FIELD OF THE INVENTION

The invention relates to a cooling system for data centers as defined in the preamble of claim 1.

BACKGROUND OF THE INVENTION

Computers and other devices in data .centers produce a great deal of heat; however, their reliable and undis- turbed operation requires an even and sufficiently low temperature. In order to ensure undisturbed operation of data centers, the heat must be removed. Conventionally, this has been achieved by sufficient ventilation, i.e. by blowing out the heat and replacing it with cool air. Generally in Finland, it has been necessary to use separate cooling only during the hottest days of summer.

As data centers and thus their power requirements are growing, it has been discovered that it would be useful to utilize the heat that has been generated instead of blowing it out. The power requirement in data centers varies according to their size generally from tens of kW to several MW, all of the consumed elec- tricity turning into heat that has to be removed.

A system has been developed for large data centers, wherein the data center is cooled by circulating cold water in the cooling system of the center. The water that has been warmed in cooling is conveyed to a heat pump plant where the heat energy contained therein is recovered by means of heat pumps and conveyed to the district heating network. The water that has been recooled by the heat pump plant is conveyed back to the data center to cool the servers. The system described above operates well and evenly, and the good operation is based on the large district heating network that is always able to receive all available heat and, on the other hand, provides in all conditions a constant-temperature cooling water circulation to the data center.

However, the known system is not functional when a district heating network or a district cooling network is not available, but, instead, it would be desirable to use the waste heat for example in the heating or in the production of warm service water for the building accommodating the data center or for an adjacent building. As the need for heating and usage of warm service water varies even to a great degree according to the time of the day, week and year, the system would not ensure a continuous and even cooling flow to the data center, an absolute requirement for reliable functioning of the data center. Another problem in prior art is high investment costs.

OBJECTIVE OF THE INVENTION

The objective of the invention is to remedy the above- mentioned defects of the prior art. In particular, the objective of the invention is to disclose a novel heat recovery system for cooling data centers, which enables the recovery and utilization of the waste heat in a property-specific fashion, i.e. on a small scale, and, despite variable load on the heat consumption, ensures an even cooling for the data center.

SUMMARY OF THE INVENTION

The cooling system according to the invention is des- ignated for cooling data centers including computers and suchlike devices. The cooling system includes an air/liquid heat exchanger for transferring the heat from the air circulation cooling the data center into the liquid, generally water, and means for cooling the liquid. According to the invention, the means for cooling the liquid include a heat recovery module including a compressor circuit. The compressor circuit has a primary circuit for conveying therein the liquid to be cooled and a secondary circuit connected to one or more heat uses. A return channel from the primary circuit includes a temperature-controlled return circulation for returning the liquid that is above a specific temperature to the primary circuit and for conveying the liquid that is below the specific temperature back to a liquid channel provided from the data center. Further according to the invention, the liquid channel from the data center includes a direct flow connection past the recovery module to a backup cooling device provided with a return channel for conveying the cooled liquid to the air/liquid heat exchanger of the data center. Thus, in the inventive system, the backup cooling device is used as needed, i.e. when the power of the heat recovery module is not sufficient or, on the other hand, when the heat requirement of the heat uses is less than the heat quantity obtained from the cooling of the data center.

A preferred embodiment of the invention includes at least two recovery modules coupled in parallel to the liquid channel provided from the data center. Thus, a suitable number of modules can be coupled to operate in parallel in in such a way that only one of the modules operates at partial power.

One of the most important features of the invention is reliability, i.e. always and in all conditions to provide even cooling and consequently an even temperature in the data center. Thus, the system preferably includes at least two different backup cooling devices coupled in series or in parallel. One cooling device may be based on the cooling effect of cold tap water. A second one may be based on the cold outdoor air and a third one for example on different heat pump solutions. Thus, in different conditions and changes of conditions, it is possible to ensure most effective and reliable cooling for the data center.

In one embodiment of the invention, the return circulation from the return channel is provided by means of a three-port valve which is controlled by measuring the liquid temperature in the return channel after the valve. If the temperature of the liquid from the primary circuit of the compressor circuit is above a specific set value, the three-port valve will return the liquid circulation back to the primary circuit. However, if the temperature of the liquid is below the set value, the three-port valve will direct the liquid out from the module and back to the liquid channel provided from the data center. .

