Abstract:
A data center cooling system is provided to maintain data center temperatures without introducing detrimental conditions into the data center. The computer data center cooling system has a cooling tower that controllably provides cooling water at a temperature in a particular range. The cooling water is then pumped through a series of filtration, treatment, monitoring and separation subsystems to reliably clean the cooling water of particles and treat the cooling water to reduce the harmful effects of corrosion and scaling. Further control subsystems utilize PID loop controllers to maintain the temperature to the air-handler unit cooling coils to within one (1) degree Fahrenheit of a set point that is determined by the computer data center air conditions. The cooling system utilizes either a primary loop or a combination of primary/secondary loops to achieve the highest system efficiency.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. The Field of the Invention 
         [0002]    This invention relates to cooling systems that provide cooling to computer data centers. 
         [0003]    2. Background and Relevant Art 
         [0004]    Generally, modern computer data centers have servers, switches, and networking equipment that are maintained to environmental standards, such as those discussed in ASHRAE TC 9.9, which is hereby incorporated by reference in its entirety. Data centers use a significant amount of energy to operate, and in fact, data center energy use is one of the fastest growing segments of energy consumption in the United States. Experts predict that by the year 2020, data center energy use will surpass the metals industry as the largest segment of energy consumption in the United States. This fact is driving data centers, especially large data centers, to find and use more energy efficient methods and systems. 
         [0005]    One way in which data centers may become more energy efficient is through increasing the efficiency of the cooling systems used to cool the data center. Conventional cooling systems may include a chiller, direct expansion gas cooling, water-side economizer, air-side economizer, or some combination of these components. In addition, conventional cooling systems often utilize water or glycol as a cooling medium in closed loop systems. Alternatively, conventional cooling systems may utilize computer room air cooling (CRAC) units placed near the server racks in a data center. In these systems, cooling is accomplished by direct expansion, water-side economizer, or chilled water. 
         [0006]    Conventional cooling systems typically use between 0.5 and 1.8 kilowatts per ton of cooling produced. As an example, a conventional large collocation facility may use 400 tons of cooling, and therefore, a data center cooling system that decreases this load would significantly reduce overall energy costs. 
         [0007]    Efforts directed at energy efficient cooling systems have focused on efficient air or other fluid distribution. For example, there have been inventions directed towards increasing the efficiency of chillers (US Pub. 20030067745), air distribution (US Pub. 20090168345, US Publ. 20040206101, U.S. Pat. No. 7,112,131, U.S. Pat. No. 6,859,366), hot and cold aisle isolation (US Pub. 20080185446), using outside air (US Pub. 20090210096), and even locating data centers on barges and using seawater to cool them (US Pub. 20080209234). 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the present invention include systems, devices and methods used to increase the energy efficiency of data center cooling systems. In particular, example embodiments of the present invention include an indirect open-loop evaporative cooling system that provides cooling to data centers. By using a unique open-loop system, higher energy efficiencies are obtained because the system cooling water is exposed to ambient air with a low wet bulb temperature. This exposure allows the cooling water to utilize the energy transfer involved in vaporization to cool the cooling water to within approximately three to five degrees Fahrenheit of the dew point. The system therefore, uses the dry ambient air as the ultimate thermal sink of the system. 
         [0009]    In this way, embodiments of the present invention can provide cooling systems that produce cooled water at an energy cost ranging from approximately 0.05 to 0.15 kilowatts per ton. At this rate, in a 400-ton conventional large collocation facility, the energy savings would be between approximately 2 and 6 gigawatt hours per year. 
         [0010]    Example embodiments of the present invention are advantageous because they provide a significant increase in the operating efficiency compared to conventional data center cooling systems. For example, the use of an open-loop system gains efficiencies in power consumption and water usage. The electrical power is saved through the increases in cooling efficiency, and water consumption is reduced by the elimination of the need to reject large amounts of heat generated by mechanical cooling devices, such as chillers. 
         [0011]    In a preferred configuration of the invention, an open-loop cooling system that provides cooling water of a desired cooling temperature is used for cooling environmentally sensitive volumes of air. This system includes an evaporative heat exchanger. Within the evaporative heat exchanger, cooling water is cooled by mixing the cooling water with air that has a low wet bulb temperature. 
         [0012]    Also, the system includes a temperature control subsystem which is connected to the evaporative heat exchanger and controls the temperature of the cooling water circulating in the open-loop cooling system. The temperature control subsystem includes a temperature monitor that measures the temperature of the cooling water. The subsystem also includes a mechanical cooler that provides supplementary mechanical cooling to the cooling water when the temperature control subsystem indicates the temperature of the cooling water is hotter than the desired cooling temperature. The subsystem also includes a mixing element that heats the cooling water if the temperature control subsystem indicates the temperature of the cooling water is cooler than the desired cooling temperature. 
         [0013]    The open-loop cooling system also includes at least one air-handler unit, which is connected to the evaporative heat exchanger and the temperature control subsystem. The air-handler unit facilitates the transfer of heat from the environmentally sensitive volume of air to the cooling water. 
         [0014]    According to another configuration of the invention, an open-loop cooling system used in cooling a data center includes at least one air-handler unit. The air-handler unit is configured to facilitate the transfer of heat from air in the data center to cooling water that circulates through a cooling water system. The cooling water system provides cooling water at a desired cooling temperature. 
         [0015]    The cooling water system includes a cooling tower, which is connected to the air-handler unit. Within the cooling tower, the cooling water mixes with air that has a low wet bulb temperature. The mixing cools the cooling water. 
