WO2020070793A1

WO2020070793A1 - Refrigeration cycle apparatus

Info

Publication number: WO2020070793A1
Application number: PCT/JP2018/036849
Authority: WO
Inventors: 駿岡田; 雅浩神田
Original assignee: 三菱電機株式会社
Priority date: 2018-10-02
Filing date: 2018-10-02
Publication date: 2020-04-09
Also published as: JP6987269B2; EP3862649A1; EP3862649A4; JPWO2020070793A1

Abstract

This refrigeration cycle apparatus has: a refrigerant circuit in which a refrigerant is circulated; an economizer circuit that branches from between an intermediate cooler and a main expansion valve or from between a condenser and the intermediate cooler, and that is coupled to a compressor via the intermediate cooler; an economizer expansion valve that is provided to the economizer circuit; an intermediate pressure sensor that detects an intermediate pressure of a refrigerant injected to the compressor; a temperature sensor that detects the temperature of the refrigerant injected to the compressor; a calculation means that calculates the degree of superheat of the economizer, the degree being a difference between a saturated gas temperature of the detected intermediate pressure and a detected value of the temperature sensor, and that obtains a target value of the degree of superheat of the economizer on the basis of an operation state of the refrigerant circuit; and a flow rate control means that controls the opening of the economizer expansion valve such that the degree of superheat of the economizer matches the target value.

Description

Refrigeration cycle device

The present invention relates to a refrigeration cycle device having a refrigerant circuit through which a refrigerant circulates.

2. Description of the Related Art Conventionally, a refrigerating apparatus in which an intermediate heat exchanger is provided in a refrigerating cycle for the purpose of improving refrigerating capacity and coefficient of performance (COP = refrigerating capacity / compressor power consumption) is known (for example, see Patent Document 1). .

The refrigerating device disclosed in Patent Literature 1 includes an economizer circuit that injects a part of the refrigerant flowing out of the condenser into the compressor via an intermediate heat exchanger, and an economizer expansion valve provided in the economizer circuit. . In this refrigeration system, a temperature-type automatic expansion valve is used as an economizer expansion valve, and the opening of the economizer expansion valve is controlled so that the degree of superheat of the intermediate heat exchanger is constant.

Japanese Patent No. 5463192

In the refrigeration apparatus disclosed in Patent Document 1, the opening degree of the economizer expansion valve is controlled so that the degree of superheat of the intermediate heat exchanger is constant, so that the period efficiency, which is an evaluation index of the annual coefficient of performance, is improved. Can not expect.

The present invention has been made to solve the above-described problems, and provides a refrigeration cycle apparatus that improves the period efficiency.

The refrigeration cycle device according to the present invention, a compressor, a condenser, an intercooler, a main expansion valve and an evaporator are connected by refrigerant piping, a refrigerant circuit in which refrigerant circulates, the intercooler and the main expansion valve, Or an economizer circuit branched from between the condenser and the intercooler and connected to the compressor via the intercooler, an economizer expansion valve provided in the economizer circuit, and the economizer. An intermediate pressure sensor that is provided in a circuit and detects an intermediate pressure of the refrigerant injected into the compressor; a temperature sensor that is provided in the economizer circuit and detects a temperature of the refrigerant injected into the compressor; Calculate the economizer superheat degree which is a difference between the saturated gas temperature of the intermediate pressure detected by the pressure sensor and the detection value of the temperature sensor, Calculating means for obtaining a target value of the economizer superheat degree based on the operating state of the refrigerant circuit; and opening the economizer expansion valve so that the economizer superheat degree matches the target value obtained by the calculation means. Control means for controlling the flow rate.

Also, the refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, a condenser, an intercooler, a main expansion valve, and an evaporator are connected by a refrigerant pipe and a refrigerant circulates, the intercooler, and the main expansion. An economizer circuit branched from a valve or from between the condenser and the intercooler, and connected to the compressor via the intercooler, an economizer expansion valve provided in the economizer circuit, An intermediate pressure sensor that is provided in the economizer circuit and detects an intermediate pressure of refrigerant injected into the compressor; and an intermediate pressure sensor that is provided between the intermediate cooler and the main expansion valve in the refrigerant circuit and detects a temperature of the refrigerant. An intercooler high-pressure outlet temperature sensor, a saturated gas temperature of the intermediate pressure detected by the intermediate pressure sensor, and the intercooler high-pressure outlet temperature sensor Calculating means for calculating a main refrigerant liquid approach temperature that is a difference from the detected value, and calculating a target value of the main refrigerant liquid approach temperature based on an operation state of the refrigerant circuit; Flow rate control means for controlling the opening of the economizer expansion valve so as to match the target value obtained by the above.

