WO2013056823A1

WO2013056823A1 - A device and a method for passive cooling of electronic equipment

Info

Publication number: WO2013056823A1
Application number: PCT/EP2012/004339
Authority: WO
Inventors: Helge Gallefoss
Original assignee: Helge Gallefoss
Priority date: 2011-10-17
Filing date: 2012-10-17
Publication date: 2013-04-25
Also published as: EP2769606A1; NO20111401A1; NO334412B1

Abstract

Device and method for, at least to a predominant extent, passive cooling of electronic equipment that releases heat and has a need for cooling. It comprises a supply channel (A) for a supply of cold air and an outlet channel (9) for the air that has been heated by the electronic equipment. The outlet channel (9) is arranged above the supply channel (A) and the circulation is essentially provided by a chimney effect. A return channel (12) for transport of a part of the heated air from the electronic equipment (2, 3), extends below or on at least one of the sides of the electronic equipment (2, 3) to the inlet side (B) of the electronic equipment (2, 3).

Description

A device and a method for passive cooling of electronic equipment

The present invention relates to a device and a method for, at least to a predominant extent, passive cooling of electronic equipment that releases heat and which has a need for cooling, such as, for example, computers and associated equipment placed in a rack. The device comprises a supply channel for cold air to the inlet side of the electronic equipment, and an outlet channel from the outlet side of the electronic equipment, for transporting out air that has been heated up by the electronic equipment, the outlet channel is situated above the supply channel and that the circulation is largely provided by a chimney effect. The method comprises the steps of providing cold air on a first side of the electronic equipment and lead this through the electronic equipment and conduct at least a part of the heated air to an outlet channel, which is situated above the electronic equipment, the air circulation largely being provided by a chimney effect.

Electronic equipment, such as computers, for example, generates significant amounts of heat when it is in use. If this heat is not transported away it can lead to the equipment becoming overheated and damaged and in the worst case it can lead to fires. In large assemblies of computer equipment there is a problem in removing this heat. Therefore, the equipment is often placed in a room with a cooling aggregate. In this case a completely closed and airtight environment is created and active components are used to remove the heat the computer equipment generates from the room with air conditioning, heat pumps or chilled water. All these solutions, which to a large extent are not very energy efficient, require a supply of energy and such traditional cooling of a computer room often uses as much energy, or more, as the computer equipment uses itself.

From US 2002/0108386 it is known a computer cooling system where cold air is fed into the system on one side and exits out on the other side. The heated air is then conducted through a cooler and back to the computer equipment. This transport is very energy consuming.

CONFIRMATION COPY From US 2008/0185446 is known a system for cooling computer equipment where cold air is supplied from external process equipment. The air is fed through the computer equipment and out again above this. It is possible to recirculate some of the hot air, but this takes place outside of the computer hall and requires at least one fan in addition to the fans in the actual computer equipment.

The device and the method according to the present invention shall, to a very little extent or not at all, use external energy for the cooling itself. Instead, a starting point of a cool climate and thermodynamic effects are used to achieve optimal operating temperature for the computers. If the system needs outside air filtering, a system for balancing outside and inside air pressure to

compensate for pressure loss through the filter should be installed. This could be a low energy fan system, but the purpose would be just to balance air pressure, not to drive air through the system.

Therefore, the present invention aims at a practically completely passive cooling without the supply of energy. For larger installations, the heat produced by the system can also be recycled as heat and one can take energy out of the air streams and regenerate electricity.

The device and the method according to the invention are especially suited to passive cooling of computer rooms and represent a new and energy efficient way to build production environments for data processing facilities (data centres). The system, due to the heat generated by the computers, produces hot air in large amounts, and a rapid flow of air in a channel which can be controlled and led out to be recycled. This represents possibilities for active recycling of the heat, both by taking out mechanical energy and transforming it to electricity, and also to use the hot air for the heating of water or use the hot air for direct heating of industrial buildings, households, greenhouses and the like.