         [0016]    The cooling water system also includes a temperature control subsystem, which is connected to the cooling tower and the air-handler unit. The temperature control subsystem controls the temperature of the cooling water circulating in the cooling water system. The subsystem includes a temperature monitor that measures the temperature of the cooling water. The subsystem also includes a mechanical cooler that provides supplementary mechanical cooling to the cooling water if the temperature control subsystem indicates the temperature of the cooling water is hotter than the desired cooling temperature. The subsystem also includes a mixing element that heats the cooling water if the temperature control subsystem indicates the temperature of the cooling water is cooler than the desired cooling temperature. 
         [0017]    The invention extends to a method for data center cooling using an open-loop evaporative system that facilitates the production of cooling water at a desired cooling temperature. The method includes the step of mixing heated cooling water with air that has a low wet bulb temperature in a cooling tower. This step utilizes the latent heat of vaporization to cool the cooling water. The cooling water circulates through one or more cooling coils of an air-handler unit. Within the air-handler unit, the air from the data center is forced across the cooling coil such that the air transfers its heat to the cooling water. This step heats the cooling water, which returns to the evaporative cooling tower. 
         [0018]    Additional features and advantages of embodiments of the present invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by the practice of such exemplary embodiments. The features and advantages of such embodiments may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such exemplary embodiments as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0020]      FIG. 1  illustrates a block diagram of an example of the data center cooling system; 
           [0021]      FIG. 2  illustrates a piping diagram of an example of the data center cooling system; 
           [0022]      FIG. 3  illustrates a psychometric chart showing the cooling process that can be accomplished by embodiments of the cooling system; 
           [0023]      FIG. 4  illustrates an embodiment of the air-handler unit; 
           [0024]      FIG. 5  illustrates air entrapment remedies used in an embodiment of the cooling system; and 
           [0025]      FIG. 6  illustrates a system that may be used for freeze protection in standby pumps. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Embodiments of the present invention include systems, devices and methods used to increase the energy efficiency of data center cooling systems, e.g., computer data centers. In particular, example embodiments of the present invention include an indirect open-loop evaporative cooling system that provides cooling to data centers. By using a unique open-loop system, higher energy efficiencies are obtained because the system cooling water is exposed to ambient air with a low wet bulb temperature. This exposure allows the cooling water to utilize the energy transfer involved in vaporization to cool the cooling water to within approximately three to five degrees Fahrenheit of the dew point. The system therefore, uses the dry ambient air as the ultimate thermal sink of the system. 
         [0027]    As an overview,  FIG. 1  shows an example of an open-loop cooling system  50  according to one embodiment of the present invention. For example,  FIG. 1  illustrates that the open-loop cooling system  50  can include a cooling tower  100 , one or more tower pumps  101 , one or more system pumps  106 , a filtration subsystem  102 , a chemical treatment and monitoring subsystem  103 , a temperature control subsystem  104 , one or more air-handler units  105 , a computer data center  140 , data center air  145 , and cooling water  55  that circulates through the open-loop cooling system  50 . 
         [0028]    Generally, the open-loop cooling system  50  can include piping sections through which the cooling water  55  circulates and which connect components making up the open-loop cooling system  50 . For example, in the embodiment illustrated in  FIG. 1 , the cooling water  55  circulates through a cooling tower outlet piping section  116 , a tower pump inlet piping section  117 , a tower pump outlet piping section  136 , a chemical treatment inlet piping section  118 , a chemical treatment outlet piping section  119 , a filter inlet piping section  120 , a filter outlet piping section  121 , a mechanical cooling inlet piping section  122 , a mechanical cooling outlet piping section  123 , a mixing element inlet piping section  128 , a mixing element outlet piping section  129 , a mixing element cross-over piping section  130 , a system pump inlet piping section  131 , a system pump outlet piping section  132 , an air-handler inlet piping section  133 , and a system return piping section  135 . In alternate embodiments, the configuration of the piping sections as well as the inclusion of various sections may vary from one embodiment to the next depending the cooling requirements of the data center  140 . 
         [0029]    Notwithstanding the various piping sections configurations,  FIG. 1  illustrates that the open-loop cooling system  50  includes cooling tower  100 . In one example embodiment, cooling tower  100  has a high efficiency counter-flow design with an induced draft fan. In alternate embodiments, the cooling tower may utilize other designs and configurations that perform the same or similar function as will be described below. 
         [0030]    In particular, the cooling tower  100  uses the induced draft fan to draw or blow atmospheric air  51  through an atmospheric air inlet  107 . The atmospheric air  51  interacts with the cooling water  55  that exits the system return piping section  135  and enters the cooling tower  100 . As the cooling water  55  exiting the return piping section  135  mixes with the atmospheric air  51 , the latent heat of vaporization is absorbed from the cooling water  55  and the atmospheric air  51 . As a result, the cooling water  55  is cooled. 
         [0031]    The rate and amount of cooling performed within the cooling tower  100  may depend on the wet bulb characteristics of the atmospheric air  51 . Generally, the lower the wet bulb temperature of the atmospheric air  51 , the more cooling that takes place within the cooling tower  100 . Thus, the open-loop cooling system  50  can be installed in geographic locations known to have atmospheric air  51  with low wet bulb temperatures, such as deserts or arid climates. In these optimal climates, the cooling tower  100 , may cool the cooling water  55  to within three to five degrees Fahrenheit of the dew point. Aside from the optimal climates, the open-loop cooling system  50  can be installed in a wide-range of geographic locations, although the exact efficiencies of the open-loop cooling system  50  may vary with atmospheric characteristics. 
         [0032]    Returning to the open-loop cooling system  50 , after the atmospheric air  51  is cooled within the cooling tower  100 , the atmospheric air  51  is exhausted to the atmosphere through an atmospheric air exhaust  110 . For example,  FIG. 1  illustrates that the cooling tower  100  includes an atmospheric air exhaust  110 . In one example embodiment, the atmospheric air exhaust  110  is located opposite of the atmospheric air inlet  107  to form a defined flow path of the atmospheric air  51  through the cooling tower  100 . In alternate embodiments, the location of the atmospheric air exhaust  110  can vary. 