According to the present invention, the target value to be monitored is set so that the coefficient of performance is increased at the operating load actually operated, so that the economizer expansion is reduced compared to the case where the target value is set to be constant. The opening degree of the valve is appropriately controlled, and the period efficiency can be improved.

FIG. 2 is a refrigerant circuit diagram illustrating an example of a refrigeration cycle device according to Embodiment 1 of the present invention. FIG. 2 is a functional block diagram illustrating a configuration example of a control device illustrated in FIG. 1. FIG. 4 is an image diagram of a graph showing an example of a method of determining a target value to be monitored from an operating state of a refrigerant circuit in the economizer flow rate control according to the first embodiment of the present invention. 2 is a flowchart illustrating an operation procedure of the refrigeration cycle device illustrated in FIG. 1. FIG. 4 is a refrigerant circuit diagram illustrating another configuration example of the refrigeration cycle device according to Embodiment 1 of the present invention. FIG. 7 is a refrigerant circuit diagram illustrating an example of a refrigeration cycle device according to Embodiment 2 of the present invention. It is a schematic diagram for explaining the main refrigerant liquid approach temperature to be monitored in the economizer flow rate control according to the second embodiment of the present invention. 7 is a flowchart showing an operation procedure of the refrigeration cycle apparatus shown in FIG.

Embodiment 1 FIG.
The configuration of the refrigeration cycle device of the first embodiment will be described. FIG. 1 is a refrigerant circuit diagram illustrating an example of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. The refrigeration cycle apparatus 1 includes a compressor 2, a condenser 3, an intercooler 4, a main expansion valve 5, an evaporator 6, an economizer circuit 11, and a control device 10. The intercooler 4 has a high-pressure section 4a and a low-pressure section 4b. The compressor 2, the condenser 3, the high-pressure section 4a of the intercooler 4, the main expansion valve 5, and the evaporator 6 are connected by a refrigerant pipe, and a refrigerant circuit 12 in which the refrigerant circulates is configured.

蒸発 An evaporation pressure sensor 8a is provided on the refrigerant outlet side of the evaporator 6. The evaporation pressure sensor 8a detects the evaporation pressure of the refrigerant flowing out of the evaporator 6. A condensation pressure sensor 8b is provided on the refrigerant inlet side of the condenser 3. The condensing pressure sensor 8b detects the condensing pressure of the refrigerant flowing into the condenser 3.

(4) The compressor 2 compresses and discharges the refrigerant to be sucked. The compressor 2 is an inverter type compressor whose capacity can be changed by controlling the rotation frequency. The compressor 2 is, for example, a single screw compressor or a twin screw compressor. The type of the compressor 2 is not limited to these compressors, and may be any type as long as the economizer circuit 11 can be connected. The condenser 3 is a heat exchanger that exchanges heat with the gas refrigerant discharged from the compressor 2 with air or water, and cools and condenses the gas refrigerant. The evaporator 6 is a heat exchanger that causes the refrigerant flowing out of the main expansion valve 5 to exchange heat with air, water, brine, or the like, and evaporates the refrigerant. The condenser 3 and the evaporator 6 are, for example, fin tube type, plate type or shell and tube type heat exchangers. The main expansion valve 5 decompresses and expands the refrigerant flowing from the intercooler 4. The main expansion valve 5 is, for example, an electronic expansion valve.

The economizer circuit 11 branches from the intercooler 4 and the main expansion valve 5, and is provided in the economizer pipe 9 and the economizer pipe 9 connected to the compressor 2 via the low-pressure section 4 b of the intercooler 4. Economizer expansion valve 7. The economizer expansion valve 7 is provided between the branch 15 between the intercooler 4 and the main expansion valve 5 and the intercooler 4. The economizer expansion valve 7 is, for example, an electronic expansion valve. A temperature sensor 13 and an intermediate pressure sensor 8c are provided between the intercooler 4 and the compressor 2 in the economizer pipe 9.

