Abstract:
A method of sensing superheat includes the steps of: (a) connecting a fluid inlet member of a superheat sensor to one of a plurality of fluid systems; (b) allowing fluid to flow from the fluid system to which the superheat sensor is connected to the superheat sensor; (c) sensing a temperature of the fluid in the fluid system with one of an internal temperature sensor mounted within a housing of the superheat sensor and an external temperature sensor mounted outside of the housing of the superheat sensor; and (d) calculating a superheat of the fluid in the fluid system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional patent application of U.S. patent application Ser. No. 13/563,017 filed Jul. 31, 2012, which claims the benefit of U.S. Provisional Application No. 61/611,747 filed Mar. 16, 2012. The disclosure of both applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Various embodiments of a fluid sensor are described herein. In particular, the embodiments described herein relate to an improved superheat sensor. 
         [0003]    There are many fluid system applications that require knowledge of a fluid&#39;s superheat in order to optimize the state of the fluid system. These systems include, but are not limited to, HVAC systems. Fluids that may be used within these systems include, but are not limited to, refrigerants. 
         [0004]    As used herein, the term superheat is defined as the condition where the fluid, regardless of the system type, has excess energy relative to the fluid&#39;s boiling point. This excess energy may be measured as the number of degrees of temperature above the fluid&#39;s boiling point, or superheat. 
         [0005]    Methods of measuring superheat are known. For example, U.S. Pat. No. 5,070,706 discloses a superheat sensor having a single coupling to a fluid channel carrying fluid through which superheat is being measured. 
         [0006]    U.S. Pat. No. 5,820,262 discloses a refrigerant sensor for calculating a superheat value for refrigerant material. The sensor has an internal pressure sensor and an internal temperature sensor. 
         [0007]    U.S. Patent Publication No. 2011/0192224 discloses a superheat sensor having a flexible wall that defines an interface between an inner cavity having a charge fluid therein and the flow channel in thermal contact with the fluid flowing therein. The flexible wall is adapted to conduct heat between the flow channel and the inner cavity. 
         [0008]    U.S. Patent Publication No. 2011/0222576 discloses a method for calibrating a superheat sensor. 
         [0009]    Typical superheat sensors do not provide automatic fluid-type detection, high sensitivity, and resolution under a wide range of pressures, store superheat and related parametric history, generate alarms, and provide a variety of industry standard reporting options. 
         [0010]    Accordingly, there remains a need in the art for an improved sensor and method of identifying and measuring superheat in fluids, especially refrigerants in HVAC systems. 
       SUMMARY OF THE INVENTION 
       [0011]    The present application describes various embodiments of a superheat sensor. One embodiment of the superheat sensor includes a housing, a pressure sensor mounted within the housing, a fluid passageway connecting the pressure sensor to a source of superheat fluid, and a processor. 
         [0012]    In a second embodiment, a method of sensing superheat includes connecting a fluid inlet member of a superheat sensor to one of a plurality of fluid systems and allowing fluid to flow from the fluid system to which the superheat sensor is connected to the superheat sensor. A temperature of the fluid in the fluid system is sensed with one of an internal temperature sensor mounted within a housing of the superheat sensor and an external temperature sensor mounted outside of the housing of the superheat sensor. A superheat of the fluid in the fluid system is then calculated. 
         [0013]    In a third embodiment, a method of sensing superheat includes calibrating a superheat sensor and connecting a fluid inlet member of the superheat sensor to one of a plurality of fluid systems. Fluid is allowed to flow from the fluid system to which the superheat sensor is connected to the superheat sensor. A temperature of the fluid in the fluid system is sensed, and a fluid type of the fluid in the fluid system is detected. A superheat of the fluid in the fluid system is then calculated and error conditions are determined. Superheat and related parametric and alarm data are stored. The superheat sensor is disconnected and subsequently connected to another of the plurality of fluid systems without re-calibrating the superheat sensor. 
         [0014]    Other advantages of the superheat sensor will become apparent to those skilled in the art from the following detailed description, when read in view of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of a first embodiment of the universal superheat sensor according to the invention. 