         [0033]    Just as the atmospheric air  51  exhausts from the cooling tower  100 , the cooling water  55  which has been cooled also exits the cooling tower  100 . In one example embodiment, the cooling tower  100  is connected to the tower pumps  101  via the tower outlet piping section  116 . In particular, after the cooling water  55  is cooled within the cooling tower  100 , the cooling water  55  accumulates within the cooling tower  100  and the tower pumps  101  pump the cooling water  55  through the tower outlet piping section  116 , into the tower pump inlet piping section  117 , and through the tower pumps  101 . 
         [0034]    Although one or more tower pumps  101  can be employed in various configurations,  FIG. 2  illustrates one example embodiment in which the tower pumps  101   a  and  101   b  are configured in parallel. In the parallel configuration, one of tower pumps is designated as the operating tower pump  101   a , while the other tower pump is designated as the standby tower pump  101   b . Thus, the operating tower pump  101   a  normally pumps the cooling water  55 , while the standby tower pump  101   b  remains in standby in case the operating tower pump  101   a  fails or another system condition requires the use of the standby tower pump  101   b . In alternate embodiments, the tower pumps  101  may be configured in series or a single pump may be utilized. 
         [0035]    The tower pumps  101  are used to circulate the cooling water  55  through various components and subsystems of the open-loop cooling system  50 . In one example embodiment, the tower pumps  101  are connected to the chemical treatment and monitoring subsystem  103  and the filtration subsystem  102  via the tower pump outlet piping section  136 . In particular, the tower pump outlet piping section  136  can connect to the chemical treatment inlet piping section  118  to circulate water through the chemical treatment and monitoring subsystem  103 . The chemical treatment outlet piping section  119  is configured to return cooling water  55  that has been chemically treated to the tower pump outlet piping section  136 . 
         [0036]    In one embodiment of the open loop cooling system  50 , at least a portion of the cooling water  55  may be routed through the chemical treatment and monitoring subsystem  103 . For example, in the configuration illustrated in  FIG. 1 , a portion of the cooling water  55  exiting the tower pumps  101  into the tower pump outlet piping section  136  enters the chemical treatment and monitoring subsystem  103  via the chemical treatment inlet piping section  118 . The remainder of the cooling water  55  exiting the tower pumps  101  remains in the tower pump outlet piping section  136  and proceeds to the filter inlet piping section  120 . In alternative embodiments, none or all of the cooling water  55  exiting the tower pumps  101  may enter the chemical treatment and monitoring subsystem  103 . 
         [0037]    The portion of cooling water that enters the chemical treatment and monitoring subsystem  103  can be controlled by one or more valves. The valves can be electronically controlled and coupled with other devices, such as flow rate meters, to direct substantially exact portions of the cooling water  55  to the chemical treatment and monitoring subsystem  103  in order to maintain consistent chemical properties in the cooling water  55 . 
         [0038]    Additionally, a dedicated chemical subsystem pump may circulate the portion of cooling water  55  that enters the chemical treatment and monitoring subsystem  103 . For example in the embodiment illustrated in  FIG. 2 , a dedicated chemical subsystem pump  210  circulates the cooling water  55  through the chemical treatment and monitoring subsystem  103 . In alternate embodiments, the open-loop cooling system  50  may utilize an alternate pressure source to circulate the cooling water  55  through the chemical treatment and monitoring subsystem  103 . 
         [0039]    In addition to the various components used to direct cooling water  55  to the chemical treatment and monitoring subsystem  103 , the chemical treatment and monitoring subsystem  103  can include various components to chemically monitor the cooling water  55  and chemically treat the cooling water  55 . For example,  FIG. 2  illustrates that the chemical treatment and monitoring subsystem  103  can include a corrosion coupon rack  202 . In operation, the corrosion coupon rack  202  includes coupons of known size/weight of a material that can corrode when exposed to the cooling water  55 , such as copper. In alternative embodiments, other corrodible materials can be used within the corrosion coupon rack  202 . 
         [0040]    The coupons are positioned on the corrosion coupon rack  202  such that the coupons interface with the cooling water  55 . The rate at which the coupons corrode depends upon the corrosive properties of the cooling water  55 . The coupons can then be removed from the corrosion coupon rack  202  and measured and/or weighed to determine and monitor the corrosive properties of the cooling water  55 . For example, if the cooling water  55  becomes too corrosive, remedial actions can be taken, such as adding additional chemicals to the cooling water  55  to make the cooling water  55  less corrosive. 
         [0041]    In one example embodiment, the chemical treatment and monitoring subsystem  103  includes a chemical injection pump  204 , as illustrated in  FIG. 2 . The chemical injection pump  204  allows an operator to inject chemicals as required into the open-loop cooling system  50  via the chemical treatment and monitoring subsystem  103 . In one example, an operator can control the chemical injection pump  204  from a control center. In alternate embodiments, the chemical treatment and monitoring subsystem  103  automatically injects chemicals as required by the open-loop cooling system  50 . 
         [0042]    In addition to the chemical injection pump  204 , the chemical treatment and monitoring subsystem  103  may include additional components. For example,  FIG. 2  illustrates an embodiment of the chemical treatment and monitoring subsystem  103  that includes a centrifuge  203 . The centrifuge  203  can separate particulate matter contained in the cooling water  55  that is routed to the chemical treatment and monitoring subsystem  103 . In alternate embodiments, the chemical treatment and monitoring subsystem  103  can include similar components and processes that separate corrosive particular matter from the cooling water  55 . 
