Environmental control system fluid sensing system and method

Abstract

A sensor system and method for analyzing a fluid contained within an environmental control system, comprising the steps of providing a system including a passage for containing a thermal change fluid; placing a sensor including a mechanical resonator in the passage; operating the resonator to have at least a portion thereof translate through the fluid; and monitoring the response of the resonator to the fluid in the passage. A preferred sensor includes a tuning fork resonator.

1 . A method for monitoring a fluid comprising at least one of a lubricant and a refrigerant in an environmental control system, the method comprising:
 contacting said fluid with a flexural mechanical resonator in the environmental control system;   applying an input signal to the flexural mechanical resonator to oscillate the resonator while it is in contact with the fluid and thereby translate at least a portion of the resonator through the fluid; and   evaluating at least one of: (a) a concentration of said refrigerant that is in said fluid; and (b) a concentration of an anti-freezing component in said fluid by analyzing a response of the flexural mechanical resonator to the fluid.   
     
     
         2 . A method as set forth in  claim 1  wherein the flexural mechanical resonator comprises a piezoelectric material. 
     
     
         3 . A method as set forth in  claim 2  wherein the flexural mechanical resonator comprises a tuning fork resonator. 
     
     
         4 . A method as set forth in  claim 1  wherein the environmental control system comprises a compressor. 
     
     
         5 . A method as set forth in  claim 1  wherein the evaluating further comprises evaluating the presence of a contaminant in the fluid. 
     
     
         6 . A method as set forth in  claim 1  wherein the fluid comprises a lubricant. 
     
     
         7 . A method as set forth in  claim 1  wherein the fluid comprises a refrigerant. 
     
     
         8 . A method as set forth in  claim 1  wherein the flexural mechanical resonator is operated at a frequency that is less than about 1 MHz. 
     
     
         9 . A method as set forth in  claim 8  wherein the flexural mechanical resonator is operated a frequency that is less than about 100 kHz. 
     
     
         10 . A method as set forth in  claim 1  wherein the evaluating is performed by a processing unit, the method further comprising using the processing unit to automatically perform at least one operation of the environmental control system in response to the said analysis by the processing unit of the response of the flexural mechanical resonator to the fluid. 
     
     
         11 . A method as set forth in  claim 10  wherein said at least one operation of the environmental control system comprises an operation selected from the group consisting of: (i) switching the environmental control system or one or more components therein to an on or off state; (ii) closing or opening a valve in the environmental control system; (iii) changing a flow rate of a refrigerant; (iv) changing a pressure of the refrigerant; (v) changing an operating speed or condition of one or more components of the environmental control system; (vi) providing a visual or audible output signal indicative of information about the operation of the environmental control system; (vii) outputting a signal to a remote telemetry device and combinations thereof. 
     
     
         12 . A method as set forth in  claim 1  wherein the evaluating comprises a step selected from: (i) monitoring a change of frequency of the flexural mechanical resonator while maintaining an input signal to the resonator as a constant; (ii) monitoring a change in electrical feedback from the flexural mechanical resonator while maintaining the input signal to the resonator as a constant; (iii) varying the frequency of a variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the flexural mechanical resonator; (iv) comparing the response of the resonator with a prior response of the resonator; (v) comparing the response of the flexural mechanical resonator with a known reference value for the fluid; (v) comparing the response of the flexural mechanical resonator with the response of another mechanical resonator in the system; (vi) and combinations thereof. 
     
     
         13 . A method as set forth in  claim 1  wherein the evaluating comprises varying the frequency of a variable frequency input signal over a predetermined frequency range to obtain a frequency-dependent resonator response of the flexural mechanical resonator. 
     
     
         14 . A method as set forth in  claim 1  wherein the evaluating comprises determining a property of the fluid selected from the group consisting of a viscosity, a density, a conductivity, and a dielectric constant. 
     
     
         15 . A method as set forth in  claim 14  wherein the evaluating comprises determining a viscosity and a density of the fluid independently. 
     
     
         16 . A method as set forth in  claim 15  wherein the evaluating further comprises determining a dielectric constant of the fluid. 
     
     
         17 . A method as set forth in  claim 1  wherein the evaluating comprises evaluating a concentration of said refrigerant that is in said fluid. 
     
