Computer implemented method of operating a RDHX system for cooling of computer servers

Abstract

The invention relates to a computer implemented method of operating a RDHx system (11) for cooling computer servers (12). Said RDHx system comprises a plurality of RDHxs (1) and at least one computer implemented RDHx controller (9) each comprising an electronic processor (10). Each of said RDHxs comprises at least one heat exchanger (4), at least two active components (5) including at least one speed controllable fan (2) providing a flow of air through said servers and at least one speed controllable pump (7) providing a flow of fluid through said at least one heat exchanger. It further comprises at least two passive components (6) including at least one temperature sensor (2) and at least one pressure sensor (13). Each of said at least one electronic processor (10) comprises a plurality of addressable I / O ports to which said active and passive components are connected.

Description

[0001] 85946PC01

[0002] 1

[0003] COMPUTER IMPLEMENTED METHOD OF OPERATING A RDHX SYSTEM FOR COOLING OF COMPUTER SERVERS

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to RDHx systems for cooling of computer servers. In particular it relates to a computer implemented method of operating such a system.

[0006] BACKGROUND OF THE INVENTION

[0007] Heat generation and cooling in data centres is under rapid development with the growth of high-performance computing and Al. Where a server rack would previously generate about 2-5 kW heat, it is now possible with commercially available components to configure a rack which will generate about 100+ kW heat. There is increasing focus on Al and the need for dense computing to speed up Al learning, where centimetres of increased distance will cause decreasing performance in the very intense processes. Therefore, the processors are arranged as close as possible resulting in higher heat generation. As a result, cooling has evolved from traditional room cooling with air conditioning units, through down flow cooling, cold aisles and cold aisle enclosures, through in row cooling, to rear door cooling and on-chip cooling.

[0008] While rear doors heat exchangers (RDHxs), also referred to as rear-doors, are being offered to meet the increasing demand for cooling, they are designed with very traditional temperature regulation methods with the expectation (based on tradition) that the room air conditioners will compensate for temperature fluctuations caused by imprecise and / or failing rear-door coolers. The amount of heat generated, however, is so large that any fluctuations in temperature by far exceeds the CRAH units (traditional room air condition) ability to compensate. As a result, simple and slow rear door cooling regulation processes fail to maintain stable temperatures in a data centre with many server racks, each typically generating 40 or more kW of heat.85946PC01

[0009] 2

[0010] Another aspect of the increased cooling taking place is that the failure of one door can be very problematic for the entire data centre as the room temperature will very quickly increase to a level where all servers in the room will shut down. It is important to design a RDHx with a high level of redundancy in the components it is made of. Furthermore, the system consisting of several RDHxs can be made redundant by designing doors with excess capacity and letting remaining RDHxs compensation, should one or more doors fail.

[0011] OBJECT OF THE INVENTION

[0012] It is an object of the present invention to provide a computer implemented method of operating a RDHx system for cooling of computer servers, which method has a high reliability.

[0013] It is another object of the present invention to provide a computer implemented method of operating a RDHx system for cooling of computer servers with which method it can be ensured that the temperature within the space where the computer servers are located does not exceed a predetermined critical threshold temperature.

[0014] It is an object of at least some embodiments of the present invention to provide a computer implemented method of operating a RDHx system for cooling of computer servers, which method includes an automatic configuration of the system and which thereby is easier to implement than traditional, corresponding methods.

[0015] It is another object of at least some embodiments the present invention to provide a computer implemented method of operating a RDHx system for cooling of computer servers, with which method it is possible to automatically compensate for malfunctioning of a part of the RDHx system during use.

[0016] It is a further object of the present invention to provide an alternative to the prior art.85946PC01

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[0018] In particular, it may be seen as an object of the present invention to provide a computer implemented method of operating a RDHx system for cooling of computer servers that solves the above-mentioned problems of the prior art.

[0019] SUMMARY OF THE INVENTION

[0020] Terms used herein are used in a manner being ordinary to a skilled person. Some to the used terms are elucidated here below.

[0021] RDHx refers to rear door heat exchanger.

[0022] "at least one" in general means that there may be only one or there may be more than one, which can also be referred to as "a plurality".

[0023] In response to the situation described above, the inventor of the present invention has developed several series of RDHx solutions, each with several products optimized for a preferred heat removal capacity. These RDHx solutions are optimized to respond very quickly to changes in heat generation for the rack they manage, and the system of RDHxs will maintain the room temperature very precisely with very little effect on the room temperature of servers starting and stopping.