         [0043]    In addition to the components described above, the chemical treatment and monitoring subsystem  103  can include a wide array of chemical monitoring equipment used to monitor a wide array of chemical properties of the cooling water  55 , depending on the desired chemical properties of the cooling water  55 . For example, in one embodiment, the cooling water  55  is substantially pure water. In alternative embodiments, however, the cooling water  55  can be chemically treated water, a water-based chemical solution, or another cooling medium with carefully engineered thermodynamic properties. 
         [0044]    Once the cooling water  55  or a portion of cooling water  55  is processed through the chemical treatment and monitoring subsystem  103 , the cooling water  55  can enter the filtration subsystem  102 . For example, as shown in  FIG. 1 , the chemical treatment and monitoring subsystem  103  is connected to the filtration subsystem  102  via the chemical treatment outlet piping section  119 , and the filter inlet piping section  120 . The cooling water  55  exiting the chemical treatment and monitoring subsystem  103  via the chemical treatment outlet piping section  119  mixes with the cooling water  55  that did not enter the chemical treatment and monitoring subsystem  103  in the filter inlet piping section  120 , and then enters the filtration subsystem  102 . In alternative embodiments, the cooling water  55  exiting the chemical treatment and monitoring subsystem  103  via the chemical treatment outlet piping section  119  may mix with the cooling water  55  that did not enter the chemical treatment and monitoring subsystem  103  at another point in the open-loop cooling system  50 . 
         [0045]    The filtration subsystem  102  filters the cooling water  55  before it enters the filter outlet piping section  121 . The filtration subsystem  102  can include, but is not limited to media filters, screen filters, disk filters, slow sand filter beds, rapid sand filters and cloth filters that can be configured to various sizes of particles from the cooling water  55 . In at least one embodiment, the filtration subsystem  102  substantially prevents a particle of a predetermined size or larger from circulating with the cooling water  55  through the portion of the open-loop cooling system  50  behind the filtration subsystem  102 . 
         [0046]    Once the cooling water  55  passes through the filtration subsystem  102 , the cooling water  55  can enter one or more subsystems within the open-loop cooling system  50 . For example, as shown in  FIG. 1 , the filtration subsystem  102  is connected to the temperature control subsystem  104  via the filter outlet piping section  121 . In alternate embodiments, the connection between the filtration subsystem  102  and the temperature control subsystem  104  can exist in an alternate location in the open-loop cooling system  50 . 
         [0047]    Generally, the temperature control subsystem  104  provides the cooling water  55  with supplementary temperature control in the event that the cooling tower  100  was unable to produce cooling water  55  with a desired temperature for the cooling cycle. For example, in the event that the atmospheric air  51  becomes humid, the atmospheric air  51  will have a higher wet bulb temperature. This condition reduces the efficiency of the cooling that occurs in the cooling tower  100  and may necessitate supplementary mechanical cooling in the temperature control subsystem  104 . 
         [0048]    Additionally, the temperature control subsystem  104  can be configured to function only if the cooling water  55  is not at the desired temperature. For example, if the cooling water  55  is at the desired temperature, the cooling water  55  can bypass the temperature control subsystem  104 . 
         [0049]    Depending on the temperature of the cooling water  55  entering the temperature control subsystem  104 , the temperature control subsystem  104  can employ various components to adjust the temperature of the cooling water  55 . In one example embodiment, the temperature control subsystem  104  can include a mechanical cooler  137 , such as a chiller, that can provide supplementary mechanical cooling to the cooling water  55  as required to produce cooling water  55  with the desired temperature for the cooling cycle. 
         [0050]    Thus, the combination of the cooling tower  100  (high efficient cooling) and the mechanical cooler  137  (lower efficient cooling) used to control the temperature of the cooling water  55  is highly energy efficient and may allow temperature control of the cooling water  55  to within one (1) degree Fahrenheit. For example, under certain conditions, the atmospheric air  51  has wet bulb temperature properties that allow the cooling tower  100  to adequately cool the cooling water  55 , thus providing the highest efficiency possible as no supplementary mechanical cooling is needed. With other conditions, for example when the atmospheric air  51  has a higher wet bulb temperature, the cooling water  55  can require supplementary mechanical cooling. However, because the cooling tower  100  has provided most of the cooling, the mechanical cooler  137  only needs to lower the temperature of the cooling water  55  a few degrees. Thus, the majority of the work performed in the open loop cooling system  50  is provided by the high efficient cooling component while the lower efficient cooling is only utilized as required and in a limited fashion. Therefore, the temperature of the cooling water  55  is controlled in a highly energy efficient manner. 
         [0051]    In addition,  FIG. 1  illustrates that the temperature control subsystem  104  can be configured in series with the cooling tower  100 . Configuring the temperature control subsystem  104  in series with the cooling tower  100  eliminates the need for an additional cooling tower, heat exchangers, or secondary closed loop for chilled water or glycol, as with conventional systems. 
         [0052]    As shown in  FIG. 1 , the mechanical cooler  137  is connected to the filter outlet piping section  121  via the mechanical cooling inlet piping section  122  and the mechanical cooling outlet piping section  123 . A controlled portion of the cooling water  55  exiting the filtration subsystem  102  through the filter outlet piping section  121  enters the mechanical cooling inlet piping section  122 . The remainder of the cooling water  55  remains in the filter outlet piping section  121 . Depending on the wet bulb temperature of the data center air  145 , the amount of cooling water  55  that enters the mechanical cooler  137  can range from none of the cooling water  55  to all of the cooling water  55 . 
         [0053]    In alternative embodiments, the portion of the cooling water  55  entering the mechanical cooler  137  could be based on other physical conditions in the open-loop cooling system  50 . For example, the portion of the cooling water that enters the mechanical cooler  137  from the filter outlet piping section  121  may be controlled such that condensation does not form in the air-handler units  105 . 
