Method and apparatus for measuring and improving efficiency in refrigeration systems
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 processor for calculating a process variable level which achieves an optimum efficiency. The process variables may include refrigerant charge and refrigerant oil concentration in evaporator.
1. A multivariate control system, comprising:
a plurality of inputs together representing a plurality of independent variables; a memory storing inter-related parameters of a computer-based model of a physical thermodynamic system, the model comprising sufficient inter-related parameters to estimate an operating efficiency of the physical thermodynamic system corresponding to the model;
a computer, configured to receive the plurality of inputs; access the stored inter-related parameters; apply the received plurality of inputs to the model to produce at least two control signals for independently controlling different physical elements of the physical thermodynamic system; determine a change in efficiency expected from a modification of the physical thermodynamic system distinct from the at least two control signals, change the inter-related parameters stored in memory in dependence on the determined change in efficiency; and output the at least two control signals and a parameter dependent on the determination; and
a port configured to present the at least two control signals for communication to the physical thermodynamic system.
2. The multivariate control system according to claim 1 , wherein the processor accounts for time delays inherent in the physical thermodynamic system.
3. The multivariate control system according to claim 1 , wherein the processor stores parameters representing a time response of the physical thermodynamic system and employs the stored parameters to avoid undesirable oscillation or instability.
4. The multivariate control system according to claim 1 , wherein the model comprises a segmented space, comprising a plurality of segments each comprising a respective set of inter-related parameters associated with the respective segment.
5. The multivariate control system according to claim 1 , wherein the model is a non-linear model.
6. The multivariate control system according to claim 1 , wherein the physical thermodynamic system comprises a closed loop refrigeration system having at least a compressor, a condenser, and an evaporator, and the plurality of inputs comprise at least two temperatures and at least two temperatures.
7. The multivariate control system according to claim 6 , wherein at least one control signal controls the compressor.
8. The multivariate control system according to claim 6 , wherein the model comprises at least one inter-related parameter dependent on a concentration of oil in the evaporator.
9. The multivariate control system according to claim 8 , wherein the modification of the physical thermodynamic system distinct from the at least two control signals comprises a change in a concentration of oil in the evaporator.
10. A multivariate control method, comprising:
storing inter-related parameters of a computer-based model of a physical thermodynamic system, the model comprising sufficient inter-related parameters to estimate an operating efficiency of the physical thermodynamic system corresponding to the model;
receiving a plurality of inputs;
applying the received plurality of inputs to the model to produce at least two control signals for independently controlling different physical elements of the physical thermodynamic system;
determining a change in efficiency expected from a modification of the physical thermodynamic system distinct from the at least two control signals, change the inter-related parameters stored in memory in dependence on the determined change in efficiency; and
outputting the at least two control signals and a parameter dependent on the determination.
11. The multivariate control method according to claim 10 , further comprising accounting for time delays inherent in the physical thermodynamic system.
12. The multivariate control method according to claim 10 , further comprising storing parameters representing a time response of the physical thermodynamic system; and employing the stored parameters to avoid undesirable oscillation or instability.
13. The multivariate control method according to claim 10 , wherein the model comprises a plurality of segments in a segmented space, each segment comprising a respective set of inter-related parameters associated with the respective segment.
14. The multivariate control method according to claim 10 , wherein the model is a non-linear model.
15. The multivariate control method according to claim 10 , wherein the physical thermodynamic system comprises a closed loop refrigeration system having at least a compressor, a condenser, and an evaporator, and the plurality of inputs comprise at least two temperatures and at least two temperatures.
16. The multivariate control method according to claim 15 , further comprising controlling a compressor with at least one control signal.
17. The multivariate control method according to claim 15 , wherein the model comprises at least one inter-related parameter dependent on a concentration of oil in the evaporator.
18. The multivariate control method according to claim 17 , wherein the modification of the physical thermodynamic system distinct from the at least two control signals comprises a change in a concentration of oil in the evaporator.
19. A computer readable medium storing thereon non-transitory instructions for a multivariate control system, to perform a method comprising:
storing inter-related parameters of a computer-based model of a physical thermodynamic system, the model comprising sufficient inter-related parameters to estimate an operating efficiency of the physical thermodynamic system corresponding to the model;
receiving a plurality of inputs;
applying the received plurality of inputs to the model to produce at least two control signals for independently controlling different physical elements of the physical thermodynamic system;
determining a change in efficiency expected from a modification of the physical thermodynamic system distinct from the at least two control signals, change in the inter-related parameters stored in memory in dependence on the determined change in efficiency; and
outputting the at least two control signals and a parameter dependent on the determination.
20. The computer readable medium according to claim 19 , wherein the physical thermodynamic system comprises a closed loop refrigeration system having at least a compressor, a condenser, and an evaporator, and the model comprises at least one inter-related parameter dependent on a concentration of oil in the evaporator, further comprising controlling a compressor with at least one control signal.