WO2019078138A1

WO2019078138A1 - Refrigeration cycle control device, heat source device, and control method therefor

Info

Publication number: WO2019078138A1
Application number: PCT/JP2018/038256
Authority: WO
Inventors: 明正横山; 剛洋河野
Original assignee: 三菱重工サーマルシステムズ株式会社
Priority date: 2017-10-20
Filing date: 2018-10-15
Publication date: 2019-04-25
Also published as: CN110637202B; JP6987598B2; JP2019078429A; US20200173693A1; CN110637202A

Abstract

Provided are a refrigeration cycle control device, a heat source device, and a control method therefor, with which a stable low-load operation can be achieved without using a hot gas bypass pipe. In the present invention a turbo refrigerator comprises a compressor for compressing a refrigerant, a condenser for condensing the refrigerant compressed by the compressor, an expansion valve for expanding the liquid refrigerant derived from the condenser, an evaporator for evaporating the refrigerant that has been expanded by the expansion valve, and a control device (10). The control device (10) comprises an air volume calculation unit (22) that uses the current actual refrigeration capacity to calculate a current air volume, and a minimum air volume calculation unit (23) that uses a parameter related to the operating capacity of the compressor to calculate a required minimum air volume for the compressor, and when the current air volume is less than the required minimum air volume for the compressor the control device controls the degree of opening of the expansion valve in the direction of increase.

Description

Control device of refrigeration cycle, heat source device, and control method thereof

The present invention relates to a control device for a refrigeration cycle, a heat source device, and a control method thereof.

For example, in a heat source apparatus having a refrigeration cycle such as a turbo refrigerator or an air conditioner, the refrigerant gas is bypassed from the compressor discharge part or condenser to the compressor suction part or evaporator using a hot gas bypass pipe, and the compressor There has been proposed a method of realizing stable operation at low load while securing the minimum air volume necessary for the air conditioner (for example, Patent Document 1 etc.).

JP, 2010-236833, A

However, since it is necessary to provide a hot gas bypass pipe and a valve, the size of the apparatus is increased and the cost is increased.

The present invention has been made in view of such circumstances, and a control device for a refrigeration cycle, a heat source device, and a control thereof that can realize stable low load operation without using a hot gas bypass pipe. Intended to provide a method.

According to a first aspect of the present invention, a compressor for compressing a refrigerant, a condenser for condensing the refrigerant compressed by the compressor, an expansion valve for expanding a liquid refrigerant introduced from the condenser, and the expansion valve Controller for a refrigeration cycle including an evaporator for evaporating the refrigerant expanded by the flow rate calculation unit, which calculates a current air volume using the current actual refrigeration capacity, and parameters related to the operating state of the compressor Controlling the minimum air volume calculation unit for calculating the required minimum air volume of the compressor using the above, and controlling the opening degree of the expansion valve to increase when the current air volume is less than the required minimum air volume of the compressor It is a control device of a refrigeration cycle.

According to the above configuration, when the current air volume is less than the required minimum air volume, the opening degree of the expansion valve is controlled to increase. As a result, it is possible to lead a larger amount of gas refrigerant to the evaporator than the refrigerant satisfying the refrigeration capacity. As a result, the required refrigeration capacity can be satisfied, and stable operation of the compressor at low load can be realized.

The control device of the refrigeration cycle calculates a reference command calculation unit that calculates a reference opening command value according to the required refrigeration capacity, and a correction opening command according to the difference between the current air volume and the required minimum air volume of the compressor. The system further comprises a correction command calculation unit that calculates a value, and an opening degree command value calculation unit that calculates the opening degree command value of the expansion valve by adding the reference opening degree command value and the correction opening degree command value. May be

According to the above configuration, the correction command calculation unit calculates the corrected opening command value according to the difference between the current air volume and the required minimum air volume, and the opening command value calculator calculates the reference opening command value and the corrected opening. An opening command value obtained by adding the command value is calculated. Then, the opening degree of the expansion valve is controlled based on the opening degree command value. As a result, when the current air volume is less than the required minimum air volume, the gas refrigerant required to secure the required minimum air volume is led from the expansion valve to the evaporator together with the liquid refrigerant. As a result, the required refrigeration capacity can be satisfied, and stable operation of the compressor at low load can be realized.

