Refrigeration cycle device, control device, control method, and control program

Abstract

A refrigeration cycle device (100) performs heat exchange with a heat medium cycle circuit (Cr1) for circulating a heat medium. The refrigeration cycle device comprises: a first compressor (C1) that is capable of compressing a first refrigerant which circulates through a first refrigerant circuit (Rc1); a first heat exchanger (Hb1) that exchanges heat between the first refrigerant and a heat medium in the heat medium cycle circuit; and a control device (10) that controls the first compressor. The control device acquires flow rate information that indicates the flow rate of the heat medium which circulates through the heat medium cycle circuit (steps S102, 107), and controls the frequency of the first compressor on the basis of the flow rate information (steps S303, 304).

Description

Refrigeration cycle device, control device, control method, and control program

[0001] The present disclosure relates to a refrigeration cycle device, a control device, a control method, and a control program.

[0002] Conventionally, there has been a so-called water-type refrigeration cycle apparatus having a refrigerant circuit that uses a compressor to circulate a refrigerant and a heat medium cycle circuit that circulates a heat medium such as antifreeze or water. In such a refrigeration cycle apparatus, the temperature of the heat medium flowing through the heat medium cycle circuit is detected, and the value of the heat medium temperature is fed back to control the drive frequency of the compressor.

[0003] The air conditioning apparatus of Patent Document 1 (WO 2015 / 025366) controls the drive frequency of the compressor taking into consideration not only the temperature of the heat medium flowing through the heat medium cycle circuit but also the output of the pump provided in the heat medium cycle circuit.

[0004] International Publication No. 2015 / 025366

[0005] The cooling capacity of such a refrigeration cycle device changes depending on the drive frequency of the compressor, but does not change immediately after the drive frequency of the compressor is changed. Rather, the cooling capacity becomes the cooling capacity corresponding to the changed drive frequency of the compressor after a predetermined time has elapsed since the drive frequency of the compressor is changed. In other words, there is a time lag between when the drive frequency of the compressor is changed and when the cooling capacity corresponding to the change is reached.

[0006] Therefore, for example, when the temperature of the heat medium in the heat medium cycle circuit drops, even if the reduced temperature of the heat medium is fed back and the drive frequency of the compressor is changed, the temperature of the heat medium may drop further.In other words, since the effect of the change in the drive frequency of the compressor occurs with a delay after the temperature of the heat medium has dropped significantly, the overshoot that occurs when controlling the temperature of the heat medium may increase.

[0007] The present disclosure has been made to solve the above problems, and an object of the present disclosure is to suppress an increase in overshoot that occurs when controlling the temperature of a heat medium in a heat medium cycle circuit.

[0008] A refrigeration cycle apparatus according to the present disclosure performs heat exchange with a heat medium cycle circuit that circulates a heat medium. The refrigeration cycle apparatus includes a first compressor capable of compressing a first refrigerant circulating through a first refrigerant circuit, a first heat exchanger that exchanges heat between the first refrigerant and a heat medium in the heat medium cycle circuit, and a control device that controls the first compressor. The control device acquires flow rate information indicating the flow rate of the heat medium circulating through the heat medium cycle circuit and controls the frequency of the first compressor based on the flow rate information.

[0009] A control device according to the present disclosure controls the circulation of a refrigerant in a refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium. The refrigeration cycle device includes a first compressor that compresses a first refrigerant circulating through a first refrigerant circuit, and a heat exchanger that exchanges heat between the first refrigerant and a heat medium in the heat medium cycle circuit. The control device includes a storage device and a controller that controls the first compressor. The controller acquires flow rate information indicating a flow rate of the heat medium in the heat medium cycle circuit, and controls a frequency of the first compressor based on the flow rate information.

[0010] A control method according to the present disclosure is a control method for controlling the circulation of a refrigerant in a refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium. The refrigeration cycle device includes a first compressor that compresses a first refrigerant circulating through a first refrigerant circuit, and a heat exchanger that exchanges heat between the first refrigerant and a heat medium in the heat medium cycle circuit. The control method includes, as processing executed by a computer, the steps of acquiring flow rate information indicating a flow rate of the heat medium in the heat medium cycle circuit, and controlling a frequency of the first compressor based on the flow rate information.