           [0016]      FIG. 2  is a cross sectional view of the universal superheat sensor illustrated in  FIG. 1 . 
           [0017]      FIG. 3  side elevational view of a second embodiment of the universal superheat sensor. 
           [0018]      FIG. 4  is a cross sectional view of a third embodiment of the universal superheat sensor. 
           [0019]      FIG. 5  is an exploded perspective view of a fourth embodiment of the universal superheat sensor. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The present invention will now be described with occasional reference to the specific embodiments of the invention. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0021]    Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
         [0022]    Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from errors found in their respective measurements. 
         [0023]    As used in the description of the invention and the appended claims, the phrase “universal superheat sensor” is defined as a superheat sensor which contains all the necessary sensors, electronics, and intelligence to automatically detect multiple fluid types, such as refrigerants, without re-calibration, and report the superheat of the multiple common fluid types used in residential, industrial, and scientific applications. 
         [0024]    The superheat sensor according to the invention is a single, self-contained, stand-alone device which contains all the necessary sensors, electronics, and intelligence to automatically detect the fluid type, such as refrigerant, and report the superheat of multiple common fluid types used in residential, industrial, and scientific applications. The superheat sensor according to the invention communicates this information in a cost effective way using industry standard reports. It stores this information in a local memory device for subsequent retrieval of historical data. Additional data storage may be provided, such as through removable memory cards, and via an off-board computer, such as a laptop computer. The superheat sensor according to the invention may also be configured to provide the user various alarms for conditions such as low pressure (fluid leakage), low and/or high superheat (indicators of system flooding and out-of-range system efficiency), excessive pressure (system overcharge or imminent hardware failure), temperature out of range, and like conditions. 
         [0025]    Referring now to  FIGS. 1 and 2 , a first embodiment of the universal superheat sensor  10  includes a housing  12 , a fluid inlet member  14 , an integrated pressure and temperature sensor  16 , a printed circuit board (PCB)  18 , a superheat processor  20 , a data-reporting or communication module  22 , and an Input/Output (IO) module  24 . It will be understood that in lieu of the PCB  18 , alternative substrates may be used for mounting electronic components. For example, electronic components, including but not limited to those disclosed below, may be mounted on a substrate formed from a polymer, ceramic, metal, or other desired material. 
         [0026]    The housing  12  is the enclosure for all or a portion of the components of the universal superheat sensor  10 . The illustrated housing  12  is provides a hermetic or airtight sealed space within which the measurement of the fluid may occur. The illustrated housing  12  includes a body  26  having an opening  28  in which the fluid inlet member  14  is mounted, and a cover  30  having an opening  32  in which the IO module  24  is mounted. If desired, a seal (not shown) may be disposed between the body  26  and the cover  30 . 
         [0027]    The body  26  and the cover  30  of the housing  12  may have any other desired size and shape, and may be formed from any desired material, such as plastic, metal, or ceramic. Alternatively, the fluid inlet member  14  may be formed from any other desired material. 
         [0028]    In the embodiment illustrated in  FIG. 2 , the fluid inlet member  14  is a brass core or fitting having a centrally formed fluid passageway  34 . The fluid inlet member  14  connects the integrated pressure and temperature sensor  16  to the source of superheat fluid (not shown). The fluid inlet member  14  may be any type of fitting, such as a standard ¼ inch port. Any other desired type of fluid inlet member may also be used. Additionally, external adapters (not shown) may be attached to the fluid inlet member  14  to connect it to a variety of fluid fittings (not shown) of fluid systems, such as HVAC systems. 
