JP6987269B2 - Refrigeration cycle device - Google Patents

Description

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

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

The refrigerating apparatus disclosed in Patent Document 1 has 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 the economizer expansion valve, and the opening degree of the economizer expansion valve is controlled so that the degree of superheat of the intermediate heat exchanger becomes constant.

Japanese Patent No. 5436192

In the refrigerating 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 becomes constant, so that the period efficiency, which is an evaluation index of the annual coefficient of performance, is improved. Cannot be expected.

The present invention has been made to solve the above-mentioned problems, and provides a refrigerating cycle apparatus for improving period efficiency.

In the refrigerating cycle device according to the present invention, a compressor, a condenser, an intermediate cooler, a main expansion valve and an evaporator are connected by a refrigerant pipe, and a refrigerant circuit in which the refrigerant circulates, and the intermediate cooler and the main expansion valve are used. An economizer circuit that branches from between or between the condenser and the intermediate cooler and is connected to the compressor via the intermediate cooler, an economizer expansion valve provided in the economizer circuit, and the economizer. An intermediate pressure sensor provided in the circuit to detect the intermediate pressure of the refrigerant injected into the compressor, and a temperature sensor provided in the economizer circuit to detect the temperature of the refrigerant injected into the compressor are intermediate. The economizer superheat degree, which is the difference between the saturated gas temperature of the intermediate pressure detected by the pressure sensor and the detected value of the temperature sensor, is calculated, and the target value of the economizer superheat degree is obtained based on the operating state of the refrigerant circuit. The calculation means includes a calculation means and a flow control means for controlling the opening degree of the economyr expansion valve so that the degree of overheating of the economyr matches the target value obtained by the calculation means, and the calculation means includes a plurality of types. In the calculation formula of the period performance coefficient calculated by the plurality of performance coefficients corresponding to the operation load of the above, the operation load having the largest weighting is selected from the plurality of types of operation loads to estimate the target value, or the above-mentioned target value is estimated. The target value is estimated from two or more operating loads having a larger weighting among a plurality of types of operating loads, and the value at which the performance coefficient is maximized in the operating load corresponding to the operating state of the refrigerant circuit is set as the target value. It is to be set.

Further, in the refrigerating cycle device according to the present invention, a refrigerant circuit in which a compressor, a condenser, an intermediate cooler, a main expansion valve and an evaporator are connected by a refrigerant pipe and a refrigerant circulates, and the intermediate cooler and the main expansion are provided. An economizer circuit that branches from between the valve or between the condenser and the intermediate cooler and is connected to the compressor via the intermediate cooler, and an economizer expansion valve provided in the economizer circuit. An intermediate pressure sensor provided in the economizer circuit to detect the intermediate pressure of the refrigerant injected into the compressor, and an intermediate pressure sensor provided between the intermediate cooler and the main expansion valve in the refrigerant circuit to detect the temperature of the refrigerant. The main refrigerant liquid approach temperature, which is the difference between the intermediate cooler high-pressure side outlet temperature sensor, the saturated gas temperature of the intermediate pressure detected by the intermediate pressure sensor, and the detected value of the intermediate cooler high-pressure side outlet temperature sensor. The calculation means for calculating and obtaining the target value of the main refrigerant liquid approach temperature based on the operating state of the refrigerant circuit, and the calculation means so that the main refrigerant liquid approach temperature matches the target value obtained by the calculation means. It has a flow control means for controlling the opening degree of the economizer expansion valve, and the calculation means is described in the calculation formula of the period performance coefficient calculated by a plurality of performance coefficients corresponding to a plurality of types of operating loads. The target value is estimated by selecting the operating load having the largest weighting among the operating loads of the above, or estimating the target value from two or more operating loads having the larger weighting among the plurality of types of operating loads. The target value may be set to a value at which the performance coefficient is maximized in the operating load corresponding to the operating state of the refrigerant circuit.

