Method for switching compressor capacity

Patent metadata

Field	Value
Publication number	US-11060767-B2
Application number	US-201615771199-A
Country	US
Kind code	B2
Filing date	Oct 31, 2016
Priority date	Nov 5, 2015
Publication date	Jul 13, 2021
Grant date	Jul 13, 2021

Abstract

A method for operating a compressor unit (2) comprising one or more compressors (8, 9, 10) is disclosed, the compressor unit (2) being arranged in a vapour compression system (1). Two or more options for distributing the available compressor capacity of the compressor unit (2) between being connected to a high pressure suction line (11) and to a medium pressure suction line (13) are defined. For each option, an expected impact on one or more operating parameters of the vapour compression system (1), resulting from distributing the available compressor capacity according to the option, is predicted. An option is selected, based on the predicted expected impact for the options, and based on current operating demands of the vapour compression system (1), and the available compressor capacity is distributed according to the selected option, e.g. by means of settings of one or more valve arrangements (14, 15).

First claim

What is claimed is:

1. A method for operating a compressor unit comprising one or more compressors, the compressor unit being arranged in a vapour compression system, the vapour compression system further comprising a heat rejecting heat exchanger, a high pressure expansion device, a receiver and at least one evaporator unit, each evaporator unit comprising an evaporator and an expansion device controlling a supply of refrigerant to the evaporator, each compressor of the compressor unit being alternately connectable to a high pressure suction line or to a medium pressure suction line, the high pressure suction line interconnecting a gaseous outlet of the receiver and the compressor unit and the medium pressure suction line interconnecting an outlet of the evaporator unit(s) and the compressor unit, wherein the vapour compression system further comprises at least one valve arrangement, each valve arrangement of the at least one valve arrangement being arranged to selectively connect one compressor of the one or more compressors to the high pressure suction line or to the medium pressure suction line, the method comprising the steps of:
defining two or more options for distributing the available compressor capacity of the compressor unit between compressors of the compressor unit being connected to the high pressure suction line and to the medium pressure suction line,
for each option, predicting an expected impact on one or more operating parameters of the vapour compression system, resulting from distributing the available compressor capacity according to the option,
selecting an option, based on the predicted expected impact for the options, and based on current operating demands of the vapour compression system, and
distributing the available compressor capacity according to the selected option by switching one or more compressors from being connected to the medium pressure suction line to being connected to the high pressure suction line, or vice versa, by operating the at least one valve arrangement.

2. The method according to claim 1 , wherein the step of switching one or more compressors is performed without stopping the compressor(s).

3. The method according to claim 2 , wherein the step of distributing the available compressor capacity according to the selected option comprises switching one or more compressors of the compressor unit on or off.

4. The method according to claim 1 , wherein the valve arrangement comprises a two-way valve arranged to connect the one compressor of the one or more compressors to the high pressure suction line and a non-return valve arranged to connect the one compressor of the one or more compressors to the medium pressure suction line.

5. The method according to claim 1 , wherein the step of distributing the available compressor capacity according to the selected option comprises switching one or more compressors of the compressor unit on or off.

6. The method according to claim 1 , wherein the one or more operating parameters of the vapour compression system comprises energy consumption, mass flow distribution, cooling capacity, heat recovery, number of starts or stops of compressors, runtime equalization of compressors, and/or oil return to the compressor unit.

7. The method according to claim 1 , wherein the step of predicting an expected impact on one or more operating parameters of the vapour compression system is performed using a model based approach.

8. The method according to claim 1 , wherein the step of selecting an option is further based on one or more expected future requirements for operating the vapour compression system, and wherein the step of distributing the available compressor capacity according to the selected option comprises switching a compressor which is currently not running from being connected to the high pressure suction line to being connected to the medium pressure suction line, or vice versa, in order to be able to meet the expected future requirements.

9. The method according to claim 1 , wherein the vapour compression system further comprises a low temperature evaporator unit, a low temperature compressor unit having an inlet connected to an outlet of the low temperature evaporator unit, and a low temperature valve arrangement arranged to selectively interconnect an outlet of the low temperature compressor unit to the high pressure suction line or to the medium pressure suction line, wherein at least some of the options define settings for the low temperature valve arrangement.

10. The method according to claim 9 , wherein the step of distributing the available compressor capacity comprises operating the low temperature valve arrangement.

11. The method according to claim 1 , wherein the step of defining two or more options for distributing the available compressor capacity is performed on the basis of current and/or expected operating conditions of the vapour compression system.

12. The method according to claim 1 , wherein the high pressure expansion device is an ejector having a primary inlet connected to an outlet of the heat rejecting heat exchanger, an outlet connected to the receiver and a secondary inlet connected to the medium pressure suction line, and wherein the method further comprises the step of monitoring oil return to the compressors.

13. The method according to claim 12 , wherein the step of selecting an option comprises selecting an option in which at least one compressor is connected to the medium pressure suction line in the case that the oil returned to the compressors decreases below a predefined minimum level.

14. A vapour compression system comprising a compressor unit comprising a plurality of compressors, a heat rejecting heat exchanger, a high pressure expansion device, a receiver and at least one evaporator unit, each evaporator unit comprising an evaporator and an expansion device controlling a supply of refrigerant to the evaporator, each compressor of the compressor unit being alternately connectable to a high pressure suction line and to a medium pressure suction line, the high pressure suction line interconnecting a gaseous outlet of the receiver and the compressor unit and the medium pressure suction line interconnecting an outlet of the evaporator unit(s) and the compressor unit, wherein the vapour compression system further comprises at least one valve arrangement arranged to selectively connect one of the compressors to the high pressure suction line or to the medium pressure suction line, the valve arrangement comprising a two-way valve arranged to connect the compressor to the high pressure suction line and a non-return valve arranged to connect the compressor to the medium pressure suction line.

15. The vapour compression system according to claim 14 , wherein the high pressure expansion device is an ejector having a primary inlet connected to an outlet of the heat rejecting heat exchanger, an outlet connected to the receiver and a secondary inlet connected to the medium pressure suction line.

16. The vapour compression system according to claim 14 , further comprising a heat recovery heat exchanger arranged in the refrigerant path between an outlet of the compressor unit and an inlet of the heat rejecting heat exchanger.

Assignees

• Danfoss As

Inventors

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

Classifications

• F25B41/39

  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

• F25B2500/18

  Optimization, e.g. high integration of refrigeration components · CPC title

• F25B2600/2519

  On-off valves · CPC title

• F25B1/10 Primary

  with multi-stage compression (with cascade operation F25B7/00) · CPC title

• F25B2500/19

  Calculation of parameters · CPC title