US20200173693A1 - Control device of refrigerating cycle, heat source device, and control method therefor - Google Patents
Control device of refrigerating cycle, heat source device, and control method therefor Download PDFInfo
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- US20200173693A1 US20200173693A1 US16/614,525 US201816614525A US2020173693A1 US 20200173693 A1 US20200173693 A1 US 20200173693A1 US 201816614525 A US201816614525 A US 201816614525A US 2020173693 A1 US2020173693 A1 US 2020173693A1
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- gas volume
- opening degree
- compressor
- expansion valve
- control device
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
- F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
- 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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B13/00—Compression machines, plants or systems, with reversible cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2339/00—Details of evaporators; Details of condensers
- F25B2339/04—Details of condensers
- F25B2339/047—Water-cooled condensers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/04—Refrigeration circuit bypassing means
- F25B2400/0411—Refrigeration circuit bypassing means for the expansion valve or capillary tube
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/13—Economisers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/23—Separators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2513—Expansion valves
Definitions
- the present invention relates to a control device of a refrigerating cycle, a heat source device, and a control method therefor.
- a heat source device such as a centrifugal chiller or an air conditioner having a refrigerating cycle
- a method for realizing a stable operation at a low load while securing a required minimum gas volume for a compressor by allowing a hot gas bypass pipe to bypass refrigerant gas from a discharge unit of a compressor or a condenser to an intake unit of the compressor or an evaporator (for example, PTL 1).
- the present invention has been made in light of the problem, and an object of the present invention is to provide a control device of a refrigerating cycle, a heat source device, and a control method therefor which are capable of realizing a stable low load operation without using a hot gas bypass pipe.
- a control device of a refrigerating cycle including a compressor compressing a refrigerant, a condenser condensing the refrigerant compressed by the compressor, an expansion valve expanding a liquid refrigerant delivered from the condenser, and an evaporator evaporating the refrigerant expanded by the expansion valve, the control device including a gas volume calculation unit that calculates a current gas volume using a current actual cooling capacity; and a minimum gas volume calculation unit that calculates a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor, in which if the current gas volume is less than the required minimum gas volume for the compressor, the control device performs control so as to increase an opening degree of the expansion valve.
- the control device performs control so as to increase the opening degree of the expansion valve. Therefore, it is possible to deliver a gaseous refrigerant, the amount of which is greater than that of the refrigerant satisfying the cooling capacity, to the evaporator. As a result, it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load.
- the control device of a refrigerating cycle may further include a reference command calculation unit that calculates a reference opening degree command value in response to a demanded cooling capacity; a correction command calculation unit that calculates a correction opening degree command value in response to a difference between the current gas volume and the required minimum gas volume for the compressor; and an opening degree command value calculation unit that calculates an opening degree command value of the expansion valve by adding the correction opening degree command value to the reference opening degree command value.
- the correction command calculation unit calculates the correction opening degree command value in response to the difference between the current gas volume and the required minimum gas volume
- the opening degree command value calculation unit calculates the opening degree command value obtained by adding the correction opening degree command value to the reference opening degree command value.
- the opening degree of the expansion valve is controlled based on the opening degree command value. Therefore, if the current gas volume is less than the required minimum gas volume, along with the liquid refrigerant, the gaseous refrigerant required to secure the required minimum gas volume is delivered from the expansion valve to the evaporator. As a result, it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load.
- the control device of a refrigerating cycle may have opening degree command information in which an opening degree command value obtained by adding a correction opening degree command value for the required minimum gas volume for the compressor to a reference opening degree command value in response to a demanded cooling capacity is mapped to the demanded cooling capacity, and determine an opening degree command value corresponding to a currently demanded cooling capacity, from the opening degree command information.
- the configuration it is possible to easily acquire the opening degree command value satisfying both the demanded cooling capacity and the required minimum gas volume, by using the opening degree command information.
- the refrigerating cycle may include an economizer provided between the condenser and the evaporator, and the expansion valve may include a first expansion valve provided between the condenser and the economizer and a second expansion valve provided between the economizer and the evaporator. Furthermore, in such configuration, if the current gas volume is less than the required minimum gas volume for the compressor, the control device of a refrigerating cycle may perform control so as to increase an opening degree of the first expansion valve and an opening degree of the second expansion valve.
- the first expansion valve and the second expansion valve can be controlled according to the opening degree command value satisfying both the demanded cooling capacity and the required minimum gas volume. Therefore, it is possible to realize a stable operation of the compressor at a low load.
- a heat source device including the control device of a refrigerating cycle.
- a method for controlling a refrigerating cycle including a compressor compressing a refrigerant, a condenser condensing the refrigerant compressed by the compressor, an expansion valve expanding a liquid refrigerant delivered from the condenser, and an evaporator evaporating the refrigerant expanded by the expansion valve, the method including calculating a current gas volume using a current actual cooling capacity; and calculating a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor, in which if the current gas volume is less than the required minimum gas volume for the compressor, control is performed so as to increase an opening degree of the expansion valve.