         [0054]    In addition, in the embodiment illustrated in  FIG. 1 , the cooling water  55  that entered the mechanical cooler  137  via the mechanical cooling inlet piping section  122  is cooled in the mechanical cooler  137  then exits the mechanical cooler  137  via the mechanical cooling outlet piping section  123 . The cooling water  55  exiting the mechanical cooler  137  via the mechanical cooling outlet piping section  123  mixes with the portion of the cooling water  55  that exited the filtration subsystem  102  via the filter outlet piping section  121 . The result of the mixing of the cooling water  55  exiting the mechanical cooler  137  via the mechanical cooling outlet piping section  123  with the cooling water  55  exiting the filtration subsystem  102  via the filter outlet piping section  121  is the cooling water  55  in the mixing element inlet piping section  128  is cooler than the cooling water  55  exiting the filtration subsystem  102 . 
         [0055]    In one example embodiment of the temperature control subsystem  104 , twenty-five percent of the cooling water  55  exiting the filtration subsystem  102  via the filter outlet piping section  121  enters the mechanical cooler  137  via the mechanical cooling inlet piping section  122 . In this example embodiment, the cooling water  55  is cooled twenty degrees Fahrenheit in the mechanical cooler  137 . The cooling water  55  then exits the mechanical cooler  137  via the mechanical cooling outlet piping section  123 . The cooling water  55  exiting the mechanical cooler  137  via the mechanical cooling outlet piping section  123  mixes with the cooling water  55  that exited the filtration subsystem  102  via the filter outlet piping section  121  and entered the mixing element inlet piping section  128 . When this mixing occurs, the cooling water  55  entering the mixing element inlet piping section  128  is cooled five degrees Fahrenheit. 
         [0056]    If a ten degree Fahrenheit cooling was needed, fifty percent of the cooling water  55  can be directed into the mechanical cooler  137  to be cooled by twenty degrees. Thus, when the fifty percent portion is mixed with the cooling water  55  that was not mechanically cooled, the overall temperature drop of the cooling water  55  would be ten degrees. 
         [0057]      FIG. 2  illustrates another example of a mechanical cooler. In particular,  FIG. 2  illustrates a temperature control subsystem  104  that includes a multi-element mechanical cooler  221  consisting of a condenser  223  and a chiller  222 . In the embodiment illustrated in  FIG. 2 , the condenser  223  is connected to the filter outlet piping section  121  via a condenser cooling inlet piping section  126 . The condenser  223  is connected to system return piping section  135  via a condenser cooling outlet piping section  127 . 
         [0058]    In the embodiment illustrated in  FIG. 2 , a portion of the cooling water  55  exiting the filtration subsystem  102  enters the condenser  223  via the condenser cooling inlet piping section  126 . The condenser  223  utilizes the cooling water  55  as the cooling medium for the chiller  222 . The cooling water  55  utilized in the condenser  223  as a cooling medium exits the condenser  223  via the condenser cooling outlet piping section  127  and is routed to the system return piping section  135 . Thus, the configuration illustrated in  FIG. 2  utilizes the cooling capacity of the cooling tower  100  to a maximum extent as well as prevents the heat absorbed in the condenser  223  from being introduced into the open-loop cooling system  50 . 
         [0059]    In some atmospheric conditions, it may be the case that the cooling tower  100  cooled the cooling water  55  to a temperature below the desired temperature of the cooling cycle. Under these conditions, the cooling water  55  needs to be heated to provide the required cooling of the data center air  145  through the air-handler units  105  (discussed further below). Thus, in one example embodiment, the temperature control subsystem  104  can include a mixing element  138  to increase the temperature of the cooling water  55  if the cooling water  55  is too cold, as illustrated in  FIG. 1 . 
         [0060]    In one example embodiment, the mixing element  138  is a valve that mixes cooling water  55  with a high temperature exiting the air-handler units  105  with the cooling water  55  with a low temperature in the temperature control subsystem  104 . For example,  FIG. 2  illustrates a mixing element  138  that is a three-way bypass valve  220 . In alternate embodiments, the mixing element  138  may be an injection pump. The mixing element  138  can be communicably connected to a control center that automatically controls the mixing element  138  based on the temperature of the cooling water  55  entering the temperature control subsystem  104 . 
         [0061]    As shown in  FIG. 1 , the mixing element  138  is connected to the mechanical cooler  137  and the filtration subsystem  102  via the mixing element inlet piping section  128  which is connected to the filter outlet piping section  121  and the mechanical cooling outlet piping section  123 . As further illustrated in  FIG. 1 , the mixing element  138  is connected to the system return piping section  135  via the mixing element cross-over piping section  130 . As further illustrated in  FIG. 1 , the mixing element  138  is connected to the system pump inlet piping section  131  via the mixing element outlet piping  129 . 
         [0062]    Furthermore,  FIG. 1  illustrates that the mixing element  138  mixes the cooling water  55  entering the mixing element  138  via the mixing element inlet piping section  128  with the cooling water  55  in the system return piping section  135  via the mixing element cross-over piping  130  then routes the cooling water  55  that has been mixed to the mixing element outlet piping section  129 . By mixing the cooling water  55  entering the mixing element  138  via the mixing element inlet piping section  128  with the cooling water  55  entering the mixing element  138  via the mixing element cross-over piping section  130  from the in the system return piping section  135 , the mixing element  138  increases the temperature of the cooling water  55  exiting the mixing element  138  into the mixing element outlet piping section  129 . 
         [0063]    In addition, in the example embodiment illustrated in  FIG. 1 , the quantity of cooling water  55  entering the mixing element  138  via the mixing element cross-over piping section  130  from the system return piping section  135  may be determined by the wet bulb temperature of the data center air  145 . In alternate embodiments, the quantity of cooling water  55  entering the mixing element  138  is determined by other physical properties of the open-loop cooling system  50 . For example, the quantity of the cooling water  55  entering the mixing element  138  via the mixing element cross-over piping section  130  from the system return piping section  135  is determined such that condensation does not form in the one or more air-handler units  105 . 