According to the present invention, by setting the target value to be monitored so that the coefficient of performance becomes large in the driving load actually operated, the economizer expands as compared with 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.

It is a refrigerant circuit diagram which shows an example of the refrigeration cycle apparatus which concerns on Embodiment 1 of this invention. It is a functional block diagram which shows one configuration example of the control apparatus shown in FIG. FIG. 5 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. It is a flowchart which shows the operation procedure of the refrigeration cycle apparatus shown in FIG. It is a refrigerant circuit diagram which shows another structural example of the refrigeration cycle apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram which shows an example of the refrigeration cycle apparatus which concerns on Embodiment 2 of this invention. It is a schematic diagram for demonstrating the approach temperature of the main refrigerant liquid to be monitored in the economizer flow rate control of Embodiment 2 of this invention. It is a flowchart which shows the operation procedure of the refrigeration cycle apparatus shown in FIG.

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

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 condensation pressure sensor 8b detects the condensation pressure of the refrigerant flowing into the condenser 3.

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, a twin screw compressor, or the like. The type of the compressor 2 is not limited to these compressors, and any compressor 2 may be used as long as it can connect the economizer circuit 11. The condenser 3 is a heat exchanger that heat-exchanges the gas refrigerant discharged from the compressor 2 with air, water, or the like, and cools and condenses the gas refrigerant. The evaporator 6 is a heat exchanger that heat-exchanges the refrigerant flowing out of the main expansion valve 5 with air, water, brine, or the like to evaporate 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 is provided in the economizer pipe 9 and the economizer pipe 9 that branch from between the intercooler 4 and the main expansion valve 5 and are connected to the compressor 2 via the low pressure portion 4b of the intercooler 4. It also has an economizer expansion valve 7. The economizer expansion valve 7 is provided between the branch portion 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. In the economizer pipe 9, a temperature sensor 13 and an intermediate pressure sensor 8c are provided between the intercooler 4 and the compressor 2.

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

The configuration of the control device 10 shown in FIG. 1 will be described. FIG. 2 is a functional block diagram showing a configuration example of the control device shown in FIG. As shown in FIG. 1, the control device 10 has a memory 31 for storing a program and a CPU (Cenral Processing Unit) 32 for executing processing according to the program. When the CPU 32 executes the program, as shown in FIG. 2, the refrigeration cycle control means 33, the calculation means 34, and the flow rate control means 35 are configured in the refrigeration cycle device 1.

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

In the first embodiment, the calculation means 34 describes the case where the target value is determined based on the compression ratio of the compressor 2 as the operating state of the refrigerant circuit 12, but the refrigerant circuit 12 which is the basis for determining the target value is described. The operating 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 calculation means 34 compresses from the evaporation pressure detected by the evaporation pressure sensor 8a and the condensation pressure detected by the condensation pressure sensor 8b. Calculate the compression ratio of the machine 2. The compression ratio is calculated by the formula of compression ratio = (condensation pressure / evaporation 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 is reduced and the operating load is reduced. The compression ratio is an index indicating the operating load. The flow rate control means 35 controls the opening degree of the economizer expansion valve 7 so that the monitored economizer superheat degree ΔTest matches the target value.

Here, the target value to be monitored for the economizer flow rate control will be described. Conventionally, the coefficient of performance under rated conditions has been the mainstream as an index for energy saving of refrigeration cycle equipment. The rated condition is an operating condition in which 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 coefficient of performance IPLV (Integrated Part Load Value).

The American Refrigeration and Air Conditioning Industry Association has established formula (1) as the formula for calculating the _{coefficient of performance IPLV US.}
IPLV _US = 0.01 x A + 0.42 x B + 0.45 x C + 0.12 x D ... (1)
In formula (1), A is the COP at 100% load, B is the COP at 75% load, C is the COP at 50% load, and D is the COP at 25% load.

