Self-optimizing subcooler control

Patent metadata

Field	Value
Publication number	US-10808984-B2
Application number	US-201916257880-A
Country	US
Kind code	B2
Filing date	Jan 25, 2019
Priority date	Jan 25, 2019
Publication date	Oct 20, 2020
Grant date	Oct 20, 2020

Abstract

According to certain embodiments, a method comprises determining a liquid outlet temperature setpoint for refrigerant discharged from a liquid outlet of a subcooler. The liquid outlet corresponds to a hot-side path of the subcooler that receives refrigerant directly from a tank, cools the refrigerant by an exchange of heat with a cold-side path of the subcooler that receives the refrigerant from the tank via an inlet expansion valve, and discharges the refrigerant to an evaporator via an outlet expansion valve. The method further comprises determining a superheat setpoint for the refrigerant discharged to a compressor via a vapor outlet of the cold-side path. The superheat setpoint is determined based on the liquid outlet temperature setpoint. The method further comprises adjusting a temperature of the refrigerant discharged to the compressor based on the superheat setpoint.

First claim

The invention claimed is:

1. A system comprising:
a subcooler, the subcooler comprising a first path and a second path, the first path adapted to cool refrigerant of the second path by an exchange of heat, wherein:
the first path comprises:
a first inlet adapted to receive the refrigerant from a tank via a first expansion valve; and
a vapor outlet adapted to discharge the refrigerant to a compressor; and

the second path comprises:
a second inlet adapted to receive the refrigerant from the tank; and
a liquid outlet adapted to discharge the refrigerant to an evaporator via a second expansion valve;

the system further comprising a controller operable to:
determine a liquid outlet temperature setpoint for the refrigerant discharged from the liquid outlet;
determine a superheat setpoint for the refrigerant discharged to the compressor via the vapor outlet, the superheat setpoint determined based on the liquid outlet temperature setpoint; and
adjust a temperature of the refrigerant discharged to the compressor via the vapor outlet based on the superheat setpoint.

2. The system of claim 1 , wherein to adjust the temperature of the refrigerant discharged to the compressor, the controller is operable to communicate a signal to adjust the degree of opening or closing of the first expansion valve.

3. The system of claim 1 , wherein the controller is operable to determine the liquid outlet temperature setpoint based at least in part on a target load capacity of the evaporator.

4. The system of claim 1 , wherein the controller is further operable to:
monitor power consumption associated with the liquid outlet temperature setpoint; and
adjust the liquid outlet temperature setpoint to a value that reduces the power consumption.

5. The system of claim 4 , wherein the controller is further operable to:
use information about at least one of a current load of the evaporator, a target load of the evaporator, a current ambient environment of the system, and a predicted ambient environment of the system to determine the value of the liquid outlet temperature setpoint that reduces the power consumption.

6. The system of claim 1 , wherein the controller is further operable to:
in response to determining that the system exceeds an operational limit when operating according to the superheat setpoint that was determined based on the liquid outlet temperature setpoint, override the superheat setpoint with an adjusted superheat setpoint that prevents the system from exceeding the operational limit.

7. The system of claim 1 , wherein a refrigerant path connecting between the vapor outlet and the compressor does not include any expansion valve.

8. The system of claim 1 , wherein the system further comprises:
the tank, wherein the tank is adapted to store the refrigerant;
the evaporator, wherein the evaporator is adapted to cool a load by evaporating the refrigerant, and to discharge the refrigerant to the compressor;
the compressor, wherein the compressor is adapted to receive the refrigerant from the evaporator and apply pressure to the refrigerant; and
a condenser adapted to receive the refrigerant form the compressor, cool the refrigerant, and discharge the refrigerant to the tank.

9. A controller comprising a non-transitory computer-readable medium storing logic and processing circuitry operable to execute the logic, whereby the controller is operable to:
determine a liquid outlet temperature setpoint for refrigerant discharged from a liquid outlet of a subcooler, the liquid outlet corresponding to a hot-side path of the subcooler that receives refrigerant directly from a tank, cools the refrigerant by an exchange of heat with a cold-side path of the subcooler that receives the refrigerant from the tank via an inlet expansion valve, and discharges the refrigerant to an evaporator via an outlet expansion valve;
determine a superheat setpoint for the refrigerant discharged to a compressor via a vapor outlet of the cold-side path of the subcooler, the superheat setpoint determined based on the liquid outlet temperature setpoint; and
adjust a temperature of the refrigerant discharged to the compressor via the vapor outlet of the cold-side path based on the superheat setpoint.

10. The controller of claim 9 , further operable to:
adjust the temperature of the refrigerant received at an inlet of the cold-side path by communicating a signal to adjust the degree of opening or closing of the first expansion valve.

11. The controller of claim 9 , further operable to:
determine the liquid outlet temperature setpoint based at least in part on a target load capacity of the evaporator.

12. The controller of claim 9 , further operable to:
monitor power consumption associated with the liquid outlet temperature setpoint; and
adjust the liquid outlet temperature setpoint to a value that reduces the power consumption.

13. The controller of claim 12 , further operable to:
use information about a current load of the evaporator and a current ambient environment of the system to determine the value of the liquid outlet temperature setpoint that reduces the power consumption.

14. The controller of claim 9 , further operable to:
in response to determining that the system exceeds an operational limit when operating according to the superheat setpoint that was determined based on the liquid outlet temperature setpoint, override the superheat setpoint with an adjusted superheat setpoint that prevents the system from exceeding the operational limit.

15. A method comprising:
determining a liquid outlet temperature setpoint for refrigerant discharged from a liquid outlet of a subcooler, the liquid outlet corresponding to a hot-side path of the subcooler that receives refrigerant directly from a tank, cools the refrigerant by an exchange of heat with a cold-side path of the subcooler that receives the refrigerant from the tank via an inlet expansion valve, and discharges the refrigerant to an evaporator via an outlet expansion valve;
determining a superheat setpoint for the refrigerant discharged to a compressor via a vapor outlet of the cold-side path, the superheat setpoint determined based on the liquid outlet temperature setpoint, and
adjusting a temperature of the refrigerant discharged to the compressor via the vapor outlet of the cold-side path based on the superheat setpoint.

16. The method of claim 15 , further comprising:
adjusting the temperature of the refrigerant received at an inlet of the cold-side path by communicating a signal to adjust the degree of opening or closing of the first expansion valve.

17. The method of claim 15 , further comprising:
determining the liquid outlet temperature setpoint based at least in part on a target load capacity of the evaporator.

18. The method of claim 15 , further comprising:
monitoring power consumption associated with the liquid outlet temperature setpoint; and
adjusting the liquid outlet temperature setpoint to a value that reduces the power consumption.

19. The method of claim 18 , further comprising:
using information about a current load of the evaporator and a current ambient environment of the system to determine the value of the liquid outlet temperature setpoint that reduces the power consumption.

20. The method of claim 15 , further comprising:
in response to determining that the system exceeds an operational limit when operating according to the superheat setpoint that was determined based on the liquid outlet temperature setpoint, overriding the su

Assignees

• Heatcraft Refrigeration Products Llc

Inventors

• Hjortland Andrew

Classifications

• F25B41/39 Primary

  Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same evaporator · CPC title

• F25D17/02 Primary

  for circulating liquids, e.g. brine · CPC title

• F25B49/02

  for compression type machines, plants or systems · CPC title

• F25B40/02

  Subcoolers · CPC title

• F25B2600/2509

  Economiser valves · CPC title