In a preferred embodiment a supply of cold air, venting, four different

temperature and pressure zones and also a return channel for automatic temperature adjustment are used to achieve the desired inlet of air onto the computer racks.

The invention is primarily meant for a mechanical installation in a room for cooling of computers. In a preferred embodiment it comprises two main zones, one cold and one warm zone divided in such a way that the front side of the racks is the cold zone and the backside is the hot zone. This is also known in the business as hot aisle/cold aisle systems. In addition to this, the present invention provides a return channel to balance the cold air with hot air from the backside of the racks, including a venting system and different pressure zones to move the air around with natural thermal effects. The return channel could be established by a floor onto which the computer racks are standing. Each rack has a chamber at the rear with a damper at the top that can be regulated automatically, and also a channel at the bottom of the rack, which channel leads hot air from the chamber up to the front of the rack. The hot air is then released out through a vertical slit or perforations in a pipe so that the hot air is

distributed evenly at the height of the rack. The return channel could also be between the racks, and the racks could be mounted in linear rows or in a circle. If desired a dampener device could regulate the amount of hot air that is distributed to the front of the racks.

The aim of the invention is primarily to make cooling of computer racks more energy efficient in an environment where the supply of air initially has a temperature low enough to cool the computer equipment sufficiently without the use of anything else other than a natural environment.

According to Gartner, which is a world-leading research institution within information technology, el-production to computer centres represented in 2007 nearly 2% of all CO₂ release in the world

(http://www.gartner.com/it/products/consulting/special/greenlT.isp). This is a higher release of greenhouse gases than the combined global air traffic. It is claimed that about 5-10% of the world's energy consumption goes to the operation of computer systems and their surrounding infrastructure. Exact numbers are difficult to find as el-consumption for smaller computer centres, the internal computer centres of the companies, networks and associated equipment go into the overall costs for buildings. Most of the energy which is used by these systems globally is produced by coal, gas or nuclear energy. It is only Norway and a few other countries that, to a large extent, base the production of energy on hydropower or other renewable sources of energy. This offers an international possibility for a new industry based on the operation of computers. Norway has, together with a few other countries, a cold climate, stable geological and political structures and also a good supply of electricity based on renewable energy. The energy "bill" for the production of data processing where the energy is produced and the distribution of the product via fibre is very favourable compared to the distribution of power, or in other words: transporting photons over distance is very much more favourable than transporting electrons. The transport net alone, from turbine to a computer room far away, can mean an energy loss of 7-15%. In Norway, the average is 10%.

Therefore, it is optimal to produce computer information where the power is produced and to produce it as efficiently as possible, i.e. to use as little energy as possible for cooling of the systems. This invention permits completely passive cooling almost without the supply of energy, and for larger installations, the heat the system produces can also be recycled as heat and one can take out energy from the air flows and regenerate electricity. The best PUE (Power Usage Effectiveness) in the industry is at the moment around 1.2. The present invention can get this down to about 1.05 or less - together with the latest generation of UPS (Uninterruptible Power Supply) that runs in ECO mode.

For the invention to function optimally it is an advantage to have a plentiful supply of air below 28 degrees and a tall chimney through which the used and heated air can rise. The invention is initially developed for a computer room that is placed in an environment with stable micro climate and a temperature up to 28 °C, e.g., inside a mountain with a low annual temperature around 6-12 °C, and a tall shaft where the hot air can rise, but it can also be used

advantageously where a limited cooling of the supplied air must be carried out. The present invention is distinguished by the feature that the system has a return channel for transporting a part of the hot air from the electronic equipment, which channel extends below or on one or both sides of the electronic equipment and to the suction side of the electronic equipment. The invention is also distinguished by a method wherein a part of the heated air is led below or on one or both sides of the electronic equipment and back again to the suction side as return air to be mixed with the could air supply.

Thereby the return air is led the shortest way between the otlet side and the suction side and will reduce or even remove the need for active fans. The system will also be substantially more compact than known solutions.

Processing equipment on the outside of the computer hall will in practice be superfluous.