The intercooler 4 has the high-pressure section 4a and the low-pressure section 4b as described above. The high-pressure side refrigerant, which is the high-pressure side refrigerant between the condenser 3 and the main expansion valve 5, flows through the high-pressure part 4a. The low-pressure section 4b is circulated with a refrigerant in which a part of the high-pressure side refrigerant is decompressed by the economizer expansion valve 7. The refrigerant flowing out of the low-pressure section 4b becomes an intermediate-pressure refrigerant that is an intermediate-pressure refrigerant in the entire refrigeration cycle. The intercooler 4 exchanges heat between the high-pressure refrigerant and the intermediate-pressure refrigerant to cool the high-pressure refrigerant. The temperature sensor 13 detects the temperature of the refrigerant injected into the compressor 2. The intermediate pressure sensor 8c detects an intermediate pressure of the refrigerant injected into the compressor 2.

構成 The configuration of the control device 10 shown in FIG. 1 will be described. FIG. 2 is a functional block diagram illustrating a configuration example of the control device illustrated in FIG. 1. As shown in FIG. 1, the control device 10 includes a memory 31 that stores a program, and a CPU (Central Processing Unit) 32 that executes processing according to the program. When the CPU 32 executes the program, the refrigeration cycle control unit 33, the calculation unit 34, and the flow rate control unit 35 are configured in the refrigeration cycle apparatus 1, as shown in FIG.

(4) The refrigeration cycle control means 33 controls the rotation frequency of the compressor 2 and the opening of the main expansion valve 5 based on the detection values of the evaporation pressure sensor 8a and the condensation pressure sensor 8b. The calculating means 34 calculates an economizer superheat degree ΔTesh which is a difference between the saturated gas temperature Tesa at the intermediate pressure and the refrigerant temperature Te detected by the temperature sensor 13 as a monitoring target of the economizer flow rate control. Further, the calculating means 34 determines a target value of the economizer superheat degree ΔTesh based on the operating state of the refrigerant circuit 12. The economizer superheat degree ΔTesh is calculated by an equation of ΔTesh = (Te−Tesa).

In the first embodiment, a case will be described where the calculating unit 34 determines the target value based on the compression ratio of the compressor 2 as the operating state of the refrigerant circuit 12, but the calculation unit 34 determines the operating state of the refrigerant circuit 12 based on the determination of the target value. The operation state is not limited to the compression ratio. When the target value is determined based on the compression ratio of the compressor 2 as the operating state of the refrigerant circuit 12, the calculating unit 34 compresses the target value based on the evaporation pressure detected by the evaporation pressure sensor 8a and the condensation pressure detected by the condensation pressure sensor 8b. The compression ratio of the machine 2 is calculated. The compression ratio is calculated by an expression of compression ratio = (condensing pressure / evaporating pressure). When the compression ratio is large, the compression work increases and the operating load increases. When the compression ratio is small, the compression work decreases, and the operating load decreases. The compression ratio is an index indicating the operating load. The flow control means 35 controls the opening of the economizer expansion valve 7 so that the monitored economizer superheat degree ΔTesh matches the target value.

Here, the target value to be monitored for economizer flow control will be described. Conventionally, as an index of energy saving of a refrigeration cycle device, a coefficient of performance under rated conditions has been mainly used. The rated condition is an operating condition where the operating load is 100%. In recent years, period efficiency has been attracting attention as an index close to actual operating conditions. As the period efficiency, for example, there is a period performance coefficient IPLV (Integrated Part Load Load Value).

The American Refrigeration and Air Conditioning Industry Association defines Equation (1) as a calculation equation for the period performance coefficient IPLV _US .
IPLV _US = 0.01 × A + 0.42 × B + 0.45 × C + 0.12 × D (1)
In the equation (1), A is a COP under a 100% load, B is a COP under a 75% load, C is a COP under a 50% load, and D is a COP under a 25% load.

期間 As shown in equation (1), the period performance coefficient is calculated by combining a plurality of performance coefficients corresponding to a plurality of types of operating loads. In the equation (1), the coefficient of each term indicates a ratio of the annual operation time. For example, assuming that the annual operation time is Tz, the operation time at the operation load of 100% is 0.01 × Tz [hour]. Each coefficient is a weight of the operation load with respect to the annual operation time. Referring to equation (1), 75% load accounts for 42% of the annual operating time, and 50% load accounts for 45% of the annual operating time. In equation (1), the weight under these two operating conditions is large.

On the other hand, the Japan Refrigeration and Air Conditioning Industry Association has set the same index as the period performance coefficient IPLV _{US in the} United States for the period performance coefficient. Formula (2) is a calculation formula indicating a period performance coefficient determined by the Japan Refrigeration and Air Conditioning Industry Association.
IPLV = 0.01 × A + 0.47 × B + 0.37 × C + 0.15 × D (2)
In the equation (2), A is a COP at 100% load, B is a COP at 75% load, C is a COP at 50% load, and D is a COP at 25% load.

