Patent Publication Number: US-2019186769-A1

Title: Cooling system

Description:
TECHNICAL FIELD 
     This disclosure relates generally to a cooling system, such as a refrigeration system. 
     BACKGROUND 
     Cooling systems are used to cool spaces, such as residential dwellings, commercial buildings, and/or refrigeration units. These systems cycle a refrigerant (also referred to as charge) that is used to cool the spaces. 
     SUMMARY OF THE DISCLOSURE 
     This disclosure contemplates an unconventional cooling system that detects and responds to refrigerant leaks based on the detected concentrations of leaked refrigerant. The system includes a sensor that detects a concentration of leaked refrigerant in a space cooled by a load. When that detected concentration exceeds a first threshold, the system closes an expansion valve supplying refrigerant to a load to stop the flow of refrigerant to that load. If the leak continues and the detected concentration exceeds a second threshold, the system activates an exhaust system designed to evacuate the leaked refrigerant from the space. Certain embodiments will be described below. 
     According to an embodiment, an apparatus includes an expansion valve, a load, a sensor, an exhaust system, and a controller. The expansion valve cools a refrigerant. The load uses the refrigerant to cool a space. The sensor detects a concentration of the refrigerant in the space. The exhaust system evacuates the refrigerant from the space. The controller determines whether the detected concentration of the refrigerant in the space exceeds a first threshold and in response to a determination that the detected concentration of the refrigerant exceeds the first threshold, closes the expansion valve. The controller also determines whether the detected concentration of the refrigerant in the space exceeds a second threshold and in response to a determination that the detected concentration of the refrigerant exceeds the second threshold, activates the exhaust system. 
     According to another embodiment, a method includes cooling a refrigerant using an expansion valve and using the refrigerant to cool a space proximate a load. The method also includes detecting a concentration of the refrigerant in the space using a sensor. The method further includes determining whether the detected concentration of the refrigerant in the space exceeds a first threshold and in response to a determination that the detected concentration of the refrigerant exceeds the first threshold, closing the expansion valve. The method also includes determining whether the detected concentration of the refrigerant in the space exceeds a second threshold and in response to a determination that the detected concentration of the refrigerant exceeds the second threshold, activating an exhaust system to evacuate the refrigerant from the space. 
     According to yet another embodiment, a system includes a high side heat exchanger, an expansion valve, a load, a sensor, an exhaust system, and a controller. The high side heat exchanger removes heat from a refrigerant. The expansion valve cools the refrigerant from the high side heat exchanger. The load uses the refrigerant to cool a space. The sensor detects a concentration of the refrigerant in the space. The exhaust system evacuates the refrigerant from the space. The controller determines whether the detected concentration of the refrigerant in the space exceeds a first threshold and in response to a determination that the detected concentration of the refrigerant exceeds the first threshold, closes the expansion valve. The controller also determines whether the detected concentration of the refrigerant in the space exceeds a second threshold and in response to a determination that the detected concentration of the refrigerant exceeds the second threshold, activates the exhaust system. 
     Certain embodiments provide one or more technical advantages. For example, an embodiment detects and isolates refrigerant leaks by closing an expansion valve when a detected refrigerant concentration in a space exceeds a first threshold. As another example, an embodiment maintains the safety of a space by activating an exhaust system to evacuate leaked refrigerant from the space when the detected concentration of the leaked refrigerant exceeds a second threshold. In some embodiments, leaks in the cooling system are isolated when they occur, which may prevent the entire cooling system from being shut down to diagnose and repair the leak. Certain embodiments may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates portions of an example cooling system; 
         FIG. 2  illustrates portions of the cooling system of  FIG. 1 ; and 
         FIG. 3  is a flowchart illustrating a method for operating the cooling system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure and its advantages are best understood by referring to  FIGS. 1 through 3  of the drawings, like numerals being used for like and corresponding parts of the various drawings. 
