WO2023233654A1

WO2023233654A1 - Refrigeration cycle device

Info

Publication number: WO2023233654A1
Application number: PCT/JP2022/022624
Authority: WO
Inventors: 英希大野; 崇憲八代; 寛也石原; 啓三福原
Original assignee: 三菱電機株式会社
Priority date: 2022-06-03
Filing date: 2022-06-03
Publication date: 2023-12-07

Abstract

The present invention is provided with: a high-stage-side refrigeration cycle circuit which connects a high-stage-side compressor, a high-stage-side condenser, a high-stage-side throttle device, and a high-stage-side evaporator to each other through piping to circulate a high-stage-side refrigerant therethrough; a low-stage-side refrigeration cycle circuit which connects a low-stage-side compressor, a low-stage-side condenser, a low-stage-side throttle device, and a low-stage-side evaporator to each other through piping to circulate a low-stage-side refrigerant therethrough; a cascade condenser which is formed of the high-stage-side condenser and the low-stage-side condenser and executes heat exchange between the high-stage-side refrigerant and the low-stage-side refrigerant; an external air temperature sensor which measures an external air temperature; a high-stage-side evaporation temperature sensor which measures a high-stage-side evaporation temperature; and a control device which executes processing of restricting the maximum drive frequency of the low-stage-side compressor when a combination of the external air temperature and the high-stage-side evaporation temperature is determined to be within an external air temperature-high-stage-side evaporation temperature restriction range in which a pressure in the low-stage-side refrigeration cycle circuit reaches a high pressure and exceeds a set pressure.

Description

Refrigeration cycle equipment

This technology relates to refrigeration cycle devices such as refrigeration and air conditioners. In particular, the present invention relates to a multi-component refrigeration cycle device in which a plurality of refrigeration cycle circuits are configured in multiple stages.

Refrigeration cycle equipment such as refrigeration and air conditioning equipment used for freezing, refrigeration, and air conditioning is used at distribution bases such as food processing factories, agricultural and fisheries processing plants, markets, and distribution warehouses, as well as retail stores such as supermarkets and convenience stores. It is used.

Here, for example, a refrigeration cycle (hereinafter referred to as a high source side refrigeration cycle circuit) that is a high source side (high stage side, primary side) and a refrigeration cycle that is a low source side (low stage side, secondary side) (hereinafter referred to as a high source side refrigeration cycle circuit) There is a refrigeration cycle device that is configured in multiple stages by forming a refrigeration cycle circuit, a lower refrigeration cycle circuit, and a lower refrigeration cycle circuit, respectively. Here, it is assumed that the refrigeration cycle device has a two-stage configuration. Here, the low-source side refrigeration cycle circuit circulates _CO2 as a refrigerant. Further, the high-end refrigeration cycle circuit circulates fluorocarbons, ammonia, hydrocarbons, or the like as a refrigerant (see, for example, Patent Document 1).

Such a multicomponent refrigeration cycle device, for example, uses the heat of evaporation (refrigeration capacity) due to evaporation of the refrigerant in the high-temperature side refrigeration cycle circuit and the condensation heat (condensation capacity) due to the condensation of the refrigerant in the low-temperature side refrigeration cycle circuit. Heat is exchanged in the cascade condenser through which each refrigerant passes. Then, in the final stage, the low-end refrigeration cycle circuit, the evaporator exchanges heat with the object to be cooled. By performing refrigeration operation (cooling operation) in cooperation with the high-temperature side refrigeration cycle circuit and the low-temperature side refrigeration cycle circuit, the evaporation heat at a low temperature of several tens of degrees below zero is generated in the evaporator of the low-temperature side refrigeration cycle circuit. can be obtained efficiently.

Japanese Patent Application Publication No. 2004-190917

In a multi-component refrigeration cycle device, the control device controls the driving frequency of the compressor in the high-source refrigeration cycle circuit based on the suction pressure of the compressor in the high-source refrigeration cycle circuit and the pressure in the low-source refrigeration cycle circuit. It's in control. On the other hand, the control device controls the driving frequency of the compressor in the reduction side cycle circuit based on the suction pressure and load temperature of the compressor in the reduction side cycle circuit. At this time, the control device controls the pressure on the high pressure side of the low source refrigeration cycle circuit (hereinafter referred to as , high pressure).

Here, when the necessary condensation capacity in the low-base refrigeration cycle circuit and the evaporation capacity in the high-base refrigeration cycle circuit are no longer balanced, the high pressure in the low-base refrigeration cycle circuit increases. By increasing the drive frequency of the compressor in the lower cycle circuit through regular control and protection control, the compressor in the lower cycle circuit is temporarily driven at a rate higher than the maximum processing capacity of the high cycle circuit. As the frequency increases, the high pressure in the reducing side cycle circuit increases. Therefore, the control device reduces the drive frequency of the compressor in the lower-side refrigeration cycle circuit by protection control. For this reason, hunting of high pressure and low pressure occurs in the low-source side refrigeration cycle circuit, making it difficult to perform stable control. Hunting is particularly likely to occur when the outside air temperature is high.

In view of the above, the objective is to obtain a refrigeration cycle device that can perform stable operation.