Referring to Equation (2), the weighting differs for each operating load, similarly to the period performance coefficient IPLV _US by the American Refrigeration and Air Conditioning Industry Association. However, when the expressions (1) and (2) are compared, there is a case where the weighting values are different even for the same operation load. For example, in equation (2), the 75% load accounts for 47% of the annual operating time, and has the highest weight.

では In a general refrigeration cycle device, the operation time under the rated conditions is very short throughout the year, and 90% or more of the operation time throughout the year is operated by the partial load operation. The partial load mainly occupies 75 to 50% of the total load. In the full load operation and the partial load operation, the refrigerant circulation flow rate and the operation compression ratio are different, and the coefficient of performance also changes. Attention has been paid to the above-mentioned period performance coefficient in consideration of such an actual driving situation. That is, the period performance coefficient is an index that emphasizes the performance coefficient under the partial load condition.

In the first embodiment, for the economizer superheat degree ΔTesh to be monitored by the economizer flow rate control, a target value that maximizes the period performance coefficient calculated by the calculation formula shown in Expression (2) is determined in advance. Can be considered. Referring to equation (2), among the four types of operating loads, 75% load accounts for 47% of the annual operating time, and has the largest weight. Therefore, it is conceivable to pay attention to the operating load having the maximum weight.

運転 The operating condition to be noted is not limited to the operating load having the maximum weight, but may be two or more operating loads in descending order of the weight. The operating condition of interest may be all of the four types of operating loads that constitute Expression (2). The number of operating conditions of interest is not limited. For example, in advance, such as during a test operation period of the refrigeration cycle apparatus 1, the calculation means 34 calculates the compression ratio of the compressor 2 when the value at which the coefficient of performance is maximized is set under each operating condition, and monitors the compression ratio. The target value of the target may be obtained. Then, the calculating unit 34 stores information indicating the relationship between the compression ratio and the target value to be monitored in the memory 31.

The calculating means 34 obtains the compression ratio of the compressor 2 and the target value to be monitored for each compression ratio for the four types of operating conditions corresponding to the four types of operating loads included in the calculation formula (2). May be. In this case, regarding the compression ratio and the target value for the operating conditions other than the four types of operating conditions, the calculating unit 34 can infer from the relationship between the compression ratio and the target value obtained under the four operating conditions.

FIG. 3 is an image diagram of a graph showing an example of a method for determining a target value to be monitored from the operating state of the refrigerant circuit in the economizer flow rate control according to the first embodiment of the present invention. FIG. 3 shows a case where the reference for determining the target value is the compression ratio in the operation state of the refrigerant circuit 12. The horizontal axis of the graph in FIG. 3 is the compression ratio, and the vertical axis is the target value to be monitored. In the first embodiment, the vertical axis in FIG. 3 is the target value of the economizer superheat degree ΔTesh.

FIG. 3 plots points indicating target values of the economizer superheat degree ΔTesh corresponding to the compression ratios under the four conditions. The four conditions are a condition Cond1 that maximizes the coefficient of performance at 100% load, a condition Cond2 that maximizes the coefficient of performance at 75% load, a condition Cond3 that maximizes the coefficient of performance at 50% load, and 25%. This is the condition Cond4 that maximizes the coefficient of performance under load. An approximate curve connecting the four plots is indicated by a broken line. From this approximation curve, the calculation means 34 can also estimate the target value for the compression ratios that do not correspond to the four plots. If there is data of the target value to be monitored corresponding to at least two conditions, the calculating means 34 can draw an approximate curve as shown in FIG.

算出 Furthermore, the calculation means 34 may determine the target values other than the four types of operating conditions corresponding to the four types of operating loads included in the calculation formula of the formula (2) as follows. The calculating means 34 calculates the compression ratio from the relationship between the compression ratio and the target value obtained under the four types of operating conditions so that each of the four compression ratio values corresponding to the four types of operating conditions is included in each region. The range of the ratio is divided into four regions. Then, the calculation means 34 sets the values of the four compression ratios corresponding to the four types of operating conditions as target values of the compression ratio in each region. In this case, when the calculated target value of the compression ratio is unknown, the calculation unit 34 specifies the region to which the calculated compression ratio belongs among the plurality of regions divided for the compression ratio, and sets the region to the specified region. The target value is determined as the target value of the compression ratio. Here, the case of four types of operating conditions has been described, but the number of operating conditions of interest is not limited.

