Abstract:
A method of detecting cooling-loss event early is provided. The method includes defining a relative humidity limit and change threshold for a given space, measuring relative humidity in the given space, determining, with a processing unit, whether the measured relative humidity is within the defined relative humidity limit, generating a warning in an event the measured relative humidity is outside the defined relative humidity limit and determining whether a change in the measured relative humidity is less than the defined change threshold for the given space and generating an alarm in an event the change is greater than the defined change threshold.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Division of U.S. Non-Provisional application Ser. No. 13/890,673 filed May 9, 2013. The disclosures of which is incorporated herein by reference. 
     
    
     STATEMENT OF FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
       [0002]    This invention was made with Government support under Contract No.: DEEE0002897 awarded by Department of Energy. The Government has certain rights in this invention. 
     
    
     BACKGROUND 
       [0003]    The present invention relates to a method and system for early detection of cooling-loss events. 
         [0004]    In instrumented buildings, such as data centers that house multiple computing devices, temperature sensors monitor the air temperature in the enclosed space where the computing devices are held. Generally, the alarm systems of such buildings are based only on temperature readings of those temperature sensors. A problem with this approach is that temperature sensors typically have large thermal constants due to the fact that they often have a strong thermal coupling to the thermal mass of their housing. This leads to the temperature sensors having characteristically slow response times to changes in air temperature. Thus, the alarm systems, which are based on the temperature readings of the temperature sensors, may also be characteristically slow to initiate. 
         [0005]    The resulting delay between a temperature increase in the buildings and the initiation of the alarm systems can be relatively long and may lead to damage to delicate or temperature sensitive tools, such as information technology (IT) equipment. 
       SUMMARY 
       [0006]    According to one embodiment of the present invention, a method of detecting cooling-loss events is provided. The method includes defining a relative humidity limit and change threshold for a given space, measuring relative humidity in the given space, determining, with a processing unit, whether the measured relative humidity is within the defined relative humidity limit, generating a warning in an event the measured relative humidity is outside the defined relative humidity limit and determining whether a change in the measured relative humidity is less than the defined change threshold for the given space and generating an alarm in an event the change is greater than the defined change threshold. 
         [0007]    According to another embodiment, a method of detecting cooling-loss events is provided. The method includes defining relative humidity and temperature limits and change thresholds for a given space, measuring relative humidity and temperature in the given space, determining, with a processing unit, whether either of the measured relative humidity and temperature is within the defined relative humidity and temperature limits and generating a warning in an event either the measured relative humidity or temperature is outside the defined relative humidity and temperature limits and determining whether a change in the measured relative humidity is less than the defined change threshold for the given space and generating an alarm in an event the change is greater than the defined change threshold. 
         [0008]    According to yet another embodiment, a system for early detection of a cooling-loss event is provided and includes an enclosure to define a given space in which multiple temperature sensitive devices are stored, a relative humidity sensor operably disposed in the given space and an early detection apparatus including an alarm system disposed in signal communication with the relative humidity sensor. The early detection apparatus is configured to initiate the alarm system to generate an alarm in accordance with the relative humidity sensor sensing that a change in a relative humidity in the given space exceeds a defined change threshold for the given space. 
         [0009]    Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with the advantages and the features, refer to the description and to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The forgoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0011]      FIG. 1  is a schematic diagram illustrating a system for early detection of a cooling-loss event; 
           [0012]      FIG. 2  is a flow diagram illustrating a method of early detection of cooling-loss events in accordance with embodiments; 
           [0013]      FIG. 3  is a graphical depiction of a response time of a relative humidity sensor; and 
           [0014]      FIG. 4  is a graphical depiction of relative humidity and temperature readings versus timing. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The description provided below relates to the use of measurements of relative humidity (RH) sensors to promptly detect critical events involving the loss of cooling capacity in buildings like data centers. The use of the RH measurements may be based on RH and temperature (T) sensor trends and measurements and can also incorporate, if available, pressure (P) sensor measurement for verifying proper air conditioning equipment functioning, air flow, etc. 
         [0016]    With reference to  FIG. 1 , a system  10  is provided for early detection of a cooling loss event. The system  10  includes an enclosure  20 , one or more relative humidity sensors  30  and an early detection apparatus  40 . The enclosure  20  may be provided as a building or room that is formed to define a given space  21  in which multiple temperature sensitive devices  22  are stored. The temperature sensitive devices  22  may include computing or information technology (IT) devices. The one or more relative humidity sensors  30  are operably disposed in the given space  21  to detect relative humidity in the given space  21 . To this end, the one or more relative humidity sensors  30  may include a capacitive transducer  31  or a similar device. 
         [0017]    In any case, the one or more relative humidity sensors  30  do not present thermal constants and notice immediate (or substantially immediate) changes in relative humidity conditions in the given space  21 . Thus, since relative humidity in the given space  21  is proportional to air temperature in the given space  21 , the one or more relative humidity sensors  30  can be relied upon to sense immediate changes in both relative humidity and air temperature in the given space  21  such that a failure of a cooling system (i.e., an instance of a cooling-loss event) can be inferred relatively quickly. Depending on its active material, the humidity sensor response characteristics may vary depending on different parameters, like capacitance, resistance or conductivity. 
