Monitoring compressor performance in a refrigeration system

• US 7,596,959 B2
• Filed: 10/21/2005
• Issued: 10/06/2009
• Est. Priority Date: 10/21/2005
• Status: Active Grant

• Current Assignee: Copeland Cold Chain LP
• Original Assignee: Emerson Retail Services, Inc. (Emerson Electric Company)
• Inventors: Mathews, Thomas J., Singh, Abtar, Churiwal, Pawan K., Woodworth, Stephen T.
• Primary Examiner(s): JIANG, CHEN WEN
• Application Number:
  US11/256,660
• Publication Number:
  US 20070089440A1
• Time in Patent Office: 1,446 Days
• Field of Search: 621/25, 621/26, 621/27, 621/29, 621/49, 621/58, 622/82, 623/241, 702/182, 702/183, 702/184
• US Class Current: 62/129
• CPC Class Codes: F04D 27/001 Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring
• CPC Class Codes: F25B 2400/075 with parallel compressors
• CPC Class Codes: F25B 2400/22 Refrigeration systems for supermarkets
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 2700/1931 Discharge pressures
• CPC Class Codes: F25B 2700/1933 Suction pressures
• CPC Class Codes: F25B 2700/21151 at the suction side of the compressor
• CPC Class Codes: F25B 2700/21152 at the discharge side of the compressor
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence

Abstract

A method for monitoring compressor performance in a refrigeration system includes calculating an isentropic efficiency of a compressor of the refrigeration system, averaging isentropic efficiency over a predetermined period, comparing the average to an efficiency threshold, and detecting a compressor malfunction based on the comparison. The method may be executed by a controller or stored in a computer-readable medium.

Claims

1. A method comprising:

calculating an isentropic efficiency of a compressor of a refrigeration system;

averaging said isentropic efficiency over a predetermined period;

comparing said average to an efficiency threshold, said efficiency threshold being based on a predetermined percentage of a benchmark isentropic efficiency that is based on at least one of an ideal suction enthalpy, an ideal intake enthalpy, and an ideal discharge enthalpy; and

detecting a compressor malfunction based on said comparison.

2. The method of claim 1, further comprising generating a notification based on said detecting.

3. The method of claim 1, further comprising receiving a suction pressure signal that corresponds to a suction pressure of said compressor, wherein said calculating said isentropic efficiency is based on said received suction pressure signal.

4. The method of claim 1, further comprising receiving a discharge pressure signal that corresponds to a discharge pressure of said compressor, wherein said calculating said isentropic efficiency is based on said received discharge pressure signal.

5. The method of claim 1, further comprising receiving a suction temperature signal that corresponds to a suction temperature of said compressor, wherein said calculating said isentropic efficiency is based on said received suction temperature signal.

6. The method of claim 1, further comprising receiving a discharge temperature signal that corresponds to a discharge temperature of said compressor, wherein said calculating said isentropic efficiency is based on said received discharge temperature signal.

7. A controller configured with programming stored in a computer readable medium to execute the method of claim 1.

8. A computer-readable medium having computer-executable instructions for execution by a controller to perform the method of claim 1.

9. The method of claim 1, wherein said predetermined efficiency minimum is about 50% and wherein said notification is generated when said isentropic efficiency is less than said predetermined efficiency minimum.

10. The method of claim 9, wherein said notification is generated to notify of a refrigeration system malfunction.

11. The method of claim 1, said method further comprising comparing said isentropic efficiency with a predetermined efficiency maximum and a predetermined efficiency minimum and generating a notification when said isentropic efficiency is one of greater than said predetermined efficiency maximum and less than said predetermined efficiency minimum.

12. The method of claim 11, wherein said predetermined efficiency maximum is about 90% and wherein said notification is generated when said isentropic efficiency is greater than said predetermined efficiency maximum.

13. The method of claim 11, wherein said notification is generated to notify of a flood back condition.

14. The method of claim 1, wherein said benchmark isentropic efficiency is based on said ideal suction enthalpy.

15. The method of claim 1, wherein said benchmark isentropic efficiency is based on said ideal intake enthalpy.

16. The method of claim 1, wherein said benchmark isentropic efficiency is based on said ideal discharge enthalpy.

17. A method comprising:

receiving a suction pressure signal that corresponds to a suction pressure of a compressor of a refrigeration system;

receiving a discharge pressure signal that corresponds to a discharge pressure of said compressor;

receiving a suction temperature signal that corresponds to a suction temperature of said compressor;

receiving a discharge temperature signal that corresponds to a discharge temperature of said compressor;

calculating a suction entropy and a suction enthalpy of said compressor based on said suction pressure signal and said suction temperature signal;

calculating a discharge enthalpy based on said discharge temperature signal and said discharge pressure signal;

calculating an intake enthalpy based on said suction entropy;

calculating an isentropic efficiency of said compressor based on said intake enthalpy, said discharge enthalpy, and said suction enthalpy;

averaging said isentropic efficiency over a predetermined period;

comparing said average to an efficiency threshold; and

detecting a compressor malfunction based on said comparison.