The operating state of the refrigerant circuit 12, which is the basis for determining the target value, may be a parameter other than the compression ratio. For example, the operating state of the refrigerant circuit 12 may be a differential pressure Pd (condensation pressure-evaporation pressure) between high pressure and low pressure in the refrigerant circuit 12 instead of the compression ratio. The calculating means 34 determines a target value to be monitored based on the differential pressure Pd. Further, the memory 31 stores target determination information for specifying a target value at which the period performance coefficient IPLV is an optimum value for the range of the condensing pressure and the range of the evaporation pressure, and the calculating means 34 refers to the target determination information. Then, the target value may be determined from the detected condensation pressure and the detected evaporation pressure. Further, the rotation frequency may be used for determining the target value.

Next, the operation of the refrigeration cycle apparatus 1 according to the first embodiment will be described. FIG. 4 is a flowchart showing an operation procedure of the refrigeration cycle apparatus shown in FIG. During the operation of the refrigeration cycle apparatus 1, the control device 10 reads the detection values of various sensors at regular intervals. The calculating means 34 calculates the economizer superheat degree ΔTesh from the refrigerant temperature Te detected by the temperature sensor 13 and the saturated gas temperature Tesa at the intermediate pressure detected by the intermediate pressure sensor 8c.

Next, the calculation means 34 calculates the compression ratio using the evaporation pressure detected by the evaporation pressure sensor 8a and the condensation pressure detected by the condensation pressure sensor 8b. The calculation means 34 determines a target value Tset1 of the economizer superheat degree ΔTesh based on the calculated compression ratio (step S101). For example, the calculating unit 34 determines the target value Tset1 from the graph shown in FIG. The graph shown in FIG. 3 is stored in the memory 31.

Then, the flow control unit 35 compares the calculated economizer superheat degree ΔTesh with the target value Tset1 (step S102). As a result of the comparison in step S102, when the economizer superheat degree ΔTesh is smaller than the target value Tset1, the flow control unit 35 reduces the opening degree of the economizer expansion valve 7 (step S103). When the opening degree of the economizer expansion valve 7 decreases, the intermediate pressure decreases, and the flow rate of the refrigerant flowing through the economizer circuit 11 decreases. As a result, the gas temperature of the refrigerant to be injected increases, so that the economizer superheat degree ΔTesh increases and approaches the target value Tset1.

On the other hand, as a result of the comparison in step S102, when the economizer superheat degree ΔTesh is larger than the target value Tset1, the flow control unit 35 increases the opening degree of the economizer expansion valve 7 in order to reduce the economizer superheat degree ΔTesh (step S102). S104). When the opening degree of the economizer expansion valve 7 increases, the intermediate pressure increases, and the flow rate of the refrigerant flowing through the economizer circuit 11 increases. As a result, the gas temperature of the injected refrigerant decreases, so that the economizer superheat degree ΔTesh decreases to approach the target value Tset1.

Furthermore, as a result of the comparison in step S102, when the economizer superheat degree ΔTesh is equal to the target value Tset1, the flow control unit 35 maintains the opening of the economizer expansion valve 7 (step S105). In this way, the amount and temperature of the refrigerant injected into the compressor 2 are automatically controlled to the optimal values at which the coefficient of performance increases according to the operating load.

In the refrigeration cycle apparatus 1 according to Embodiment 1, the connection configuration of the economizer circuit 11 is not limited to the configuration illustrated in FIG. FIG. 5 is a refrigerant circuit diagram illustrating another configuration example of the refrigeration cycle device according to Embodiment 1 of the present invention. In the refrigeration cycle apparatus 1a shown in FIG. 5, the economizer circuit 11 branches from between the intercooler 4 and the condenser 3, and flows to the compressor 2 via the economizer expansion valve 7 and the low-pressure section 4b of the intercooler 4. It is connected. The economizer expansion valve 7 is provided between the intercooler 4 and a branch portion 15 a between the intercooler 4 and the condenser 3.

冷凍 The refrigeration cycle apparatus 1 of the first embodiment calculates the economizer superheat degree ΔTesh as a monitoring target. Then, the refrigeration cycle apparatus 1 obtains a target value of the economizer superheat degree ΔTesh based on the operation state of the refrigerant circuit 12, and controls the opening degree of the economizer expansion valve 7 so that the economizer superheat degree ΔTesh matches the target value.

In the first embodiment, when the target value of the superheat degree of the economizer to be monitored is set so that the coefficient of performance becomes large at the actual operating load, the target value is set to be constant. In comparison, the opening of the economizer expansion valve is appropriately controlled, and the period efficiency can be improved.