The control device of the refrigeration cycle corresponds to the opening degree command value obtained by adding the correction opening degree command value to the required minimum air volume of the compressor to the reference opening degree command value corresponding to the required refrigeration capacity, and the required refrigeration capacity It is good also as having the opening degree command information attached and determining the opening degree command value corresponding to the present demand refrigeration capacity from the opening degree command information.

According to the above configuration, by using the opening degree command information, it becomes possible to easily obtain an opening degree command value that satisfies both the required refrigeration capacity and the required minimum air volume.

The refrigeration cycle includes an intercooler provided between the condenser and the evaporator, and the expansion valve is a first expansion valve provided between the condenser and the intercooler. A second expansion valve may be provided between the intercooler and the evaporator. Furthermore, in such a configuration, the control device of the refrigeration cycle may open the first expansion valve and open the second expansion valve when the current air volume is less than the required minimum air volume of the compressor. It is good also as each controlling in the direction which makes degree increase.

According to such a configuration, the first expansion valve and the second expansion valve can be controlled by the opening degree command value that satisfies both the required refrigeration capacity and the required minimum air volume also for the two-stage compression type compressor. It becomes possible. As a result, stable operation of the compressor at low load can be realized.

A second aspect of the present invention is a heat source device provided with the control device of the above-mentioned refrigeration cycle.

A third aspect of the present invention relates to a compressor for compressing a refrigerant, a condenser for condensing the refrigerant compressed by the compressor, an expansion valve for expanding a liquid refrigerant introduced from the condenser, and the expansion valve A control method of a refrigeration cycle including an evaporator for evaporating the refrigerant expanded by the control unit, calculating a current air volume using the current actual refrigeration capacity, and using the parameter related to the operating state of the compressor. It is a control method of a refrigeration cycle which calculates the required minimum air volume of a compressor, and when the current air volume is less than the required minimum air volume of the compressor, increases the opening degree of the expansion valve.

According to the present invention, there is an effect that stable low load operation can be realized without using a hot gas bypass pipe.

FIG. 1 is a schematic configuration view showing a turbo refrigerator according to an embodiment of the present invention. It is a figure showing the functional block diagram of the control device concerning one embodiment of the present invention. It is the figure which showed the relationship between the air volume (∝ refrigeration capacity) and opening degree command value (CV value) which concern on one Embodiment of this invention. It is a figure explaining the opening degree control of the expansion valve concerning one embodiment of the present invention using the Mollier chart of a refrigerant. It is a schematic block diagram showing a turbo refrigerator concerning other embodiments of the present invention. It is the figure which demonstrated opening degree control of the expansion valve which concerns on other embodiment of this invention using the Mollier diagram of a refrigerant | coolant.

Hereinafter, a control device for a refrigeration 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, although a turbo refrigerator is illustrated and explained as a heat source apparatus provided with a refrigerating cycle, the present invention is not limited to this example, and a heat source apparatus is an air conditioner, a water heater, etc. It is also good. The refrigerant applied to the refrigeration cycle is not particularly limited and may be appropriately selected according to the purpose and the like.

FIG. 1 is a schematic configuration view showing a turbo refrigerator 1 according to an embodiment of the present invention.
As shown in FIG. 1, the turbo refrigerator 1 includes a compressor 3 for compressing a refrigerant, a condenser 5 for condensing a high temperature and high pressure refrigerant compressed by the compressor 3, and a refrigerant led from the condenser 5. And an evaporator 9 for evaporating the refrigerant expanded by the expansion valve 7, and a control device 10 for controlling the turbo refrigerator 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 a motor 12 whose rotational speed is controlled by an inverter 11. The output of inverter 11 is controlled by controller 10. Although a variable speed compressor is illustrated in this embodiment, a fixed speed compressor may be used.
At a refrigerant suction port of the compressor 3, an inlet guide vane (hereinafter referred to as “IGV”) 13 for controlling the flow rate of the suctioned refrigerant is provided, and capacity control of the turbo refrigerator 1 is enabled. The control of the opening degree of the IGV 13 is performed by the control device 10.