- the present invention provides the effect that it is possible to realize a stable low load operation without using the hot gas bypass pipe.
- FIG. 1 is a schematic configuration diagram illustrating a centrifugal chiller according to an embodiment of the present invention.
- FIG. 2 is a functional block diagram of a control device according to the embodiment of the present invention.
- FIG. 3 is a graph illustrating the relationship between a gas volume ( ⁇ cooling capacity) and an opening degree command value (CV value) according to the embodiment of the present invention.
- FIG. 4 is a graph for describing opening degree control for an expansion valve according to the embodiment of the present invention using the Mollier diagram of a refrigerant.
- FIG. 5 is a schematic configuration diagram illustrating a centrifugal chiller according to another embodiment of the present invention.
- FIG. 6 is a graph for describing opening degree control for an expansion valve according to the other embodiment of the present invention using the Mollier diagram of the refrigerant.
- a centrifugal chiller is exemplified as the heat source device including a refrigerating cycle, but the present invention is not limited to this one example, and the heat source device may be an air conditioner, a water heater, or the like.
- a refrigerant applied to the refrigerating cycle is not specifically limited, but may be properly selected in response to the application or the like.
- FIG. 1 is a schematic configuration diagram illustrating a centrifugal chiller 1 according to the embodiment of the present invention.
- the turbo chiller 1 includes a compressor 3 that compresses a refrigerant; a condenser 5 that condenses the high-temperature high-pressure refrigerant compressed by the compressor 3 ; an expansion valve 7 that expands the refrigerant delivered from the condenser 5 ; an evaporator 9 that evaporates the refrigerant expanded by the expansion valve 7 ; and a control device 10 that controls the centrifugal chiller 1 .
- the compressor 3 is, for example, a turbo compressor, and a centrifugal compressor is used as an example.
- the compressor 3 is driven by an electric motor 12 , the rotation speed of which is controlled by an inverter 11 .
- An output of the inverter 11 is controlled by the control device 10 .
- a variable speed compressor is exemplified, but a fixed speed compressor may be used.
- An inlet guide vane (hereinbelow, referred to as “IGV”) 13 is provided at a refrigerant intake port of the compressor 3 to control a refrigerant intake flow rate, and is capable of controlling the capacity of the centrifugal chiller 1 .
- the opening degree of the IGV 13 is controlled by the control device 10 .
- the compressor 3 includes an impeller rotating around a rotary shaft. A rotational power is transmitted from the electric motor 12 to the rotary shaft via a speed-increasing gear.
- the rotary shaft is supported by bearings.
- the condenser 5 is a shell and tube type heat exchanger or a plate type heat exchanger.
- a coolant for cooling the refrigerant is supplied to the condenser 5 .
- the coolant delivered to the condenser 5 is released to the outside in a cooling tower or an air heat exchanger which is not illustrated, and then is delivered back to the condenser 5 .
- the expansion valve 7 is an electric type.
- the low-temperature high-pressure refrigerant delivered from the condenser 5 is enthalpically expanded by the expansion valve 7 .
- the opening degree of the expansion valve 7 is controlled by the control device 10 so as to be able to obtain a desired head difference (difference between the high pressure and the low pressure of the refrigerant in the refrigerating cycle).
- the evaporator 9 is a shell and tube type heat exchanger or a plate type heat exchanger. Chilled water to be supplied to an external load (not illustrated) is delivered to the evaporator 9 . The chilled water is cooled down to a rated temperature (for example, 7° C.) by exchanging heat with the refrigerant in the evaporator 9 , and is fed to the external load (not illustrated).
- a rated temperature for example, 7° C.
- the control device 10 is configured to include a central processing unit (CPU); a random access memory (RAM); a read only memory (ROM); a computer-readable storage medium; and the like.
- the control device 10 realizes various functions, as an example, by storing a series of processes for realizing various functions in the storage medium or the like in the form of a program (for example, control program), and causing the CPU to read the program into the RAM or the like and to process information and execute a calculation process.
- a form where the program is preinstalled on the ROM or other storage mediums, a form where the program is stored in the computer-readable storage medium and is provided to the control device, or a form where the program is transmitted to the control device via wired or wireless communication means may be applied.
- the computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory.
- FIG. 2 is a functional block diagram of the control device 10 .
- the control device 10 includes an expansion valve control unit 20 that controls the expansion valve 7 , a reference command calculation unit 21 , a gas volume calculation unit 22 , a minimum gas volume calculation unit 23 , a correction command calculation unit 24 , and an opening degree command calculation unit 25 .
- the reference command calculation unit 21 calculates a reference opening degree command value in response to a demanded cooling capacity.
- the reference command calculation unit 21 calculates the reference opening degree command value (reference CV value) of the expansion valve 7 , for example, from a target refrigerant circulation volume, which is calculated from the demanded cooling capacity, and a pressure difference between before and after the expansion valve 7 .
