System and method for monitoring compressor floodback

• US 9,057,549 B2
• Filed: 09/19/2013
• Issued: 06/16/2015
• Est. Priority Date: 10/08/2007
• Status: Active Grant

• Current Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Original Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Inventors: McSweeney, Daniel L.
• Primary Examiner(s): Bradford, Jonathan
• Application Number:
  US14/031,905
• Publication Number:
  US 20140033746A1
• Time in Patent Office: 635 Days
• Field of Search: 622/25, 622/281, 622/30
• US Class Current: 1/1
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 2600/02 Compressor control
• CPC Class Codes: F25B 2600/2513 Expansion valves
• CPC Class Codes: F25B 2700/171 of the compressor
• CPC Class Codes: F25B 2700/21151 at the suction side of the compressor
• CPC Class Codes: F25B 2700/2117 of an evaporator
• CPC Class Codes: F25B 2700/21174 of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 2700/21175 of the refrigerant at the outlet of the evaporator
• CPC Class Codes: F25B 41/34 with the valve member being actuated by electric means, e.g. by piezoelectric actuators
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A system and method for a compressor includes a compressor connected to an evaporator, a suction sensor that outputs a suction temperature signal corresponding to a suction temperature of refrigerant entering the compressor, and a control module connected to the suction sensor. The control module determines a saturated evaporator temperature, calculates a suction superheat temperature based on the saturated evaporator temperature and the suction temperature, and monitors a floodback condition of the compressor by comparing the suction superheat temperature with a predetermined threshold. When the suction superheat temperature is less than or equal to the predetermined threshold, the control module increases a speed of the compressor or decreases an opening of an expansion valve associated with the compressor.

Claims

1. A system comprising:

a compressor connected to an evaporator;

a suction sensor that outputs a suction temperature signal corresponding to a suction temperature of refrigerant entering the compressor;

a control module connected to the suction sensor, said control module determining a saturated evaporator temperature based on a speed of the compressor, calculating a suction superheat temperature based on the saturated evaporator temperature and the suction temperature, monitoring a floodback condition of the compressor by comparing the suction superheat temperature with a predetermined threshold, and, when the suction superheat temperature is less than or equal to the predetermined threshold, increasing the speed of the compressor or decreasing an opening of an expansion valve associated with the compressor.

2. The system of claim 1 wherein the predetermined threshold is zero degrees Fahrenheit.

3. The system of claim 1 wherein the control module increases the speed of the compressor when the suction superheat temperature is less than or equal to the predetermined threshold.

4. The system of claim 1 wherein the control module decreases the opening of the expansion valve when the suction superheat temperature is less than or equal to the predetermined threshold.

5. The system of claim 1 further comprising a condenser connected to the compressor and the evaporator, wherein the control module determines a discharge line temperature corresponding to a temperature of refrigerant leaving the compressor, determines a saturated condenser temperature, and determines the saturated evaporator temperature as a function of the saturated condenser temperature, the discharge line temperature, and the speed of the compressor.

6. The system of claim 5 wherein the control module receives compressor power data and determines the saturated condenser temperature as a function of the compressor power data, the speed of the compressor, and the saturated evaporator temperature.

7. The system of claim 6 wherein the control module performs multiple iterations of determining the saturated condenser temperature and the saturated evaporator temperature to achieve convergence.

8. The system of claim 1 wherein the control module determines a discharge line temperature corresponding to a temperature of refrigerant leaving the compressor, receives compressor power data, and determines the saturated evaporator temperature as a function of the compressor power data, the speed of the compressor, and the discharge line temperature.

9. The system of claim 1 further comprising a condenser connected to the compressor and the evaporator, wherein the control module determines a saturated condenser temperature, determines a mass flow of the compressor, and determines the saturated evaporator temperature as a function of the speed of the compressor, the saturated condenser temperature, and the mass flow.

10. A method comprising:

determining, with a control module, a saturated evaporator temperature of an evaporator based on a speed of a compressor connected to the evaporator;

receiving, with the control module, a suction temperature signal that corresponds to a suction temperature of refrigerant entering the compressor;

calculating, with the control module, a suction superheat temperature based on the saturated evaporator temperature and the suction temperature;

monitoring, with the control module, a floodback condition of the compressor by comparing the suction superheat with a predetermined threshold; and

increasing the speed of the compressor or decreasing an opening of an expansion valve, with the control module, when the suction superheat temperature is less than or equal to the predetermined threshold.

11. The method of claim 10 wherein the predetermined threshold is zero degrees Fahrenheit.

12. The method of claim 10 wherein the control module increases the speed of the compressor when the suction superheat temperature is less than or equal to the predetermined threshold.

13. The method of claim 10 wherein the control module decreases the opening of the expansion valve when the suction superheat temperature is less than or equal to the predetermined threshold.

14. The method of claim 10 further comprising determining, with the control module, a discharge line temperature corresponding to a temperature of refrigerant leaving the compressor, determining a saturated condenser temperature of a condenser connected to the evaporator and the compressor, and determining the saturated evaporator temperature as a function of the saturated condenser temperature, the discharge line temperature, and the speed of the compressor.

15. The method of claim 14 further comprising receiving, with the control module, compressor power data and determining the saturated condenser temperature as a function of the compressor power data, the speed of the compressor, and the saturated evaporator temperature.

16. The method of claim 15 further comprising performing multiple iterations of determining the saturated condenser temperature and determining the saturated evaporator temperature to achieve convergence.

17. The method of claim 10 further comprising determining, with the control module, a discharge line temperature corresponding to a temperature of refrigerant leaving the compressor, receiving compressor power data, and determining the saturated evaporator temperature as a function of the compressor power data, the speed of the compressor, and the discharge line temperature.

18. The method of claim 10 further comprising determining, with the control module, a saturated condenser temperature of a condenser connected to the evaporator and the compressor, determining a mass flow of the compressor, and determining the saturated evaporator temperature as a function of the speed of the compressor, the saturated condenser temperature, and the mass flow.