The compressor 3 includes an impeller that rotates around the rotation axis. The rotational power is transmitted from the motor 12 to the rotational shaft via the speed-increasing gear. The rotating shaft is supported by a bearing.

The condenser 5 is a heat exchanger such as a shell and tube type or a plate type. The condenser 5 is supplied with cooling water for cooling the refrigerant. The cooling water led to the condenser 5 is led to the condenser 5 again after being exhausted to the outside in a cooling tower or an air heat exchanger (not shown).

The expansion valve 7 is electrically operated. The low-temperature and high-pressure refrigerant introduced from the condenser 5 is isenthalpically expanded by the expansion valve 7. The opening degree of the expansion valve 7 is controlled by the control device 10 so as to obtain a desired head difference (high and low pressure difference of the refrigerant in the refrigeration cycle).

The evaporator 9 is a heat exchanger such as a shell and tube type or a plate type. Cold water supplied to an external load (not shown) is led to the evaporator 9. The cold water is cooled to a rated temperature (e.g. 7 [deg.] C.) by heat exchange with the refrigerant in the evaporator 9 and sent to an external load (not shown).

The control device 10 is configured to include, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a computer readable storage medium, and the like. A series of processes for the control device 10 to realize various functions are, for example, stored in a storage medium or the like in the form of a program (for example, a control program), and the CPU reads this program into a RAM or the like to obtain information. Various functions are realized by executing the processing and arithmetic processing of the above. The program may be installed in advance in a ROM or other storage medium, may be provided as stored in a computer-readable storage medium, may be distributed via a wired or wireless communication means, etc. It may be applied. The computer readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory or the like.

FIG. 2 is a diagram showing a functional block diagram of the control device 10. As shown in FIG. As shown in FIG. 2, the control device 10 includes, as an expansion valve control unit 20 that controls the expansion valve 7, a reference command calculation unit 21, an air volume calculation unit 22, a minimum air volume calculation unit 23, and a correction command calculation unit 24. And an opening command calculator 25.

The reference command calculation unit 21 calculates a reference opening degree command value corresponding to the required refrigeration capacity. The reference command calculation unit 21 calculates a reference opening degree command value (reference CV value) of the expansion valve 7 from, for example, the target refrigerant circulation amount calculated from the required refrigeration capacity and the differential pressure across the expansion valve 7. For example, based on the required heat exchange amount in the evaporator 9 required to match the temperature measurement value of the cold water supplied from the evaporator 9 to the external load to the set temperature (for example, 7 ° C.) Calculate the circulation amount. Then, the reference opening degree command value of the expansion valve 7 is calculated from the differential pressure of the expansion valve 7 so as to obtain the target refrigerant circulation amount.

The air volume calculator 22 calculates the current air volume using the current actual refrigeration capacity.
The minimum air volume calculation unit 23 calculates the necessary minimum air volume of the compressor 3 using parameters relating to the operating state of the compressor 3. More specifically, the minimum air volume calculation unit 23 is calculated using a flow rate variable (refrigerating capacity) representing the operating state of the compressor 3 and a pressure variable (lift head).
Well-known techniques may be employed for current wind power calculation and minimum air flow calculation.

The correction command calculation unit 24 calculates a correction opening degree command value (corrected CV value) based on the current air volume calculated by the air volume calculation unit 22 and the necessary minimum air volume calculated by the minimum air volume calculation unit 23. Specifically, the correction command calculation unit 24 sets the correction opening command value to zero when the current air volume is equal to or more than the required minimum air volume, and when the current air volume is less than the required minimum air volume, A corrected opening degree command value is calculated according to the difference between the current air volume and the required minimum air volume. The correction command computation unit 24 calculates, for example, the difference between the current air volume and the required minimum air volume as a corrected opening degree command value.