         [0029]    The illustrated integrated pressure and temperature sensor  16  is mounted to the PCB  18  and includes a wide-range pressure sensor portion  36  that converts fluid pressure to an electrical signal. The generated electrical signal may be subsequently used by the superheat processor  20 . As used in the description of the invention and the appended claims, the phrase “wide-range pressure sensor” is defined as a pressure sensor that it will support common ranges of system pressures that occur in known refrigerant systems while maintaining accuracy. The pressure sensor portion  36  may be any type of pressure sensor; including silicon, piezo-ceramic, capacitive, and integrated hall-effect transducers, and any other device that produces an electrical analogue of pressure. In the illustrated embodiment, the pressure sensor portion  36  of the integrated pressure and temperature sensor  16  is a silicon transducer. As shown in  FIG. 2 , the integrated pressure and temperature sensor  16  is exposed directly to the pressurized superheat fluid via the fluid inlet member  14  for fast and accurate measurement. 
         [0030]    The illustrated integrated pressure and temperature sensor  16  includes a temperature sensor portion  38  that converts temperature to an electrical signal. The generated electrical signal may be subsequently used by the superheat processor  20 . The illustrated temperature sensor portion  38  is provided to measure the internal liquid refrigerant temperature and is structured and configured to support a wide range of fluid system temperatures, such as temperatures within the range of from about −50 degrees C. to about +125 degrees C., while maintaining an acceptable accuracy for a specific application. In some applications, an acceptable accuracy may be +/−0.5 degrees C. In other applications, an acceptable accuracy may be a range smaller or larger than +/−0.5 degrees C. Alternatively, the temperature sensor portion  38  may support fluid system temperatures within the range of from about −25 degrees C. to about +150 degrees C. The temperature sensor portion  38  may be any type of temperature sensor, including a thermistor, a thermocouple, a resistive element etched onto a substrate, a diode, or any other device that produces an electrical analogue of temperature. Advantageously, the illustrated integrated pressure and temperature sensor  16  is relatively small and physically close to the fluid to maximize both response time and measurement accuracy. It will be understood that the temperature sensor and the pressure sensor may be separate sensors as described below. 
         [0031]    The illustrated superheat processor  20  is mounted to the PCB  18  and is a high-resolution, high accuracy device that processes the input signals from the pressure and temperature sensor portions  36  and  38 , respectively, of the integrated pressure and temperature sensor  16 , detects the fluid type, calculates the superheat of the fluid, and provides an output that identifies the level of the calculated superheat. The superheat processor  20  may also be configured to provide other data, such as fluid temperature, fluid pressure, fluid type, historical date maintained in an onboard memory (such as alarm and on-off history), and other desired information. The superheat processor  20  may be configured as a high-resolution processor that is able to detect and process, with a single pressure sensor and a single temperature sensor, or with the illustrated integrated pressure and temperature sensor  16 , the wide-range of system pressures and temperatures that may be encountered in the fluids of the fluid systems with which the universal superheat sensor  10  will be used, for example refrigerants of HVAC systems. Advantageously, the superheat processor  20  maintains a high level of accuracy through one-time calibration over the operating range of pressure and temperature input. Non-limiting examples of suitable superheat processors include microcontrollers, Field Programmable Arrays (FPGA), and Application Specific Integrated Circuits (ASIC) with embedded and/or off-board memory and peripherals. 
         [0032]    The illustrated communication module  22  is mounted to the PCB  18  and is a configurable hardware module that provides industry-standard Modbus data over a hard-wired backbone, such as an RS485 hard-wired backbone, schematically illustrated at  40  in  FIG. 2 . If desired, the communication module  22  may provide Modbus data and other communication protocols over communications means, such as RS232, I2C, SPI, and 4-20 mA, Current Loop, USB 2.0, Bluetooth, an RF module, and wireless information to a cell-phone application. An internal antenna (not shown) may be provided to support the RF module. The illustrated communication module  22  is flexible enough to support other current and future communication protocols as they become available. 
         [0033]    The illustrated IO module  24  is a physical hardware interface that accepts input power and reports data through the available hard-wired interfaces. Common target devices that may be connected to the universal superheat sensor  10  via the IO module  24  are schematically illustrated at  42  in  FIG. 2 , and include, but are not limited to: additional temperature sensors (such as the temperature sensor  44  illustrated in  FIG. 3 ) industry standard controller modules, laptop and notebook computers, cell phones, and memory cards such as non-volatile memory cards. 