The refrigeration cycle device according to this disclosure is a high-base refrigeration cycle in which a high-base compressor, a high-base condenser, a high-base throttle device, and a high-base evaporator are connected via piping to circulate a high-base refrigerant. A low-side refrigeration cycle circuit that circulates low-side refrigerant by connecting the low-side compressor, low-side condenser, low-side throttle device, and low-side evaporator to the low-side refrigeration cycle circuit, and the high-side side A cascade condenser that is composed of an evaporator and a low-source side condenser, and performs heat exchange between the high-source side refrigerant and the low-source side refrigerant, an outside air temperature sensor that measures the outside air temperature, and a cascade condenser that The combination of the high source side evaporation temperature sensor that measures the high source side evaporation temperature, the outside air temperature measured by the outside air temperature sensor, and the high source side evaporation temperature measured by the high source side evaporation temperature sensor is the low source side refrigeration cycle circuit. A control device that performs processing to limit the maximum drive frequency of the low source compressor when it is determined that the outside air temperature is in the range where the high pressure exceeds the set pressure - the high source side evaporation temperature limit range. It is.

In the disclosed refrigeration cycle device, when the control device determines that the combination of the outside air temperature and the high source side evaporation temperature is included in the outside air temperature - high source side evaporation temperature limit range, the control device controls the low source side compressor to a maximum Performs control to limit the drive frequency. Therefore, by lowering the high pressure in the low source side refrigeration cycle, the refrigeration cycle device can prevent hunting of the low source side compressor and perform stable operation, thereby stably cooling the object to be cooled. I can do it.

1 is a diagram illustrating an example of a configuration of a refrigeration cycle device according to a first embodiment; FIG. FIG. 3 is a diagram illustrating control in the refrigeration cycle device according to the first embodiment. FIG. 3 is a diagram illustrating a process for determining a limit on the maximum drive frequency of the low-end compressor 11 in the refrigeration cycle device according to the first embodiment. FIG. 7 is a diagram illustrating control in the refrigeration cycle device according to the second embodiment. FIG. 7 is a diagram illustrating a process for determining a limit on the maximum drive frequency of the low-end compressor 11 in the refrigeration cycle device according to the second embodiment.

Hereinafter, a refrigeration cycle device according to an embodiment will be described with reference to drawings and the like. In the following drawings, the same reference numerals are the same or equivalent, and are common throughout the entire embodiment described below. Further, in the drawings, the size relationship of each component may differ from the actual one. The forms of the constituent elements shown in the entire specification are merely examples, and are not limited to the forms described in the specification. In particular, the combinations of components are not limited to those in each embodiment, and components described in other embodiments can be applied to other embodiments. In addition, the height of pressure and temperature is not determined particularly in relation to absolute values, but is determined relatively depending on the state and operation of the device etc. Additionally, if there is no need to distinguish or specify multiple devices of the same type that are distinguished by subscripts, the subscripts may be omitted from the description.

Embodiment 1.
FIG. 1 is a diagram illustrating an example of the configuration of a refrigeration cycle device according to a first embodiment. FIG. 1 shows a binary refrigeration system as an example of a refrigeration cycle system. As shown in FIG. 1, the binary refrigeration system according to the first embodiment includes a low-temperature side refrigeration cycle circuit 10 and a high-temperature side refrigeration cycle circuit 20, each of which constitutes a refrigerant circuit that circulates refrigerant independently. do. In order to configure the two refrigerant circuits in multiple stages, the binary refrigeration system is coupled so that heat exchange can be performed between the refrigerants passing through the high-temperature side evaporator 24 and the low-temperature side condenser 12, respectively. It has a cascade condenser C that serves as a refrigerant heat exchanger. The binary refrigeration system also includes a control device 30 that controls the operation of the entire system.

In FIG. 1, the low-base refrigeration cycle circuit 10 includes a low-base compressor 11, an auxiliary heat exchanger 15, a low-base condenser 12, a low-base expansion valve 13, and a low-base evaporator 14 through refrigerant pipes in this order. This is a refrigerant circulation circuit (hereinafter also referred to as a low-side refrigerant circuit) configured by connecting the two. On the other hand, the high-temperature side refrigeration cycle circuit 20 is a refrigerant circulation configured by sequentially connecting a high-temperature side compressor 21, a high-temperature side condenser 22, a high-temperature side expansion valve 23, and a high-temperature side evaporator 24 through refrigerant piping. circuit (hereinafter also referred to as high-side refrigerant circuit).

The low end compressor 11 of the low end refrigeration cycle circuit 10 sucks in refrigerant, compresses it, makes it high temperature and high pressure, and discharges it. Here, the low-end compressor 11 is constituted by a type of compressor whose rotational speed is controlled by an inverter circuit or the like, and the amount of refrigerant discharged can be adjusted.