- the target refrigerant circulation volume is calculated, for example, based on a required heat exchange amount required for the evaporator 9 to make a measured temperature value of the chilled water, which is supplied from the evaporator 9 to the external load, identical to a set temperature (for example, 7° C.).
- the reference opening degree command value of the expansion valve 7 is calculated from the pressure difference between before and after the expansion valve 7 so as to be able to obtain the target refrigerant circulation amount.
- the gas volume calculation unit 22 calculates a current gas volume using a current actual cooling capacity.
- the minimum gas volume calculation unit 23 calculates a required minimum gas volume for the compressor 3 using a parameter related to an operating condition of the compressor 3 . More specifically, the minimum gas volume calculation unit 23 calculates the required minimum gas volume using a flow rate variable (cooling capacity) and a pressure variable (head) which indicate the operating condition of the compressor 3 .
- the correction command calculation unit 24 calculates a correction opening degree command value (correction CV value) based on the current gas volume calculated by the gas volume calculation unit 22 and the required minimum gas volume calculated by the minimum gas volume calculation unit 23 . Specifically, if the current gas volume is greater than or equal to the required minimum gas volume, the correction command calculation unit 24 sets the correction opening degree command value at zero, and if the current gas volume is less than the required minimum gas volume, the correction command calculation unit 24 calculates the correction opening degree command value in response to a difference between the current gas volume and the required minimum gas volume. For example, as the correction opening degree command value, the correction command calculation unit 24 calculates the difference between the current gas volume and the required minimum gas volume.
- the opening degree command calculation unit 25 calculates a value obtained by adding the reference opening degree command value (reference CV value) calculated by the reference command calculation unit 21 to the correction opening degree command value (correction CV value) calculated by the correction command calculation unit 24 . Therefore, the opening degree of the expansion valve 7 is controlled based on the opening degree command value.
- FIG. 3 is a graph illustrating the relationship between the gas volume ( ⁇ cooling capacity) and the opening degree command value (CV value).
- the opening degree command value is set in response to the gas volume. Namely, the greater the gas volume is, the larger value the opening degree command value is set at.
- the gas volume is less than the required minimum gas volume
- the less the gas volume is, the larger value the opening degree command value is set at. The reason is that the less the gas volume is, the larger the difference between the required minimum gas volume and the gas volume becomes, and thus the correction opening degree command value has a large value.
- the refrigerant is depressurized by the expansion valve 7 in a two-phase gas-liquid phase region.
- the refrigerant is depressurized in a state where the refrigerant has a specific enthalpy higher than a specific enthalpy point A corresponding to an intersection point between an isobaric line of an outlet pressure of the compressor 3 and a saturated liquid line.
- a gaseous refrigerant required to secure the required minimum gas volume is delivered from the expansion valve 7 to the evaporator 9 .
- the present invention is not limited to the example, but as illustrated in FIG. 3 , opening degree command information in which the gas volume ( ⁇ cooling capacity) is mapped to the opening degree command value (CV value) may be prepared in advance, and an opening degree command value corresponding to a currently demanded cooling capacity (gas volume) may be determined from the opening degree command information.
- the opening degree command value is an opening degree command value obtained by adding the correction opening degree command value for the required minimum gas volume for the compressor 3 to the reference opening degree command value in response to the demanded cooling capacity.
- a centrifugal chiller 1 ′ may employ a double-stage compression type compressor 3 ′, and include an economizer 15 provided between the condenser 5 and the evaporator 9 . Since other configuration elements are the same as those of the centrifugal chiller 1 illustrated in FIG. 1 , the same reference signs are assigned thereto, and descriptions thereof will be omitted.
- a first expansion valve 7 a is provided between the condenser 5 and the economizer 15
- a second expansion valve 7 b is provided between the economizer 15 and the evaporator 9 .
- a gaseous refrigerant in the economizer 15 is supplied to an inlet side of a second-stage compressor.
- the valve opening degree of each of the first expansion valve 7 a and the second expansion valve 7 b is controlled by a control device 10 ′. Since a specific method for controlling the first expansion valve 7 a and the second expansion valve 7 b is the same as that of the embodiment, a description thereof will be omitted.
- controlling the expansion valve in the present invention can be applied also to a heat source device using the double-stage compression type compressor 3 ′, and a refrigerant state in the Mollier diagram of the refrigerant at that time has the trajectory illustrated in FIG. 6 .
- FIG. 6 illustrates refrigerant characteristics when the current gas volume is less than the required minimum gas volume, in the Mollier diagram of the refrigerant when the double-stage compression type compressor 3 ′ is employed. As illustrated in FIG.