As shown in the equation (1), the period coefficient of performance is calculated by synthesizing a plurality of coefficient of performance corresponding to a plurality of types of driving loads. In the formula (1), the coefficient of each term indicates the ratio to the annual operating time. For example, assuming that the annual operating time is Tz, the time for operating with a 100% operating load is 0.01 × Tz [hours]. Each coefficient is a weighting of the driving load with respect to the annual operating time. With reference to equation (1), a 75% load accounts for 42% of the annual operating time, and a 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 also set an index similar to _{the period coefficient of performance IPLV US in the United States.} Formula (2) is a calculation formula showing the coefficient of performance for a period set by the Japan Refrigeration and Air Conditioning Industry Association.
IPLV = 0.01 x A + 0.47 x B + 0.37 x C + 0.15 x D ... (2)
In formula (2), A is the COP at 100% load, B is the COP at 75% load, C is the COP at 50% load, and D is the COP at 25% load.

Referring to equation (2), the weighting is different for each operating load, as in the _{period coefficient of performance IPLV US} by the American Refrigeration and Air Conditioning Industry Association. However, when the equations (1) and (2) are compared, the weighting values may differ even with the same operating load. For example, in equation (2), the 75% load accounts for 47% of the annual operating time, with the largest weighting.

In a general refrigeration cycle device, the operation time under rated conditions is very short throughout the year, and 90% or more of the operation time throughout the year is operated by partial load operation. Most of the partial load is operated with a load of 75 to 50% of the total load. The refrigerant circulation flow rate and the operation compression ratio are different between the full load operation and the partial load operation, and the coefficient of performance also changes. The above-mentioned coefficient of performance for a period in consideration of such an actual operation situation is attracting attention. In other words, the coefficient of performance for a period is an index that emphasizes the coefficient of performance under partial load conditions.

In the first embodiment, for the economizer superheat degree ΔTest to be monitored by the economizer flow rate control, the target value at which the period coefficient of performance calculated by the formula shown in the formula (2) is the largest is obtained in advance. Can be considered. With reference to equation (2), of the four types of operating load, the 75% load accounts for 47% of the annual operating time, and the weighting is the largest. Therefore, it is conceivable to pay attention to the operating load having the maximum weighting.

The operating condition of interest is not limited to the case of the operating load having the maximum weighting value, and may be an operating load of 2 or more from the one with the largest weighting. The operating conditions of interest may be all of the four types of operating loads constituting the equation (2). The number of driving conditions of interest is not limited. For example, the calculation means 34 calculates the compression ratio of the compressor 2 when the value having the largest coefficient of performance is set in each operation condition in advance such as the trial run period of the refrigeration cycle device 1, and monitors each compression ratio. The target value of the target may be obtained. Then, the calculation means 34 stores in the memory 31 information indicating the relationship between the compression ratio and the target value to be monitored.

The calculation 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). You may. In this case, the calculation means 34 can estimate the compression ratio and the target value for the operating conditions other than the four types of operating conditions 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 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. FIG. 3 shows a case where the reference for determining the target value is the compression ratio in the operating state of the refrigerant circuit 12. The horizontal axis of the graph of FIG. 3 is the compression ratio, and the vertical axis is the target value to be monitored. In the first embodiment, the vertical axis of FIG. 3 is the target value of the economizer superheat degree ΔTest.

In FIG. 3, the points indicating the target value of the economizer superheat degree ΔTest corresponding to the compression ratio are plotted under the four conditions. The four conditions are the condition that the coefficient of performance at 100% load is maximum, the condition that the coefficient of performance at 75% load is maximum, and the condition that the coefficient of performance at 50% load is maximum, Cond3 and 25%. Condition 4 is the condition in which the coefficient of performance under load is maximized. The approximate curve connecting the four plots is shown by the broken line. From this approximate curve, the calculation means 34 can estimate the target value even for the compression ratios that do not correspond to the four plots. If there is data on the target value to be monitored corresponding to at least two conditions, the calculation means 34 can draw an approximate curve as shown in FIG.