         [0064]    In addition, in an embodiment of the invention, the temperature control subsystem  104  may use a dedicated condenser pump and a dedicated chiller pump. For example, in the embodiment illustrated in  FIG. 2 , the temperature control subsystem  104  includes a dedicated condenser pump  212  and a dedicated chiller pump  211 . 
         [0065]    In this embodiment, an alternative piping configuration can be utilized. For example, as illustrated in  FIG. 2 , the condenser cooling inlet piping section  126  is connected to the filter outlet piping section  121 . The mechanical cooling inlet piping section  122  is connected to the mixing element outlet piping section  129  rather than the filter outlet piping section  121  as illustrated in  FIG. 1 . Additionally, in this embodiment, cooling water  55  exiting the chiller  222  circulates into the system pump inlet piping section  131  rather than into the mixing element inlet piping section  128  as illustrated in  FIG. 1 . In alternate embodiments, the piping configuration between the temperature control subsystem  104  and the open-loop cooling system  50  may take other configurations. 
         [0066]    In the embodiment illustrated in  FIG. 2 , the dedicated condenser pump  212  circulates cooling water  55  through the condenser  223  via the condenser cooling inlet piping section  126 . The dedicated condenser pump  212  then circulates the cooling water  55  out of the condenser  223  into the system return piping section  135  via the condenser cooling outlet piping section  127 . 
         [0067]    As further illustrated in  FIG. 2 , the dedicated chiller pump  211  circulates cooling water  55  into the chiller  222  via the mechanical cooling inlet piping section  122 . The dedicated chiller pump  211  then circulates the cooling water  55  out of the chiller  222  into the system pump inlet piping section  131  via the mechanical cooling outlet piping section  123 . In alternate embodiments, the open-loop cooling system  50  may utilize configurations without a dedicated condenser pump and/or a dedicated chiller pump. 
         [0068]    As discussed above, the cooling tower  100  is in series with the temperature control subsystem  104 . This allows the cooling tower  100  and the temperature control subsystem  104  to cool the cooling water  55  to within a zone of efficient cooling. For example,  FIG. 3  illustrates a zone of efficient cooling  301  for the example embodiment illustrated in  FIG. 1  at average atmospheric conditions at approximately 4200 feet above sea level. In alternate embodiments, the zone of efficient cooling would shift due to atmospheric conditions. 
         [0069]    The open-loop cooling system  50  would be most efficient below a given atmospheric wet bulb temperature. For example, the open-loop cooling system  50  illustrated in  FIG. 1  may be most efficient in areas of the world with a maximum atmospheric wet bulb temperature of 70 degrees Fahrenheit.  FIG. 3  illustrates the psychometric properties below the maximum wet bulb temperature of 70 degrees Fahrenheit  302 . This physical condition produces the highest efficiencies in the cooling tower  100 . In alternate embodiments, the maximum atmospheric wet bulb temperature producing the highest efficiencies may vary with the particular system configuration, ambient atmospheric conditions, and elevation. 
         [0070]    As the cooling water  55  circulates through the open-loop cooling system  50  the cooling water  55  is subject to psychometric changes. A psychometric change of cooling water  55  in a cooling tower  100  includes an initial physical state, a final physical state, and a change line illustrating the intermediate physical states between the initial and final physical state. For example,  FIG. 3  illustrates a cooling tower psychometric change  303  of the cooling water  55  in the cooling tower  100 . The cooling tower psychometric change  303 , for example, includes an initial physical state  304 , a final physical state  305 , and a change line  306 . 
         [0071]    The cooling tower psychometric change  303  represents the psychometric changes of the cooling water  55  as the cooling water  55  circulates from the system return piping section  135  through the cooling tower  100  and into the cooling tower outlet piping section  116 . The initial physical state  304  represents the physical properties of the cooling water  55  in the system return piping section  135 . The final physical state  305  represents the physical properties of the cooling water  55  in the cooling tower outlet piping section  116 . The change line  306  represents the cooling occurring in the cooling tower  100  due to the mixing of the cooling water  55  with the atmospheric air  51  with a low wet bulb temperature. In alternate embodiments, the cooling tower psychometric change  303  will vary with physical properties of the system and the ambient conditions of the atmospheric air  51 . 
         [0072]    As illustrated in  FIG. 3 , the final physical state  305  is located in the zone of efficient cooling  301 . This illustrates that in the embodiment illustrated in  FIG. 1  during the cooling tower psychometric change  303  the cooling tower  100  normally has the ability of to provide sufficient cooling to the cooling water  55  for circulation in the open-loop cooling system  50 . 
         [0073]    Alternatively, if adverse ambient conditions exist such as atmospheric air  51  with a high wet bulb temperature, the cooling tower  100  may produce a cooling tower psychometric change in which the final physical state of the cooling water  55  is outside the zone of efficient cooling  301 . For example,  FIG. 3  illustrates an inadequate cooling tower psychometric change  303   a . The inadequate cooling tower psychometric change  303   a  includes the initial physical state  304 , an intermediate physical state  305   a , and an intermediate change line  306   a.    
         [0074]    The inadequate cooling tower psychometric change  303   a  represents the psychometric changes of the cooling water  55  as the cooling water  55  circulates from the system return piping section  135  through the cooling tower  100  and into the cooling tower outlet piping section  116 . The initial physical state  304  represents the physical properties of the cooling water  55  in the system return piping section  135 . The intermediate physical state  305   a  represents the physical properties of the cooling water  55  in the cooling tower outlet piping section  116 . The intermediate change line  306   a  represents the cooling occurring in the cooling tower  100  due to the mixing of the cooling water  55  and atmospheric air  51  with a higher-than-optimal wet bulb temperature. In alternate embodiments, the inadequate cooling tower psychometric change  303   a  will vary with physical properties of the system and the ambient conditions of the atmospheric air  51 . 