In addition, in the first embodiment, the calculating means 34 sets the value at which the coefficient of performance becomes maximum at the operating load corresponding to the frequency and the compression ratio as the target value. By performing the economizer flow rate control such that the coefficient of performance increases in accordance with the actual operation load, the refrigeration cycle apparatus 1 can improve the period coefficient of performance.

In this case, as a method of determining the target value, the calculating means 34 may estimate the target value corresponding to the compression ratio from a plurality of types of operating loads constituting the calculation formula for calculating the period performance coefficient. In this case, the calculating means 34 can determine the estimated optimum target value of the monitoring target also for operating conditions other than the plurality of types of operating loads shown in the calculation formula.

As a method of determining the target value, the calculating means 34 divides the compression ratio into a plurality of regions based on the compression ratios of a plurality of types of operating loads constituting the calculation formula for calculating the period performance coefficient, and May be determined.

Further, when determining the target value, the calculating means 34 may pay attention to the operating load with the largest weight, or may pay attention to two or more operating loads with the larger weight among the plurality of types of operating loads. . In this case, the calculation unit 34 can determine the target value to be monitored more quickly because the number of operating loads on which the target value of the compression ratio is determined is small.

Embodiment 2 FIG.
Embodiment 1 has been described with respect to the economizer flow rate control in the case where the economizer superheat degree is used, but Embodiment 2 illustrates a case where attention is paid to the temperature of the refrigerant at the high-pressure side refrigerant outlet of the intercooler. In the second embodiment, the same components as those of the refrigeration cycle device of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the refrigerant circuit shown in FIG. 1, part of the refrigerant flowing through the refrigerant circuit 12 is diverted to the economizer circuit 11 and flows through the low-pressure section 4 b of the intercooler 4. The refrigerant flowing through the low-pressure section 4b of the intercooler 4 cools the refrigerant flowing through the high-pressure section 4a of the intercooler 4. Therefore, the refrigerant flowing through the economizer circuit 11 lowers the temperature of the refrigerant flowing through the high-pressure section 4 a of the intercooler 4. In the first embodiment, the opening degree of the economizer expansion valve 7 is controlled by detecting the temperature and pressure of the refrigerant flowing through the economizer circuit 11. On the other hand, in the second embodiment, a change in the refrigerant temperature at the high pressure side refrigerant outlet of the intercooler 4 is detected, and the opening of the economizer expansion valve 7 is controlled.

構成 The configuration of the refrigeration cycle apparatus according to Embodiment 2 will be described. FIG. 6 is a refrigerant circuit diagram illustrating an example of a refrigeration cycle device according to Embodiment 2 of the present invention. The refrigeration cycle apparatus 1b according to the second embodiment includes an intercooler high-pressure outlet temperature sensor 14 provided at the high-pressure refrigerant outlet of the intercooler 4. In the refrigeration cycle apparatus 1b shown in FIG. 6, the temperature sensor 13 shown in FIG. 1 is not provided. In the configuration example shown in FIG. 6, the intercooler high-pressure-side outlet temperature sensor 14 is provided between the branch portion 15 and the main expansion valve 5. The intercooler high-pressure outlet temperature sensor 14 detects the temperature of the liquid refrigerant flowing through the refrigerant circuit 12 and flowing out of the intercooler 4.

In the second embodiment, the calculating means 34 calculates the main refrigerant liquid approach temperature ΔTsca, which is the difference between the refrigerant temperature Tm detected by the intercooler high-pressure outlet temperature sensor 14 and the saturated gas temperature Tesa at the intermediate pressure. The main refrigerant liquid approach temperature ΔTsca is calculated by an equation of main refrigerant liquid approach temperature ΔTsca = (Tm-Tesa). In the second embodiment, the monitoring target used for the economizer flow rate control is the main refrigerant liquid approach temperature ΔTsca.

FIG. 7 is a schematic diagram for explaining a main refrigerant liquid approach temperature to be monitored in the economizer flow control according to the second embodiment of the present invention. FIG. 7 is a ph diagram showing the pressure on the vertical axis and the specific enthalpy on the horizontal axis. FIG. 7 schematically shows the main refrigerant liquid approach temperature ΔTsca.

Next, the operation of the refrigeration cycle apparatus 1b according to the second embodiment will be described. FIG. 8 is a flowchart showing an operation procedure of the refrigeration cycle apparatus shown in FIG. Also in the second embodiment, a graph that determines a target value when the monitoring target is the main refrigerant liquid approach temperature ΔTsca is stored in the memory 31. The graph is, for example, the graph shown in FIG.