         [0034]    As shown in  FIG. 3 , an external temperature sensor  44  may be connected to the IO module  24  via the backbone  40 . Also, the external temperature sensor  44  may be positioned near various components of a refrigeration system, such as an evaporator outlet and a compressor to measure the evaporator core temperature, the discharge temperature, and the like. It will be understood that any desired number of external temperature sensors  44  may be connected to the IO module  24  to simultaneously measure the temperature internally and at multiple components or devices. 
         [0035]    Advantageously, the superheat processor  20  may process the pressure and temperature inputs from the integrated pressure and temperature sensor  16  and the external temperature sensors  44 , if provided. The superheat processor  20  is calibrated to detect and identify a plurality of fluid types. The superheat processor  20  further calculates the superheat of any of the plurality of fluid types with a high degree of resolution and accuracy. The superheat processor  20  may also determine error conditions and store superheat and related parametric and alarm data. The superheat processor  20  may then report the superheat of the fluid system to which the superheat sensor  10  is attached. The superheat processor  20  may also report additional data such as temperature, pressure, fluid type, on-time, alarms, operational history, and the like. Advantageously, the superheat processor  20  needs to be calibrated only one time, and may thereafter calculate superheat and perform any of the tasks described above for any of a plurality of fluid types. 
         [0036]    Additionally, the embodiments of the universal superheat sensor  10 ,  60 ,  70 , and  80  described herein allow real-time data to be presented to a user, such as a contractor. 
         [0037]    Referring again to  FIG. 3 , a second embodiment of the universal superheat sensor is shown at  60 . The illustrated universal superheat sensor  60  includes the housing  12 , the fluid inlet member  14 , the PCB  18 , the superheat processor (not shown in  FIG. 3 ), the communication module (not shown in  FIG. 3 ), the IO module  24 , an internal pressure sensor  62 , and an external temperature sensor  44 , as described above. As described above, any desired number of external temperature sensors  44  may be connected to the IO module  24  to simultaneously measure the temperature at multiple components or devices. 
         [0038]    Referring now to  FIG. 4 , a third embodiment of the universal superheat sensor is shown at  70 . The illustrated universal superheat sensor  70  includes the housing  12 , the fluid inlet member  14 , the PCB  18 , the superheat processor (not shown in  FIG. 4 ), the communication module (not shown in  FIG. 4 ), the IO module  24 , an internal pressure sensor  62 , and an internal temperature sensor  72 . It will be understood the any desired number of external temperature sensors  44  may also be connected to the IO module  24  to simultaneously measure the temperature internally and at multiple components or devices. In addition to one or more external temperature sensors  44 , if desired, the universal superheat sensor  80  may also include one or more of the target devices  42  that may be connected to the IO module  24  of the universal superheat sensor  80  via the backbone  40 , as described above. 
         [0039]    Referring now to  FIG. 5 , a fourth embodiment of the universal superheat sensor is shown at  80 . The illustrated universal superheat sensor  80  includes a housing  82 , a fluid inlet member  84 , the PCB  88 , the superheat processor  90 , the communication module  92 , and the IO module  94 . The universal superheat sensor  80  may include the integrated pressure and temperature sensor  16 . Alternatively, the universal superheat sensor  80  may include an internal temperature sensor and an internal pressure sensor, neither of which are shown in  FIG. 5 , but both of which are described above. The illustrated housing  82  includes a body  100  having an opening (not shown) in which the fluid inlet member  84  is mounted, and a cover  102 . A seal  104  may be disposed between the body  100  and the cover  102 . If desired, the universal superheat sensor  70  may also include one or more external temperature sensors  44 , as described above, and may further include one or more target devices  42  that may be connected to the IO module  24  of the universal superheat sensor  70  via the backbone  40 , as described above. 
         [0040]    The principle and mode of operation of the universal superheat sensor have been described in its preferred embodiments. However, it should be noted that the universal superheat sensor described herein may be practiced otherwise than as specifically illustrated and described without departing from its scope.