Further, 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 (2) as follows. From the relationship between the compression ratio and the target value obtained under the four types of operating conditions, the calculation means 34 compresses so that each region contains one value of the four compression ratios corresponding to the above four types of operating conditions. Divide the range of ratios into four areas. Then, the calculation means 34 sets the values of the four compression ratios corresponding to the above four types of operating conditions as the target values of the compression ratios in each region. In this case, when the target value of the calculated compression ratio is unknown, the calculation means 34 identifies a region to which the calculated compression ratio belongs among a plurality of regions divided about the compression ratio, and is set 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 the differential pressure Pd (condensation pressure-evaporation pressure) between the high pressure and the low pressure in the refrigerant circuit 12 instead of the compression ratio. The calculation means 34 determines the target value to be monitored based on the differential pressure Pd. Further, the memory 31 stores the target determination information in which the target value at which the period performance coefficient IPLV becomes the optimum value for the range of the condensation pressure and the range of the evaporation pressure is stored, and the calculation 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 to determine the target value.

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

Subsequently, 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 the target value Tset1 of the economizer superheat degree ΔTest based on the calculated compression ratio (step S101). For example, the calculation means 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 rate control means 35 compares the calculated economizer superheat degree ΔTest with the target value Tset1 (step S102). As a result of the comparison in step S102, when the economizer superheat degree ΔTest is smaller than the target value Tset1, the flow rate control means 35 reduces the opening degree of the economizer expansion valve 7 (step S103). When the opening degree of the economizer expansion valve 7 becomes small, 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 injected refrigerant rises, so that the economizer superheat degree ΔTest rises and approaches the target value Tset1.

On the other hand, as a result of comparison in step S102, when the economizer superheat degree ΔTest is larger than the target value Tset1, the flow rate control means 35 increases the opening degree of the economizer expansion valve 7 in order to reduce the economizer superheat degree ΔTest (step). S104). When the opening degree of the economizer expansion valve 7 becomes large, 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 ΔTest decreases and approaches the target value Tset1.

Further, as a result of the comparison in step S102, when the economizer superheat degree ΔTest is equivalent to the target value Tset1, the flow rate control means 35 maintains the opening degree 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 optimum values in which the coefficient of performance increases in accordance with the operating load.

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

The refrigerating cycle device 1 of the first embodiment calculates the economizer superheat degree ΔTest as a monitoring target. Then, the refrigeration cycle device 1 obtains a target value of the economizer superheat degree ΔTesh based on the operating 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 economizer superheat degree to be monitored is set so that the coefficient of performance becomes large in the driving load actually operated, so that the target value becomes constant. In comparison, the opening degree of the economizer expansion valve is appropriately controlled, and the period efficiency can be improved.

Further, in the first embodiment, the calculation means 34 sets the value at which the coefficient of performance is maximized by the operating load corresponding to the frequency, the compression ratio, and the like as the target value. By controlling the flow rate of the economizer so that the coefficient of performance increases according to the actual operating load, the refrigeration cycle apparatus 1 can improve the coefficient of performance for a period of time.

In this case, as a method of determining the target value, the calculation 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 coefficient of performance. In this case, the calculation means 34 can determine the estimated optimum target value to be monitored even for operating conditions other than the plurality of types of driving loads shown in the calculation formula.

Further, as a method of determining the target value, the calculation 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 coefficient of performance, and the target value for each region. May be determined.

Further, when determining the target value, the calculation means 34 may pay attention to the driving load having the largest weighting, or may pay attention to two or more driving loads having the larger weighting among the plurality of types of driving loads. .. In this case, since the calculation means 34 has a small number of operating loads that are the basis for determining the target value of the compression ratio, the target value to be monitored can be determined more quickly.