[0024] The above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a computer implemented method of operating a RDHx system for cooling of computer servers, said RDHx system comprising a plurality of RDHxs and at least one computer implemented RDHx controller each comprising an electronic processor, wherein:

[0025] • each of said RDHxs comprises:

[0026] o at least one heat exchanger,

[0027] o at least two active components including at least one speed controllable fan at least assisting in providing a flow of air through said servers, and at least one speed controllable pump providing a flow of fluid through said at least one heat exchanger,

[0028] o at least two passive components including at least one temperature sensor, and at least one pressure sensor,85946PC01

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[0030] • each of said at least one electronic processor comprises a plurality of addressable I / O ports to which said active and passive components are connected, such as wiredly connected,

[0031] • each of said at least one RDHx controller being configured to:

[0032] o scan said I / O ports and for each I / O port detect whether one of said active components or said passive components is connected to that port, and when one of said active or passive components is detected, registering said detected active or passive component by registering a port address of said addressable I / O ports to which said detected component is connected, such as wiredly connected, thereby providing configured at least one RDHx controller,

[0033] o control said registered active components based on input from said registered passive components to obtain a preselected temperature inside said servers and / or in the vicinity of each of said RDHxs.

[0034] The heat exchangers typically used in the present invention are air-to-liquid heat exchangers; they may also be referred to as cooling coils.

[0035] Other types of sensors than those specifically mentioned in the following description may also be used. Examples of such sensors are leakage sensors and humidity sensors. Such sensors would be passive components.

[0036] The method according to the invention is based on the overall idea of optimising the cooling of computer servers by making it possible to autonomously control the flow of air through the server rack and the cooling fluid through the heat exchangers of the RDHx system used for the cooling by using predictive control based on pressure and air flow analysis.

[0037] In preferred embodiments, the heat exchanger is of a type where heat transport is between two fluids, where one of the fluids is air and the other fluid is a coolant, such as water or glycol. To accomplish a transport of the coolant, each of the RDHxs has a pump fluidicly connected to a source of coolant and fluidicly connected to feed the coolant to and through the heat exchanger.

[0038] The presence of heat exchanger(s) in a RDHx may be detected indirectly by measurements from the pump, such as flow rate, pressure, and / or pressure drop. However, in many preferred embodiments, it is implicit that at least one heat85946PC01

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[0040] exchanger is present due to the presence of a pump, as such a pump is provided to provide flow of a coolant, such as water, through the heat exchanger(s). The coolant could also be referred to as "cooling fluid" or "cooling liquid"

[0041] Even though a RDHx comprises the active and passive components, at least some of these components may be arranged outside a housing surrounding the RDHx. As an example, temperature and / or pressure sensors may be arranged at different locations, such as between the computer servers or in the space between rows of computer servers.

[0042] The computer servers to be cooled by the RDHx system may be arranged in a datacentre, such as a datacentre with more than 100, such as more than 1000 computer servers.

[0043] As presented herein, preferred embodiments of the invention relate to a computer implemented method of operating a RDHx system for cooling computer servers. Such computer servers may be contained in a server rack having a rear side. In such embodiments, the RDHx system comprises a plurality of RDHxs. Such RDHxs are arranged at the rear side of the server rack and is configured to cool air from the servers to transport heat generated by servers to the coolant fluid, such as water. The cooled air is used as inlet air to a server rack thereby providing cool air to a server rack. In many preferred embodiments, the system comprises a plurality of server racks each having a RDHx arranged at the rear side of the server rack. These server racks suck in cooled air from the room, the servers heat the air, which is then inlet into the RDHx, cooled by the heat exchanger and then outlet into the room again as cooled air. The transport of air and cooling is provided by at least one heat exchanger and at least on fan as detailed e.g. below.

[0044] In relation to the feature that "each of said at least one RDHx controller is configured to scan said I / O ports", this scanning and the following registration is preferably performed automatically. The scanning preferably includes automatically measuring on each port to determine whether or not plausible measures can be obtained, such measures being correlated to the components being connected to the I / O ports. This is an advantage compared to systems in85946PC01

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[0046] which this process is at least partly manually performed, because of the higher efficiency in the installation process.

[0047] In any of the embodiments of the invention, there may also be unused ports.

[0048] In some embodiments of the invention, each of the RDHxs comprises a computer implemented RDHx controller. In other embodiments, two or more RDHxs share a RDHx controller. In such embodiments, there may be one or more RDHx controllers. In embodiments wherein each of the RDHxs comprises a computer implemented RDHx controller, such a RDHx can be considered as being autonomous. At least in embodiments wherein each of the RDHxs comprises a computer implemented RDHx controller, an advantage of the method is that when a RDHx controller measures a "room temperature", i.e. the temperature of the air being sucked into a server rack, and it is different from a "target room temperature", the RDHx controller will assume that a nearby RDHx is malfunctioning, and it will attempt to compensate for it by changing its own "air out" temperature, i.e. the temperature of the air leaving the RDHx. By using this principle, the cooling in a datacentre becomes more reliable than with known systems, since one or more RDHxs can fail without the room temperature changing significantly.

[0049] The speed of the at least one fan, such as a plurality of fans, for each RDHx may be controlled by providing an analogue voltage signal, such as 0-10V, to each fan. The speed of the at least one pump, such as pumps, for each RDHx may be controlled in a similar manner by providing an analogue voltage signal. In some embodiments, the speed of the pump is controlled by a frequency converter, and such a converter may be configured to provide a voltage with a given frequency to the pump based on a digital or analogue signal received from the electronic processor. Fans may also be frequency controlled, and in such cases, a fan may be controlled by a frequency converter similar to the control of a pump by a frequency converter. Preferably the fans and pumps are individually controllable to ensure precise control of the temperature around the computer servers. The use of pumps instead of motor valves traditionally used in RDHx systems has been found to allow for a lower power consumption. It also provides faster reaction times thereby allowing for maintenance of a more stable room85946PC01

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[0051] temperature with shorter transient behaviour periods and a better reliability compared to corresponding systems based on motor valves.

[0052] By "preselected temperature" is preferably meant one value, but it may vary by a small amount, such as + / - 0.5 degrees Celsius.

[0053] In at least some embodiment of the invention, the at least one electronic processor comprises a plurality of addressable I / O ports to which active components, such as pumps, fans and motorized flow valves and passive components, such as pressure sensors and temperature sensors are connected. The addressable I / O ports may be multiplexed to allow for a broader bandwidth. While it may be tempting to make such connections wireless, it may be preferred that such connections are provided by wires, as wireless connection could cause radio interference, which in some cases is to be avoided.

[0054] In some embodiments of the invention, for each of said detected active and / or passive components one or more characteristics thereof is determined by sequentially:

[0055] - outputting a control signal via said registered port address of said addressable I / O port to which said active and / or passive component is connected,

[0056] - receiving a feedback signal resulting from the control signal, and

[0057] - based on known correlations between input and resulting output for possible active and / or passive components, determining the characteristics of said detected active and / or passive component.

[0058] A control signal output via said registered port address becomes an input for the component, and the resulting output from the component becomes the corresponding feedback signal. The feedback signals received from the different components are preferably received by different I / O ports.

[0059] In some embodiments of the invention, for each of said detected active components, an operation map is determined by sequentially outputting, via said registered port address to which said active component is connected, a number of different control signals, and for each output control signal:

[0060] - receiving a feedback signal resulting from the output control signal,85946PC01

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[0062] - recording an operation state of said active component, the operation state corresponding to said control signal. The control signals may e.g. be analogue signals. Based on the response returned in dependence of the control signals, the presence and type of components can be determined based on known correspondences between the output control signals and the feedback signals. Such an operation map may be considered as a mapping of how a specific RDHx system operates as determined from measurements performed on the actual physical system. Such a procedure provides an automated configuration of the system which is considered to be more efficient and reliable than a traditional system in which the software is either hardcoded to a specific configuration, or it is entered manually as a part of the provisioning of the RDHx system. This configuration will be relevant both during installation of a new RDHx system and if one of the components is replaced after a period of operation. It may even be possible to take into account, e.g. by replacement, that one or more of the components may have failed while the RDHx systems continues operation.

[0063] The use of an operation map as just described may also be used for monitoring the performance of the components so that necessary action, such as repair or replacement, can be taken as early as possible thereby lowering the risk of malfunctioning of the whole RDHx system.

[0064] A few examples of the above-described scanning are: For fans, a value of fan speed is set on the output port and sent as a control signal. The feedback signal received on the feedback port will typically be a measure of the rotational speed (RPM) of the fan. Based on this information, it is possible ot determine what type of fan is connected to this port. If no feedback signal is received, this is typically a sign of no fan (or other component) being connected. For a pump, the communication can be performed via a protocol, such as a RS485 Genibus, and it can be determined whether a pump is connected and whether it is responding. For valves, the control signal may be a position for the valve, and the resulting reading on the feedback port may be that the valve is actually moving to the set position. By monitoring the speed at which the valve moves, it is possible to determine what type of valve it is and how fast it is.85946PC01

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[0066] In some embodiments, each combination of control signal and resulting feedback signal is used to calibrate the settings of each of the active and / or passive components. Such a calibration thus takes into account the found relations between an actual setting of the speed of the at least one fan and the resulting amount of air being moved in order to provide the cooling. This resulting amount of air could also be referred to as the actual effect. This is done to obtain the desired cooling as precisely as possible.

[0067] In some of the embodiments as just described, said RDHx controller is configured to obtain said preselected temperature and / or a preselected temperature profile by said system comprising a computer implemented simulator, said computer implemented simulator being configured to determine a new operation state for at least one, such as all, of the registered active components, said new operation state providing said preset temperature and / or temperature profile based on a current operation state of the registered active components, readings by said registered passive components, and said operation map.

[0068] The computer implemented simulator may be considered as a simulator to which a current version of the at least one RDHx controller is copied into, so that a simulation is based on the current version of the at least one RDHx controller.

[0069] In some embodiments of the invention, such a simulator could be in the form of an algoritm describing the functioning of the system.

[0070] The computer implemented simulator preferably mimics the real physical system, including the computer servers to be cooled by the RDHx system. The behaviour of such computer servers arranged in racks can be defined through a set of parameters characteristic for the performance as well as a randomization of current load, based on weighted load profiles. Therefore, the use of such a simulator enables a very dynamic simulation environment configured for testing the extremes of the RDHx controller's ability to handle transients and fluctuations as well as calculations of typical flow of coolant and energy consumption in the RDHx system. The information obtained from simulations can therefore be used to improve the performance of the RDHx system, including taking into account malfunctioning when / if it occurs.85946PC01

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[0072] In embodiments comprising a computer implemented simulator, said computer implemented simulator may comprise or may have access to an operation space spanned by operation states for said active components and corresponding temperatures at positions in said RDHx system of said registered passive components being temperature sensors.

[0073] In preferred embodiments, an operation space spanned by operation states is a multi-dimensional space in which the one or more operation states are correlated with temperatures. As a simplified example, a pump may have operation states expressed in rotational speed, RPM, between 0 and 1,000 RPM. Corresponding to such a span of operation speeds, the corresponding temperature for the coolant out of the heat exchanger may span between 15°C and 30°C.

[0074] In embodiments of the invention comprising a computer implemented simulator, said new operation state may be provided by a Monte Carlo simulation or modelbased simulation. It may e.g. be based on Computational Fluid Dynamics.

[0075] In some embodiments of the invention, for each detected active component, said detection of said active components comprises determination of:

[0076] • a component type, and

[0077] • a control parameter range.

[0078] In such embodiments of the invention as just described, said component type and control parameter range may be determined, for a selected RDHx at a time, for one or more of said RDHxs by said RDHx controller(s) providing a number of control inputs to one of said detected active components forming part of said selected RDHx and registering changes in temperature(s) sensed by said at least one temperature sensor (2) and / or registering changes in pressure(s) sensed by said at least one pressure sensor, the sensors forming part of said selected RDHx. By "at a time" is meant that the described steps are performed for a specific RDHx. It does not exclude that determinations of component type and control parameter range for two or more RDHxs may be determined in parallel, such as by use of fully or partially overlapping processes.85946PC01

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[0080] In the determination of a component type and a control parameter range, said control inputs and said changes in temperature(s) may be used to look-up in an inventory database said component type and said control parameter range.

[0081] In some embodiments of the invention, said active components may further comprise one or more of:

[0082] • pumps for pumping liquid, preferably water, through one or more heat exchangers, and

[0083] • motorized valves for controlling volume flow of said liquid through one or more of said heat exchangers.

[0084] In some embodiments of the invention, said configured RDHx controller(s) may be configured for balancing operation of one or more of said active components to compensate for a malfunction of one or more of said active components. Such a malfunction should preferably not arise, but if it does, this feature of some embodiments of the invention enables the RDHx controller(s) to compensate therefore so that the RDHx system can continue to operate satisfactorily despite the malfunction. Hereby a more reliable system is obtained than what is known for traditional systems without this feature.

[0085] In embodiments of the invention wherein said configured RDHx controller(s) is configured for balancing the operation as just described, said malfunction of one of said active components may be detected by determining that:

[0086] • operation of a selected one of said active components in different operation conditions does substantially not, such as does not, affect a temperature otherwise affectable by said selected active component when it functions satisfactorily.

[0087] Said compensation may comprise increasing an operation state for at least one of said active components not being malfunctioning to obtain said preselected temperature. By "increasing an operation state" is meant that the effect provided by the active component is increased. As an example, increasing an operation state of a pump or a fan refers to that the flow rate provided by the pump or fan, respectively, is increased.85946PC01

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[0089] In any of the embodiments of the invention, said scanning for said active and passive components may be carried out recurrently to obtain configured RDHx controller(s) based a most recent registration of said active and passive components. Hereby the system can act fast and thereby lower the risk of breakdown of the computer servers - especially when the temperature increases rapidly.

[0090] Said recurrence may be more than once every 1 hours, such as more than once every 30 minutes, such as more than once every 10 minutes, such as once every minute, such as once every 1-5 seconds, such as every 2 seconds.

[0091] In some embodiments of the invention, at least one, such as a plurality of, such as each, RDHx controller several times per second, such as up to ten times per second, analyses:

[0092] - an actual flow of air calculated from an actual fan speed setting of the at least one fan,

[0093] - an actual air pressure determined by the at least one pressure sensor, and - an expected air pressure development based on pressure trend analysis and extrapolation through non-linear curves,

[0094] wherein in each calculation:

[0095] - the controller calculates a fan speed setting a configurable number of seconds into the future,

[0096] - a relation between air flow, input temperature of the fluid, and the resulting steady state temperature is mapped and stored, and

[0097] - an eventual flow is mapped and stored based on steady-state observations;

[0098] thereby enabling the RDHx controller to precisely set the speed of the at least one fan and the speed of the at least one pump to obtain the preselected temperature inside said servers and / or in the vicinity of each of said RDHxs.

[0099] By "steady state" is preferably meant a state in which the flow rate of the fluid, the temperature of the fluid, and the temperature of the air are constant for a certain period of time, such as for at least a predetermined number of seconds.

[0100] By "an eventual flow" is preferably meant the estimated flow when the curve is flattening out and becomes stady state.85946PC01

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[0102] Thus, with such embodiments of the invention, the method will allow the at least one RDHx controller to compensate for the delay in pumps and fans to reach the set speed / flow that could otherwise result in critical temperatures.

[0103] In some embodiments of the invention, said computer implemented method comprises using:

[0104] • a computer implemented simulation model of said RDHx system operated by said configured RDHx controller(s), wherein said simulation model:

[0105] o comprises a functional representation of said active and said passive components of said RDHx system, and

[0106] o is configured to estimate temperatures in said RDHx system based on operation conditions of said active components, heat produced by said servers and temperature(s) of air surrounding said servers, • a computer implemented optimizer configured to provide optimized configured RDHx controller(s) on the basis of simulations carried out by said simulation model,

[0107] wherein

[0108] • said optimized configured RDHx controller(s) is / are used as said configured RDHx controller(s) for controlling said registered active components.

[0109] In such embodiments as just described, said optimization may be a minimization of temperature variations in the air output of the RDHx system.

[0110] Said optimization may be based on a Monte Carlo simulation.

[0111] In any of the above-described embodiments, at least one, such as all, of said RDHxs may be configured to provide a directed air flow in directions different from straight out of the server rack, by comprising one or more directed air flow guides being active components controlled by said configured RDHx controller(s), wherein a stream of air flowing through said directed air flow guides away from one of said servers is directed in at least one selectable direction by controlling said directed air flow guides. The directed air flow guides are preferably configured to provide an air flow in different directions which are controllable to adjust it to where additional air flow is required to ensure a sufficient cooling. This85946PC01

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[0113] is particularly advantageous in case of malfunctioning of some components, such as fans, because the RDHx system has a build-in possibility of compensating for such malfunctioning.

[0114] In some embodiments configured to provide a directed air flow as just described, said configured RDHx controller(s) may be configured to direct said stream of air towards neighbouring RDHxs to ensure good mixture of air and thereby the required cooling and preferably avoiding areas of varying temperature.

[0115] An efficient heat transfer from the coolant to the air in the heat exchanger is obtained by ensuring that there is turbulence in the coolant so that the heat is transferred to as much of the coolant volume as possible. It has been found that if there is no turbulence in the coolant, the heat transfer is reduced up to 90%. Such a situation may arise, if the actual determined requirements for cooling to be performed by a heat exchanger of a RDHx are far below its maximum capacity and / or when the flow rate of the coolant is low, such as below 0.8 m / s for ethanol glycol or below 0.25 m / s for water. In order to avoid this and to ensure a turbulent flow, the flow of coolant may be pulsed. With water as coolant, this can e.g. be done by pumping with a coolant flow above 0.25 m / s for a short period, such as 1-2 seconds, and then 0 m / s for a short period, and so on.

[0116] In a second aspect, the invention relates to a RDHx system comprising a plurality of RDHxs, the RDHX system being configured for being operated by a computer implemented method according to the first aspect of the invention.

[0117] In a third aspect, the invention relates to a computer program product being adapted to enable a RDHx controller having data storage means in connection therewith to carry out a method according to the first aspect of the invention.

[0118] The first, second, and third aspects of the present invention may be combined so that what is described in relation to the first aspect also applies to the second or third aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.85946PC01

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[0120] BRIEF DESCRIPTION OF THE FIGURES

[0121] The computer implemented method according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0122] Figure 1 schematically shows an example of a datacentre.

[0123] Figure 2 schematically shows an example of a RDHx of a RDHx system for cooling of computer servers by a method according to the present invention.

[0124] Figure 3 schematically shows an example of a RDHx.

[0125] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0126] Figure 1 schematically shows an example of a datacentre with a large number of computer servers 12. In the illustrated embodiment, each of the server racks of the RDHx system 11 is provided with a RDHx 1. The arrows show directions in which cooling air is blown out of the RDHx. This cooling air is only shown for some of the RDHxs in the figure.

[0127] In preferred embodiments, each RDHx comprises in the region of 7-10 temperature sensors for sensing air temperature, and in the region of 1-2 temperature sensors for sensing coolant temperature. The positions and number of sensors for sensing air temperature is selected so as to obtain a spatial resolution of prevailing temperatures in the server rack and around, such as upstream and downstream of, the heat exchanger(s), typically sufficient to avoid hot spots and temperature spikes. The forward temperature of the coolant is often provided e.g. by a system whereby determination of the coolant temperature upstream of the heat exchanger may not be needed; however, a sensor may be equipped to determine this temperature. The temperature of the coolant downstream of the heat exchanger is preferably determined by one of the temperature sensors.85946PC01

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[0129] In preferred embodiments, at least one computer implemented RDHx controller 9 is provided, where each of the RDHx controller comprises an electronic processor 10. Such a RDHx controller 9 besides comprising an electronic processor typically also has a number of addressable ports allowing the electronic processor to communicate with electric or electronic equipment controlled and / or monitored by the RDHx controller 9.

[0130] Figure 2 schematically shows an example of a RDHx 1 of a RDHx system 11 for cooling of computer servers 12 by a method according to the present invention. The illustrated RDHx 1 comprises a computer implemented RDHx controller 9 for the RDHx 1. The RDHx controller 9 comprises an electronic processor 10. The RDHx 1 comprises a heat exchanger 4 and two active components 5 in the form of a speed controllable fan 2 and a speed controllable pump 7. The fan 2 at least assists in providing a flow of air through the server 12, and the pump 7 provides a flow of fluid through the heat exchanger 4. This fluid may also be referred to as coolant. The fluid may be liquid, such as water or ethylene glycol. In the illustrated embodiment, the active components also include a motorized valve 8 for controlling the volume flow of said liquid through the heat exchanger. The motorised valve 8 may e.g. control the flow by being arranged and configured to throttle the coolant by an amount controllable by a motor of the motorised flow valve. The electronic processor is configured to control said motor to provide a coolant mass flow. The RDHx 1 further comprises two passive components 6 in the form of a fluid temperature sensor 3 and a fluid pressure sensor 13. The electronic processor 10 comprises a plurality of addressable I / O ports to which said active and passive components 5, 6 are wiredly connected. Each of the electronic controllers is configured to control said at least two active components based on input from said at least one component being 1-2 temperature sensors 2 to obtain a preselected temperature inside said servers and / or in the vicinity of each of said RDHxs 1.

[0131] Figure 2 schematically shows the components but not necessarily their mutual arrangement. As mentioned above, even though a RDHx 1 comprises the active and passive components 5,6, at least some of these components may be arranged outside a housing surrounding the RDHx. As an example, the pressure sensor 1385946PC01

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[0133] shown in figure 2 may be arranged at other locations than where it is shown in the figure, such as between the computer servers 12 or in the space between rows of computer servers.

[0134] Thus, in the RDHx 1 illustrated in figure 2, a passive component in the form of a pressure sensor 13 is arranged to determine air pressure inside said server rack. By use of this pressure sensor 13, the electronic processor 10 is configured to detect a pressure change in said air pressure. Signals received from this pressure sensor 13 thereby enables the electronic processor 10 to determine an operation point for the pump 7 and / or the fan 2.

[0135] In a RDHx system 11 having a RDHx 1 as shown in figure 2, each RDHx 1 is autonomous and has its own RDHx controller 9. In slightly different embodiments, each RDHx 1 has two RDHx controllers 9 for redundancy. The system level control is that each RDHx 1 monitors changes in room temperature and assumes that one or more RDHx has failed if the room temperature rises. The RDHxs that observe rising room temperature will then compensate by increasing the difference between the temperature of their exhaust air and the target room temperature. As an example, if the target room temperature is 24 degrees Celsius, the RDHx will try to blow out air with a temperature of 22 degrees Celsius. If the target room temperature is 24 degrees Celsius, but the RDHx controller 9 measures that it is actually e.g. 28 degrees Celsius, the RDHx 1 will compensate by aiming to blow out air with a temperature of 18 degrees Celsius, if possible, and it will typically also try to increase the airflow. This may be limited by the RDHx's max capacity, the temperature of the coolant etc.

[0136] It is noted that in some embodiments, a pump 7 may be shared between a plurality of RDHxs and feed coolant in parallel to heat exchangers of a plurality of RDHxs. The flow rate of coolant to a specific heat exchanger may be controlled by a motorized flow valve as otherwise disclosed herein.

[0137] In preferred embodiments, a RDHx comprises at least one passive component being a least one pressure sensor 13. Such sensor(s) may be arranged to determine air pressure inside in relation to the servers. In preferred embodiments, one or more pressure sensors are arranged upstream and85946PC01

[0138] 18

[0139] downstream of a fan of the RDHx. Further, many servers have fans which tend to provide a higher than atmospheric pressure conditions upstream of a RDHx. In such and other preferred embodiments, the pressure sensors upstream and downstream of the fan of a RDHx is used to control the fan of the RDHx to provide essentially atmospheric pressure upstream of the fan of the RDHX. Such pressure sensors may be advantageous in the sense that an increase / decrease in heat production inside a server often increases / decreases the pressure behind the server. Such an increase / decrease in pressure may advantageously be counteracted to maintain a substantially constant temperature inside the server.

[0140] Figure 3 schematically shows an example of a RDHxs 1 comprising directed air flow guides (not shown) for providing a directed air flow in directions different from straight out of the server rack. Such air flow guides are considered as active components 5 controlled by the RDHx controllers 9. Hereby a stream of air flowing through said directed air flow guides is directed away from one of said servers 12 in at least one selectable direction by controlling said directed air flow guides Preferably, the RDHx controller(s) 9 is / are configured to direct said stream towards neighbouring RDHxs 1 to ensure good mixture of air and thereby the required cooling even in case some of the RDHxs 1 stop working as intended.

[0141] The invention can be implemented by means of hardware, software, firmware or any combination of these. The invention or some of the features thereof can also be implemented as software running on one or more electronic processors.

[0142] The individual elements of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way such as in a single unit, in a plurality of units or as part of separate functional units. The invention may be implemented in a single unit, or it may be both physically and functionally distributed between different units and processors.85946PC01

[0143] 19

[0144] LIST OF REFERENCE SYMBOLS USED

[0145] 1 RDHx

[0146] 2 Fan

[0147] 3 Temperature sensor

[0148] 4 Heat exchanger

[0149] 5 Active component

[0150] 6 Passive component

[0151] 7 Pump

[0152] 8 Motorized valve

[0153] 9 RDHx controller

[0154] 10 Processor

[0155] 11 RDHx system

[0156] 12 Computer server

[0157] 13 Pressure sensor

[0158] Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is to be interpreted in the light of the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

85946PC0120CLAIMS1. A computer implemented method of operating a RDHx system (11) for cooling of computer servers (12), said RDHx system (11) comprising a plurality of RDHxs (1) and at least one computer implemented RDHx controller (9) each comprising an electronic processor (10), wherein:• each of said RDHxs (1) comprises:o at least one heat exchanger (4),o at least two active components (5) including at least one speed controllable fan (2) at least assisting in providing a flow of air through said servers (12), and at least one speed controllable pump (7) providing a flow of fluid through said at least one heat exchanger (4), o at least two passive components (6) including at least one temperature sensor (3), and at least one pressure sensor (13),• each of said at least one electronic processor (10) comprises a plurality of addressable I / O ports to which said active and passive components (5, 6) are connected, such as wiredly connected,• each of said at least one RDHx controller (9) being configured to:o scan said I / O ports and for each I / O port detect whether one of said active components (5) or said passive components (6) is connected to that port, and when one of said active or passive components (5,6) is detected, registering said detected active or passive component (5,6) by registering a port address of said addressable I / O ports to which said detected component is connected, such as wiredly connected, thereby providing at least one configured RDHx controller (9),o control said registered active components (5) based on input from said registered passive components (6) to obtain a preselected temperature inside said servers (12) and / or in the vicinity of each of said RDHxs (1).

2. A method according to claim 1, wherein for each of said detected active and / or passive components (5,6) one or more characteristics thereof is determined by sequentially:- outputting a control signal via said registered port address of said addressable I / O port to which said active and / or passive component (5,6) is connected, - receiving a feedback signal resulting from the control signal, and85946PC0121- based on known correlations between input and resulting output for possible active and / or passive components, determining the characteristics of said detected active and / or passive component (5,6).

3. A method according to claim 1, wherein for each of said detected active components (5), an operation map is determined by sequentially outputting, via said registered port address to which said active component (5) is connected, a number of different control signals , and for each output control signal:- receiving a feedback signal resulting from the output control signal,- recording an operation state of said active component (5), the operation state corresponding to said control signal.

4. A method according to claim 2 or 3, wherein each combination of control signal and resulting feedback signal is used to calibrate the settings of each of the active and / or passive components (5,6).

5. A method according to claim 3 or 4, wherein said RDHx controller (9) is configured to obtain said preselected temperature or a preselected temperature profile by said RDHx system (11) comprising a computer implemented simulator, wherein said computer implemented simulator is configured to determine a new operation state for at least one, such as all, of the registered active components (5), said new operation state providing said preset temperature and / or temperature profile based on a present operation state of the registered active components (5), readings by said registered passive components (6), and said operation map.

6. A method according to claim 5, wherein said computer implemented simulator comprises or has access to an operation space spanned by operation states for said active components (5) and corresponding temperatures at positions in said RDHx system (11) of said registered passive components (6) being temperature sensors (3).

7. A method according to any one of the preceding claims, wherein, for each detected active component (5), said detection of said active components (5) comprises determination of:85946PC0122a component type, anda control parameter range.

8. A method according to claim 7, wherein said component type and control parameter range are determined, for a selected RDHx (1) at a time, for one or more of said RDHxs (1) by said RDHx controller(s) (9) providing a number of control inputs to one of said detected active component (5) forming part of said selected RDHx (1) and registering changes in temperature(s) sensed by said at least one temperature sensor (2) and / or registering changes in pressure(s) sensed by said at least one pressure sensor (13), the sensors (2,13) forming part of said selected RDHx (1).

9. A method according to any one of the preceding claims, wherein said active components (5) further comprises one or more of:• pumps (7) for pumping liquid, preferably water, through one or more heat exchangers, and• motorized valves (8) for controlling volume flow of said liquid through one or more of said heat exchangers.

10. A method according to any one of the preceding claims, wherein said configured RDHx controller(s) (9) is / are configured for balancing operation of one or more of said active components (5) to compensate for a malfunction of one or more of said active components (5).

11. A method according to claim 10, wherein said malfunction of one of said active components (5) is detected by determining that:• operation of a selected one of said active components (5) in different operation conditions does substantially not, such as does not, affect a temperature otherwise affectable by said selected active component (5) when it functions satisfactorily.

12. A method according to claim 10 or 11, wherein said compensation comprises increasing an operation state for at least one of said active components (5) not being malfunctioning to obtain said preselected temperature.85946PC012313. A method according to any one of the preceding claims, wherein• said scanning for said active and passive components (5,6) is carried out recurrently to obtain configured RDHx controller(s) (9) based a most recent registration of said active and passive components (5,6).

14. A method according to any one of the preceding claims, wherein at least one, such as a plurality of, such as each, RDHx controller (9) several times per second, such as up to ten times per second, analyses:- an actual flow of air calculated from an actual fan speed setting of the at least one fan,- an actual air pressure determined by the at least one pressure sensor (13), and- an expected air pressure development based on pressure trend analysis and extrapolation through non-linear curves,wherein in each calculation:- the controller calculates a fan speed setting a configurable number of seconds into the future,- a relation between air flow, input temperature of the fluid, and the resulting steady state temperature is mapped and stored, and- an eventual flow is mapped and stored based on steady-state observations;thereby enabling the RDHx controller to precisely set the speed of the at least one fan and the speed of the at least one pump to obtain the preselected temperature inside said servers (12) and / or in the vicinity of each of said RDHxs (1).

15. A method according to any one of the preceding claims, wherein said computer implemented method comprises using:• a computer implemented simulation model of said RDHx system (11) operated by said configured RDHx controller(s) (9), wherein said simulation model: o comprises a functional representation of said active and said passive components (5,6) of said RDHx system (11), ando is configured to estimate temperatures in said RDHx system (11) based on operation conditions of said active components (5), heat produced by said servers (12) and temperature(s) of air surrounding said servers,85946PC0124• a computer implemented optimizer configured to provide optimized configured RDHx controller(s) (9) on the basis of simulations carried out by said simulation model,wherein• said optimized configured RDHx controller(s) (9) is / are used as said configured RDHx controller(s) for controlling said registered active components (5).

16. A method according to claim 15, wherein said optimization is a minimization of temperature variations in the air output of the RDHx system (11).

17. A method according to any one of the preceding claims, wherein at least one, such as all, of said RDHxs (1) is configured to provide a directed air flow in directions different from straight out of the server rack, by comprising one or more directed air flow guides being active components (5) controlled by said configured RDHx controller(s) (9), wherein a stream of air flowing through said directed air flow guides away from one of said servers (12) is directed in at least one selectable direction by controlling said directed air flow guides.

18. A method according to claim 17, wherein said configured RDHx controller(s) (9) is / are configured to direct said stream of air towards neighbouring RDHxs (1) to ensure good mixture of air and thereby the required cooling and preferably avoiding areas of varying temperature.

19. A RDHx system comprising a plurality of RDHxs, the RDHX system being configured for being operated by a computer implemented method according to any one of the preceding claims.

20. A computer program product being adapted to enable a RDHx controller having data storage means in connection therewith to carry out a method according to any one of claims 1 to 18.

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