(4) During operation of the refrigeration cycle device 1b, the control device 10 reads the detection values of various sensors at regular intervals. The calculating means 34 calculates the main refrigerant liquid approach temperature ΔTsca from the refrigerant temperature Tm detected by the intermediate cooler high pressure side outlet temperature sensor 14 and the saturated gas temperature Tesa at the intermediate pressure detected by the intermediate pressure sensor 8c. The calculation means 34 calculates the compression ratio using the detection values of the evaporation pressure sensor 8a and the condensation pressure sensor 8b. The calculating means 34 determines a target value Tset2 of the main refrigerant liquid approach temperature ΔTsca based on the calculated compression ratio (step S201). The calculating means 34 determines the target value Tset2 from the graph shown in FIG.

Then, the flow control unit 35 compares the calculated main refrigerant liquid approach temperature ΔTsca with the target value Tset2 (step S202). As a result of the comparison in step S202, when the main refrigerant liquid approach temperature ΔTsca is lower than the target value Tset2, the flow control unit 35 reduces the opening of the economizer expansion valve 7 (step S203). When the opening degree of the economizer expansion valve 7 decreases, the intermediate pressure decreases, and the flow rate of the refrigerant flowing through the economizer circuit 11 decreases. As a result, the amount of heat exchange between the high-pressure refrigerant and the low-pressure refrigerant in the intercooler decreases, and the refrigerant temperature Tm increases. Therefore, the main refrigerant liquid approach temperature ΔTsca increases and approaches the target value Tset2.

On the other hand, as a result of the comparison in step S202, when the main refrigerant liquid approach temperature ΔTsca is higher than the target value Tset2, the flow control unit 35 sets the opening degree of the economizer expansion valve 7 to reduce the main refrigerant liquid approach temperature ΔTsca. It is increased (step S204). When the opening degree of the economizer expansion valve 7 increases, the intermediate pressure increases, and the flow rate of the refrigerant flowing through the economizer circuit 11 increases. As a result, the amount of heat exchange between the high-pressure side refrigerant and the low-pressure side refrigerant in the intercooler increases, and the refrigerant temperature Tm decreases. Therefore, the main refrigerant liquid approach temperature ΔTsca decreases and approaches the target value Tset2.

Further, as a result of the comparison in step S202, when the main refrigerant liquid approach temperature ΔTsca is equal to the target value Tset2, the flow control unit 35 maintains the opening of the economizer expansion valve 7 (step S205). In this way, the amount and temperature of the refrigerant injected into the compressor 2 are automatically controlled to the optimal values at which the coefficient of performance increases according to the operating load.

In the second embodiment as well, the target value of the main refrigerant liquid approach temperature ΔTsca is not limited to the graph shown in FIG. The target value of the main refrigerant liquid approach temperature ΔTsca may be obtained from the relationship between the coefficient of performance of the four types of operating loads and the compression ratio of the compressor 2 that constitute the calculation formula of Expression (2). In addition, the coefficient of performance that is the basis for determining the target value may be the coefficient of performance having the largest weight among the four types of operating loads constituting the calculation formula of equation (2). It may be estimated from one or more performance coefficients.

The refrigeration cycle apparatus 1b of the second embodiment calculates the main refrigerant liquid approach temperature ΔTsca, obtains a target value of the main refrigerant liquid approach temperature ΔTsca based on the compression ratio, and the main refrigerant liquid approach temperature ΔTsca matches the target value. The opening degree of the economizer expansion valve 7 is controlled in such a manner as to perform the above operation.

Also in the second embodiment, by setting the target value of the main refrigerant liquid approach temperature so that the coefficient of performance becomes large at the operating load actually operated, the target value is set to be constant. In comparison, the opening of the economizer expansion valve is appropriately controlled, and the period efficiency can be improved.

In the second embodiment, the connection configuration of the economizer circuit 11 has been described with reference to the configuration shown in FIG. 1, but the connection configuration of the economizer circuit 11 may be the configuration shown in FIG. Further, the form of each component described in the first and second embodiments is an example, and is not limited to the configuration described in the description of the embodiment and the drawings. Further, the level of the pressure is not determined particularly in relation to an absolute value, but means that the level is relatively determined in the state and operation of the refrigeration cycle apparatus.