The opening command calculator 25 adds the reference opening command value (reference CV value) calculated by the reference command calculator 21 and the corrected opening command value (corrected CV value) calculated by the correction command calculator 24. The calculated value is calculated as an opening degree command value (CV value). Thus, the opening degree of the expansion valve 7 is controlled based on the opening degree command value.

FIG. 3 is a diagram showing the relationship between the air flow rate (∝ refrigeration capacity) and the opening degree command value (CV value). As shown in FIG. 3, in the region where the air volume is equal to or more than the necessary minimum air volume, an opening degree command value corresponding to the air volume is set. That is, the opening degree command value is also set to a larger value as the air volume is larger. On the other hand, in the region where the air volume is less than the required minimum air volume, the opening degree command value is set to a larger value as the air volume decreases. This is because, in this region, as the air volume decreases, the difference from the required minimum air volume increases, and the correction opening degree command value takes a large value.

By controlling the expansion valve 7 as described above, the expansion valve 7 decompresses the refrigerant in the gas-liquid two-phase region as shown in FIG. 4 in the region where the current air volume is less than the required minimum air volume. . Specifically, in the Mollier diagram of the refrigerant shown in FIG. 4, the state of the refrigerant having a specific enthalpy higher than the point A of the specific enthalpy corresponding to the intersection of the pressure line of the outlet pressure of the compressor 3 and the saturated liquid line. The refrigerant is depressurized in

As a result, in the region where the current air volume is less than the required minimum air volume, the gas refrigerant required to secure the required minimum air volume is led from the expansion valve 7 to the evaporator 9 together with the liquid refrigerant. As a result, the required refrigeration capacity can be satisfied, and at least the required minimum air volume can be secured, and stable operation of the compressor at low load can be realized.

As described above, according to the control device, the heat source device, and the control method of the refrigeration cycle according to the present embodiment, when the current air volume is equal to or more than the required minimum air volume, the correction opening command value is set to zero. Since it is set, the opening degree of the expansion valve 7 is controlled based on the reference opening degree command value (= opening degree command value). On the other hand, when the current air volume is less than the required minimum air volume, an opening degree command value obtained by adding a corrected opening degree command value according to the difference between the current air volume and the required minimum air volume to the reference opening degree command value Thus, the opening degree of the expansion valve 7 is controlled. That is, when the current air volume is less than the required minimum air volume, the opening degree of the expansion valve 7 is controlled to increase (see FIG. 3). As a result, the gas refrigerant necessary for securing the necessary minimum air flow rate is led from the expansion valve 7 to the evaporator 9 together with the liquid refrigerant. As a result, the required refrigeration capacity can be satisfied, and stable operation of the compressor at low load can be realized.

In the present embodiment, the case where the reference command calculation unit 21 and the correction command calculation unit 24 calculate the opening degree command value according to the required refrigeration load at that time, the operating state of the compressor, etc. The present invention is not limited to this example, and for example, opening degree instruction information in which the air volume (the freezing capacity) and the opening degree command value (CV value) as shown in FIG. 3 are associated is prepared in advance. An opening degree command value corresponding to the current required refrigeration capacity (air volume) may be determined from the information. In FIG. 3, the opening degree command value is an opening degree command value obtained by adding a correction opening degree command value for the required minimum air flow of the compressor 3 to a reference opening degree command value corresponding to the required refrigeration capacity.