- the valve opening degree of each of both the first expansion valve 7 a and the second expansion valve 7 b is controlled by the control device 10 ′ so as to depressurize the refrigerant in a two-phase gas-liquid phase region, namely, in a state where the refrigerant has a specific enthalpy higher than a specific enthalpy point B corresponding to an intersection point between an isobaric line of an outlet pressure of a first stage of the compressor 3 ′ and a saturated liquid line, and a specific enthalpy point C corresponding to an intersection point between an isobaric line of an outlet pressure of a second stage of the compressor 3 ′ and the saturated liquid line.
- the gaseous refrigerant required to secure the required minimum gas volume is delivered to the evaporator 9 , and thus it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load.
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Abstract
To provide a control device of a refrigerating cycle, a heat source device, and a control method therefor which are capable of realizing a stable low-load operation without using a hot gas bypass pipe. A centrifugal chiller includes a compressor compressing a refrigerant; a condenser condensing the refrigerant compressed by the compressor; an expansion valve expanding a liquid refrigerant delivered from the condenser; an evaporator evaporating the refrigerant expanded by the expansion valve; and a control device (10). The control device (10) includes a gas volume calculation unit (22) that calculates a current gas volume using a current actual cooling capacity; and a minimum gas volume calculation unit (23) that calculates a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor, in which if the current gas volume is less than the required minimum gas volume for the compressor, control is performed so as to increase an opening degree of the expansion valve.
Description
- The present invention relates to a control device of a refrigerating cycle, a heat source device, and a control method therefor.
- In a heat source device such as a centrifugal chiller or an air conditioner having a refrigerating cycle, there is proposed, for example, a method for realizing a stable operation at a low load while securing a required minimum gas volume for a compressor by allowing a hot gas bypass pipe to bypass refrigerant gas from a discharge unit of a compressor or a condenser to an intake unit of the compressor or an evaporator (for example, PTL 1).
- [PTL 1] Japanese Unexamined Patent Application Publication No. 2010-236833
- However, it is necessary to the hot gas bypass pipe or a valve, thereby causing the size increase or cost increase of the device.
- The present invention has been made in light of the problem, and an object of the present invention is to provide a control device of a refrigerating cycle, a heat source device, and a control method therefor which are capable of realizing a stable low load operation without using a hot gas bypass pipe.
- According to a first aspect of the present invention, there is provided a control device of a refrigerating cycle including a compressor compressing a refrigerant, a condenser condensing the refrigerant compressed by the compressor, an expansion valve expanding a liquid refrigerant delivered from the condenser, and an evaporator evaporating the refrigerant expanded by the expansion valve, the control device including a gas volume calculation unit that calculates a current gas volume using a current actual cooling capacity; and a minimum gas volume calculation unit that calculates a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor, in which if the current gas volume is less than the required minimum gas volume for the compressor, the control device performs control so as to increase an opening degree of the expansion valve.
- According to the configuration, if the current gas volume is less than the required minimum gas volume, the control device performs control so as to increase the opening degree of the expansion valve. Therefore, it is possible to deliver a gaseous refrigerant, the amount of which is greater than that of the refrigerant satisfying the cooling capacity, to the evaporator. As a result, it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load.
- The control device of a refrigerating cycle may further include a reference command calculation unit that calculates a reference opening degree command value in response to a demanded cooling capacity; a correction command calculation unit that calculates a correction opening degree command value in response to a difference between the current gas volume and the required minimum gas volume for the compressor; and an opening degree command value calculation unit that calculates an opening degree command value of the expansion valve by adding the correction opening degree command value to the reference opening degree command value.
- According to the configuration, the correction command calculation unit calculates the correction opening degree command value in response to the difference between the current gas volume and the required minimum gas volume, and the opening degree command value calculation unit calculates the opening degree command value obtained by adding the correction opening degree command value to the reference opening degree command value. The opening degree of the expansion valve is controlled based on the opening degree command value. Therefore, if the current gas volume is less than the required minimum gas volume, along with the liquid refrigerant, the gaseous refrigerant required to secure the required minimum gas volume is delivered from the expansion valve to the evaporator. As a result, it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load.
- The control device of a refrigerating cycle may have opening degree command information in which an opening degree command value obtained by adding a correction opening degree command value for the required minimum gas volume for the compressor to a reference opening degree command value in response to a demanded cooling capacity is mapped to the demanded cooling capacity, and determine an opening degree command value corresponding to a currently demanded cooling capacity, from the opening degree command information.
- According to the configuration, it is possible to easily acquire the opening degree command value satisfying both the demanded cooling capacity and the required minimum gas volume, by using the opening degree command information.
- The refrigerating cycle may include an economizer provided between the condenser and the evaporator, and the expansion valve may include a first expansion valve provided between the condenser and the economizer and a second expansion valve provided between the economizer and the evaporator. Furthermore, in such configuration, if the current gas volume is less than the required minimum gas volume for the compressor, the control device of a refrigerating cycle may perform control so as to increase an opening degree of the first expansion valve and an opening degree of the second expansion valve.