     
         18 . A method for monitoring a thermal change fluid in an environmental control system, the method comprising
 operating a mechanical resonator in an environmental control system selected from heating, ventilation, air conditioning and refrigeration systems, the environmental control system including a passage for a thermal change fluid, the mechanical resonator being a flexural resonator, a torsional resonator or a combination thereof;   translating at least a portion of the resonator through the thermal change fluid, the thermal change fluid comprising one or more of: (i) a hydrocarbon refrigerant; (ii) a chlorofluorocarbon refrigerant; (iii) a hydrochlorofluorocarbon refrigerant; (iv) a hydrofluorocarbon refrigerant; (v) a synthetic refrigerant; (vi) naturally occurring refrigerants; and (vii) CFC-free refrigerants; and   monitoring the response of the resonator to the thermal change fluid in the passage.   
     
     
         19 . A method for monitoring a thermal change fluid as set forth in  claim 18  wherein the thermal change fluid comprises a chlorofluorocarbon refrigerant. 
     
     
         20 . A method as set forth in  claim 18  wherein the mechanical resonator is a flexural resonator. 
     
     
         21 . A method as set forth in  claim 20  wherein the mechanical resonator is a tuning fork resonator. 
     
     
         22 . A method as set forth in  claim 18  wherein the resonator is operated at a frequency that is less than about 1 MHz. 
     
     
         23 . A method as set forth in  claim 22  wherein the resonator is operated at a frequency that is less than about 1 kHz. 
     
     
         24 . A method as set forth in  claim 18  further comprising detecting the presence of a contaminant in the thermal change fluid based on the response of the mechanical resonator to the thermal change fluid. 
     
     
         25 . An environmental control system selected from heating, ventilation, air conditioning and refrigeration systems, the system comprising:
 a passage containing a thermal change fluid, the thermal change fluid comprising one or more of: (i) a hydrocarbon refrigerant; (ii) a chlorofluorocarbon refrigerant; (iii) a hydrochlorofluorocarbon refrigerant; (iv) a hydrofluorocarbon refrigerant; (v) a synthetic refrigerant; (vi) naturally occurring refrigerants; and (vii) CFC-free refrigerants;   at least one mechanical resonator for relative translation with the thermal change fluid, the mechanical resonator being a flexural resonator, a torsional resonator or a combination thereof; and   a circuit for monitoring a response of the resonator to the thermal change fluid.   
     
     
         26 . An environmental control system as set forth in  claim 25  wherein the thermal change fluid in the passage comprises a chlorofluorocarbon refrigerant. 
     
     
         27 . An environmental control system as set forth in  claim 25  wherein the mechanical resonator is a flexural resonator. 
     
     
         28 . An environmental control system as set forth in  claim 25  wherein the mechanical resonator is a tuning fork resonator. 
     
     
         29 . An environmental control system as set forth in  claim 25  wherein the resonator is operable at a frequency that is less than about 1 MHz. 
     
     
         30 . An environmental control system as set forth in  claim 29  wherein the resonator is operable at a frequency that is less than about 1 kHz. 
     
     
         31 . An environmental control system as set forth in  claim 25  wherein the thermal change fluid further comprises a contaminant. 
     
     
         32 . A method for monitoring a fluid comprising at least one of a lubricant and a refrigerant in an environmental control system selected from heating, ventilation, and refrigeration systems, the method comprising:
 contacting said fluid with a flexural mechanical resonator in the environmental control system;   applying an input signal to the mechanical resonator to oscillate the mechanical resonator while it is in contact with the fluid and thereby translate at least a portion of the resonator through the fluid; and   evaluating a condition of said fluid by analyzing a response of the flexural resonator to the fluid.   
     
     
         33 . A method for monitoring a fluid as set forth in  claim 31  wherein the flexural resonator comprises a tuning fork resonator. 
     
     
         34 . A method for monitoring a fluid as set forth in  claim 32  wherein the evaluating comprises determining one of more properties of the fluid, said properties comprising one or more properties selected from the group consisting of density, viscosity, dielectric constant, and conductivity. 
     
     
         35 . A method for monitoring a fluid as set forth in  claim 34  wherein the evaluating comprises determining a viscosity of the fluid and a density of the fluid independent of said viscosity. 
     
     
         36 . A method for monitoring a fluid as set forth in  claim 35  wherein the evaluating further comprises determining a dielectric constant of the fluid. 
     
     
         37 . A method as set forth in  claim 31  wherein the evaluating comprises detecting the presence of a contaminant in the thermal change fluid.