaporator includes an evaporator housing 40, in which a working liquid such as water is contained up to a certain level, as shown at 42. In the evaporator housing 40, further, a negative pressure is kept which is so low that the working liquid supplied by the hot inlet 20b evaporates as shown at 44. To increase the evaporation efficiency, the hot liquid runs via an intake 46, which may, for example, be centrally disposed in an evaporator body 48, onto the funnel-shaped evaporator body 48, and runs down the inclined surfaces 50. The coolant which has run down and has not evaporated is collected, and is cooled by the evaporation 44 and drained via the cold outlet 20b. Preferably, the hot outlet and the cold outlet are directly coupled to the evaporator 40, so that in the embodiment shown in Fig. 3 the evaporator performs the functionalities of the heat sink 20 and the negative pressure generator 14. Alternatively, there may also be pressure adjusters or pressure controllers which ensure that the pressure in the lines 20a, 20b is slightly higher than the pressure in the evaporation chamber of the evaporator housing 40 in which evaporation 44 takes place, the negative pressure in the cooling circuit, however, not necessarily having to be specially generated but being provided by the negative pressure in the evaporation chamber. Thus, the evaporator and/or the compressor equally functions as a negative pressure generator for the cooling circuit. The vapor generated is constantly discharged, via a vapor discharge line 54, to the compressor, where it is compressed and is liquefied in a liquefier shown at 26 in Fig. 2. Compression takes place such that a "hot" temperature of e.g. 60°C (or in a range of 40°C to 80°C) is maintained in the liquefier. This temperature is suitable, for example, for a dissipator 28 disposed on a roof, which even in warmer countries where external temperatures are already around 40°C still provides sufficient heat dissipation. In a preferred embodiment, the cooling section 14 extends in direct contact with the object to be cooled, such as on a board, under a board or within a board on which heat-generating electronic components are disposed. Alternatively or additionally the cooling section, in the form of a pipe containing a flow of cooling liquid, also extends along the cooling body or even flows around the cooling body of a component, or runs through special cooling ducts within a computer rack in a computing center.

Although particular elements have been described as elements of a device, it should be understood that this description should be equally regarded as a description of steps of a method for cooling. Thus, for example, the block diagram shown in Fig. 1 equally represents a flow chart of a corresponding inventive method, which is also true in particular for the block diagrams of Figs. 2 and 3.

Claims

A device for cooling an object to be cooled (10) which is disposed in an atmosphere having an atmospheric pressure, the device comprising: a pump (12) for moving a cooling liquid in a cooling section (14); a negative pressure generator (14) configured to generate a pressure in the cooling section which is less than the atmospheric pressure; and an evaporator (22) of a heat pump, comprising a liquid intake (20b) and a liquid outlet (20a), the liquid intake and the liquid outlet being part of the cooling section, the cooling section being fluidically coupled directly to a liquid stored in the evaporator, so that the pressure in the cooling section is at least partially influenced by a negative pressure in the evaporator, wherein the evaporator is configured to be coupled to a compressor (24) adapted to compress and transport evaporated liquid to a liquefier.

The device according to claim 1, further comprising: a pressure generator (16) for monitoring whether an actual pressure in the cooling circuit exceeds a target pressure in the cooling circuit which is less than the atmospheric pressure by more than a threshold, or whether a pressure rise in the cooling circuit takes place faster than a permissible pressure rise.

The device according to claim 2, further comprising: an alarm generator for taking an alarm measure if the pressure detector (16) registers an exceedance of the threshold or registers a pressure rise which is higher than the permissible pressure rise.

The device according to any of the preceding claims, wherein the object to be cooled includes electronic components.

The device according to any of the preceding claims, including a computer rack in a computing center.

The device according to any of the preceding claims, wherein the cooling liquid is water, the device further comprising the water in the cooling section.

The device according to any of the preceding claims, wherein the object to be cooled includes a computer in a computer rack of a computing center, wherein the cooling liquid is water, wherein a pressure detector (16) is provided which is configured to detect an abnormal situation in the cooling section, the device further comprising an alarm generator for taking an alarm measure, the alarm measure including emergency cooling, optical or acoustic alarm display, influencing the operation of a computer to dissipate less energy, or shutting down the one or more computers.

The device according to any of the preceding claims, wherein the negative pressure generator is configured to generate pressure in the cooling circuit so that the pressure at the object to be cooled is less than 0.8 times the atmospheric pressure.

The device according to any of the preceding claims, wherein the object to be cooled is a board comprising electric components of a computer, wherein the cooling circuit comprises a pipe section, the pipe section being disposed, in touching contact with the board, on the board or under the board or in the board, or wherein the pipe section extends on a cooling body or a circuit housing or surrounding a circuit housing.

A computer rack comprising one or more computers which are mounted in a rack carrier and are disposed in an atmosphere having an atmospheric pressure; a pipe section (14) which is mounted on the computer rack or on the one or more computers; a pump (12) for moving a cooling liquid through the pipe section; a negative pressure generator (14) for generating a pressure which is less than the atmospheric pressure; and an evaporator (22) of a heat pump, comprising a liquid intake (20b) and a liquid outlet (20a), the liquid intake and the liquid outlet being part of the cooling section, the cooling section being fluidically coupled directly to a liquid stored in the evaporator, so that the pressure in the cooling section is at least partially influenced by a negative pressure in the evaporator, wherein the evaporator is configured to be coupled to a compressor (24) adapted to compress and transport evaporated liquid to a liquefier.

1 1. The computer rack according to claim 10, wherein the cooling liquid is water, or wherein the pressure generated by the negative pressure generator is less or equal to 0.8 times the atmospheric pressure.

12. The computer rack according to claim 10 or 1 1, further comprising: an evaporator (22) of a heat pump, comprising a liquid intake (20b) and a liquid outlet (20a), the liquid intake and the liquid outlet being part of the cooling circuit, the cooling circuit being fluidically coupled directly to a liquid stored in the evaporator so that the pressure in the cooling circuit is equal to a negative pressure in the evaporator or is higher than a pressure in the evaporator, and is dependent on the pressure in the evaporator, and wherein the evaporator can be coupled to a compressor (24), which is disposed to compress and transport evaporated working liquid to a liquefier.

13. A method for cooling an object to be cooled which is disposed in an atmosphere having an atmospheric pressure, comprising: moving a cooling liquid in a cooling section; and generating a pressure in the cooling section which is less than the atmospheric pressure, wherein the step of generating comprises using an evaporator (22) of a heat pump, comprising a liquid intake (20b) and a liquid outlet (20a), the liquid intake and the liquid outlet being part of the cooling section, the cooling section being fluidically coupled directly to a liquid stored in the evaporator, so that the pressure in the cooling section is at least partially influenced by a negative pressure in the evaporator, wherein the evaporator is configured to be coupled to a compressor (24) adapted to compress and transport evaporated liquid to a liquefier.