[0011] A control program according to the present disclosure controls the circulation of a refrigerant in a refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium. The refrigeration cycle device includes a first compressor that compresses a first refrigerant circulating through a first refrigerant circuit, and a heat exchanger that exchanges heat between the first refrigerant and a heat medium in the heat medium cycle circuit. The control program causes a computer to execute the steps of acquiring flow rate information indicating a flow rate of the heat medium in the heat medium cycle circuit, and controlling a frequency of the first compressor based on the flow rate information.

[0012] According to the present disclosure, it is possible to suppress an increase in overshoot that occurs when controlling the temperature of the heat medium in the heat medium cycle circuit.

[0013] FIG. 1 is a diagram for explaining an air conditioning system in embodiment 1. FIG. 2 is a block diagram showing the configuration of a control device. FIG. 3 is a flowchart showing a data set acquisition process in a stable state. FIG. 4 is a flowchart for explaining a flow rate acquisition process in embodiment 1. FIG. 5 is a flowchart showing a prediction process for a convergence value of an outlet temperature in this embodiment. FIG. 6 is a diagram for explaining transition of an outlet temperature. FIG. 7 is a diagram for explaining an air conditioning system in embodiment 2. FIG. 8 is a flowchart for explaining a flow rate acquisition process in embodiment 2. FIG. 9 is a diagram for explaining an air conditioning system in embodiment 3.

[0014] Hereinafter, embodiments of the technical concept according to the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0015] First embodiment <Configuration of air conditioning system> Fig. 1 is a diagram for explaining an air conditioning system 1000 in a first embodiment. The air conditioning system 1000 is a system for adjusting the air temperature in a space in which a load side unit NU1 is arranged. The air conditioning system 1000 has a load side unit NU1, a heat source side unit HS1, and a heat medium cycle circuit Cr1. The heat source side unit HS1 and the load side unit NU1 are arranged on the heat medium cycle circuit Cr1. Furthermore, the air conditioning system 1000 of the first embodiment has a flow rate (m ３ The flow sensor PA1 detects the flow rate (flow rate / time).

[0016] In the air conditioning system 1000, a heat medium circulates in a heat medium cycle circuit Cr1. The heat medium may be water, antifreeze, or the like. The heat medium circulating in the heat medium cycle circuit Cr1 is cooled by a heat source side unit HS1. The heat medium cooled by the heat source side unit HS1 flows into a heat exchanger Hc1 of a load side unit NU1. The load side unit NU1 includes the heat exchanger Hc1, a fan Fb1, and a flow control valve Eb1.

[0017] The heat exchanger Hc1 exchanges heat between the heat medium cooled by the heat source unit HS1 and the air surrounding the heat exchanger Hc1. The fan Fb1 blows air toward the heat exchanger Hc1 to promote heat exchange by the heat exchanger Hc1. The heat exchanger Hc1 can be placed, for example, indoors in a building.

[0018] In the air conditioning system 1000, the heat medium cooled by the heat source side unit HS1 is circulated in the heat medium cycle circuit Cr1 to adjust the temperature of the air around the heat exchanger Hc1. The flow rate control valve Eb1 adjusts the flow rate of the heat medium circulating in the heat medium cycle circuit Cr1.

[0019] The heat source side unit HS1 includes the refrigeration cycle apparatus 100 of the first embodiment, the control device 10, a pump Pm1, an inlet temperature sensor In1, and an outlet temperature sensor Ex1. The pump Pm1, the inlet temperature sensor In1, and the outlet temperature sensor Ex1 are arranged on the heat medium cycle circuit Cr1. The heat exchanger Hb1 included in the refrigeration cycle apparatus 100 is also arranged on the heat medium cycle circuit Cr1.