- According to such configuration, also in a double-stage compression type compressor, the first expansion valve and the second expansion valve can be controlled according to the opening degree command value satisfying both the demanded cooling capacity and the required minimum gas volume. Therefore, it is possible to realize a stable operation of the compressor at a low load.
- According to a second aspect of the present invention, there is provided a heat source device including the control device of a refrigerating cycle.
- According to a third aspect of the present invention, there is provided a method for controlling a refrigerating cycle including a compressor compressing a refrigerant, a condenser condensing the refrigerant compressed by the compressor, an expansion valve expanding a liquid refrigerant delivered from the condenser, and an evaporator evaporating the refrigerant expanded by the expansion valve, the method including calculating a current gas volume using a current actual cooling capacity; and calculating a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor, in which if the current gas volume is less than the required minimum gas volume for the compressor, control is performed so as to increase an opening degree of the expansion valve.
- The present invention provides the effect that it is possible to realize a stable low load operation without using the hot gas bypass pipe.
-
FIG. 1 is a schematic configuration diagram illustrating a centrifugal chiller according to an embodiment of the present invention. -
FIG. 2 is a functional block diagram of a control device according to the embodiment of the present invention. -
FIG. 3 is a graph illustrating the relationship between a gas volume (∝ cooling capacity) and an opening degree command value (CV value) according to the embodiment of the present invention. -
FIG. 4 is a graph for describing opening degree control for an expansion valve according to the embodiment of the present invention using the Mollier diagram of a refrigerant. -
FIG. 5 is a schematic configuration diagram illustrating a centrifugal chiller according to another embodiment of the present invention. -
FIG. 6 is a graph for describing opening degree control for an expansion valve according to the other embodiment of the present invention using the Mollier diagram of the refrigerant. - Hereinbelow, a control device of a refrigerating cycle, a heat source device, and a control method therefor according to an embodiment of the present invention will be described with reference to the drawings. In the following description, a centrifugal chiller is exemplified as the heat source device including a refrigerating cycle, but the present invention is not limited to this one example, and the heat source device may be an air conditioner, a water heater, or the like. A refrigerant applied to the refrigerating cycle is not specifically limited, but may be properly selected in response to the application or the like.
-
FIG. 1 is a schematic configuration diagram illustrating acentrifugal chiller 1 according to the embodiment of the present invention. - As illustrated in
FIG. 1 , theturbo chiller 1 includes acompressor 3 that compresses a refrigerant; acondenser 5 that condenses the high-temperature high-pressure refrigerant compressed by thecompressor 3; anexpansion valve 7 that expands the refrigerant delivered from thecondenser 5; anevaporator 9 that evaporates the refrigerant expanded by theexpansion valve 7; and acontrol device 10 that controls thecentrifugal chiller 1. - The
compressor 3 is, for example, a turbo compressor, and a centrifugal compressor is used as an example. Thecompressor 3 is driven by anelectric motor 12, the rotation speed of which is controlled by aninverter 11. An output of theinverter 11 is controlled by thecontrol device 10. In the embodiment, a variable speed compressor is exemplified, but a fixed speed compressor may be used. - An inlet guide vane (hereinbelow, referred to as “IGV”) 13 is provided at a refrigerant intake port of the
compressor 3 to control a refrigerant intake flow rate, and is capable of controlling the capacity of thecentrifugal chiller 1. The opening degree of theIGV 13 is controlled by thecontrol device 10. - The
compressor 3 includes an impeller rotating around a rotary shaft. A rotational power is transmitted from theelectric motor 12 to the rotary shaft via a speed-increasing gear. The rotary shaft is supported by bearings. - The
condenser 5 is a shell and tube type heat exchanger or a plate type heat exchanger. A coolant for cooling the refrigerant is supplied to thecondenser 5. The coolant delivered to thecondenser 5 is released to the outside in a cooling tower or an air heat exchanger which is not illustrated, and then is delivered back to thecondenser 5. - The
expansion valve 7 is an electric type. The low-temperature high-pressure refrigerant delivered from thecondenser 5 is enthalpically expanded by theexpansion valve 7. The opening degree of theexpansion valve 7 is controlled by thecontrol device 10 so as to be able to obtain a desired head difference (difference between the high pressure and the low pressure of the refrigerant in the refrigerating cycle). - The
evaporator 9 is a shell and tube type heat exchanger or a plate type heat exchanger. Chilled water to be supplied to an external load (not illustrated) is delivered to theevaporator 9. The chilled water is cooled down to a rated temperature (for example, 7° C.) by exchanging heat with the refrigerant in theevaporator 9, and is fed to the external load (not illustrated). - The
control device 10 is configured to include a central processing unit (CPU); a random access memory (RAM); a read only memory (ROM); a computer-readable storage medium; and the like. Thecontrol device 10 realizes various functions, as an example, by storing a series of processes for realizing various functions in the storage medium or the like in the form of a program (for example, control program), and causing the CPU to read the program into the RAM or the like and to process information and execute a calculation process. A form where the program is preinstalled on the ROM or other storage mediums, a form where the program is stored in the computer-readable storage medium and is provided to the control device, or a form where the program is transmitted to the control device via wired or wireless communication means may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory. -