To ensure even operation of the system, the return channel is preferably provided with an equalizing tank of a volume sized so as to have sufficiently long running and rest periods for the compressor or compressors and so that they do not continuously start and stop due to small temperature fluctuations. The equal- izing tank receives cold liquid flow and mixes it in such a way that the temperature of the liquid flowing into the liquid channel provided from the data center is always close to constant. A pump for circulating the liquid in the heat recovery module is suitably located after the primary circuit and before the three-port valve. Thus, the pump can circulate the liquid in the module under both operating positions of the three-port valve. Preferably, the return channel from the module is connected to the liquid channel provided from the data center in the flow direction before the liquid circulation of the heat recovery module. The heat recovered by the system according to the invention can be utilized as such in any use that requires heat. The most suitable heat use is warm service water of the building in question or one that is as close as possible, as such consumption is relative- ly even throughout the year. Another use is heating of the building; however, such heat requirement varies greatly according to season.

The cooling system according to the invention provides considerable advantages as compared to prior art. The system is structurally small-sized and simple. In terms of adjustments and operation, it is very flexible in such a way that it is always possible to utilize the needed quantity of heat from the even thermal load provided and remove the excess heat without the most important variable, i.e. even temperature in the data center, being changed or endangered in any way.

LIST OF FIGURES

In the following, the invention will be described in detail with reference to the accompanying drawing, which schematically illustrates one cooling system according to the invention. DETAILED DESCRIPTION OF THE INVENTION The schematic illustration presented in the drawing represents a large data center 1 with a power consumption of for example on the MW order. The data center has an air/liquid heat exchanger (not shown in the figure) in which the warm air from the data center circulates and releases the heat into the liquid, usually water, circulating in a secondary circuit of the heat exchanger. The warmed liquid, the temperature of which may be on the order of 25-30°C, is conveyed to a liquid circulation 18 of a heat recovery module 2, wherein it flows into a primary circuit 4 of a compressor circuit 3. By the effect of the compressor structure known per se, the temperature of the liquid in the primary circuit drops while the temperature of the secondary circuit 5 rises. The water circulating in the secondary circuit conveys heat by means of pumps 19 for uses 6 in a manner known per se so as to return back to the secondary circuit as a cooled return flow 20.

The liquid flow cooled in the primary circuit 4 is moved forward along a return channel 7 to a three-port valve 14 by means of a pump 17. Forward of the three- port valve in the flow direction, the return channel has a meter 15 which measures the temperature of the liquid and which is used to control the three-port valve. Thus, when the temperature of the liquid flowing in the return channel 7 is higher than a set value, the three-port valve directs the liquid to a re- turn circulation 8 and back to the primary circuit 4 of the compressor 3. The liquid circulates in the return circulation until its temperature drops below the set value, whereupon the valve directs the liquid circulation partially or entirely along the return chan- nel 7 into an equalizing tank 16. Here, the cold liquid is mixed into a larger quantity of liquid, where- upon the temperature variations of the liquid from the return channel are equalized and the equalizing tank substantially releases a constant-temperature cooled return liquid flow into a liquid channel 9 in the flow direction before the liquid circulation 18 of the heat recovery module 2.

Thus, the cooled liquid circulation is mixed with the warm liquid of the liquid channel 9 provided from the heat exchanger of the data center. After this, part of the liquid returns to the heat recovery module 2 and part of the liquid flows into backup cooling devices 10,11 and 12, by which the liquid can be cooled further if necessary. In case the module 2 provides a 100 percent heat recovery, the backup cooling devices are not needed; instead, they operate only as a backup with the liquid just flowing through them. With partial power functions, i.e. when the heat uses 6 do not utilize all of the heat, the backup cooling devices, i.e. water cooling 10, plate heat exchanger 11 and compressor 12, together or separately carry out part of the cooling. In case of providing a 100 percent heat recovery in the IT data center, it is possible that the cooled solution be directly returned to the data center. Adjustment of the cooling can be provided by limiting the running of the compressors in the modules. In case the property does not have any energy requirements, the excess energy can be removed for example via a free cooler from the circulation of warm service water.

Most suitably, the cold circuit of the system uses refrigerant rl34a to provide higher temperature for the supply water, which is more useful for the property. In parallel to the first heat recovery module 2, the drawing also shows a second similar heat recovery mod- ule. The modules may even be present in a greater number and can be always used in the required number according to the warm service water and heating power requirement of the building. Instead, there is no need for more than one backup cooling device, even if the modules 2 were coupled in a greater number.

The invention is not limited merely to the example referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims .