Abstract:
The invention is a cooling module for one or more data centers. The cooling module accepts coolant from a data center, chills the coolant, then returns the coolant to the data center. The coolant is subject to cooling via a free cooling system and a then chiller. The chiller includes a bypass. The free cooling system and the chiller are fluidly connected in a second cooling loop that includes a dry cooling tower. A pump maintains pressure at a predetermined level.

Description:
CLAIM FOR PRIORITY 
     The present application is a national stage filing under 35 U.S.C 371 of PCT application number PCT/EP2010/058130, having an international filing date of Jun. 10, 2010, which is incorporated by reference in its entirety. 
     BACKGROUND 
     For various economic and business reasons enterprises are increasingly centralizing their backend computer systems in purpose built data centers. Data centers typically house high concentrations and densities of such computer systems and additionally provide facilities such as uninterruptible power supplies and cooling systems necessary for the operation of the computer systems in the data center. 
     Different data centers are typically unique in their requirements and capacity, since the requirements of data centre customers are highly individual. Accordingly, the cooling requirements of data centers are also highly individual and must be carefully designed to provide an appropriate amount of cooling for their associated data center. 
     However, designing and building custom cooling facilities is a complex, time-consuming and expensive task. Furthermore, as data center requirements change over time, for example through the addition of extra computing capacity, corresponding changes may be required to the cooling facilities. 
     SUMMARY 
     According to one embodiment, there is provided cooling apparatus comprising an outlet for supplying chilled liquid, an inlet for receiving return chilled liquid, a free cooling system for providing first cooling the return chilled liquid, a chiller unit for further cooling the first cooled return liquid to a predetermined temperature, a pressure difference sensor for measuring the pressure difference between the chilled liquid supplied at the outlet and the return liquid received at the inlet, and a flow control module for maintaining a predetermined pressure difference between the liquid supplied at the outlet and the return liquid received at the inlet. 
    
    
     
       BRIEF DESCRIPTION 
       Embodiments of the invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram showing an overview of a data center according to one embodiment of the present invention; 
         FIG. 2  is a block diagram showing a simplified overview of a cooling module according an embodiment of the present invention; and 
         FIG. 3  is a block diagram of a modular cooling system according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , there is shown an overview of a facility  100  according to an embodiment of the present invention. 
     The facility  100  comprises a number of data center modules  110 . In one embodiment each data center module is a containerized data center module housed, for example, in any suitable transportable container such as an Intermodal Transport Unit (ITU), shipping container, POD (portable on demand), or the like. In a further embodiment one or more of the data center modules may be a ‘bricks and mortar’ data center. 
     Each of the data center modules  110  house internal cooling equipment, such as computer room air handling (GRAN) units, and air handling units (AHU), that require a supply of chilled liquid, such as chilled water, in order to operate. 
     To supply chilled water to the data center modules  110 , one or more cooling modules  102  are provided. The cooling modules  102  may, for example, be housed in a transportable container, such as an ITU, a POD, a shipping container, or the like. 
     Each cooling module  102  has a chilled water supply outlet  116  and a warmed chilled water return inlet  118  which are connected to distribution pipework  112  and  114  respectively. Each data center module  102  is removably connected to the distribution pipework  112  and  114  through isolation valves  104  and  106 . 
     Cooling equipment, such as CRAHs and AHUs, within each data center module  110  is also removably connected to the distribution pipework  112  and  114 . 
     In this way, chilled water provided from the outlets  116  of the cooling modules  102  is provided to cool the internal cooling equipment of each data center module  110 . Warmed return chilled water is returned to the cooling modules  102  through return inlets  118 . 
     Each cooling module  102  provides up to a predetermined cooling capacity and is factory tested and configured to supply chilled water against a predetermined external differential pressure. The pressure difference between the inlets and outlets of each cooling module may be set individually to ensure that all cooling loads in the data centre may be met. In this way, each cooling module  102  provides a variable flow of chilled water to the distribution pipework  112 . The cooling modules  102  are described in further detail below. 
     In one embodiment, the cooling modules  102  are configured to supply a variable flow of chilled water at a substantially constant supply temperature. In a further embodiment, the cooling modules  102  are configured to supply a variable flow of chilled water at a substantially constant return temperature. 
     Advantageously, by providing modular cooling modules  102  the design and implementation of a data center cooling system can be substantially simplified. For example, when the data center  100  is designed, the cooling requirements of the initial design can be determined and one or more cooling modules  102  can be included in the data center to provide an appropriate amount of cooling. This avoids the need to design from scratch a ‘bricks and mortar’ type custom built chilled water system. Additionally, since the cooling modules  102  provide a variable flow of chilled water, the cooling modules  102  provide only the amount of chilled water required by the cooling systems of the data center modules. 
     Furthermore, if the cooling requirements of the data center change overtime, for example, through the addition or removal of computing equipment, cooling modules may be added or removed from the data center in a simple manner. Additionally, since each cooling module is factory tested, installation of such a module is greatly simplified, requiring little more than connection to the distribution pipework  112  and  114 , an appropriate power supply, and a water supply. If applicable, connection may also be made to an evaporative cooling plant, such as adiabatic coolers and cooling towers. Yet further, the cooling modules  102  are configured to use free cooling when ambient conditions allow thereby increasing their energy efficiency. 
       FIG. 2  shows a simplified block diagram of a cooling module  200  according to an embodiment of the present invention. In the accompanying drawings solid connecting lines are used to represent pipework and dashed connecting lines are used to represent control signals. 
     The cooling module  200  has an outlet  202  which supplies chilled water and an inlet  204  which receives warmed return chilled water. The warmed return chilled water is chilled water that has been warmed, for example, during the creation of cooled air, such as by mechanical air conditioning units. The warmed return chilled water is fed through a chiller unit  210  that cools the warmed return chilled water to a desired temperature. 
     The chiller unit  210  comprises a free cooling module  212  for cooling the return water through non-mechanical chilling means such as heat exchangers. The chiller unit  210  also includes a mechanical chiller  211 , such as a refrigeration loop, for further chilling the cooled return water when free cooler module  212  is unable to cool the return water to the desired temperature. In one embodiment, the mechanical chiller unit  211  is configured to cool the warmed return chilled water by 5 to 10 degrees, although those skilled in the art will appreciate that in other embodiments a greater or lesser degree of cooling may be obtained to meet specific requirements. 
     In alternative embodiments, the non-mechanical and mechanical chilling means are used in parallel, so that the system can operate either with mechanical cooling, free cooling, or both mechanical and free cooling. 
     The cooling module  200  additionally includes a pressure sensor  206  for measuring the outlet water pressure at, or in close proximity to, the outlet  202 . A further pressure sensor  208  is provided for measuring the return water pressure at, or in close proximity to, the return inlet  204 . A control logic module  214  obtains the two pressure measurements and determines the pressure differential between the inlet and outlet pressures. The control logic  214  controls a flow control module  216  to maintain a predetermined pressure differential between the inlet  202  and outlet  204 . Additionally, a pressurization module (not shown) may used to maintain a liquid pressure above atmospheric pressure, to prevent cavitation within the flow control module  216 . The flow control module may comprise, for example, one or more variable speed pumps. 
     One advantage this arrangement brings about is that all the control loops and cabling are contained within the chilled water supply module, thereby avoiding having connections and wiring further down the chilled water distribution system. This increases the modularity of the cooling module  200 . 
     Referring now to  FIG. 3 , there is shown a more detailed view of a modular cooling module  300  according to one embodiment of the present invention. 
     The cooling module  300  has a chilled water outlet  116  through which chilled water is output, and a return inlet  118  through which warmed chilled water is returned to the cooling module. The outlet  116  and inlet  118  are connected respectively to isolating valves  304  and  302 . These valves enable the cooling module  300  to be isolated and transported with ease, and enable quick and easy connection within a facility  100  such as a data center. 
     Warmed return chilled water is received at inlet  118  from, for example, a data center module  110 . The warmed return chilled water passes through a heat exchanger  306 , such as a plate heat exchanger. The heat exchanger  306  is arranged to cool the warmed return chilled water through free cooling. The cooled chilled water is then pumped, by pump  308 , through a chiller unit  309 . The pump  308  is used to ensure a predetermined differential pressure, as previously described. The chiller unit  309  is comprised of an evaporator  310 , a condenser  316 , a compressor  312 , an expansion device  314 , and control logic  317 . The control logic is configured so the chiller unit  309  outputs water at a substantially constant predetermined or programmed temperature. 
     Depending on the temperature of the water cooled by the heat exchanger, the chiller unit  9  may or may not need to function, or may need to function partially at a reduced part load. For the purposes of this example, assume that the cooling module  300  is configured to supply chilled water at 15 degrees Celsius. If warmed return chilled water is input to the heat exchanger at 20 degrees Celsius, and is cooled by the heat exchanger, through free cooling, to 15 degrees Celsius no further mechanical cooling of the water is required. In this case, the chiller unit control logic  317  may stop or reduce the functioning of the chiller unit. 
     If, however, the heat exchanger is only able to cool the water to, say, 17 degrees Celsius, for example if the return water is at a higher temperature or if ambient conditions do not allow for sufficient free cooling of the return water, the chiller unit control logic  317  controls the operation of the chiller unit  309  to provide the water output from the chiller unit  309  at the predetermined temperature. Such control may be achieved, for example, in any suitable manner, such as by controlling the compressor  312  speed, inlet guide vanes, control valves, cycle time, etc. 
     The condenser water warmed by the heat exchanger  306  is cooled using, for example, a dry/adiabatic cooler or cooling tower  318 . 
     A condenser water bypass  319  is provided to allow water from the output of the condenser  316  to be fed back to the input of the condenser  316  or to bypass it to avoid problems with the condenser temperature becoming too low. The opening and closing of the condenser water bypass  319  is controlled by an automatic valve  321 , controlled by the chiller control logic  317 . 
     To ensure that the chilled water supplied at outlet  116  is supplied at a constant differential pressure, pressure gauges  326  and  324  are provided. Pressure gauge  324  measures the pressure of the return chilled water at, or in close proximity to, inlet  118 , and pressure gauge  326  measures the pressure of the chilled water at, or in close proximity to, outlet  116 . Based on the measured inlet and outlet pressures the controller  322  ensures that an adequate pressure difference is maintained between the returned water and the chilled water output by controlling the speed of the pump  308 , through a variable frequency drive module  320 . By ensuring an adequate pressure difference ensures that the chilled water supplied by the cooling module  300  is able to circulate in distribution pipework  112  and  114  of a data center  100 , whilst ensuring correct operation of any other cooling modules present in the data center. Typical differential pressures may be in the range from approximately 100 kPa to 500 kPa, although this may be varied depending on specific circumstances. The pressure differential is controlled to avoid problems of pump cavitation at low pressures and to keep the pressures below maximum design pressures of the facility. 
     An evaporator bypass  311  is provided to allow the chiller unit  309  to operate below its minimum flow rate, for example with low cooling loads. The chiller unit  309  will normally have its own differential pressure controller across the evaporator to ensure its minimum flow rate is satisfied. Below this minimum flow rate it will disable the chiller. The bypass  311  bypasses chilled water from the chiller unit  309  back to the input of the chiller unit  309 . The evaporator bypass  311  is controlled through an automatic valve  313  controlled by controller  317 . 
     When assembling the cooling module  300  factory testing is performed to ensure that the cooling module  300  is able to provide the required amount of cooling and that all its control functions operate correctly. Testing is achieved using a load bank  328  that is detachably connected to the outlet  116  and inlet  118 . When the load bank  328  is present, the valves  304  and  302  are shut and the valves  330  and  232  are opened. 
     The load bank  328  may be any suitable heat source, such as a boiler, used for generating a predetermined amount of heat for heating up chilled water output from the cooling module  300 . The load bank  328  may also reduce the pressure of the supplied chilled water, to simulate the pressure reduction experienced in a typical data center  100 . In this way, the cooling module  300  can be fully configured and tested to ensure correct operation over a wide range of conditions. 
     Once the correct operation of the cooling module  300  has been verified, the load bank  328  may be removed from the cooling module  300 , and the cooling module  300  is then ready to be installed and used in a data center, such as data center  100 . 
     In a further embodiment, the cooling module  300  is configured to provide return water at a substantially constant temperature. This may be achieved, for example, by monitoring to the temperature of the return water and by adjusting the output temperature of the chiller unit  309  in accordance therewith, such that the return water is at a substantially constant temperature. One advantage of maintaining a substantially constant return water temperature is that the chilled water temperature may be raised, depending on the current cooling load, leading to potentially large energy savings. 
     Those skilled in the art will appreciate that reference made herein to water and water cooling systems is not limited thereto, and that any other suitable liquids, such as brines (i.e. glycol/water), refrigerants (i.e. carbon dioxide, etc), may alternatively be used. 
     Those skilled in the art will also appreciate that reference herein to data centers may include any other types of facilities having cooling requirements, such as power plants, mechanical installations, and the like.