Embodiment 2.
Regarding the economizer flow control, the first embodiment has described the case where the economizer superheat degree is used, but the second embodiment exemplifies the 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 refrigerating cycle apparatus of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

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

The configuration of the refrigeration cycle apparatus of the second embodiment will be described. FIG. 6 is a refrigerant circuit diagram showing an example of the refrigeration cycle device according to the second embodiment of the present invention. The refrigerating cycle device 1b of the second embodiment has an intercooler high-pressure side outlet temperature sensor 14 provided at the high-pressure side refrigerant outlet of the intercooler 4. The refrigeration cycle device 1b shown in FIG. 6 is not provided with the temperature sensor 13 shown in FIG. 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 high-pressure side outlet temperature sensor 14 of the intercooler is a refrigerant flowing through the refrigerant circuit 12, and detects the temperature of the liquid refrigerant flowing out of the intercooler 4.

In the second embodiment, the calculation means 34 calculates the main refrigerant liquid approach temperature ΔTsca, which is the difference between the refrigerant temperature Tm detected by the intermediate cooler high pressure side outlet temperature sensor 14 and the saturated gas temperature Tessa of the intermediate pressure. The main refrigerant liquid approach temperature ΔTsca is calculated by the formula of the main refrigerant liquid approach temperature ΔTs a = (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 the approach temperature of the main refrigerant liquid to be monitored in the economizer flow rate control according to the second embodiment of the present invention. FIG. 7 is a ph diagram showing pressure on the vertical axis and specific enthalpy on the horizontal axis. FIG. 7 schematically shows the main refrigerant liquid approach temperature ΔTsca.

Next, the operation of the refrigeration cycle device 1b according to the second embodiment will be described. FIG. 8 is a flowchart showing an operating procedure of the refrigeration cycle apparatus shown in FIG. Also in the second embodiment, a graph for determining 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.

During the operation of the refrigerating cycle device 1b, the control device 10 reads the detected values of various sensors at a constant cycle. The calculation 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 Tessa of 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 calculation means 34 determines the target value Tset2 of the main refrigerant liquid approach temperature ΔTsca based on the calculated compression ratio (step S201). The calculation means 34 determines the target value Tset2 from the graph shown in FIG.

Then, the flow rate control means 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 smaller than the target value Tset2, the flow rate control means 35 reduces the opening degree of the economizer expansion valve 7 (step S203). When the opening degree of the economizer expansion valve 7 becomes small, 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 side refrigerant and the low-pressure side refrigerant in the intercooler decreases, and the refrigerant temperature Tm rises. 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 larger than the target value Tset2, the flow rate control means 35 increases the opening degree of the economizer expansion valve 7 in order to reduce the main refrigerant liquid approach temperature ΔTsca. Increase (step S204). When the opening degree of the economizer expansion valve 7 becomes large, 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 equivalent to the target value Tset2, the flow rate control means 35 maintains the opening degree 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 optimum values in which the coefficient of performance increases in accordance with the operating load.

Also in the second embodiment, 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 constituting the calculation formula (2) and the compression ratio of the compressor 2. Further, the coefficient of performance that is the basis for determining the target value may be the coefficient of performance with the maximum weighting among the four types of driving loads constituting the calculation formula of the formula (2), and the coefficient of performance having the largest weighting is 2 from the one with the largest weighting. It may be estimated from one or more coefficients of performance.

The refrigeration cycle apparatus 1b of the second embodiment calculates the main refrigerant liquid approach temperature ΔTsca, obtains the 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 so as to do so.

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

Although the connection configuration of the economizer circuit 11 has been described in the case of the configuration shown in FIG. 1 in the second embodiment, 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 description of the embodiment and the configuration shown in the drawings. Further, the high and low pressures are not determined in relation to the absolute value, but are relatively determined in the state and operation of the refrigeration cycle apparatus.

1, 1a, 1b Refrigerating cycle device, 2 Compressor, 3 Condenser, 4 Intermediate cooler, 4a High pressure part, 4b Low pressure part, 5 Main expansion valve, 6 Evaporator, 7 Economizer expansion valve, 8a Evaporation pressure sensor, 8b Condensation 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 side outlet temperature sensor, 15, 15a branch, 31 memory, 32 CPU , 33 Refrigeration cycle control means, 34 Calculation means, 35 Flow control means.