The auxiliary heat exchanger 15 functions as, for example, a gas cooler, and cools the gas refrigerant discharged by the low-end compressor 11 by heat exchange with outdoor air (outside air). Here, it is assumed that the binary refrigeration system in the first embodiment includes an auxiliary heat exchanger fan 16 that is a blower that promotes heat exchange between the outside air and the refrigerant in the auxiliary heat exchanger 15. Auxiliary heat exchanger fan 16 creates a flow of air through auxiliary heat exchanger 15 . The auxiliary heat exchanger fan 16 is constituted by a type of fan whose rotational speed is controlled by an inverter circuit or the like and whose air volume can be adjusted, for example.

Furthermore, the low-source condenser 12 exchanges heat with the refrigerant that has passed through the auxiliary heat exchanger 15, and condenses the refrigerant into a liquid refrigerant (condenses and liquefies it). For example, here, in the cascade condenser C, a heat transfer tube through which the low-base refrigerant flowing through the low-base refrigerant cycle circuit 10 passes becomes the low-base condenser 12, and the high-base refrigerant flowing through the high-base refrigerant cycle circuit 20 serves as the low-base condenser 12. It is assumed that heat exchange with the refrigerant takes place.

The low-base expansion valve 13, which serves as a pressure reducing device or a throttle device, decompresses and expands the refrigerant flowing through the low-base refrigeration cycle circuit 10. The low-side expansion valve 13 is composed of, for example, a flow rate control device such as an electronic expansion valve, a capillary tube, a refrigerant flow rate adjustment device such as a temperature-sensitive expansion valve, and the like. The low-temperature side evaporator 14 evaporates the low-temperature side refrigerant flowing through the low-temperature side refrigeration cycle circuit 10 into a gaseous refrigerant by heat exchange with the object to be cooled, such as the air in the refrigerator room. (evaporates into gas). The object to be cooled is directly or indirectly cooled by heat exchange with the low-source refrigerant.

On the other hand, the high-temperature side compressor 21 of the high-temperature side refrigeration cycle circuit 20 sucks in the high-temperature side refrigerant flowing through the high-temperature side refrigeration cycle circuit 20, compresses the refrigerant, and discharges it in a high temperature and high pressure state. . Like the low-end compressor 11, the high-end compressor 21 is configured of a type of compressor that includes, for example, an inverter circuit and can adjust the amount of refrigerant discharged. The high end condenser 22 is a heat exchanger that exchanges heat between air, brine, etc. and the high end refrigerant flowing through the high end refrigeration cycle circuit 20, and condenses and liquefies the refrigerant. Here, in the first embodiment, the high source condenser 22 is assumed to exchange heat between the outside air and the refrigerant. For this reason, the high end refrigeration cycle circuit 20 is assumed to have a high end condenser fan 25 that promotes heat exchange. Like the auxiliary heat exchanger fan 16, the high-side condenser fan 25 in the first embodiment is configured of a type of fan whose air volume can be adjusted.

The high-end expansion valve 23, which serves as a pressure reducing device or a throttle device, decompresses and expands the high-end refrigerant flowing through the high-end refrigeration cycle circuit 20. The high-end expansion valve 23 is composed of, for example, a flow rate control device such as the electronic expansion valve described above, a refrigerant flow rate adjustment device such as a capillary tube, and the like. The high end evaporator 24 evaporates and gasifies the high end refrigerant flowing through the high end refrigeration cycle circuit 20 by heat exchange. For example, here, in the cascade condenser C, the heat exchanger tube through which the high-temperature side refrigerant flowing through the high-temperature side refrigeration cycle circuit 20 passes serves as the high-temperature side evaporator 24, and the low-temperature side refrigerant flowing through the low-temperature side refrigeration cycle circuit It is assumed that heat exchange with the refrigerant takes place.

In addition, the cascade condenser C has the functions of the above-mentioned high temperature side evaporator 24 and low temperature side condenser 12, and is an inter-refrigerant heat exchanger that enables heat exchange between the high temperature side refrigerant and the low temperature side refrigerant. It is. By configuring the high-temperature side refrigeration cycle circuit 20 and the low-temperature side refrigeration cycle circuit 10 in a multi-stage configuration via the cascade capacitor C, and performing heat exchange between the refrigerants, independent refrigerant circuits can be linked. .

The outside air temperature sensor 41 is a temperature sensor that detects and measures outside air temperature. Hereinafter, the outside air temperature is assumed to be the temperature measured by the outside air temperature sensor 41. Further, the high source side evaporation temperature sensor 42 is a temperature sensor that detects and measures the high source side evaporation temperature of the refrigerant passing through the high source side evaporator 24 in the cascade condenser C. The low-base evaporation temperature sensor 43 is a temperature sensor that detects and measures the low-base evaporation temperature of the refrigerant passing through the low-base evaporator 14 . Each sensor sends a signal containing detected and measured temperature data to the controller 30.

The control device 30 also includes a control processing section 31 and a storage section 32. The control processing unit 31 of the control device 30 has a microcomputer as hardware. A microcomputer includes, for example, a control processing unit such as a CPU (Central Processing Unit), an I/O port that manages input and output of various signals, and the like. The control processing unit 31 executes processing based on a program, for example, to control devices. The control processing unit 31 performs operation control of each device constituting the binary refrigeration system. In particular, the control processing unit 31 in the first embodiment controls the low source compressor 11 based on the outside air temperature detected by the outside air temperature sensor 41 and the high source side evaporation temperature detected by the high source side evaporation temperature sensor 42. Performs controls such as lowering and limiting the set maximum drive frequency.