     Cooling systems are used to cool spaces such as residential dwellings, commercial buildings and/or refrigeration units. These systems cycle a refrigerant that is used to cool the spaces. In a retail setting, the cooling system may include several cooling units such as for example freezer cases, freezer rooms, produce shelves, and refrigeration cases. Each unit uses the refrigerant to cool certain spaces to different temperatures. 
     In some instances, one or more of the units in a cooling system may leak refrigerant into the retail space. For example, piping in the unit or a joint in the piping may become loose and create a leak. In existing systems, the entire cooling system may need to be shut down to diagnose, locate, and/or repair the leak. Additionally, the retail space may need to be evacuated to prevent customers and employees from being harmed by the refrigerant leaking into the retail space. Thus, a simple refrigerant leak may result in substantial loss of revenue for the store. 
     This disclosure contemplates an unconventional cooling system that detects and responds to refrigerant leaks based on the detected concentrations of leaked refrigerant. The system includes a sensor that detects the concentration of leaked refrigerant in a space cooled by a load. When that detected concentration exceeds a first threshold, the system closes an expansion valve supplying refrigerant to the load to stop the flow of refrigerant to that load. If the leak continues and the detected concentration exceeds a second threshold, the system activates an exhaust system designed to evacuate the leaked refrigerant from the space. In this manner, when a leak is first detected, the leak may be isolated from the rest of the cooling system, which may cause the leak to stop. The leaking unit may then be inspected and repaired without shutting down the rest of the cooling system. If the leak continues after the unit is isolated, the exhaust system may expel the leaked refrigerant from the store. As a result, the store may not need to be evacuated even though there is a refrigerant leak. The cooling system will be described in more detail using  FIGS. 1 through 3 . 
       FIG. 1  illustrates portions of an example cooling system  100 . As shown in  FIG. 1 , system  100  includes one or more high side heat exchangers  105 , one or more loads  110 , one or more compressors  120 , and one or more controllers  125 . Although not illustrated in  FIG. 1 , system  100  may include any suitable component of a cooling system, such as for example expansion valves, flash tanks, oil separators, etc. In particular embodiments, system  100  isolates refrigerant leaks and if the leak does not stop, expels the refrigerant from system  100 . 
     High side heat exchanger  105  may remove heat from a refrigerant. When heat is removed from the refrigerant, the refrigerant is cooled. This disclosure contemplates high side heat exchanger  105  being operated as a condenser, a fluid cooler, and/or a gas cooler. When operating as a condenser, high side heat exchanger  105  cools the refrigerant such that the state of the refrigerant changes from a gas to a liquid. When operating as a fluid cooler, high side heat exchanger  105  cools liquid refrigerant and the refrigerant remains a liquid. When operating as a gas cooler, high side heat exchanger  105  cools gaseous refrigerant and the refrigerant remains a gas. In certain configurations, high side heat exchanger  105  is positioned such that heat removed from the refrigerant may be discharged into the air. For example, high side heat exchanger  105  may be positioned on a rooftop so that heat removed from the refrigerant may be discharged into the air. As another example, high side heat exchanger  105  may be positioned external to a building and/or on the side of a building. 
     System  100  includes one or more loads  110  that use the refrigerant to cool a space  115 . System  100  may include multiple loads  110  that each cool their own respective spaces  115 . In a retail setting, loads  110  may be any cooling unit within the store such as for example produce shelves, refrigeration cases, freezer cases, and/or freezer rooms. Each of these units may cool a respective space  115  to a different temperature. For example, freezer cases and freezer rooms may cool a space  115  below freezing temperatures (e.g., at or below 32 degrees Fahrenheit). Refrigeration cases and produce shelves may cool a space  115  to temperatures above freezing (e.g., above 32 degrees Fahrenheit). 