[0020] The pump Pm1 circulates the heat medium in the heat medium cycle circuit Cr1. In the example of FIG. 1 , the pump Pm1 discharges the heat medium toward the inlet temperature sensor In1. The inlet temperature sensor In1 and the outlet temperature sensor Ex1 detect the temperature of the heat medium passing through their respective locations. The inlet temperature sensor In1 and the outlet temperature sensor Ex1 are, for example, thermistors.

[0021] The refrigeration cycle apparatus 100 has a refrigerant circuit Rc1 through which a refrigerant circulates. The refrigeration cycle apparatus 100 exchanges heat with a heat medium cycle circuit Cr1. More specifically, the refrigeration cycle apparatus 100 exchanges heat between the refrigerant circulating through the refrigerant circuit Rc1 and the heat medium circulating through the heat medium cycle circuit Cr1.

[0022] The refrigeration cycle apparatus 100 includes a four-way valve Fw1, a compressor C1, heat exchangers Ha1 and Hb1, a fan Fa1, and a pressure reducing device Ea1. The four-way valve Fw1, the compressor C1, the heat exchangers Ha1 and Hb1, and the pressure reducing device Ea1 are arranged on a refrigerant circuit Rc1. The refrigerant circuit Rc1 may correspond to the "first refrigerant circuit" in this disclosure. The refrigerant circulating within the refrigerant circuit Rc1 may correspond to the "first refrigerant" in this disclosure. The compressor C1 may correspond to the "first compressor" in this disclosure.

[0023] The compressor C1 compresses the refrigerant to change its state to a high-temperature, high-pressure gaseous state and sends it to the heat exchanger Ha1 via the four-way valve Fw1. The heat exchanger Ha1 exchanges heat between the air surrounding the heat exchanger Ha1 and the high-temperature, high-pressure gaseous refrigerant. The fan Fa1 blows air toward the heat exchanger Ha1 to promote heat exchange by the heat exchanger Ha1. The heat exchanger Ha1 condenses the high-temperature, high-pressure gaseous refrigerant, changing the state of the refrigerant in the refrigerant circuit Rc1 to a high-temperature, high-pressure gas-liquid mixed state.

[0024] The refrigerant that has changed into a gas-liquid mixed state is sent to the pressure reducing device Ea1 via the heat exchanger Ha1. The pressure reducing device Ea1 is a device that reduces the pressure of the refrigerant, such as a capillary tube or an expansion valve. The pressure reducing device Ea1 reduces the pressure of the refrigerant in a high-temperature, high-pressure gas-liquid mixed state, changing it into a low-temperature, low-pressure gas-liquid mixed state. The low-temperature, low-pressure gas-liquid mixed refrigerant reaches the heat exchanger Hb1, where it exchanges heat with the heat medium in the heat medium cycle circuit Cr1. This cools the heat medium circulating in the heat medium cycle circuit Cr1. The heat exchanger Hb1 may correspond to the "first heat exchanger" in this disclosure.

[0025] As a result of heat exchange in the heat exchanger Hb1, the refrigerant in the refrigerant circuit Rc1 changes from a low-temperature, low-pressure gas-liquid mixture to a low-temperature, low-pressure gaseous refrigerant. The refrigerant that has changed to a low-temperature, low-pressure gaseous state returns from the heat exchanger Hb1 to the compressor C1 via the four-way valve Fw1, and circulates within the refrigerant circuit Rc1.

[0026] 1 , the inlet temperature sensor In1 and the outlet temperature sensor Ex1 are disposed on both ends of the heat exchanger Hb1 in the heat medium cycle circuit Cr1. The inlet temperature sensor In1 detects the temperature of the heat medium flowing from the pump Pm1 into the heat exchanger Hb1. That is, the inlet temperature sensor In1 detects the temperature of the heat medium before heat exchange by the heat exchanger Hb1.