Furthermore, the storage unit 32 of the control device 30 stores various data necessary for the control processing unit 31 to perform processing. Here, the storage unit 32 particularly includes a limit range data storage unit 33, which stores limit range data in which a range for limiting the maximum drive frequency of the low-power compressor 11 is defined. In the first embodiment, the limit range data storage unit 33 has outside air temperature-higher side evaporation temperature limit range data defined by the outside air temperature and the higher side evaporation temperature. Here, the range in which the maximum drive frequency of the low-side compressor 11 is limited varies depending on the performance of equipment in the refrigeration cycle apparatus, and is therefore defined, for example, according to the equipment configuration of the refrigeration cycle apparatus. Furthermore, the storage unit 32 stores programs executed by the control processing unit 31. The storage unit 32 includes, for example, a volatile storage device (not shown) such as a random access memory (RAM) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as a flash memory. Have it as a wear.

In a binary refrigeration system, a part of the equipment (for example, the low-side evaporator 14) of the low-side refrigeration cycle circuit 10 may be included in an indoor load device such as a supermarket showcase. For example, if the showcase is rearranged or the piping connections are changed and the circuit becomes open in the low-end refrigeration cycle circuit 10, there is a high possibility that refrigerant leakage will occur. Therefore, in consideration of refrigerant leakage, CO ₂ (carbon dioxide), which has a small effect on global warming, is used as the low-base refrigerant to be circulated in the low-base refrigerating cycle circuit 10. On the other hand, the high-end refrigeration cycle circuit 20 is not replaced and is not opened. Therefore, the high temperature side refrigerant used in the high temperature side refrigeration cycle circuit 20 can be, for example, an HFC refrigerant with a high global warming potential. Still, it is desirable to use refrigerants that have a small impact on global warming, such as, for example, HFO (hydrofluoroolefin) refrigerants (HFO1234yf, HFO1234ze, etc.), HC refrigerants, _CO2 , ammonia, water, and the like. Therefore, the binary refrigeration system of Embodiment 1 uses HFO refrigerant as the refrigerant that circulates in the high-end refrigerant circuit of the high-end refrigeration cycle circuit 20.

Furthermore, in the binary refrigeration system of Embodiment 1, the lower refrigeration cycle circuit 10 uses CO ₂ and the higher refrigeration cycle circuit 20 uses HFO refrigerant, so the refrigerating machine oil used in each refrigeration cycle circuit is different. For example, the low-base refrigeration cycle circuit 10 uses ether-based refrigeration oil, and the high-base refrigeration cycle circuit 20 uses ester-based refrigeration oil. However, the combination is not limited to such a combination, and the refrigerant of the low-temperature side refrigeration cycle circuit 10 and the high-temperature side refrigeration cycle circuit 20, the kinematic viscosity, pour point, Additives or acid value refrigerating machine oil can be selected as appropriate.

The operation of each component during the cooling operation of the binary refrigeration system as described above will be explained based on the flow of refrigerant circulating through each refrigeration cycle circuit. First, the operation of the high-end refrigeration cycle circuit 20 will be explained. The high-end compressor 21 takes in HFO refrigerant, compresses it, makes it high temperature and high pressure state, and discharges it. The discharged refrigerant flows into the high-side condenser 22. The high source condenser 22 exchanges heat between the outside air supplied from the high source condenser fan 25 and the HFO refrigerant, and condenses and liquefies the HFO refrigerant. The condensed and liquefied refrigerant passes through the high-end expansion valve 23. The high-end expansion valve 23 reduces the pressure of the condensed and liquefied refrigerant. The depressurized refrigerant flows into the high-side evaporator 24 (cascade condenser C). The high-source side evaporator 24 evaporates and gasifies the refrigerant through heat exchange with the refrigerant passing through the low-source condenser 12 . The high-end compressor 21 sucks the evaporated HFO refrigerant.

Next, the operation of the low-temperature side refrigeration cycle circuit 10 will be explained. The low-end compressor 11 takes in CO ₂ refrigerant, compresses it, makes it high temperature and high pressure, and discharges it. The discharged refrigerant is cooled by the auxiliary heat exchanger 15 and flows into the lower-end condenser 12 (cascade condenser C). The low-base condenser 12 condenses and liquefies the refrigerant through heat exchange with the refrigerant passing through the high-base evaporator 24 . The condensed and liquefied refrigerant passes through the low-end expansion valve 13 . The low-base expansion valve 13 reduces the pressure of the condensed and liquefied refrigerant. The depressurized refrigerant flows into the low-side evaporator 14 . The low-source side evaporator 14 evaporates and gasifies the refrigerant through heat exchange with the object to be cooled. The low-end compressor 11 sucks in the evaporated and gasified CO ₂ refrigerant.