     In some instances, leaks may occur in a load  110  of system  100 . For example, piping carrying the refrigerant or a joint in the piping may come loose and spring a leak. When the leak occurs, refrigerant may leak into space  115  and out into the retail store. As described in more detail in  FIG. 2 , system  100  can detect the leak and in response, isolate the load  110  and/or the space  115  where the leak is occurring. By isolating the leak, the leaking load  110  may be stopped to prevent the leak from continuing. If the leak continues then system  100  may activate an exhaust system in space  115  to expel leaked refrigerant from space  115  and from the retail store. As a result, system  100  may stop refrigerant leaks without shutting down the entire system  100 . Additionally, when leaks occur, they may be located, diagnosed, and repaired without evacuating the store. 
     Refrigerant may flow from load  110  to compressors  120 . This disclosure contemplates system  100  including any number of compressors  120 . Compressor  120  may compress the refrigerant and increase the pressure of the refrigerant. As a result, the heat in the refrigerant may become concentrated and the refrigerant may become a high pressure gas, which may make it easier for high side heat exchanger  105  to remove heat from the refrigerant. Compressor  120  directs the compressed refrigerant to high side heat exchanger  105 . 
     Controller  125  controls the operation of the various components of system  100 . For example, controller  125  can activate one or more of high side heat exchanger  105 , load  110 , and compressor  120 . Controller  125  may also deactivate these components. Controller  125  may activate and/or deactivate any component of system  100 . As shown in  FIG. 1 , controller  125  includes a processor  130  and a memory  135 . This disclosure contemplates processor  130  and memory  135  being configured to perform any of the functions of controller  125  described herein. 
     Processor  130  is any electronic circuitry, including, but not limited to microprocessors, application specific integrated circuits (ASIC), application specific instruction set processor (ASIP), and/or state machines, that communicatively couples to memory  135  and controls the operation of controller  125 . Processor  130  may be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. Processor  130  may include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory and executes them by directing the coordinated operations of the ALU, registers and other components. Processor  130  may include other hardware and software that operates to control and process information. Processor  130  executes software stored on memory to perform any of the functions described herein. Processor  130  controls the operation and administration of controller  125  by processing information received from various components of system  100 . Processor  130  may be a programmable logic device, a microcontroller, a microprocessor, any suitable processing device, or any suitable combination of the preceding. Processor  130  is not limited to a single processing device and may encompass multiple processing devices. 
     Memory  135  may store, either permanently or temporarily, data, operational software, or other information for processor  130 . Memory  135  may include any one or a combination of volatile or non-volatile local or remote devices suitable for storing information. For example, memory  135  may include random access memory (RAM), read only memory (ROM), magnetic storage devices, optical storage devices, or any other suitable information storage device or a combination of these devices. The software represents any suitable set of instructions, logic, or code embodied in a computer-readable storage medium. For example, the software may be embodied in memory  135 , a disk, a CD, or a flash drive. In particular embodiments, the software may include an application executable by processor  130  to perform one or more of the functions of controller  125  described herein. 
       FIG. 2  illustrates portions of the cooling system  100  of  FIG. 1 . As shown in  FIG. 2 , a load  110  is used to cool a space  115 . Additionally, system  100  includes one or more expansion valves  205 , one or more sensors  210 , one or more exhaust systems  215 , one or more case controllers  220 , and one or more check valves  225 .  FIG. 2  illustrates these components as being located within space  115 . This disclosure contemplates that these components may be located outside space  115 . In particular embodiments, these components may operate to isolate refrigerant leaks so that they may be located, diagnosed, and repaired without shutting down the entirety of system  100 . 
     Expansion valve  205  is used to cool refrigerant entering load  110 . Expansion valve  205  may receive refrigerant from any component of system  100  such as for example high side heat exchanger  105  and/or a flash tank. Expansion valve  205  reduces the pressure and therefore the temperature of the refrigerant. Expansion valve  205  reduces pressure from the refrigerant flowing into the expansion valve  205 . The temperature of the refrigerant may then drop as pressure is reduced. As a result, refrigerant entering expansion valve  205  may be cooler when leaving expansion valve  205 . The refrigerant leaving expansion valve  205  is fed to load  110 . 