The invention shall now be explained in more detail with reference to the enclosed figures, where:

Figure 1 shows an example of a device according to the invention seen from the side, Figure 2 shows the device according td the invention seen from above, and

Figure 3 shows an alternative embodiment of the present invention.

Reference is first made to figure Un a preferred embodiment of the invention a room is established which is divided horizontally into two, where the lower part functions as a cold zone A. The dividing of the room is carried out by a floor 1 on which the computer racks 2, 3 shall stand. The floor 1 can, if necessary, be fitted on a load-bearing construction of pillars (not shown) and the floor 1 ought to be a certain height above a ground base 4 so that large volumes of supplied air can be moved without much resistance or that a noticeable overpressure is created. Cold air may also come from a vertical supply in the cold zone. A tunnel-like corridor (not shown) can be used in which the supplied air below the floor 1 has travelled a certain distance in the rock and reached a low

temperature from the surroundings, i.e. the near-lying rock masses. Above the ground base 4 a regulated water level 5 can be provided that contributes to the air in the cold zone A having an appropriate air humidity. This is preferably regulated so that the supplied air and mixed air in the system reaches about 50% relative air humidity before the air is sucked into the computers by the internal fans. One has found that about 50% relative air humidity is optimal for most electronic equipment.

The computer racks 2, 3 are fitted on the floor 1 in a line, for example, in two rows that are facing each other, as shown. In the middle between these rows, the floor has an open grid 6 (see also figure 2) down towards the cold zone. Alternatively, the air may be supplied from a vertical supply channel. At the top of the rows there is a ceiling 7 that stretches between the rows 2, 3 and which ends the cold zone A upwards. The warm zone D for the air outlet from the system is above this roof 7. Hot air rises and the upper limitation 8 of the warm zone D ought to have a dome shape so that the hot air can rise unhindered up to an opening 9 for the shaft (not shown) where the hot air can rise further into free air or into a system that can recycle the heat and the energy. An air mixing appliance 10, 11 is arranged at each of the computer racks 2, 3, that encompasses a chamber C that receives hot air that has been led through the computer rack 2, 3, a hot air channel 12 which is set up to lead a part of the hot air past the computer rack 2, 3 to a diffuser 13. The diffuser 13

encompasses, as shown in figure 2, a number of pipes that run vertically some distance from the front of the computer racks 2, 3 and there are openings along the pipe for the outflow of hot air. The air that flows out of the diffusers 13 flows into a room B in front of the face of the computer racks 2, 3.

During operation, cold air that preferably has a low temperature of up to 28 °C,and more preferably between 6 and 18 °C, will flow into the cold zone A. Here, the air is supplied moisture from the water surface 5 so that it reaches a relative air humidity of up to 95%, depending on the temperature. The moist and cold air then flows up through the grid 6. Here, it is forced to flow sidewise between the diffusers 13 to the room B. Here, the air is mixed with the hot air that is supplied via the diffusers 13. The air will then get a temperature of preferably 27-32 °C and the relative air humidity is reduced to about 50%.

The heated air is then pulled through the computer racks 2, 3 by the built-in fans in the computers and flows out into the chamber C. The air has then been heated up to between 35 and 50 °C and the relative air humidity is further reduced to 30%. From the chamber C, one part of the air will flow out into the hot zone D and further out through the opening 9 to open air or heat recovery. One part of the air is led down in the channel 12 to the diffuser 13 for new mixing with the cold and moist air from the cold zone D.

The mixing ratio between hot return air from the chamber C and cold air from the cold zone A is mainly regulated with the help of the damper 14 in connection with the opening 9. The less of the air that is let out through the opening 9, the more of the air will be led back to the diffuser 13. The temperature sensors in the cold zone A, the mixing zone B and the hot air chamber C are used to control the damper 14.

Figure 3 shows an alternative embodiment of the system according to the invention. In this embodiment the hot and cold sides of the racks 2, 3 have been reversed, so that the hot zone C is situated between the racks 2, 3 and the cold zone A extends around and above the racks 2, 3. Moreover, the water surface below the racks 2, 3 has been removed. Instead a humidifier may be installed outside of the computer hall.