Claims (6)

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 the refrigerant circulates,
An economizer circuit that branches from between the intercooler and the main expansion valve or between the condenser and the intercooler and is connected to the compressor via the intercooler.
The economizer expansion valve provided in the economizer circuit and
An intermediate pressure sensor provided in the economizer circuit to detect the intermediate pressure of the refrigerant injected into the compressor, and
A temperature sensor provided in the economizer circuit to detect the temperature of the refrigerant injected into the compressor, and
The economizer superheat degree, which is the difference between the saturated gas temperature of the intermediate pressure detected by the intermediate pressure sensor and the detected value of the temperature sensor, is calculated, and the target value of the economizer superheat degree is calculated based on the operating state of the refrigerant circuit. And the calculation method to find
A 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.
Have,
The calculation means is
In the calculation formula of the period coefficient of performance calculated by a plurality of coefficient of performance corresponding to a plurality of types of driving loads, the driving load having the largest weighting is selected from the plurality of types of driving loads and the target value is estimated. Alternatively, the target value is estimated from two or more operating loads having the larger weighting among the plurality of types of operating loads.
The target value is set to the value at which the coefficient of performance is maximized in the operating load corresponding to the operating state of the refrigerant circuit.
Refrigeration cycle equipment. 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 the refrigerant circulates,
An economizer circuit that branches from between the intercooler and the main expansion valve or between the condenser and the intercooler and is connected to the compressor via the intercooler.
The economizer expansion valve provided in the economizer circuit and
An intermediate pressure sensor provided in the economizer circuit to detect the intermediate pressure of the refrigerant injected into the compressor, and
In the refrigerant circuit, an intercooler high-pressure side outlet temperature sensor provided between the intercooler and the main expansion valve to detect the temperature of the refrigerant, and
The main refrigerant liquid approach temperature, which is the difference between the saturated gas temperature of the intermediate pressure detected by the intermediate pressure sensor and the detected value of the high pressure side outlet temperature sensor of the intermediate cooler, is calculated and based on the operating state of the refrigerant circuit. And the calculation means for obtaining the target value of the main refrigerant liquid approach temperature,
A 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.
Have,
The calculation means is
In the calculation formula of the period coefficient of performance calculated by a plurality of coefficient of performance corresponding to a plurality of types of driving loads, the driving load having the largest weighting is selected from the plurality of types of driving loads and the target value is estimated. Alternatively, the target value is estimated from two or more operating loads having the larger weighting among the plurality of types of operating loads.
The target value is set to the value at which the coefficient of performance is maximized in the operating load corresponding to the operating state of the refrigerant circuit.
Refrigeration cycle equipment. The plurality of types of operating loads include 100% load, 75% load, 50% load and 25% load, and the operating load having the highest weighting is 75% load or 50% in the calculation formula of the period coefficient of performance. Is a load,
The refrigeration cycle apparatus according to claim 1 or 2. The operating load having the largest weighting is a 75% load in the calculation formula of the coefficient of performance, and the two or more operating loads having the larger weighting are 75% in the calculation formula of the coefficient of performance. Load and 50% load,
The refrigeration cycle apparatus according to claim 3. The operating load having the largest weighting is a 50% load in the calculation formula of the coefficient of performance, and the two or more operating loads having the larger weighting are 50% in the calculation formula of the coefficient of performance. Load and 75% load,
The refrigeration cycle apparatus according to claim 3. An evaporative pressure sensor provided on the refrigerant outlet side of the evaporator and detecting the evaporative pressure of the refrigerant,
Further, a condensed pressure sensor provided on the refrigerant inlet side of the condenser and detecting the condensed pressure of the refrigerant is provided.
The calculation means is
The operating 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.
The refrigeration cycle apparatus according to any one of claims 1 to 5.

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