In the cooling operation of the binary refrigeration system, for example, the control device 30 sets the low source side evaporation temperature to such a cooling capacity that the low source side evaporator 14 maintains the temperature of the object to be cooled, which is the load. At this time, the control device 30 adjusts the high pressure in the low source side refrigeration cycle circuit 10, and balances the evaporation capacity in the high source side evaporator 24 and the condensation amount in the low source side condenser 12 in the cascade condenser C. . For this reason, the control device 30 controls the drive of the low end compressor 11 so that the evaporation capacity in the high end evaporator 24 equals the condensing capacity in the low end condenser 12.

Here, evaporation capacity in the high-temperature side evaporator 24 = refrigerant circulation amount in the high-temperature side refrigeration cycle circuit 20 × (enthalpy of the refrigerant at the refrigerant outlet side of the high-temperature side evaporator 24 - enthalpy of the refrigerant at the refrigerant inlet side) ). Further, the refrigerant circulation amount of the high-end refrigeration cycle circuit 20 = the driving frequency of the high-end compressor 21 x the suction refrigerant density x the displacement amount of the compressor x efficiency.

On the other hand, the amount of condensation in the low-base condenser 12 = the amount of refrigerant circulated in the low-base refrigeration cycle circuit 10 x (enthalpy of refrigerant at the refrigerant inlet side of the low-base condenser 12 - enthalpy of refrigerant at the refrigerant outlet side) becomes. Further, the amount of refrigerant circulated in the low source side refrigeration cycle circuit 10 = the driving frequency of the low source side compressor 11 x the suction refrigerant density x the displacement amount of the compressor x efficiency.

For example, at a certain low temperature side condensation temperature of the low temperature side condenser 12, the evaporation capacity in the high temperature side evaporator 24 is insufficient for the required condensation amount required by the low temperature side refrigeration cycle circuit 10. At this time, the control device 30 usually increases the high pressure in the low source side refrigeration cycle circuit 10, increases the condensation temperature in the low source side refrigeration cycle circuit 10, and increases the evaporation capacity in the high source side evaporator 24. balance.

Generally, the evaporation capacity is determined by the drive frequency of the compressor and the density of the refrigerant sucked into the compressor. Basically, as the evaporation temperature increases, the suction refrigerant density increases. Furthermore, when the outside air temperature becomes high, the refrigeration cycle device performs control to suppress the maximum drive frequency in order to suppress the current. Therefore, the maximum evaporation capacity in the refrigeration cycle becomes large when the evaporation temperature in the evaporator is high, the outside air temperature is not too high, and the drive frequency of the compressor is not suppressed. Therefore, the maximum evaporation capacity in the high source side evaporator 24 is determined by the outside air temperature and the high source side evaporation temperature.

Therefore, when the maximum evaporation capacity in the high source side evaporator 24 is small, the control device 30 does not increase the high pressure in the low source side refrigeration cycle circuit 10 to increase the evaporation capacity and balance it with the condensation amount. , the amount of condensation in the low-source condenser 12 is suppressed. For this reason, the control device 30 controls the maximum driving frequency, which is the maximum value of the drive frequency of the low source side compressor 11, so that the condensing capacity in the low source side condenser 12 does not exceed the maximum evaporation capacity in the high source side evaporator 24. Limit the frequency to be lower than the set drive frequency.

FIG. 2 is a diagram illustrating control in the refrigeration cycle device according to the first embodiment. FIG. 2 illustrates the combination of the outside air temperature and the high source evaporation temperature, which define the range in which the maximum drive frequency in the low source compressor 11 is limited, as a region. In FIG. 2, the range surrounded by connecting points ABCD is the range in which the binary refrigeration system is operated in relation to the outside air temperature and the high-side evaporation temperature. In addition, point E determines whether or not the maximum drive frequency of the low source compressor 11 can be limited on the DA line, which is the lower limit of the high source evaporation temperature, in the range in which the binary refrigeration system is operated. It becomes a boundary point. Point F is a boundary point for determining whether or not to limit the maximum drive frequency of the lower side compressor 11 on the CD line, which is the limit on the higher side of outside air temperature, in the range in which the binary refrigeration system is operated. . The boundary line is a line connecting point E and point F, and is a curved line convex in the direction of point B, which is the limit between the high source side evaporation temperature and the low outside air temperature.

Here, the storage unit 32 of the control device 30 stores, for example, the combination of the outside air temperature and the high-side evaporation temperature related to the area illustrated in FIG. 2 as the outside air temperature-high-side evaporation temperature limit range data. , is stored in the limit range data storage unit 33 in table format. The outside air temperature - high source side evaporation temperature limit range is a relationship between the outside air temperature and the high source side evaporation temperature, and when the control device 30 performs normal control, the high pressure of the low source side refrigeration cycle circuit 10 exceeds the set pressure. range. The outside air temperature - high source side evaporation temperature limit range is, as shown in Figure 2, in the range where the binary refrigeration system is operated, the outside air temperature is a temperature equal to or higher than the set point E, and the high source side evaporation temperature is It is within the range where the temperature is below the set point F. In FIG. 2, the region shown by the combination of the outside air temperature and the high-side evaporation temperature is an example. The combination of the outside air temperature and the high source evaporation temperature that limit the maximum drive frequency in the low source compressor 11 changes depending on the environment of the site where the equipment is installed, the length of the piping, and the like. For example, a trial run of the high-end refrigeration cycle circuit 20 is performed at the site to obtain outside air temperature-high-end evaporation temperature limit range data.