     When a refrigerant leak is detected, expansion valve  205  may be closed to stop refrigerant from flowing to load  110 . As a result, load  110  may shut down. Load  110  and the leak are then effectively isolated from the rest of system  100 . The leak may then be located, diagnosed, and repaired by locating load  110  and inspecting the piping around load  110  for leaks. Any leaks may then be patched and/or repaired before activating load  110  and opening expansion valve  205 . 
     Sensor  210  may detect concentrations of refrigerant in system  100  such as for example in space  115 . Sensor  210  may report any detected concentrations of refrigerant to controller  125 . When sensor  210  reports a concentration of refrigerant in space  115  that exceeds a first threshold, controller  125  may determine that a refrigerant leak is occurring. In response, controller  125  may instruct case controller  220  to close expansion valve  205 . As a result, case controller  220  may close expansion valve  205  and shut down load  110 , thereby effectively isolating and stopping the refrigerant leak. If the refrigerant leak continues, sensor  210  may detect a concentration of refrigerant that exceeds a second threshold. The second threshold is higher than the first threshold. In response, controller  125  may activate exhaust system  215 . This disclosure contemplates sensor  210  being configured to detect any concentration of refrigerant in space  115 . Additionally, this disclosure contemplates the first and second thresholds being any value. Furthermore, this disclosure contemplates controller  125  performing any action in response to any number of thresholds of detected concentrations of refrigerants. In particular embodiments, the first threshold is 1,000 parts per million and the second threshold is 5,000 parts per million. 
     Exhaust system  215  may include any number of vents, fans, exhaust tubing, and any other appropriate components. Exhaust system  215  may operate these components (e.g., activating fans) to expel leaked refrigerant from space  115  and cooling system  100 . In certain embodiments, when sensor  210  detects a particular concentration of refrigerant in space  115 , controller  125  may determine that the detected concentration is above a second threshold. In response, controller  125  may activate exhaust system  215  to expel refrigerant from space  115 . In response, exhaust system  215  may activate (e.g., activating a fan) to expel refrigerant from space  115 . As a result, exhaust system  215  may remove refrigerant from space  115  and keep a retail space safe. The leak may then be located, diagnosed, and/or repaired without needing to evacuate the retail space. 
     Case controller  220  may control the operation of various components of system  100 . For example, case controller  220  may activate and/or deactivate expansion valve  205  and/or load  110 . When sensor  210  detects a particular concentration of refrigerant in space  115 , controller  125  may determine that the detected concentration exceeds a first threshold. In response, controller  125  may instruct case controller  220  to close expansion valve  205  and/or to deactivate load  110 . In response, case controller  220  may close expansion valve  205  and/or deactivate load  110  to isolate and potentially stop the leak. When the leak has been repaired, case controller  220  may instruct expansion valve  205  to open and load  110  to activate. This disclosure contemplates case controller  220  being located in space  115 . In some embodiments, case controller  220  may form a part of controller  125 . This disclosure also contemplates case controller  220  being located with controller  125  and/or being a subcomponent of controller  125 . This disclosure also contemplates case controller  220  being a distributed controller along with controller  125 . Case controller  220  may operate independently and separately from controller  125  or case controller  220  may operate in conjunction with controller  125 . As shown in  FIG. 2 , case controller  220  includes a processor  230  and memory  235 . This disclosure contemplates processor  230  and memory  235  being configured to perform any of the functions of case controller  220 . 
     Processor  230  is any electronic circuitry, including, but not limited to microprocessors, application specific integrated circuits (ASIC), application specific instruction set processor (ASIP), and/or state machines, that communicatively couples to memory  235  and controls the operation of case controller  220 . Processor  230  may be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. Processor  230  may include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory and executes them by directing the coordinated operations of the ALU, registers and other components. Processor  230  may include other hardware and software that operates to control and process information. Processor  230  executes software stored on memory  235  to perform any of the functions described herein. Processor  230  controls the operation and administration of case controller  220  by processing information received from various components of system  100 . Processor  230  may be a programmable logic device, a microcontroller, a microprocessor, any suitable processing device, or any suitable combination of the preceding. Processor  230  is not limited to a single processing device and may encompass multiple processing devices. 
