Method and apparatus for measuring and improving efficiency in refrigeration systems

• US 6,505,475 B1
• Filed: 05/23/2000
• Issued: 01/14/2003
• Est. Priority Date: 08/20/1999
• Status: Expired due to Term

• Current Assignee: Hudson Technologies, Inc.
• Original Assignee: Hudson Technologies, Inc.
• Inventors: Zugibe, Kevin, Schmidt, Douglas
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US09/577,703
• Time in Patent Office: 966 Days
• Field of Search: 621/92, 621/93, 622/08, 621/25, 62/77, 621/26, 621/27, 621/29, 621/49, 621/74, 622/09
• US Class Current: 62/192
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/32 Responding to malfunctions or emergencies
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2130/40 Noise
• CPC Class Codes: F24F 2140/60 Energy consumption
• CPC Class Codes: F25B 2339/0242 having tubular elements
• CPC Class Codes: F25B 2500/05 Cost reduction
• CPC Class Codes: F25B 2500/18 Optimization, e.g. high integration of refrigeration components
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 2600/2523 Receiver valves
• CPC Class Codes: F25B 2700/03 Oil level
• CPC Class Codes: F25B 2700/151 of the compressor motor
• CPC Class Codes: F25B 2700/195 of the condenser
• CPC Class Codes: F25B 2700/197 of the evaporator
• CPC Class Codes: F25B 2700/2116 of a condenser
• CPC Class Codes: F25B 2700/2117 of an evaporator
• CPC Class Codes: F25B 2700/21171 of the fluid cooled by the evaporator
• CPC Class Codes: F25B 31/004 oil recirculating arrangements
• CPC Class Codes: F25B 39/02 : Evaporators
• CPC Class Codes: F25B 43/02 : for separating lubricants from the refrigerant
• CPC Class Codes: F25B 45/00 : Arrangements for charging or discharging refrigerant
• CPC Class Codes: F25B 49/02 : for compression type machines, plants or systems
• CPC Class Codes: F25B 6/04 : arranged in series
• CPC Class Codes: G05B 13/041 : in which a variable is automatically adjusted to optimise the performance

Abstract

An apparatus for optimizing an efficiency of a refrigeration system comprising means for measuring a refrigeration efficiency of an operating refrigeration system: means for altering a process variable of the refrigeration system during efficiency measurement: and a process for calculating a process variable level which achieves an optimum efficiency. The process variables may include refrigerant charge and refrigerant oil concentration in evaporator.

Claims

1. A method for optimizing a refrigeration system, comprising:

measuring a refrigeration efficiency of an operating refrigeration system;

altering a process variable of the refrigeration system;

determining a process variable level which achieves optimum efficiency, wherein the process variable is compressor oil dissolved in the refrigerant in the evaporator;

establishing the operating point of the refrigeration near the determined optimum efficiency.

2. The method according to claim 1, wherein a further process variable is refrigerant charge condition, the operating point being established based on both compressor oil dissolved in the refrigerant in the evaporator and refrigerant charge condition.

3. The method according to claim 1, wherein optimum efficiency is determined based on surrogate process variables.

4. The method according to claim 1, wherein the operating point is maintained by closed loop control based on the determined optimum efficiency process variable level.

5. The method according to claim 1, wherein the efficiency is measured during operation to estimate a deviation of the process variable level from the determined optimum efficiency process variable level.

6. The method according to claim 1, wherein the oil content is measured optically.

7. The method according to claim 1, wherein the process variable is altered by a fractional distillation of refrigerant mixed with oil to remove oil.

8. The method according to claim 1, wherein the process variable is altered by a periodic evaporative separation of refrigerant and oil based on an oil concentration in the refrigerant.

9. The method according to claim 1, wherein the process variable is altered by a periodic evaporative separation of refrigerant and oil based on the measured refrigeration efficiency.

10. The method according to claim 1, wherein said determining step is performed based on an output from a neural network.

11. The method according to claim 1, wherein said determining step is performed based on an output of an adaptive controller.

12. The method according to claim 1, further comprising the step of providing an adaptive model of the refrigeration system for predicting a sensitivity of the system to changes in a process variable.

13. The method according to claim 1, wherein a further process variable is refrigerant charge condition, further comprising the step of altering a refrigerant charge condition of the refrigeration system.

15. The method according to claim 1, wherein

said determining step comprises the substeps of;

determining a sensitivity of the refrigeration system to at least one operational parameter which varies between maintenance treatments;

defining an efficient operating regime for the refrigeration system based on the determined sensitivity; and

estimating the at least one operational parameter during use of the refrigeration system;

and wherein said establishing step comprises the substep of;

performing a maintenance treatment when the refrigeration system is operating outside the defined efficient operating regime.

16. The method according to claim 15, wherein the operating regime has a non-trivial double ended range of values and continued operation of the refrigeration system follows a consistent trend in change in operating point from a beginning of cycle operating point to an end of cycle operating point, wherein the maintenance treatment alters the at least one operational parameter to within a boundary of the non-trivial double ended range of values near the beginning of cycle operating point.

17. The method according to claim 15, wherein the maintenance treatment comprises a partial distillation treatment of the refrigerant.

18. The method according to claim 15, wherein the at least one operational parameter is estimated by measuring an energy efficiency of the refrigeration system.

19. The method according to claim 15, wherein the at least one operational parameter is estimated by measuring an energy consumption of the refrigeration system.

20. The method according to claim 15, wherein the at least one operational parameter is estimated by measuring a refrigeration capacity of the refrigeration system.

21. The method according to claim 15, wherein the determined sensitivity follows a non-monotonic relationship with respect to energy efficiency.

14. An apparatus for optimizing an efficiency of a refrigeration system, comprising:

an evaporator;

a condensed refrigerant line feeding the evaporator;

means for measuring a refrigeration efficiency of an operating refrigeration system, comprising;

an oil sensor for measuring an oil concentration in liquefied refrigerant in the evaporator;

an oil removal system for reducing an oil concentration in the evaporator; and

a control system for controlling the oil removal system based on the oil sensor;

means for altering a process variable of the refrigeration system during efficiency measurement; and

a processor for calculating a process variable level which achieves an optimum efficiency.

22. A method of optimizing operation of a refrigeration system comprising an evaporator, comprising the steps of:

determining a sensitivity of the refrigeration system to a change in refrigerant charge, compressor oil dissolved in the refrigerant in the evaporator, and refrigeration system load;

defining an efficient operating regime for the refrigeration system based on the determined sensitivity;

controlling refrigerant charge to achieve the defined efficient operating regime.

23. The method according to claim 22, wherein said defining step further comprises evaluating a neural network model of the refrigeration system.

24. The method according to claim 22, wherein said defining step is adaptive.