Refrigeration cycle device

Patent metadata

Field	Value
Publication number	US-2022011020-A1
Application number	US-202117484858-A
Country	US
Kind code	A1
Filing date	Sep 24, 2021
Priority date	Mar 29, 2019
Publication date	Jan 13, 2022
Grant date	—

Abstract

A refrigerant circuit includes a first compressor, a second compressor, a heat-source-side heat exchanger, an expansion mechanism, and a use-side heat exchanger. The refrigerant circuit is capable of performing a single-stage compression operation in which one of the first compressor and the second compressor is driven and the other is stopped, and a two-stage compression operation in which both the first compressor and the second compressor are driven. The control unit controls the refrigerant circuit so that, of the single-stage compression operation and the two-stage compression operation, an operation with a higher compression efficiency is performed.

First claim

1 . A refrigeration cycle device comprising:
a refrigerant circuit including a first compressor, a second compressor, a heat-source-side heat exchanger, an expansion mechanism, and a use-side heat exchanger, and capable of performing a single-stage compression operation in which one of the first compressor and the second compressor is driven and an other is stopped, and a two-stage compression operation in which both the first compressor and the second compressor are driven; and a control unit configured to control the refrigerant circuit so that, of the single-stage compression operation and the two-stage compression operation, an operation with a higher compression efficiency is performed.

2 . The refrigeration cycle device according to claim 1 , wherein
the control unit is configured to control the refrigerant circuit so that the single-stage compression operation is performed if a required capacity of the refrigerant circuit is below a predetermined capacity threshold, and control the refrigerant circuit so that the two-stage compression operation is performed if the required capacity of the refrigerant circuit is not below the capacity threshold, and the capacity threshold is a value that changes in accordance with a physical quantity correlated with a difference between a high pressure and a low pressure in the refrigerant circuit, and corresponds to the required capacity of the refrigerant circuit at a boundary at which a compression efficiency in the two-stage compression operation becomes higher than a compression efficiency in the single-stage compression operation under a condition that the physical quantity is a physical quantity corresponding to the capacity threshold.

3 . The refrigeration cycle device according to claim 2 , wherein
the capacity threshold gradually decreases as the physical quantity increases.

4 . The refrigeration cycle device according to claim 2 , wherein
the control unit is configured to
control the refrigerant circuit so that the single-stage compression operation is performed regardless of the required capacity of the refrigerant circuit if the physical quantity is below a predetermined first physical quantity threshold, and
control the refrigerant circuit so that the two-stage compression operation is performed regardless of the required capacity of the refrigerant circuit if the physical quantity is above a second physical quantity threshold that is greater than the first physical quantity threshold.

5 . The refrigeration cycle device according to claim 2 , comprising
an injection circuit, wherein the second compressor is configured to suck refrigerant discharged by the first compressor in the two-stage compression operation, and the injection circuit is configured to supply, to a suction side of the second compressor, part of refrigerant flowing from, of the heat-source-side heat exchanger and the use-side heat exchanger, a heat exchanger serving as a radiator toward the expansion mechanism in the two-stage compression operation.

6 . The refrigeration cycle device according to claim 5 , wherein
one of the first compressor and the second compressor is an injection compressor, the injection compressor includes a compression chamber for compressing refrigerant and is configured to be able to supply refrigerant to the compression chamber that is performing compression, the injection compressor is driven in the single-stage compression operation, and the injection circuit is configured to
be switched, in the single-stage compression operation, between a first state in which the part of the refrigerant flowing from, of the heat-source-side heat exchanger and the use-side heat exchanger, the heat exchanger serving as a radiator toward the expansion mechanism is not supplied to either of the suction side of the second compressor and the compression chamber that is performing compression of the injection compressor, and a second state in which the part of the refrigerant is supplied to the compression chamber that is performing compression of the injection compressor, and
be switched, in the two-stage compression operation, to a third state in which the part of the refrigerant flowing from, of the heat-source-side heat exchanger and the use-side heat exchanger, the heat exchanger serving as a radiator toward the expansion mechanism is supplied to the suction side of the second compressor.

7 . The refrigeration cycle device according to claim 6 , wherein
the control unit is configured to, under a condition of controlling the refrigerant circuit so that the single-stage compression operation is performed, switch the injection circuit to the first state if the required capacity of the refrigerant circuit is below a predetermined single-stage capacity threshold and switch the injection circuit to the second state if the required capacity of the refrigerant circuit is not below the single-stage capacity threshold, and the single-stage capacity threshold is a value that changes in accordance with the physical quantity, and corresponds to the required capacity of the refrigerant circuit at a boundary at which a compression efficiency in the single-stage compression operation when the injection circuit is in the second state becomes higher than a compression efficiency in the single-stage compression operation when the injection circuit is in the first state under a condition that the physical quantity is a physical quantity corresponding to the single-stage capacity threshold.

8 . The refrigeration cycle device according to claim 7 , wherein
the single-stage capacity threshold gradually decreases as the physical quantity increases.

9 . The refrigeration cycle device according to claim 6 , wherein
the injection circuit is configured to be switched, in the two-stage compression operation, between the third state and a fourth state in which the part of the refrigerant flowing from, of the heat-source-side heat exchanger and the use-side heat exchanger, the heat exchanger serving as a radiator toward the expansion mechanism is supplied to both the suction side of the second compressor and the compression chamber that is performing compression of the injection compressor.

10 . The refrigeration cycle device according to claim 9 , wherein
the control unit is configured to, under a condition of controlling the refrigerant circuit so that the two-stage compression operation is performed, switch the injection circuit to the third state if the required capacity of the refrigerant circuit is below a predetermined two-stage capacity threshold and switch the injection circuit to the fourth state if the required capacity of the refrigerant circuit is not below the two-stage capacity threshold, and the two-stage capacity threshold is a value that changes in accordance with the physical quantity, and corresponds to the required capacity of the refrigerant circuit at a boundary at which a temperature of refrigerant discharged by the second compressor becomes higher than a predetermined allowed discharge temperature in the two-stage compression operation when the injection circuit is in the third state under a condition that the physical quantity is a physical quantity corresponding to the two-stage capacity threshold.

11 . The refrigeration cycle device according to claim 10 , wherein
the two-stage capacity threshold gradually decreases as the physical quantity increases.

12 . The refrigeration cycle device according to claim 3 , wherein
the control unit is configured to
control the refrigerant circuit so that the single-stage compression operation is performed regardless of the required capacity of the refrigerant circuit if the p

Assignees

• Daikin Ind Ltd

Inventors

• Hisayama Kazushi
• Chen Kebi
• Okamoto Tetsuya

Classifications

• F25B1/10 Primary

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

• F25B2700/21

  Temperatures · CPC title

• F25B2600/022

  for multi-stage operation · CPC title

• F25B49/02

  for compression type machines, plants or systems · CPC title

• F25B2700/21152

  at the discharge side of the compressor · CPC title