FIG. 2 is a functional block diagram of thecontrol device 10. As illustrated inFIG. 2 , as main configuration elements, thecontrol device 10 includes an expansionvalve control unit 20 that controls theexpansion valve 7, a referencecommand calculation unit 21, a gasvolume calculation unit 22, a minimum gasvolume calculation unit 23, a correctioncommand calculation unit 24, and an opening degreecommand calculation unit 25. - The reference
command calculation unit 21 calculates a reference opening degree command value in response to a demanded cooling capacity. The referencecommand calculation unit 21 calculates the reference opening degree command value (reference CV value) of theexpansion valve 7, for example, from a target refrigerant circulation volume, which is calculated from the demanded cooling capacity, and a pressure difference between before and after theexpansion valve 7. The target refrigerant circulation volume is calculated, for example, based on a required heat exchange amount required for theevaporator 9 to make a measured temperature value of the chilled water, which is supplied from theevaporator 9 to the external load, identical to a set temperature (for example, 7° C.). The reference opening degree command value of theexpansion valve 7 is calculated from the pressure difference between before and after theexpansion valve 7 so as to be able to obtain the target refrigerant circulation amount. - The gas
volume calculation unit 22 calculates a current gas volume using a current actual cooling capacity. - The minimum gas
volume calculation unit 23 calculates a required minimum gas volume for thecompressor 3 using a parameter related to an operating condition of thecompressor 3. More specifically, the minimum gasvolume calculation unit 23 calculates the required minimum gas volume using a flow rate variable (cooling capacity) and a pressure variable (head) which indicate the operating condition of thecompressor 3. - Well-known techniques may be employed for gas power calculation and minimum gas volume calculation.
- The correction
command calculation unit 24 calculates a correction opening degree command value (correction CV value) based on the current gas volume calculated by the gasvolume calculation unit 22 and the required minimum gas volume calculated by the minimum gasvolume calculation unit 23. Specifically, if the current gas volume is greater than or equal to the required minimum gas volume, the correctioncommand calculation unit 24 sets the correction opening degree command value at zero, and if the current gas volume is less than the required minimum gas volume, the correctioncommand calculation unit 24 calculates the correction opening degree command value in response to a difference between the current gas volume and the required minimum gas volume. For example, as the correction opening degree command value, the correctioncommand calculation unit 24 calculates the difference between the current gas volume and the required minimum gas volume. - As the opening degree command value (CV value), the opening degree
command calculation unit 25 calculates a value obtained by adding the reference opening degree command value (reference CV value) calculated by the referencecommand calculation unit 21 to the correction opening degree command value (correction CV value) calculated by the correctioncommand calculation unit 24. Therefore, the opening degree of theexpansion valve 7 is controlled based on the opening degree command value. -
FIG. 3 is a graph illustrating the relationship between the gas volume (∝ cooling capacity) and the opening degree command value (CV value). As illustrated inFIG. 3 , in a region where the gas volume is greater than or equal to the required minimum gas volume, the opening degree command value is set in response to the gas volume. Namely, the greater the gas volume is, the larger value the opening degree command value is set at. On the contrary, in a region where the gas volume is less than the required minimum gas volume, the less the gas volume is, the larger value the opening degree command value is set at. The reason is that the less the gas volume is, the larger the difference between the required minimum gas volume and the gas volume becomes, and thus the correction opening degree command value has a large value. - If the
expansion valve 7 is controlled as described above, in the region where the current gas volume is less than the required minimum gas volume, as illustrated inFIG. 4 , the refrigerant is depressurized by theexpansion valve 7 in a two-phase gas-liquid phase region. Specifically, in the Mollier diagram of the refrigerant illustrated inFIG. 4 , the refrigerant is depressurized in a state where the refrigerant has a specific enthalpy higher than a specific enthalpy point A corresponding to an intersection point between an isobaric line of an outlet pressure of thecompressor 3 and a saturated liquid line. - Therefore, in the region where the current gas volume is less than the required minimum gas volume, along with a liquid refrigerant, a gaseous refrigerant required to secure the required minimum gas volume is delivered from the
expansion valve 7 to theevaporator 9. As a result, it is possible to satisfy the demanded cooling capacity, to secure the gas volume greater than or equal to the required minimum gas volume, and to realize a stable operation of the compressor at a low load. - As described above, according to the control device of a refrigerating cycle, the heat source device, and the control method therefor according to the embodiment, if the current gas volume is greater than or equal to the required minimum gas volume, since the correction opening degree command value is to be set at zero, the opening degree of the