[0027] On the other hand, the outlet temperature sensor Ex1 detects the temperature of the heat medium flowing out of the heat exchanger Hb1. That is, the outlet temperature sensor Ex1 detects the temperature of the heat medium after heat exchange by the heat exchanger Hb1. Hereinafter, the detected value of the outlet temperature sensor Ex1 may be simply referred to as the "outlet temperature," and the detected value of the inlet temperature sensor In1 may be simply referred to as the "inlet temperature."

[0028] The control device 10 controls the compressor C1. The control device 10 is configured to be able to communicate with the compressor C1, the pump Pm1, the flow sensor PA1, the inlet temperature sensor In1, and the outlet temperature sensor Ex1. The control device 10 is able to acquire data indicating the drive frequency of the compressor C1, data indicating the output of the pump Pm1, data indicating the detected value of the inlet temperature sensor In1, data indicating the detected value of the outlet temperature sensor Ex1, and data indicating the detected value of the flow sensor PA1. Hereinafter, the drive frequency of the compressor C1 will be simply referred to as the "frequency of the compressor C1."

[0029] 2 is a block diagram showing the configuration of the control device 10. The control device 10 includes one or more processors 11, a communication interface (I / F) 12, a memory 13, and a storage 14. These elements are connected to each other via a bus (not shown) so as to be able to communicate data with each other. The control device 10 may be an information processing device dedicated to the refrigeration cycle apparatus 100, or may be realized using a general-purpose PC.

[0030] The communication interface 12 communicates with the compressor C1, the pump Pm1, the flow rate sensor PA1, the inlet temperature sensor In1, and the outlet temperature sensor Ex1 via a network. The communication interface 12 includes hardware necessary for wired communication and / or hardware necessary for wireless communication. Note that all or part of the processing of the communication interface 12 may be implemented by the processor 11.

[0031] The processor 11 is a processing entity (processing means) for controlling the circulation of the refrigerant. In this disclosure, the term "processor" refers to a processing circuit such as a central processing unit (CPU), a micro processing unit (MPU), or a graphics processing unit (GPU). The term "processor" encompasses a processing circuit that executes processing according to instruction codes written in a program, a processing circuit that integrates multiple functions such as a system on chip (SoC), a hardwired circuit, and the like.

[0032] The memory 13 is a volatile storage device (storage medium) accessible by the processor 11, and may be, for example, a dynamic random access memory (DRAM) or a static random access memory (SRAM). The storage 14 is a non-volatile storage device (storage medium) accessible by the processor 11, and may be, for example, a hard disk or a flash memory. The storage 14 may also be a storage medium that is detachable from the control device 10, such as an optical disk or a cartridge.

[0033] The storage 14 stores a program 15 to be executed by the processor 11. The processor 11 reads the program 15, expands it in the memory 13, and executes it. The program 15 is a program for controlling the circulation of the refrigerant. The program 15 stored in the memory 13 includes instruction codes for implementing the processes described later in FIGS. 3 and 4. The memory 13 is not limited to a volatile storage device (auxiliary storage device), and may also be a non-volatile storage device (main storage device). In this specification, the term "memory" encompasses at least volatile memory and non-volatile storage.

[0034] In a refrigeration cycle apparatus 100 including a control device 10 that controls the compressor C1, it is conceivable to feedback-control the frequency of the compressor C1 using a detection value of an outlet temperature sensor Ex1 that indicates the temperature of the heat medium after heat exchange. For example, the control device 10 reduces the frequency of the compressor C1 to prevent the heat medium from freezing due to an excessive decrease in temperature of the heat medium, thereby reducing the cooling capacity of the refrigeration cycle apparatus 100. On the other hand, if the temperature of the heat medium rises too much, the space in which the heat exchanger Hc1 is located will not be sufficiently cooled, so the control device 10 increases the frequency of the compressor C1 to increase the cooling capacity of the refrigeration cycle apparatus 100.

[0035] In this way, when feedback control of the frequency of the compressor C1 is performed using the detection value of the outlet temperature sensor Ex1, the overshoot that occurs in the waveform indicating the detection value of the outlet temperature sensor Ex1 may increase when maintaining the temperature of the heat medium at the target temperature. More specifically, when the temperature of the heat medium in the heat medium cycle circuit Cr1 suddenly drops due to an external factor or the like, the control device 10 reduces the frequency of the compressor C1 after receiving feedback that the temperature of the heat medium has started to drop.