FIG. 3 is a diagram illustrating a process for determining a limit on the maximum drive frequency of the low-end compressor 11 in the refrigeration cycle device according to the first embodiment. The control device 30 receives signals sent from the outside air temperature sensor 41 and the high-side evaporation temperature sensor 42 (step S1). The control device 30 acquires the outside air temperature and the high-side evaporation temperature as data based on the received signal (step S2).

The control device 30 determines whether the combination of the acquired outside air temperature and high-side evaporation temperature is included in the limit range defined by the outside air temperature - high-side evaporation temperature limit range data stored in the limit range data storage unit 33. is determined (step S3).

If it is determined that the control device 30 falls within the limit range, the control device 30 sets the maximum drive frequency of the low-source compressor 11 to a drive frequency (for example, a first maximum drive frequency) lower than a preset drive frequency (for example, a first maximum drive frequency). 2 maximum driving frequency) (step S4). Therefore, the second maximum drive frequency is less than the first maximum drive frequency. The control device 30 lowers the high pressure of the low-source refrigeration cycle circuit 10 by limiting the maximum drive frequency. At this time, the control device 30 controls the drive frequency of the low source compressor 11 such that the amount of condensation in the low source condenser 12 matches the evaporation capacity of the high source evaporator 24. However, if the drive frequency of the low-source compressor 11 is below the limited maximum drive frequency, the control device 30 continues the same control.

Here, the second maximum drive frequency may not be uniform. For example, the higher the outside air temperature and the lower the high-side evaporation temperature (in the upper left direction in FIG. 2), the lower the second maximum drive frequency is set by the control device 30, based on the outside air temperature and the high-side evaporation temperature. The amount of restriction may be changed depending on the amount. Since the control device 30 limits the maximum drive frequency of the low source side compressor 11, the evaporation capacity in the low source side evaporator 14, which is the cooling capacity, becomes slightly lower, but the operation in the low source side refrigeration cycle circuit 10 is stable. do. Therefore, it is better for the control device 30 to limit the maximum drive frequency of the low-power side compressor 11 than to cause unstable operation in which the low-power side compressor 11 repeats hunting and repeats unstable driving. can be maintained.

On the other hand, if the control device 30 determines that it is not within the limit range, it does not limit the maximum drive frequency of the low-power side compressor 11 (step S5). Here, for example, if the maximum drive frequency of the low source compressor 11 is limited to the second maximum drive frequency, the control device 30 cancels the limitation and returns it to the set first maximum drive frequency. . The control device 30 repeats the above restriction determination process.

As described above, according to the binary refrigeration system according to the first embodiment, the control device 30 includes the outside air temperature and the high source side evaporation temperature in the limit range in the outside air temperature - high source side evaporation temperature limit range data. If it is determined that the maximum driving frequency of the low-power side compressor 11 is limited, control is performed to limit the maximum driving frequency of the low-power side compressor 11. Therefore, the binary refrigeration system according to the first embodiment can suppress the rise in high pressure in the low-power side refrigeration cycle circuit 10, prevent hunting of the low-power side compressor 11, and perform stable operation. . Therefore, the object to be cooled can be cooled stably. In addition, the binary refrigeration system can save energy by performing stable operation. In addition, since the low-base compressor 11 is free from transient load fluctuations, it is possible to obtain durability of the parts.

Embodiment 2.
As described above, in the operation of the refrigeration cycle device, the control device 30 controls the drive of the low-temperature side compressor 11 so that the evaporation capacity in the high-temperature side evaporator 24 = the condensation amount in the low-temperature side condenser 12. Control. At this time, in the first embodiment, the control device 30 controls the maximum evaporation capacity of the high source side evaporator 24 for the required condensation amount of the low source side refrigeration cycle circuit 10 based on the outside air temperature and the high source side evaporation temperature. is small, the maximum drive frequency of the low-power side compressor 11 is limited.

Here, depending on the low-base evaporation temperature of the low-base evaporator 14, the required condensation amount of the low-base refrigeration cycle circuit 10 may be large. For example, when the low-side evaporation temperature in the low-side evaporator 14 becomes high, the refrigerant circulation amount increases and the required condensation amount increases. Moreover, when the outside air temperature becomes high, the condensation capacity of the auxiliary heat exchanger 15 decreases, and the amount of condensation in the low-source condenser 12 increases.

Therefore, in the refrigeration cycle device of the second embodiment, when the required condensation amount of the low source side refrigeration cycle circuit 10 is large with respect to the evaporation capacity of the high source side evaporator 24 due to the low source side evaporation temperature, the low source side evaporation temperature A case will be described in which the maximum driving frequency of the compressor 11 is limited. Here, in the second embodiment, the limit range data storage section 33 will be described as having outside air temperature-lower side evaporation temperature limit range data defined by the outside air temperature and the lower side evaporation temperature.