     Memory  235  may store, either permanently or temporarily, data, operational software, or other information for processor  230 . Memory  235  may include any one or a combination of volatile or non-volatile local or remote devices suitable for storing information. For example, memory  235  may include random access memory (RAM), read only memory (ROM), magnetic storage devices, optical storage devices, or any other suitable information storage device or a combination of these devices. The software represents any suitable set of instructions, logic, or code embodied in a computer-readable storage medium. For example, the software may be embodied in memory  235 , a disk, a CD, or a flash drive. In particular embodiments, the software may include an application executable by processor  230  to perform one or more of the functions of case controller  220  described herein. 
     Check valve  225  prevents refrigerant from flowing back into load  110  when expansion valve  205  is closed and when load  110  is deactivated. When load  110  is deactivated and expansion valve  205  is closed, a drop in pressure may occur in load  110 , which effectively creates a suction at the discharge of load  110 . If check valve  225  is not present, then refrigerant from other components of system  100  may be sucked into load  110  through the discharge of load  110 . Check valve  225  prevents refrigerant from backflowing through the discharge of load  110 , which protects load  110  from damage. In particular embodiments, instead of using a check valve  225 , a full port solenoid valve may be used instead. 
     In some embodiments, when sensor  210  detects a particular concentration of refrigerant, controller  125  may determine that the detected concentration exceeds a particular threshold such as for example a second threshold. In response controller  125  may activate an alarm to alert individuals in the retail space that a refrigerant leak is occurring. The alarm may produce a visible and/or audible signal that alerts others of the refrigerant leak. In some embodiments, the visual and audible signals may also alert others of the location of the leak such as for example in space  115 . 
     In particular embodiments, system  100  includes a pressure transducer that converts a pressure of the refrigerant to an electric signal. For example, the pressure transducer may be located near load  110  and it may respond to a pressure of the refrigerant at load  110 . The pressure transducer may convert a pressure of the refrigerant at load  110  into an electric signal and communicate that signal to controller  125 . Controller  125  may determine that a refrigerant leak is occurring in load  110  based on the electric signal. For example, when a refrigerant leak is occurring, the electric signal communicated by the pressure transducer will indicate that the pressure of the refrigerant at load  110  is decreasing. Controller  125  may determine based on that electric signal that a leak is occurring and instruct case controller  220  to close expansion valve  205 , deactivate load  110 , and/or activate exhaust system  215 . 
       FIG. 3  is a flowchart illustrating a method  300  for operating the cooling system  100  of  FIG. 1 . In particular embodiments, various components of system  100  perform the steps of method  300 . By performing method  300  refrigerant leaks may be isolated, located, and repaired without shutting down the entire system  100  and without evacuating a retail space served by cooling system  100 . 
     A high side heat exchanger may begin by cooling a refrigerant in step  305 . In step  310 , a load uses the refrigerant to cool a space. A sensor detects a concentration of the refrigerant in the space in step  315 . In step  320 , a controller determines whether the detected concentration is above a first threshold. If the detected concentration is not above the first threshold, method  300  concludes. If the detected concentration is above the first threshold, then the controller may close an expansion valve in step  325 . For example, the controller may instruct a case controller to close the expansion valve. In step  330 , the controller then determines whether a detected concentration is above a second threshold. If the detected concentration is not above the second threshold, method  300  concludes. If the detected concentration is above the second threshold, then the controller activates an exhaust system in step  335 . By activating the exhaust system, the leaked refrigerant may be expelled from the space. 
     Modifications, additions, or omissions may be made to method  300  depicted in  FIG. 3 . Method  300  may include more, fewer, or other steps. For example, steps may be performed in parallel or in any suitable order. While discussed as system  100  (or components thereof) performing the steps, any suitable component of system  100  may perform one or more steps of the method. 
     Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the disclosure. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. Additionally, operations of the systems and apparatuses may be performed using any suitable logic comprising software, hardware, and/or other logic. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
     Although the present disclosure includes several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.