[0036] However, the cooling capacity of the refrigeration cycle apparatus 100 is not affected by the change in the drive frequency of the compressor C1 immediately after the change. The cooling capacity of the refrigeration cycle apparatus 100 becomes the cooling capacity corresponding to the changed drive frequency of the compressor C1 after a predetermined time has elapsed since the frequency of the compressor C1 was changed. In other words, there is a time lag between when the drive frequency of the compressor C1 is changed and when the cooling capacity corresponding to the change is reached.

[0037] Therefore, when feedback control of the frequency of the compressor C1 in the refrigerant circuit Rc1 is performed based on the temperature of the heat medium in the heat medium cycle circuit Cr1, an overshoot may increase in the waveform of the detection value of the outlet temperature sensor Ex1. In this embodiment, the control device 10 suppresses the increase in overshoot in the waveform of the detection value of the outlet temperature sensor Ex1 by executing the processes described in Figures 3 and 4.

[0038] <Processing Procedure> Fig. 3 is a flowchart showing a data set acquisition process in a stable state. The control device 10 executes the program 15 to realize the processing shown in Fig. 3.

[0039] The control device 10 acquires the frequency of the compressor C1 (step S101). The control device 10 acquires the flow rate (step S102). FIG. 4 is a flowchart for explaining the flow rate acquisition process in the first embodiment. As shown in FIG. 4, the control device 10 in the first embodiment acquires the detection value of the flow rate sensor PA1 (step S201). As a result, the control device 10 in the first embodiment can acquire the flow rate of the heat medium in the heat medium cycle circuit Cr1 using the flow rate sensor PA1.

[0040] 3, the control device 10 acquires the outlet temperature and the inlet temperature (step S103). That is, the control device 10 acquires the detected values ​​of the outlet temperature sensor Ex1 and the inlet temperature sensor In1. The control device 10 acquires the current time using a timer (not shown) (step S104).

[0041] In this way, the control device 10 acquires data indicating the frequency of the compressor C1, data indicating the flow rate of the heat medium, and data indicating the outlet temperature and inlet temperature in steps S101 to S103, and stores time data indicating the time when these data were acquired in step S104. In this embodiment, the data indicating the frequency of the compressor C1, data indicating the flow rate of the heat medium, and data indicating the outlet temperature and inlet temperature are referred to as a "data set."

[0042] The control device 10 determines whether a specified period has elapsed since the time the data set was last acquired (step S105). The specified period may be, for example, one minute, five minutes, or ten minutes. If the specified period has not elapsed (NO in step S105), the control device 10 repeats the process of step S105. That is, the control device 10 waits until the specified period has elapsed since the time the data set was last acquired.

[0043] If the specified period has elapsed (YES in step S105), the control device 10 acquires the frequency of the compressor C1 (step S106). The control device 10 acquires the flow rate (step S107). In step S107, the control device 10 executes the process of the flowchart shown in FIG. 4, similar to step S102. The control device 10 acquires the outlet temperature and the inlet temperature (step S108). The control device 10 acquires the current time (step S109). That is, the control device 10 acquires a new data set in steps S106 to S108, and saves time data indicating the time when the new data set was acquired in step S109.

[0044] Next, the control device 10 compares the data set acquired in steps S106 to S108 with the previously acquired data set to determine whether the rate of change of each data is within a predetermined range (step S110). The rate of change is the percentage change from the previous value of each data set. A smaller rate of change indicates that the value of each data set has not changed between before and after the specified period has elapsed. "Within the predetermined range" may be, for example, within 1%, 3%, 5%, etc. In step S110, the control device 10 determines whether the rate of change of the data indicating the frequency of the compressor C1 is within a predetermined range, the rate of change of the data indicating the flow rate of the heat medium is within a predetermined range, and the rate of change of the data indicating the outlet temperature and the inlet temperature is within a predetermined range.