         [0075]    As illustrated in  FIG. 3 , the intermediate physical state  305   a  is located outside of the zone of efficient cooling  301 . This illustrates that in the embodiment illustrated in  FIG. 1  during the inadequate cooling tower psychometric change  303   a  when adverse atmospheric conditions exist, the cooling tower  100  may be unable to provide sufficient cooling to the cooling water  55  for circulation in the open-loop cooling system  50 . 
         [0076]    In this situation, additional cooling may be necessary. For example,  FIG. 3  illustrates a mechanical cooler psychometric change  307  of the cooling water  55  in the mechanical cooler  137 . In this situation, the open-loop cooling system  50  embodied in  FIG. 1  introduces the cooling water  55  into a mechanical cooler  137 . Within the mechanical cooler  137 , the cooling water  55  undergoes psychometric changes. For example,  FIG. 3  illustrates a mechanical cooler psychometric change  307  of the cooling water  55  in the mechanical cooler  137 . 
         [0077]    As with the cooling tower psychometric change  303 , the mechanical cooler psychometric change  307  can include an initial psychometric state, a final psychometric state, and a trend line illustrating the intermediate psychometric states between the initial and final psychometric states. For example, in  FIG. 3 , the mechanical cooling psychometric change  307  includes an initial psychometric state  308  (which may coincide with intermediate physical state  305   a ), a final psychometric state  310 , and a trend line  309 . 
         [0078]    The mechanical cooler psychometric change  307  represents the psychometric changes of the cooling water  55  as the cooling water  55  circulates from the filter outlet piping section  121  through the mechanical cooler  137  and into the mixing element inlet piping section  128 . The initial psychometric state  308  represents the physical properties of the cooling water  55  in the filter outlet piping section  121 . The final psychometric state  310  represents the physical properties of the cooling water  55  in the mixing element inlet piping section  128 . The trend line  309  represents the cooling occurring due to the mechanical cooler  137 . In alternate embodiments, the mechanical cooler psychometric change  307  will vary with physical properties of the mechanical cooler  137  and the system configuration. 
         [0079]    As illustrated in  FIG. 3 , the final psychometric state  310  is located within the zone of efficient cooling  301 . Thus, the cooling water  55  mechanically has been cooled from a physical state outside the zone of efficient cooling  301 , such as the intermediate physical state  305   a  that resulted from the inadequate cooling tower psychometric change  303   a , to be within the zone of efficient cooling  301 . This illustrates that during the mechanical cooling psychometric change  307  the mechanical cooler  137  has the ability to provide supplemental mechanical cooling to the cooling water  55  for circulation in the open-loop cooling system  50 . 
         [0080]    Returning to  FIG. 1 , the remaining components of the open-loop cooling system  50  will be described. As shown in  FIG. 1 , the mixing element  138  is connected to the one or more system pumps  106  via the mixing element outlet piping section  129  and the system pump inlet piping section  131 . In the example embodiment illustrated in  FIG. 1 , after the cooling water  55  exits the mixing element  138  via the mixing element outlet piping section  129 , the one or more system pumps  106  pump the cooling water  55  in through the system pump inlet piping section  131 , out through the system pump outlet piping section  132 , and into the air-handler inlet piping section  133 . In alternate embodiments, the particular configuration of these components may vary. 
         [0081]    In addition to the system pumps  106  pumping the cooling water exiting the mixing element  138 , the system pumps  106  can have various configurations. For example, in the embodiment illustrated in  FIG. 2 , the system pumps  106   a  and  106   b  are configured in parallel. In this configuration, one of system pumps is designated as the operating system pump  106   a , and the other system pump is designated as the standby system pump  106   b . That is, the operating system pump  106   a  pumps the cooling water  55  while the standby system pump  106   b  remains in standby. In alternate embodiments, the system pumps  106  may be configured in series or a single pump may be utilized. 
         [0082]    As shown in  FIG. 1 , the one or more system pumps  106  are connected to the one or more air-handler units  105  via the system pump outlet piping section  132  and the air-handler inlet piping section  133 . As further shown in  FIG. 1 , the air-handler units  105  are connected to the cooling tower  100  via the system return piping section  135 . 
         [0083]    Generally, the air-handler units  105  provide an interface between the cooling water  55  cooled by the open-loop cooling system  50  and data center air  145  that has been heated in the computer data center  140 . For example,  FIG. 1  illustrates that the data center air  145  is moved into the air-handler units  105  though ducting. Specifically,  FIG. 1  illustrates the air-handler units  105  connected to the computer data center  140  via inlet ducting  141  and outlet ducting  142 . 
         [0084]    Because the cooling water  55  entering the air-handler units  105  via the air-handler inlet piping section  133 , is cooler than the data center air  145  entering the air-handler units  105  via the inlet ducting  141 , the heat in the data center air  145  transfers to the cooling water  55 , thus cooling the data center air  145 . The data center air  145  having been cooled, returns to the computer data center  140  via the outlet ducting  142 , while the cooling water  55  which has been heated enters the system return piping section  135  to be directed to the cooling tower  100  to begin the cooling cycle as described above. 
         [0085]    In one example embodiment of the air-handler units  105 , the air-handler units  105  contain a cooling coil  401 . For example,  FIG. 4  illustrates an air-handler unit  105  containing a cooling coil  401 . In the embodiment illustrated in  FIG. 4 , the air-handler inlet piping section  133  connects to the cooling coil  401 . The system pumps  106  pump the cooling water  55  into the cooling coil  401  via the air-handler inlet piping section  133 . The cooling water  55  circulates through the cooling coil  401  then exits the cooling coil  401  into the system return piping section  135 . 