1, 1a, 1b refrigeration cycle device, 2 compressor, 3 condenser, 4 intercooler, 4a high pressure section, 4b low pressure section, 5 main expansion valve, 6 evaporator, 7 economizer expansion valve, 8a evaporating pressure sensor, 8b Condensing pressure sensor, 8c intermediate pressure sensor, 9 economizer piping, 10 controller, 11 economizer circuit, 12 refrigerant circuit, 13 temperature sensor, 14 intermediate cooler high-pressure outlet temperature sensor, 15, 15a branch, 31 memory, 32 CPU , 33 ° refrigeration cycle control means, 34 ° calculation means, 35 ° flow rate control means.

Claims

A refrigerant circuit in which a compressor, a condenser, an intercooler, a main expansion valve, and an evaporator are connected by refrigerant piping, and the refrigerant circulates;
An economizer circuit branched from between the intercooler and the main expansion valve or between the condenser and the intercooler and connected to the compressor via the intercooler;
An economizer expansion valve provided in the economizer circuit,
An intermediate pressure sensor that is provided in the economizer circuit and detects an intermediate pressure of the refrigerant injected into the compressor;
A temperature sensor provided in the economizer circuit and detecting a temperature of a refrigerant injected into the compressor;
Calculate an economizer superheat degree which is a difference between the saturated gas temperature of the intermediate pressure detected by the intermediate pressure sensor and a detection value of the temperature sensor, and set a target value of the economizer superheat degree based on an operation state of the refrigerant circuit. Calculating means for determining
Flow rate control means for controlling the opening degree of the economizer expansion valve so that the degree of superheat of the economizer matches the target value obtained by the calculation means,
A refrigeration cycle device having:
A refrigerant circuit in which a compressor, a condenser, an intercooler, a main expansion valve, and an evaporator are connected by refrigerant piping, and the refrigerant circulates;
An economizer circuit branched from between the intercooler and the main expansion valve or between the condenser and the intercooler and connected to the compressor via the intercooler;
An economizer expansion valve provided in the economizer circuit,
An intermediate pressure sensor that is provided in the economizer circuit and detects an intermediate pressure of the refrigerant injected into the compressor;
In the refrigerant circuit, provided between the intercooler and the main expansion valve, an intercooler high-pressure outlet temperature sensor that detects the temperature of the refrigerant,
A main refrigerant liquid approach temperature, which is a difference between the saturated gas temperature of the intermediate pressure detected by the intermediate pressure sensor and a detection value of the intermediate cooler high pressure side outlet temperature sensor, is calculated, based on an operation state of the refrigerant circuit. Calculating means for determining a target value of the main refrigerant liquid approach temperature,
Flow rate control means for controlling the opening degree of the economizer expansion valve so that the main refrigerant liquid approach temperature matches the target value obtained by the calculation means,
A refrigeration cycle device having:
The calculating means,
The refrigeration cycle apparatus according to claim 1, wherein a value that maximizes a coefficient of performance at an operation load corresponding to an operation state of the refrigerant circuit is set to the target value.
The calculating means,
The target value corresponding to the operating state of the refrigerant circuit is estimated from the plurality of operating loads in a calculation formula of a period performance coefficient calculated by a plurality of performance coefficients corresponding to a plurality of operating loads. A refrigeration cycle apparatus according to item 1.
The calculating means,
In a calculation formula of a period performance coefficient calculated by a plurality of performance coefficients corresponding to a plurality of operation loads, an operation state of the refrigerant circuit corresponding to the plurality of operation loads is divided into a plurality of regions, and the plurality of regions are divided into a plurality of regions. The refrigeration cycle apparatus according to claim 3, wherein the target value is determined for each cycle.
The calculating means,
In the calculation formula of the period performance coefficient calculated by a plurality of performance coefficients corresponding to a plurality of types of operation loads, among the plurality of types of operation loads, the operation load with the largest weight is selected to estimate the target value, 4. The refrigeration cycle apparatus according to claim 3, wherein the target value is estimated from two or more operation loads having a larger weight among the plurality of types of operation loads. 5.
An evaporation pressure sensor provided on the refrigerant outlet side of the evaporator and detecting an evaporation pressure of the refrigerant,
A condensing pressure sensor that is provided on the refrigerant inlet side of the condenser and detects a condensing pressure of the refrigerant,
The calculating means,
The operation state of the refrigerant circuit according to any one of claims 1 to 6, wherein an operation state of the refrigerant circuit is calculated using the evaporation pressure detected by the evaporation pressure sensor and the condensation pressure detected by the condensation pressure sensor. Refrigeration cycle device.