This reversing of the racks enables a much more compact design of the computer hall. In fact it would be possible to fit it within the boundaries of a 20 foot standard transport container, which makes it possible to move the complete computer hall if necessary. Moving the computer hall may be required if the system is threatened by fire, terror attacks, earthquakes etc.

In figure 3, the racks 2, 3 are placed on a platform 20. The platform 20 has a cavity 12 that extends over substantially the width and length of the platform 20. This cavity acts as the return channel 12 for a part of the hot air. Between the racks 2, 3 is the hot zone C. The hot zone C is enclosed from the cold zone A by walls 22, 23 that extend all the way to the ceiling of the computer hall. The hot zone C is open to a shaft 24 for letting out hot air. The outlet of hot air though the shaft 24 is regulated by a damper 14. The hot zone C is also open towards the cavity 12 in the platform 20.

At the cold side of the racks 2, 3 are arranged diffusers 13. These are in communication with the cavity 12. The remaining space within the computer hall is the cold zone A. This gives room for a large quantum of cold air. Cold air is let in through vents 25, which at least are situated at each end of the computer hall. Hot return air from the diffusers 13 is mixed with the cold air before the air is sucked into the computer racks 2, 3.

For both embodiments of the present invention it is also possible to have a return channel 12 that extends on one or both sides of the racks instead of or in addition to below the racks. This may be convenient if it is desirable to reduce the height of the computer hall at the expense of the width.

Thus, the system is a complete thermodynamic system with two main zones A and D, and four different temperature and pressure zones A, B, C and D. Air in the main system will move due to different driving sources;

1- the internal fan system of the computers that pulls air from the mixing zone B to the hot air zone C.

2- The chimney effect in the hot zone which makes the hot air rise and thereby also contributes to pull air through the system.

It is also possible to control the supply of cold air from the cold zone A. In the embodiment of figures 1 and 2, this can be carried out, for example, with the help of a damper that can close and open at the grid 6. In the embodiment of figure 3, this can be done by a damper in the vents 25. On its way through the computers the air is heated up and expands. The fans that are a conventional part of the computers move the expanded and hot air into the chamber C. At the top of this chamber C, a variable damper or other through-flow regulator can be arranged, which regulates the pressure in the chamber C so that the hot air is forced down into the channel 12 below the rack 2, 3 and up in the diffuser 13 in front of the rack 2, 3. The channel 12 below the rack goes up through the floor/platform, for the embodiment of figures 1 and 2 possibly through the grid 6, and ends up in a pipe end/host socket onto which the diffuser 13 can be put. The diffuser 13 is preferably a pipe with a vertical slit or perforations that distributes the hot air in the whole height of the rack 2, 3. The diffuser 13 should be easy to pull from the host socket so that one can take equipment into and out of the rack 2, 3.

Regulated hot air flows from the top of the chamber C and into the zone D. The hot air rises past the damper 14 and up the channel/shaft above the damper 14, as the chimney effect ensures that there is a draught in the system. Hot air rises and the thermal effect will contribute to drawing air through the system. In a typical installation in a mountain hall, cold air will be pulled in from a tunnel and the channel above the damper 14 will let the hot air out. With the considerable energy/heat generation that occurs in the computer room there will be a great difference in the temperature of the air which is let out and the surroundings.

