Method for controlling a vapour compression system with an ejector

Patent metadata

Field	Value
Publication number	US-10544971-B2
Application number	US-201515527545-A
Country	US
Kind code	B2
Filing date	Oct 7, 2015
Priority date	Nov 19, 2014
Publication date	Jan 28, 2020
Grant date	Jan 28, 2020

Abstract

A method for controlling a vapor compression system (1) is disclosed, the vapor compression system (1) comprising an ejector (5). The method comprises controlling a compressor unit (2) in order to adjust a pressure inside a receiver (6), on the basis of a detected pressure of refrigerant leaving an evaporator (8). The portion of refrigerant leaving the evaporator (8) which is supplied to a secondary inlet (15) of the ejector is maximized and the portion of refrigerant supplied directly to the compressor unit (2) is minimized, while ensuring that the pressure of refrigerant leaving the evaporator (8) does not decrease below an acceptable level.

First claim

What is claimed is:

1. A method for controlling a vapour compression system, the vapour compression system comprising a compressor unit comprising one or more compressors, a heat rejecting heat exchanger, an ejector, a receiver, an expansion device and an evaporator arranged in a refrigerant path, wherein an outlet of the heat rejecting heat exchanger is connected to a primary inlet of the ejector, an outlet of the ejector is connected to the receiver and an outlet of the evaporator is selectively connected to a secondary inlet of the ejector and/or to an inlet of the compressor unit, and wherein a gaseous outlet of the receiver is connected to the inlet of the compressor unit, the method comprising the steps of:
detecting a pressure of refrigerant leaving the evaporator,
detecting a state of the compressor unit, said state of the compressor unit indicating whether or not refrigerant is supplied from the outlet of the evaporator to the inlet of the compressor unit,
in the case that the step of detecting a state of the compressor unit reveals that refrigerant is supplied from the outlet of the evaporator to the inlet of the compressor unit, operating the compressor unit in order to decrease a pressure inside the receiver,
in the case that the step of detecting a state of the compressor unit reveals that refrigerant is not supplied from the outlet of the evaporator to the inlet of the compressor unit, comparing the detected pressure of refrigerant leaving the evaporator to a lower threshold value and to an upper threshold value, and
operating the compressor unit in order to:
increase the pressure inside the receiver in the case that the detected pressure of refrigerant leaving the evaporator is below the lower threshold value,
decrease the pressure inside the receiver in the case that the detected pressure of refrigerant leaving the evaporator is above the upper threshold value, and
maintain the pressure inside the receiver in the case that the detected pressure of refrigerant leaving the evaporator is between the lower threshold value and the upper threshold value.

2. The method according to claim 1 , wherein the one or more compressors comprises one or more main compressors and one or more receiver compressors, the main compressor(s) being connected to the outlet of the evaporator, and the receiver compressor(s) being connected to the gaseous outlet of the receiver, and wherein the step of detecting the state of the compressor unit further comprises detecting whether or not one or more of the main compressor(s) is/are operating.

3. The method according to claim 2 , wherein the step of operating the compressor unit to increase or decrease the pressure inside the receiver comprises operating the receiver compressor(s) to adjust the pressure inside the receiver.

4. The method according to claim 2 , further comprising the steps of detecting whether or not one or more of the receiver compressor(s) is/are operating, and operating the one or more main compressor(s) in order to decrease the pressure inside the receiver in the case that the receiver compressor(s) is/are not operating.

5. The method according to claim 1 , wherein the compressor unit comprises one or more valves arranged to control whether the inlet of the compressor unit is connected to the gaseous outlet of the receiver or to the outlet of the evaporator, and wherein the step of detecting a state of the compressor unit comprises detecting a state of the one or more valves.

6. The method according to claim 5 , wherein the step of operating the compressor unit to decrease the pressure inside the receiver, in the case that refrigerant is supplied from the outlet of the evaporator to the inlet of the compressor unit, comprises switching at least one of the one or more valves to a position where the inlet of the compressor unit is connected to the gaseous outlet of the receiver.

7. The method according to claim 5 , wherein the step of operating the compressor unit to decrease or increase the pressure inside the receiver, in the case that refrigerant is not supplied from the outlet of the evaporator to the inlet of the compressor unit, comprises increasing or decreasing a compressor capacity of the compressor unit.

8. The method according to claim 1 , wherein the step of operating the compressor unit comprises the steps of:
adjusting a setpoint value for the pressure inside the receiver, in accordance with the detected pressure of refrigerant leaving the evaporator, and
operating the compressor unit in accordance with the adjusted setpoint value.

9. The method according claim 1 , wherein the vapour compression system further comprises a high pressure valve interconnecting an outlet of the heat rejecting heat exchanger and an inlet of the receiver, the high pressure valve being arranged in parallel to the ejector, and wherein refrigerant leaving the heat rejecting heat exchanger is divided into a flow passing through the high pressure valve and a flow passing through the ejector, via the primary inlet of the ejector.

10. The method according to claim 1 , wherein the vapour compression system is arranged to have the refrigerant be a transcritical refrigerant flowing in the refrigerant path.

11. The method according to claim 1 , wherein the heat rejecting heat exchanger is a gas cooler.

12. The method according to claim 1 , wherein the vapour compression system further comprises a bypass valve arranged in the refrigerant path interconnecting the gaseous outlet of the receiver and the inlet of the compressor unit, and wherein the method further comprises the step of opening the bypass valve in the case that the pressure inside the receiver decreases below a minimum value.

13. The method according to claim 3 , further comprising the steps of detecting whether or not one or more of the receiver compressor(s) is/are operating, and operating the compressor unit in order to decrease the pressure inside the receiver in the case that the receiver compressor(s) is/are not operating.

14. The method according to claim 6 , wherein the step of operating the compressor unit to decrease or increase the pressure inside the receiver, in the case that refrigerant is not supplied from the outlet of the evaporator to the inlet of the compressor unit, comprises increasing or decreasing a compressor capacity of the compressor unit.

15. The method according to claim 2 , wherein the step of operating the compressor unit comprises the steps of:
adjusting a setpoint value for the pressure inside the receiver, in accordance with the detected pressure of refrigerant leaving the evaporator, and
operating the compressor unit in accordance with the adjusted setpoint value.

16. The method according to claim 3 , wherein the step of operating the compressor unit comprises the steps of:
adjusting a setpoint value for the pressure inside the receiver, in accordance with the detected pressure of refrigerant leaving the evaporator, and
operating the compressor unit in accordance with the adjusted setpoint value.

17. The method according to claim 4 , wherein the step of operating the compressor unit comprises the steps of:
adjusting a setpoint value for the pressure inside the receiver, in accordance with the detected pressure of refrigerant leaving the evaporator, and
operating the compressor unit in accordance with the adjusted setpoint value.

18. The method according to claim 5 , wherein the step of operating the compressor unit comprises the steps of:
adjusting a setpoint value for the pressure inside the receiver, in accordance wi

Assignees

• Danfoss As

Inventors

• Fredslund Kristian
• Schmidt Frede
• Madsen Kenneth Bank
• Prins Jan

Classifications

• F25B2700/197

  of the evaporator · CPC title

• F25B2600/0253

  with variable speed · CPC title

• F25B2500/29

  High ambient temperatures · CPC title

• F25B2500/31

  Low ambient temperatures · CPC title

• F25B49/02 Primary

  for compression type machines, plants or systems · CPC title