expansion valve 7 is controlled based on the reference opening degree command value (=opening degree command value). However, if the current gas volume is less than the required minimum gas volume, the opening degree of theexpansion valve 7 is controlled according to the opening degree command value obtained by adding the correction opening degree command value in response to the difference between the current gas volume and the required minimum gas volume to the reference opening degree command value. Namely, if the current gas volume is less than the required minimum gas volume, control is performed so as to increase the opening degree of the expansion valve 7 (refer toFIG. 3 ). Therefore, along with the liquid refrigerant, the gaseous refrigerant required to secure the required minimum gas volume is delivered from theexpansion valve 7 to theevaporator 9. As a result, it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load. - In the embodiment, a case where the reference
command calculation unit 21 and the correctioncommand calculation unit 24 calculate the opening degree command value in response to the demanded cooling load, the operating condition of the compressor, or the like on each occasion has been exemplarily described. However, the present invention is not limited to the example, but as illustrated inFIG. 3 , opening degree command information in which the gas volume (∝ cooling capacity) is mapped to the opening degree command value (CV value) may be prepared in advance, and an opening degree command value corresponding to a currently demanded cooling capacity (gas volume) may be determined from the opening degree command information. InFIG. 3 , the opening degree command value is an opening degree command value obtained by adding the correction opening degree command value for the required minimum gas volume for thecompressor 3 to the reference opening degree command value in response to the demanded cooling capacity. - In the embodiment, a case where the
compressor 3 with single-stage compression is used has been exemplarily described. However, as illustrated inFIG. 5 , acentrifugal chiller 1′ may employ a double-stagecompression type compressor 3′, and include aneconomizer 15 provided between thecondenser 5 and theevaporator 9. Since other configuration elements are the same as those of thecentrifugal chiller 1 illustrated inFIG. 1 , the same reference signs are assigned thereto, and descriptions thereof will be omitted. - In the
centrifugal chiller 1′ according to another embodiment, afirst expansion valve 7 a is provided between thecondenser 5 and theeconomizer 15, and asecond expansion valve 7 b is provided between theeconomizer 15 and theevaporator 9. A gaseous refrigerant in theeconomizer 15 is supplied to an inlet side of a second-stage compressor. The valve opening degree of each of thefirst expansion valve 7 a and thesecond expansion valve 7 b is controlled by acontrol device 10′. Since a specific method for controlling thefirst expansion valve 7 a and thesecond expansion valve 7 b is the same as that of the embodiment, a description thereof will be omitted. As described above, controlling the expansion valve in the present invention can be applied also to a heat source device using the double-stagecompression type compressor 3′, and a refrigerant state in the Mollier diagram of the refrigerant at that time has the trajectory illustrated inFIG. 6 .FIG. 6 illustrates refrigerant characteristics when the current gas volume is less than the required minimum gas volume, in the Mollier diagram of the refrigerant when the double-stagecompression type compressor 3′ is employed. As illustrated inFIG. 6 , the valve opening degree of each of both thefirst expansion valve 7 a and thesecond expansion valve 7 b is controlled by thecontrol device 10′ so as to depressurize the refrigerant in a two-phase gas-liquid phase region, namely, in a state where the refrigerant has a specific enthalpy higher than a specific enthalpy point B corresponding to an intersection point between an isobaric line of an outlet pressure of a first stage of thecompressor 3′ and a saturated liquid line, and a specific enthalpy point C corresponding to an intersection point between an isobaric line of an outlet pressure of a second stage of thecompressor 3′ and the saturated liquid line. - Therefore, the gaseous refrigerant required to secure the required minimum gas volume is delivered to the
evaporator 9, and thus it is possible to satisfy the demanded cooling capacity, and to realize a stable operation of the compressor at a low load. -
-
- 1, 1′: centrifugal chiller
- 3, 3′: compressor
- 5: condenser
- 7: expansion valve
- 7 a: first expansion valve
- 7 b: second expansion valve
- 9: evaporator
- 10, 10′: control device
- 15: economizer
Claims (6)
1. A control device of a refrigerating cycle including a compressor compressing a refrigerant, a condenser condensing the refrigerant compressed by the compressor, an expansion valve expanding a liquid refrigerant delivered from the condenser, and an evaporator evaporating the refrigerant expanded by the expansion valve, the control device comprising:
a gas volume calculation unit that calculates a current gas volume using a current actual cooling capacity; and
a minimum gas volume calculation unit that calculates a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor,
wherein if the current gas volume is less than the required minimum gas volume for the compressor, the control device performs control so as to increase an opening degree of the expansion valve.
2. The control device of a refrigerating cycle according to claim 1 , further comprising:
a reference command calculation unit that calculates a reference opening degree command value in response to a demanded cooling capacity;
a correction command calculation unit that calculates a correction opening degree command value in response to a difference between the current gas volume and the required minimum gas volume for the compressor; and
an opening degree command value calculation unit that calculates an opening degree command value of the expansion valve by adding the correction opening degree command value to the reference opening degree command value.