The present invention also makes it possible to perform an efficient and direct extinguishing of small fires in the computer racks. A nozzle 15 can be arranged in the return channel 12. This nozzle 15 is capable of spraying in atomised water to bring the air humidity up to 100%. This saturated air is then led into the diffuser (s) 13 and further to the computer rack(s) 2, 3. Such saturated air will effectively cool the build-up of fires and ensure that the fire does not spread further. By arranging one nozzle 15 below each of the diffusers, one will be able to extinguish any initiation of fire in the relevant computer rack 2, 3 without the next computer rack being affected. A temperature sensor in each computer rack monitors the temperature and if the temperature in any given computer rack exceeds a pre-set temperature, the nozzle 15 connected to the computer rack will start to spray in atomised water. At the same time, the flow to the actual computer rack will preferably be closed to prevent any short-circuiting. A smoke/fire detection/alarm for one rack may immediately shut down the power to this rack. Even if the invention above is described as a completely passive system for air cooling, where the fans in the computers are the only active means that are used to make the air circulate, it is, of course, also possible to use fans elsewhere, either periodically or permanently, to help the circulation of air. It is also possible to cool the supplied air, at least periodically, if the temperature is not sufficiently low. However, what is important is that the cooling system, in the main, is a passive system with minimal need for additional cooling.

Claims

1. Device for, at least to a predominant extent, passive cooling of electronic equipment that releases heat and has a need for cooling, comprising a supply channel (A, 6) for cold air to the inlet side (B) of the electronic equipment (2, 3), and an outlet channel (D, 9) from the outlet side (C) of the electronic equipment (2, 3), for transporting out air that has been heated up by the electronic equipment (2, 3), the outlet channel (D, 9) is situated above the supply channel (A, 6) and that the circulation is largely provided by a chimney effect,

characterised in that a return channel (12) for transport of a part of the heated air from the electronic equipment (2, 3), extends below or on at least one of the sides of the electronic equipment (2, 3) to the inlet side (B) of the electronic equipment (2, 3).

2. Device according to claim 1, characterised in that it comprises an air moisturising device (5) to increase the relative humidity of the supplied air.

3. Device according to claim 1 or 2, characterised in that it comprises a lower cold air chamber (A) for the receipt of cold supplied air, a floor (1 ) above the cold air chamber (A) whereupon the electronic equipment (2, 3) is placed, one or more openings (6) in the floor near the suction side (B) of the electronic equipment (2, 3), a receiving chamber (C) at an outlet side of the electronic equipment (2, 3) for air that has passed through the electronic equipment (2, 3).

4. Device according to claim 1 or 2, characterised in that it comprises a receiving chamber (C) at an outlet side of the electronic equipment (2, 3) for air that has passed through the electronic equipment (2, 3), the receiving chamber being situated between to racks of electronic equipment (2, 3).

5. Device according to claim 4, characterised in that the receiving chamber extends upwards to an outlet shaft (24).

6. Device according to claim 5, characterised in that a cold zone (A) extends around the racks of electronic equipment (2, 3).

7. Device according to claim 3 or any of the claims 4 - 6,

characterised in that the return channel (12) is in communication with a diffuser (13) to mix the returned air with the cold supplied air.

8. Device according to one of the preceding claims,

characterised in that a closing element (14) that can be regulated is arranged at the outlet channel (4).

9. Device according to one of the preceding claims, characterised i n that the electronic equipment is arranged in, at least, one rack (2, 3), where the one side of the rack (2, 3) is exposed to the supplied cold air and the other side of the rack is exposed to the heated air and that fans in the rack promote the flow of air through the rack.

10. Device according to one of the preceding claims 3-9,

characterised in that it comprises a nozzle placed in the return channel (12) or the diffuser (13) to supply atomised water to extinguish any fires that may start in the rack.

11. Method for, at least to a predominant extent, passive cooling of electronic equipment that releases heat and has a need for cooling, where cold air is provided on a first side (B) of the electronic equipment (2, 3) and is led through the electronic equipment (2, 3) and that at least a part of the heated air is conducted to an outlet channel (9), which is situated above the electronic equipment (2, 3), the air circulation largely being provided by a chimney effect, characterised in that a part of the heated air is conducted below or on at least one of the sides of the electronic equipment (2, 3) and brought back as return air to the first side (B) to be mixed with the supplied cold air.

12. Method according to claim 11, characterised in that the cold air is humidified.

13. Method according to claim 12, characterised in that the mixing ratio between the supply of cold, moist air and hot, drier return air is regulated so that the relative humidity of the air that is led through the electronic equipment is around 50%.