FIG. 4 is a diagram illustrating control in the refrigeration cycle device according to the second embodiment. FIG. 4 illustrates a combination of the outside air temperature and the low source evaporation temperature that defines the range that limits the maximum drive frequency in the low source compressor 11 as a region. In FIG. 4, the range connected and surrounded by points GHIJ is the range in which the binary refrigeration system is operated in relation to the outside air temperature and the low-side evaporation temperature. In addition, point K determines whether or not the maximum drive frequency of the low source side compressor 11 can be limited on the IH line, which is the high limit of the low source side evaporation temperature, in the range in which the binary refrigeration system is operated. It becomes a boundary point. Point L is a boundary point for determining whether or not to limit the maximum drive frequency of the lower side compressor 11 on the IJ line, which is the limit on the higher side of outside air temperature, in the range in which the binary refrigeration system is operated. . The boundary line is a line connecting points K and L, and is a curved line convex in the direction of point G, which is the limit of the lower side evaporation temperature and the lower outside air temperature.

Here, the storage unit 32 of the control device 30 stores, for example, the combination of the outside air temperature and the low-side evaporation temperature related to the area illustrated in FIG. 4 as the outside air temperature-low-side evaporation temperature limit range data. , is stored in the limit range data storage unit 33 in table format. The outside air temperature - low source side evaporation temperature limit range is a relationship between the outside air temperature and the low source side evaporation temperature, and when the control device 30 performs normal control, the high pressure of the low source side refrigeration cycle circuit 10 exceeds the set pressure. range. The outside air temperature - low side evaporation temperature limit range is, as shown in Figure 4, within the range where the binary refrigeration system is operated, the outside air temperature is a temperature equal to or higher than the set point K, and the low side evaporation temperature is It is within the range where the temperature is equal to or higher than the set point L. In FIG. 4, the area shown by the combination of the outside air temperature and the lower side evaporation temperature is an example. The combination of the outside air temperature and the low source evaporation temperature that limit the maximum drive frequency in the low source compressor 11 changes depending on the environment of the site where the equipment is installed, the length of the piping, and the like. For example, a test run of the refrigeration cycle device is performed at the site to obtain outside air temperature-lower side evaporation temperature limit range data.

FIG. 5 is a diagram illustrating a process for determining a limit on the maximum drive frequency of the low-end compressor 11 in the refrigeration cycle device according to the second embodiment. The control device 30 receives signals sent from the outside air temperature sensor 41 and the low-side evaporation temperature sensor 43 (step S11). The control device 30 acquires the outside air temperature and the low-side evaporation temperature as data based on the signal (step S12).

The control device 30 determines whether the acquired combination of the outside air temperature and the low-side evaporation temperature is included in the limit range in the outside-air temperature-low-side evaporation temperature limit range data stored in the limit range data storage unit 33. (Step S13).

If it is determined that the control device 30 falls within the limit range, the control device 30 changes the maximum drive frequency of the low-side compressor 11 to a second maximum drive frequency lower than the first maximum drive frequency set in advance, as in the first embodiment. Limit to frequency. The control device 30 lowers the high pressure of the low-source refrigeration cycle circuit 10 by limiting the maximum drive frequency (step S15). At this time, the control device 30 controls the drive frequency of the low source compressor 11 such that the amount of condensation in the low source condenser 12 matches the evaporation capacity of the high source evaporator 24. Here, similarly to Embodiment 1, if the drive frequency of the low-end compressor 11 is equal to or lower than the limited maximum drive frequency, the control device 30 continues the same control.

Here, the second maximum drive frequency may not be uniform. For example, the higher the outside air temperature and the higher the low source evaporation temperature (in the upper right direction in FIG. 4), the lower the second maximum drive frequency is set by the control device 30. The amount of restriction may be changed depending on the amount.

On the other hand, if the control device 30 determines that it is not within the limit range, it does not limit the maximum drive frequency of the low-end compressor 11 (step S15). Here, for example, if the maximum drive frequency of the low source compressor 11 is limited to the second maximum drive frequency, the control device 30 cancels the limitation and returns it to the set first maximum drive frequency. . The control device 30 repeats the above restriction determination process.

As described above, according to the binary refrigeration system according to the second embodiment, the control device 30 includes the outside air temperature and the low-side evaporation temperature in the limit range in the outside-air temperature - low-side evaporation temperature limit range data. If it is determined that the maximum driving frequency of the low-power side compressor 11 is limited, control is performed to limit the maximum driving frequency of the low-power side compressor 11. Therefore, the binary refrigeration system according to the second embodiment can suppress the rise in high pressure in the low-source side refrigeration cycle circuit 10, prevent hunting of the low-source side compressor 11, and perform stable operation. . Therefore, the object to be cooled can be cooled stably. In addition, the binary refrigeration system can save energy by performing stable operation. In addition, since the low-base compressor 11 is free from transient load fluctuations, it is possible to obtain durability of the parts.

Embodiment 3.
In the binary refrigeration system according to the first embodiment described above, the control device 30 performed a restriction determination process to limit the maximum drive frequency of the low source side compressor 11 based on the outside air temperature and the high source side evaporation temperature. Furthermore, in the binary refrigeration system according to the second embodiment, the control device 30 performed a restriction determination process to limit the maximum drive frequency of the low source compressor 11 based on the outside air temperature and the low source side evaporation temperature. For example, the control device 30 in the third embodiment performs a restriction determination process that is a combination of these restriction determination processes. The contents of each restriction determination process are the same as those described above. The control device 30 can perform stable operation of the binary refrigeration system by performing both the restriction determination processes described in the first embodiment and the second embodiment.