Other Embodiments
In the present embodiment, the case where the compressor 3 of one-stage compression is used is described as an example, but as shown in FIG. 5, for example, the turbo refrigerator 1 ′ is a two-stage compression type compressor 3 ′. It may be further provided with an intercooler 15 provided between the condenser 5 and the evaporator 9. The other configuration is the same as that of the turbo refrigerator 1 shown in FIG.
In a turbo refrigerator 1 'according to another embodiment, a first expansion valve 7a is provided between the condenser 5 and the intercooler 15, and a second expansion valve is provided between the intercooler 15 and the evaporator 9. 7b is provided. The gas refrigerant in the intercooler 15 is supplied to the inlet side of the second stage compressor. The opening degree of the first expansion valve 7a and the second expansion valve 7b is controlled by the control device 10 '. About the concrete control method of the 1st expansion valve 7a and the 2nd expansion valve 7b, since it is the same as that of the above-mentioned embodiment, it omits explanation. Thus, the control of the expansion valve in the present invention is also applicable to a heat source apparatus using a two-stage compression type compressor 3 ', and the refrigerant state in the Mollier diagram of the refrigerant at that time is shown in FIG. It becomes like a track. FIG. 6 shows a refrigerant characteristic in the case where the current air volume is less than the required minimum air volume in the Mollier chart of the refrigerant in the case of employing the two-stage compression type compressor 3 '. As shown in FIG. 6, both the first expansion valve 7a and the second expansion valve 7b correspond to the gas-liquid two-phase region, that is, the intersection of the isobar of the first stage outlet pressure of the compressor 3 'and the saturated liquid line. Depressurization of the refrigerant in the state of a refrigerant having a specific enthalpy higher than that of the specific enthalpy corresponding to the point of specific enthalpy B and the point of intersection of the pressure line of the outlet of the second stage of the compressor 3 'and the saturated liquid line Thus, the valve opening degree is controlled by the control device 10 '.
As a result, the gas refrigerant required to secure the necessary minimum air volume is introduced to the evaporator 9, so that the required refrigeration capacity can be satisfied, and stable operation of the compressor at low load can be realized. it can.

DESCRIPTION OF SYMBOLS 1, 1 'Turbo refrigerator 3, 3' Compressor 5 Condenser 7 Expansion valve 7a 1st expansion valve 7b 2nd expansion valve 9 Evaporator 10, 10 'Control apparatus 15 Intercooler

Claims

A compressor for compressing a refrigerant,
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve that expands liquid refrigerant introduced from the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
Control device of a refrigeration cycle provided with
An air volume calculator that calculates the current air volume using the current actual refrigeration capacity;
A minimum air volume calculation unit that calculates a required minimum air volume of the compressor using a parameter related to the operating state of the compressor;
A control device of a refrigeration cycle which performs control to increase the opening degree of the expansion valve when the current air volume is less than a required minimum air volume of the compressor.
A reference command calculation unit that calculates a reference opening command value according to the required refrigeration capacity;
A correction command calculation unit that calculates a correction opening degree command value according to a difference between the current air volume and the required minimum air volume of the compressor;
An opening command value calculation unit that calculates the opening command value of the expansion valve by adding the reference opening command value and the correction opening command value;
The control device of the refrigeration cycle according to claim 1, comprising:
Opening command information in which the opening command value obtained by adding the correction opening command value for the required minimum air flow of the compressor to the reference opening command value corresponding to the required refrigeration capacity, and the required refrigeration capacity are associated Have
The control device for a refrigeration cycle according to claim 1, wherein an opening degree command value corresponding to a current required refrigeration capacity is determined from the opening degree command information.
The refrigeration cycle includes an intercooler provided between the condenser and the evaporator, and the expansion valve is a first expansion valve provided between the condenser and the intercooler. A second expansion valve provided between the intercooler and the evaporator;
The refrigeration according to claim 1, wherein the opening degree of the first expansion valve and the opening degree of the second expansion valve are respectively controlled to be increased when the current air volume is less than the required minimum air volume of the compressor. Controller of cycle.
The heat-source apparatus provided with the control apparatus of the refrigerating cycle in any one of Claims 1-4.
A compressor for compressing a refrigerant,
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve that expands liquid refrigerant introduced from the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
A control method of a refrigeration cycle provided with
Calculate the current air volume using the current actual refrigeration capacity,
The required minimum air volume of the compressor is calculated using parameters related to the operating state of the compressor,
The control method of the refrigerating cycle controlled to the direction to which the opening degree of the said expansion valve is made to be increased, when the present air volume is less than the required minimum air volume of the said compressor.