18. The method of claim 17, further comprising:

calculating an intake enthalpy difference as a difference between said intake enthalpy and said suction enthalpy; and

calculating a discharge enthalpy difference as a difference between said discharge enthalpy and said suction enthalpy;

wherein said calculating said isentropic efficiency is based on a quotient of said intake enthalpy difference and said discharge enthalpy difference.

19. The method of claim 17, wherein said efficiency threshold is based on a predetermined percentage of a benchmark isentropic efficiency that is based on at least one of an ideal suction enthalpy, an ideal intake enthalpy, and an ideal discharge enthalpy.

20. The method of claim 17, said method further comprising comparing said isentropic efficiency with a predetermined efficiency maximum and a predetermined efficiency minimum and generating a notification when said isentropic efficiency is one of greater than said predetermined efficiency maximum and less than said predetermined efficiency minimum.

21. The method of claim 20, wherein said predetermined efficiency maximum is about 90% and wherein said notification is generated when said isentropic efficiency is greater than said predetermined efficiency maximum.

22. The method of claim 20, wherein said notification is generated to notify of a flood back condition.

23. The method of claim 20, wherein said predetermined efficiency minimum is about 50% and wherein said notification is generated when said isentropic efficiency is less than said predetermined efficiency minimum.

24. The method of claim 23, wherein said notification is generated to notify of a refrigeration system malfunction.

25. A controller configured with programming stored in a computer readable medium to execute the method of claim 17.

26. A computer-readable medium having computer-executable instructions for execution by a controller to perform the method of claim 17.

27. The method of claim 17, further comprising generating a notification based on said detecting.

28. The method of claim 17 wherein said efficiency threshold is based on a predetermined percentage of a benchmark isentropic efficiency that is based on an enthalpy.

29. A method comprising:

calculating an isentropic efficiency of a compressor of a refrigeration system;

averaging said isentropic efficiency over a predetermined period;

comparing said average to an efficiency threshold;

detecting a compressor malfunction based on said comparison; and

comparing said isentropic efficiency with a predetermined efficiency maximum and a predetermined efficiency minimum and generating said notification when said isentropic efficiency is one of greater than said predetermined efficiency maximum and less than said predetermined efficiency minimum.

30. A controller configured with programming stored in a computer readable medium to execute the method of claim 29.

31. A computer-readable medium having computer-executable instructions for execution by a controller to perform the method of claim 29.

32. The method of claim 29, further comprising generating a notification based on said detecting.

33. The method of claim 29, further comprising receiving a suction pressure signal that corresponds to a suction pressure of said compressor, wherein said calculating said isentropic efficiency is based on said received suction pressure signal.

34. The method of claim 29, further comprising receiving a discharge pressure signal that corresponds to a discharge pressure of said compressor, wherein said calculating said isentropic efficiency is based on said received discharge pressure signal.

35. The method of claim 29, further comprising receiving a suction temperature signal that corresponds to a suction temperature of said compressor, wherein said calculating said isentropic efficiency is based on said received suction temperature signal.

36. The method of claim 29, further comprising receiving a discharge temperature signal that corresponds to a discharge temperature of said compressor, wherein said calculating said isentropic efficiency is based on said received discharge temperature signal.

37. The method of claim 29, wherein said efficiency threshold is based on a predetermined percentage of a benchmark isentropic efficiency that is based on an enthalpy.

38. The method of claim 37 wherein said enthalpy includes at least one of an ideal suction enthalpy, an ideal intake enthalpy, and an ideal discharge enthalpy.

39. The method of claim 29, wherein said predetermined efficiency maximum is about 90% and wherein a notification is generated when said isentropic efficiency is greater than said predetermined efficiency maximum.

40. The method of claim 29, wherein a notification is generated to notify of a flood back condition.

41. The method of claim 29, wherein said predetermined efficiency minimum is about 50 % and wherein a notification is generated when said isentropic efficiency is less than said predetermined efficiency minimum.

42. The method of claim 41, wherein said notification is generated to notify of a refrigeration system malfunction.