         [0086]    In the example embodiment of the air-handler unit  105  illustrated in  FIG. 4 , the data center air  145  enters the air-handler unit  105  via the inlet ducting  141  then moves across the cooling coil  401 . As the data center air  145  moves across the cooling coil  401 , the data center air  145  transfers heat to the cooling water  55  moving through the cooling coil  401 . The data center air  145  exits the air-handler unit  105  through the outlet ducting  142 . 
         [0087]    As shown in  FIG. 1 , the inlet ducting  141  may contain a humidification element  143 . In the embodiment illustrated in  FIG. 1 , the humidity of the data center air  145  may be controlled by the humidification element  143 . For example, if the humidity level needs to be increased to maintain the correct data center environment, the humidification element  143  may inject water into the inlet ducting  141  as the data center air  145  enters the air-handler units  105 . In alternate embodiments, the humidity of the data center air  145  could be controlled through use of an evaporative media section, or directly in the data center  140 . 
         [0088]    In an example embodiment of the open-loop cooling system  50 , an air removal subsystem  500  may be included to remove atmospheric air  51  from the cooling water  55 . For example,  FIG. 5  illustrates an example of an air removal subsystem  500  that may be included in an embodiment of the open loop cooling system  50  to remove atmospheric air  51  from the cooling water  55 . In the embodiment illustrated in  FIG. 5 , the air removal subsystem  500  includes a supply piping port  502 , a vent piping section  504 , and a return piping port  505 . 
         [0089]    As shown in  FIG. 5 , the supply piping port  502  is provided on the top of the air-handler inlet piping section  133 . The return piping port  505  is provided on the top of the system return piping section  135 . The supply piping port  502  is connected via the vent piping section  504  to the return piping port  505 . In alternate embodiments, the supply piping port  502  may be located on a different section or multiple piping sections of the open-loop cooling system  50 . 
         [0090]    In addition, in the embodiment illustrated in  FIG. 5 , the air removal subsystem  500  may function due to a differential pressure between the air-handler inlet piping section  133  and the system return piping section  135 . The differential pressure forces atmospheric air  51  in the air-handler inlet piping section  133  through the supply piping port  502 , through vent piping section  504 , and through the return piping port  505 . The atmospheric air  51  is mixed with the cooling water  55  in the system return piping section  135  and is directed back to the cooling tower  100 . The air removal subsystem  500  illustrated in  FIG. 5  can be located at a high point of the open-loop cooling system  50 . In alternate embodiments, multiple air removal subsystems  500  may be located throughout the system. 
         [0091]    In an example embodiment of the open-loop cooling system  50 , air prevention subsystems  510  and  510   a  may be included to prevent air from entering the air-handler units  105 . For example,  FIG. 5  illustrates examples of air prevention subsystems  510  and  510   a  that may be included in an embodiment of the open loop cooling system to prevent atmospheric air  51  remaining in the cooling water  55  from entering the air-handler units  105 . 
         [0092]    As illustrated in  FIG. 5 , the air prevention subsystems  510  and  510   a  include the air-handler inlet piping section  133  connected to the system pump outlet piping section  132  at the bottom (illustrated in  510 ) or the side (illustrated in  510   a ) of the piping and a vent valve  511 . In alternate embodiments, the specific piping sections utilized to prevent air from entering the air-handler units  105  may vary. 
         [0093]    As illustrated in  FIG. 5 , the cooling water  55  is allowed to exit the system pump outlet piping section  132  and enter the air-handler inlet piping section  133  without the atmospheric air  51  entering the air-handler inlet piping section  133 . Therefore, the cooling water  55  enters the air-handler units  105  without the atmospheric air  51 . The atmospheric air  51  is vented via the vent valve  511 . In alternate embodiments, the air remaining may be disposed of through other means known in the art. 
         [0094]    In an example embodiment illustrated in  FIG. 2  of the open-loop cooling system  50 , the system pumps  106   a  and  106   b  and the tower pumps  101   a  and  101   b  are configured in parallel (as discussed above,  FIG. 2  specifically illustrates examples of the operating tower pump  101   a  and standby tower pump  101   b  along with the operating system pump  106   a  and the standby system pump  106   b  configured in parallel) that may require a freeze protection subsystem  600  to prevent damage if the parallel pumps are exposed to temperatures below thirty-two degrees Fahrenheit. For example,  FIG. 6  illustrates an embodiment of a freeze protection subsystem  600 . The freeze protection subsystem  600  includes a standby pump  602 , a standby pump check valve  603 , a freeze protection cross-over piping section  606 , a standby pump outlet piping section  607 , an operating pump  601 , an operating pump outlet piping section  605 , and a temperature sensor  604 . 
         [0095]    The freeze protection subsystem  600  operates by forming a hole in the disc of the standby pump check valve  603 . This hole allows a small amount of the cooling water  55  pumped by the operating pump  601  to flow from the operating pump outlet piping section  605 , through the freeze protection cross-over piping section  606 , down the standby pump outlet piping section  607 , through the hole drilled in the disc of the standby pump check valve  603 , and into the standby pump  602 . 
         [0096]    In addition, the freeze protection subsystem  600  may include a temperature sensor  604 . The temperature sensor  604  measures the temperature of the cooling water  55  backflowing through the standby pump  602 . If the temperature of the cooling water  55  backflowing through the standby pump  602  is below a preset temperature, the standby pump  602  becomes the operating pump  601  and the operating pump  601  becomes the standby pump  602 . 
         [0097]    The present invention can be embodied in other specific forms without departing from its spirit or essential characteristics. Thus, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.