REFRIGERATING APPARATUS AND CONTROL DEVICE FOR REFRIGERATING MACHINE

• US 20140260388A1
• Filed: 03/14/2014
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Applied Americas Inc (Daikin Industries Ltd), Daikin Industries Ltd
• Inventors: UMEDA, Nobuhiro, TAKIGAWA, Takatoshi, ONODERA, Fumiaki, KOZONO, Nobutoshi, TAKADA, Yasutaka, NISHIO, Tsubasa
• Granted Patent: US 10,539,353 B2
• Time in Patent Office: Days
• US Class Current: 62/208
• CPC Class Codes: F25B 1/053 of turbine type
• CPC Class Codes: F25B 1/10 with multi-stage compression with cascade operation F25B7/00
• CPC Class Codes: F25B 2339/047 Water-cooled condensers
• CPC Class Codes: F25B 2400/13 Economisers
• CPC Class Codes: F25B 2400/23 Separators
• CPC Class Codes: F25B 25/005 using primary and secondary systems
• CPC Class Codes: F25B 2600/0253 with variable speed
• CPC Class Codes: F25B 2600/2513 Expansion valves
• CPC Class Codes: F25B 2700/195 of the condenser
• CPC Class Codes: F25B 2700/197 of the evaporator
• CPC Class Codes: F25B 2700/2109 of a separator
• CPC Class Codes: F25B 2700/21161 of the fluid heated by the condenser
• CPC Class Codes: F25B 2700/21162 of the refrigerant at the inlet of the condenser
• CPC Class Codes: F25B 2700/21171 of the fluid cooled by the evaporator
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• 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 refrigerating apparatus includes a centrifugal compressor, suction and discharge capacity control mechanisms that control capacity of the compressor by changing opening degrees of the suction and discharge capacity control mechanisms, and a controller that compares a compressor-specific surge curve with an isentropic head to perform rotational speed control of the compressor, rotational speed adjustment control of the compressor in order to avoid surge, and emergency shutdown control of the compressor upon detection of surge. The compressor-specific surge curve is stored in the controller in advance, and is defined by an actual rotational speed of the compressor and opening degrees of the suction and discharge capacity control mechanisms. The isentropic head is calculated based on a suction pressure, a discharge pressure, and a suction temperature during operation.

Claims

1. A refrigerating apparatus comprising:

a centrifugal compressor;

a suction capacity control mechanism and a discharge capacity control mechanism configured to control a capacity of the compressor by changing opening degrees of the suction capacity control mechanism and the discharge capacity control mechanism; and

a controller configured to compare a compressor-specific surge curve with an isentropic head to perform

rotational speed control of the compressor,

rotational speed adjustment control of the compressor in order to avoid surge, and

emergency shutdown control of the compressor upon detection of surge,

the compressor-specific surge curve being stored in the controller in advance, and the compressor-specific surge curve being defined by an actual rotational speed of the compressor, an opening degree of the suction capacity control mechanism, and an opening degree of the discharge capacity control mechanism, and

the isentropic head being calculated based on a suction pressure, a discharge pressure, and a suction temperature during operation.

2. A refrigerating apparatus according to claim 1, wherein

the compressor is a two stage compressor, and

the isentropic head is expressed in a pseudo single stage enthalpy basis.

3. A refrigerating apparatus according to claim 1, wherein

the suction pressure and the discharge pressure are converted into absolute pressure according to a height of a location where the refrigerating apparatus is installed, and the height of the location is set in the controller.

4. A refrigerating apparatus according to claim 1, further comprising

a condenser pressure sensor attached to a condenser of the refrigerating apparatus;

and

an evaporator pressure sensor attached to an evaporator of the refrigerating apparatus,

the suction pressure and the discharge pressure being obtained respectively by applying correction to a reading of the evaporator pressure sensor and a reading of the condenser pressure sensor by an amount of pressure loss in a suction pipe and a discharge pipe calculated at any time on the basis of a gas flow of the compressor.

5. A refrigerating apparatus according to claim 4, wherein

the controller is configured to determine a surge abnormality and to stop the compressor when an integrated time in which the isentropic head surpasses the compressor-specific surge curve exceeds a preset time in a most recent fixed time period.

6. A refrigerating apparatus according to claim 3, wherein

the controller is configured to determine a surge abnormality and to stop the compressor when an integrated time in which the isentropic head surpasses the compressor-specific surge curve exceeds a preset time in a most recent fixed time period.

7. A control device adapted for a refrigerating machine having a centrifugal compressor, and a suction capacity control mechanism and a discharge capacity control mechanism configured to control a capacity of the compressor by changing opening degree of the suction capacity control mechanism and a discharge capacity control mechanism, the control device comprising:

a storing unit configured to store a compressor-specific surge curve; and

a processing unit,

the processing unit being configured to compare the compressor-specific surge curve stored in the storing unit with an isentropic head to perform

rotational speed control of the compressor,

rotational speed adjustment control of the compressor in order to avoid surge, and

emergency shutdown control of the compressor upon detection of surge,

the compressor-specific surge curve being defined by an actual rotational speed of the compressor, an opening degree of the suction capacity control mechanism, and an opening degree of the discharge capacity control mechanism, and

the isentropic head being calculated based on a suction pressure, a discharge pressure, and a suction temperature of the compressor during operation.

8. A control device according to claim 7, wherein

the compressor is a two stage compressor, and

the isentropic head is expressed in a pseudo single stage enthalpy basis.

9. A control device according to claim 7, wherein

the suction pressure and the discharge pressure are converted into absolute pressure according to a height of a location where the refrigerating machine is installed, and the height of the location is stored in the storing unit.

10. A control device according to claim 7, wherein

the refrigerating machine has a condenser pressure sensor attached to a condenser and an evaporator pressure sensor attached to an evaporator, and

the suction pressure and the discharge pressure are obtained respectively by applying correction to a reading of the evaporator pressure sensor and a reading of the condenser pressure sensor by an amount of pressure loss in a suction pipe and a discharge pipe of the compressor calculated at any time on the basis of a gas flow of the compressor.

11. A control device according to claim 10, wherein

the processing unit is configured to determine a surge abnormality and to stop the compressor when an integrated time in which the isentropic head surpasses the compressor-specific surge curve exceeds a preset time in a most recent fixed time period.

12. A control device according to claim 9, wherein

the processing unit is configured to determine a surge abnormality and to stop the compressor when an integrated time in which the isentropic head surpasses the compressor-specific surge curve exceeds a preset time in a most recent fixed time period.