In the binary refrigeration system according to the third embodiment, for example, the storage unit 32 of the control device 30 stores the outside air temperature-high side evaporation temperature limit range data and the outside air temperature-low side evaporation temperature limit range data as limit range data. 33 is stored. Then, the control device 30 determines that the combination of the acquired outside air temperature and high-side evaporation temperature and the outside air temperature and low-side evaporation temperature are included in one or both of the areas shown in FIGS. 2 and 4 described above. If it is determined that the maximum driving frequency of the low-power side compressor 11 is determined to be high, the maximum driving frequency of the low-power side compressor 11 is limited.

Embodiment 4.
In the binary refrigeration systems of Embodiments 1 to 3, as shown in FIGS. 2 and 4, the boundary between the restricted range area and the non-restricted area is distinguished by a line, and the low element based on the maximum driving frequency is Although the control of the side compressor 11 is switched, the present invention is not limited to this. The boundary may not be a line, but may be an area with width, such as a transition area.

10 Low source side refrigeration cycle circuit, 11 Low source side compressor, 12 Low source side condenser, 13 Low source side expansion valve, 14 Low source side evaporator, 15 Auxiliary heat exchanger, 16 Auxiliary heat exchanger fan, 20 High source side refrigeration cycle circuit, 21 High source side compressor, 22 High source side condenser, 23 High source side expansion valve, 24 High source side evaporator, 25 High source side condenser fan, 30 Control device, 31 Control processing part, 32 storage part, 33 limit range data storage part, 41 outside air temperature sensor, 42 high source side evaporation temperature sensor, 43 low source side evaporation temperature sensor, C cascade capacitor.

Claims

a high-temperature side refrigeration cycle circuit in which a high-temperature side compressor, a high-temperature side condenser, a high-temperature side throttle device, and a high-temperature side evaporator are connected via piping to circulate a high-temperature side refrigerant;
a low-base refrigeration cycle circuit in which a low-base compressor, a low-base condenser, a low-base throttle device, and a low-base evaporator are connected via piping to circulate a low-base refrigerant;
a cascade condenser configured with the high-base evaporator and the low-base condenser, and performs heat exchange between the high-base refrigerant and the low-base refrigerant;
an outside air temperature sensor that measures outside air temperature;
a high source side evaporation temperature sensor that measures a high source side evaporation temperature in the high source side evaporator;
A range in which the combination of the outside air temperature measured by the outside air temperature sensor and the high-side evaporation temperature measured by the high-side evaporation temperature sensor causes a pressure at which high pressure in the low-side refrigeration cycle circuit exceeds a set pressure. A refrigeration cycle device comprising: a control device that performs processing to limit a maximum drive frequency of the low source compressor when it is determined that the outside air temperature is within the high source side evaporation temperature limit range.
2. The outside air temperature - high source side evaporation temperature limit range is a range that is greater than or equal to the set outside air temperature and less than or equal to the set high source side evaporation temperature in the range where the operation is performed. Refrigeration cycle equipment.
a low source side evaporation temperature sensor that measures a low source side evaporation temperature in the low source side evaporator;
The control device includes:
A range in which the combination of the outside air temperature measured by the outside air temperature sensor and the low-side evaporation temperature measured by the low-side evaporation temperature sensor causes a pressure at which high pressure in the low-side refrigeration cycle circuit exceeds a set pressure. 3. The refrigeration cycle apparatus according to claim 1, wherein the maximum driving frequency of the low source compressor is limited even when it is determined that the outside air temperature is within the low source side evaporation temperature limit range.
a high-temperature side refrigeration cycle circuit in which a high-temperature side compressor, a high-temperature side condenser, a high-temperature side throttle device, and a high-temperature side evaporator are connected via piping to circulate a high-temperature side refrigerant;
a low-base refrigeration cycle circuit in which a low-base compressor, a low-base condenser, a low-base throttle device, and a low-base evaporator are connected via piping to circulate a low-base refrigerant;
a cascade condenser configured with the high-base evaporator and the low-base condenser, and performs heat exchange between the high-base refrigerant and the low-base refrigerant;
an outside air temperature sensor that measures outside air temperature;
a low source side evaporation temperature sensor that measures a low source side evaporation temperature in the low source side evaporator;
A range in which the combination of the outside air temperature measured by the outside air temperature sensor and the low-side evaporation temperature measured by the low-side evaporation temperature sensor causes a pressure at which high pressure in the low-side refrigeration cycle circuit exceeds a set pressure. A refrigeration cycle device comprising: a control device that performs processing to limit a maximum drive frequency of the low source compressor when it is determined that the outside air temperature is within the low source side evaporation temperature limit range.
3. The outside air temperature-lower side evaporation temperature limit range is a range in which the outside air temperature is equal to or higher than the set lower side evaporation temperature within the range where the operation is performed. 4. The refrigeration cycle device according to 4.