3. The control device of a refrigerating cycle according to claim 1 ,
wherein the control device has opening degree command information in which an opening degree command value obtained by adding a correction opening degree command value for the required minimum gas volume for the compressor to a reference opening degree command value in response to a demanded cooling capacity is mapped to the demanded cooling capacity, and
wherein the control device determines an opening degree command value corresponding to a currently demanded cooling capacity, from the opening degree command information.
4. The control device of a refrigerating cycle according to claim 1 ,
wherein the refrigerating cycle includes an economizer provided between the condenser and the evaporator, and the expansion valve includes a first expansion valve provided between the condenser and the economizer and a second expansion valve provided between the economizer and the evaporator, and
wherein if the current gas volume is less than the required minimum gas volume for the compressor, the control device performs control so as to increase an opening degree of the first expansion valve and an opening degree of the second expansion valve.
5. A heat source device comprising:
the control device of a refrigerating cycle according to claim 1 .
6. A control method of a refrigerating cycle including a compressor compressing a refrigerant, a condenser condensing the refrigerant compressed by the compressor, an expansion valve expanding a liquid refrigerant delivered from the condenser, and an evaporator evaporating the refrigerant expanded by the expansion valve, the method comprising:
calculating a current gas volume using a current actual cooling capacity; and
calculating a required minimum gas volume for the compressor using a parameter related to an operating condition of the compressor,
wherein if the current gas volume is less than the required minimum gas volume for the compressor, control is performed so as to increase an opening degree of the expansion valve.
Applications Claiming Priority (3)
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JP2017203806A JP6987598B2 (en) | 2017-10-20 | 2017-10-20 | Refrigeration cycle control device, heat source device, and its control method |
JP2017-203806 | 2017-10-20 | ||
PCT/JP2018/038256 WO2019078138A1 (en) | 2017-10-20 | 2018-10-15 | Refrigeration cycle control device, heat source device, and control method therefor |
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US20200173693A1 true US20200173693A1 (en) | 2020-06-04 |
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US16/614,525 Abandoned US20200173693A1 (en) | 2017-10-20 | 2018-10-15 | Control device of refrigerating cycle, heat source device, and control method therefor |
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US (1) | US20200173693A1 (en) |
JP (1) | JP6987598B2 (en) |
CN (1) | CN110637202B (en) |
WO (1) | WO2019078138A1 (en) |
Cited By (1)
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CN112097424A (en) * | 2020-09-17 | 2020-12-18 | 珠海格力电器股份有限公司 | Refrigerating system, air supply control method and device and air conditioning equipment |
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JP2022032788A (en) | 2020-08-14 | 2022-02-25 | 日本電気株式会社 | Cooling device, cooling system, and cooling method |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2001201189A (en) * | 2000-01-20 | 2001-07-27 | Toho Gas Co Ltd | Control device for circulating refrigerant amount of heat pump |
JP2006266635A (en) * | 2005-03-25 | 2006-10-05 | Saginomiya Seisakusho Inc | Control device for cooling system |
JP5244420B2 (en) * | 2008-02-28 | 2013-07-24 | 三菱重工業株式会社 | Turbo refrigerator, heat source system, and control method thereof |
JP2012202672A (en) * | 2011-03-28 | 2012-10-22 | Mitsubishi Heavy Ind Ltd | Expansion valve control device, heat source machine, and expansion valve control method |
JP5981180B2 (en) * | 2012-03-21 | 2016-08-31 | 荏原冷熱システム株式会社 | Turbo refrigerator and control method thereof |
JP6321363B2 (en) * | 2013-12-06 | 2018-05-09 | シャープ株式会社 | Air conditioner |
JP5999163B2 (en) * | 2014-10-22 | 2016-09-28 | ダイキン工業株式会社 | Air conditioner |
CN105571181B (en) * | 2016-01-12 | 2017-11-28 | 珠海格力电器股份有限公司 | A kind of variable speed centrifugal chiller plants and its control and regulation method |
-
2017
- 2017-10-20 JP JP2017203806A patent/JP6987598B2/en active Active
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2018
- 2018-10-15 CN CN201880032929.9A patent/CN110637202B/en active Active
- 2018-10-15 WO PCT/JP2018/038256 patent/WO2019078138A1/en active Application Filing
- 2018-10-15 US US16/614,525 patent/US20200173693A1/en not_active Abandoned
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN112097424A (en) * | 2020-09-17 | 2020-12-18 | 珠海格力电器股份有限公司 | Refrigerating system, air supply control method and device and air conditioning equipment |
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CN110637202B (en) | 2021-08-03 |
JP2019078429A (en) | 2019-05-23 |
CN110637202A (en) | 2019-12-31 |
WO2019078138A1 (en) | 2019-04-25 |
JP6987598B2 (en) | 2022-01-05 |
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