         [0018]    The system  10  may further include one or more pressure sensors  32  and one or more temperature sensors  33  in the given space  21 . The pressure sensors  32  can be employed to verify that the air conditioning units in system  10  have their fans operating correctly. The one or more temperature sensors  33  can be used to determine air temperature in the given space  21  as well as a change in the air temperature but will tend to react more slowly than the one or more relative humidity sensors  30  due to their relatively large thermal constants. 
         [0019]    The early detection apparatus  40  may include a processing unit  41  and a computer readable medium  42 , such as a memory or data storage unit. The computer readable medium  42  has executable instructions stored thereon. When executed, the executable instructions cause the processing unit  41  to operate as described below. In particular, the processing unit  41  may include a warning system  410  and an alarm system  411 . The warning system  410  is disposed in signal communication with at least the one or more relative humidity sensors  30  and the one or more temperature sensors  33 . The alarm system  411  is disposed in signal communication with at least the one or more relative humidity sensors  30 . 
         [0020]    The executable instructions of the computer readable medium  42  of the early detection apparatus  40  are provided such that the processing unit  41  of the early detection apparatus  40  is configured to operate in accordance with at least the exemplary method illustrated in  FIG. 2 . As shown in  FIG. 2 , the processing unit  41  defines initial operational parameters of relative humidity (RH 0 ) and air temperature (T 0 ) for the given space  21  in operation  200 . In accordance with embodiments, the initial operational parameters of relative humidity (RH 0 ) may be a baseline relative humidity, high and low relative humidity limits and a relative humidity change threshold within a certain period. Similarly, in accordance with embodiments, the initial operational parameters of air temperature (T 0 ) may be a baseline air temperature, high and low air temperature limits and an air temperature change threshold. 
         [0021]    Once the initial operational parameters of relative humidity (RH 0 ) and temperature (T 0 ) for the given space  21  are defined, the processing unit  41  causes the one or more relative humidity sensors  30  and the one or more temperature sensors  33  to measure the relative humidity and air temperature in the given space  21  in operation  210 . The processing unit  41  then interrogates the one or more relative humidity sensors  30  and the one or more temperature sensors  33  for their respective readings and determines, in operation  220 , whether the relative humidity and air temperature of the given space  21  is within the limits defined in operation  200 . 
         [0022]    In an event that the relative humidity and air temperature of the given space  21  is within the limits defined in operation  200 , the processing unit  41  updates historical trends in operation  230  and returns control to operation  200 . In operation  200 , the historical trends are considered in the definition of the initial operational parameters. In an event that one of the relative humidity and air temperature of the given space  21  is not within the limits defined in operation  200 , the processing unit  41  initiates the warning system  410  to generate a warning that there may be a current risk of a cooling-loss event in operation  240 . 
         [0023]    Once the warning is generated, in operation  250 , the processing unit  41  determines whether a change in the relative humidity of the given space  21  exceeds the relative humidity change threshold defined in operation  200 . In an event that the relative humidity of the given space  21  does not exceed the relative humidity change threshold defined in operation  200 , the processing unit  41  updates historical trends in operation  230  and returns control to operation  200 . In an event that the relative humidity of the given space  21  exceeds the relative humidity change threshold defined in operation  200 , the processing unit  41  initiates the alarm system  411  to generate an alarm that there is a cooling-loss event in operation  260  and returns control to operation  200 . 
         [0024]    With reference to  FIGS. 3 and 4 , the advantages of using the one or more relative humidity sensors  30  can be seen. As described above, relative humidity is a unit-less parameter that describes an amount of water vapor in the air of the given space  21  and directly depends on the air temperature.  FIG. 3  is a graphical depiction of a typical response of a relative humidity sensor to changes in relative humidity and illustrates that the response time can be measured in seconds. By contrast, with reference to the graphical depiction of relative humidity and temperature readings versus timing in  FIG. 4 , it can be seen that an increase in a relative humidity of an 80,000 square foot data center that loses cooling capacity precedes the corresponding increase in air temperature by several minutes. As to the disclosure of  FIG. 4 , a relevant metric is the change in RH, not its absolute value. For example, if water vapor in air is not being extracted during a cooling loss event, everything else being the same, the RH level can increase even if the temperature increases, until equilibrium is reached. 
         [0025]    Thus, from the fast response time illustrated in the graph of  FIG. 3 , it can be inferred that the relative humidity increase will be observed and reacted to by the early detection apparatus  40  due to its reliance upon the one or more relative humidity sensors well before the temperature increase and certainly before a detection apparatus relying only on temperature sensors would be able to react. 
         [0026]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
         [0027]    The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 
         [0028]    The flow diagrams depicted herein are just one example. There may be many variations to this diagram or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention. 
         [0029]    While the preferred embodiment to the invention had been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.