[0045] If the fluctuation rate of each data is within a predetermined range (YES in step S110), the control device 10 saves the latest data set acquired in steps S106 to S108 as a stable data set (step S111). In step S111, if data has already been saved as a stable data set, the control device 10 overwrites the latest data set acquired in steps S106 to S108. The control device 10 then proceeds to step S113.

[0046] On the other hand, if the fluctuation rate of each data is outside the predetermined range (NO in step S110), the control device 10 initializes the stable data set (step S112). That is, the control device 10 discards the values ​​of the data set saved as the stable data set. Thereafter, the control device 10 proceeds to step S113.

[0047] The control device 10 determines whether or not an end command for the stable data set acquisition process has been received (step S113). The end command for the stable data set acquisition process is generated, for example, when the power supply to the control device 10 is cut off. If the end command for the stable data set acquisition process has not been received (NO in step S113), the control device 10 returns the process to step S105 and repeats the stable data set update process. If the end command for the stable data set acquisition process has been received (YES in step S113), the control device 10 ends the process.

[0048] Fig. 5 is a flowchart showing the process of predicting the convergence value of the outlet temperature in this embodiment. As in Fig. 4, the control device 10 realizes the process shown in Fig. 5 by executing the program 15. The control device 10 starts the process of the flowchart in Fig. 5, for example, in step S111 based on the stable data set being updated.

[0049] The control device 10 predicts the convergence value of the outlet temperature based on the stable data set (step S301). That is, the control device 10 predicts the convergence value of the outlet temperature using data indicating the frequency of the compressor C1, data indicating the flow rate of the heat medium, and data indicating the outlet temperature and inlet temperature, which are included in the stable data set. The outlet temperature is uniquely determined by the frequency of the compressor C1 and the flow rate of the heat medium. For example, a decrease in the flow rate of the heat medium also reduces the outlet temperature. As the flow rate of the heat medium decreases, the period during which the heat medium passes through the heat exchanger Hb1 becomes longer. That is, the period during which the heat medium is cooled by the refrigeration cycle apparatus 100 becomes longer, and the outlet temperature decreases.

[0050] The temperature difference between the outlet temperature and the inlet temperature is proportional to the frequency of the compressor C1. The temperature difference between the outlet temperature and the inlet temperature is inversely proportional to the flow rate of the heat medium. When the flow rate of the heat medium suddenly decreases, the outlet temperature does not decrease immediately after the flow rate of the heat medium decreases, but rather there is a time lag between the decrease in the flow rate of the heat medium and the change in the outlet temperature. By using the proportional relationship between the temperature difference between the outlet temperature and the inlet temperature and the frequency of the compressor C1 and the inversely proportional relationship between the temperature difference between the outlet temperature and the inlet temperature and the flow rate of the heat medium, the control device 10 can predict an outlet temperature (convergence value) that is uniquely determined based on the decreased flow rate of the heat medium and the frequency of the compressor C1, even immediately after the flow rate of the heat medium decreases.

[0051] The control device 10 determines whether the convergence value of the outlet temperature predicted in step S301 is less than a specified threshold value (step S302). The specified threshold value is, for example, a temperature that is higher than the freezing point of the heat medium by a predetermined temperature. For example, if the heat medium is water, the specified threshold value is 4°C. Alternatively, the specified threshold value is determined based on the target temperature of the air temperature in the space where the load-side unit NU1 is located. In this case, the specified threshold value may be, for example, 6°C, 8°C, or 10°C.

[0052] If the convergence value of the outlet temperature is less than the specified threshold value (YES in step S302), the control device 10 reduces the frequency of the compressor C1 (step S303) and ends the process. For example, the control device 10 reduces the frequency of the compressor C1 to the minimum within a range that does not stop the refrigeration cycle apparatus 100. In this way, in the present embodiment, the frequency of the compressor C1 is reduced in advance based on a decrease in the flow rate of the heat medium before the temperature of the heat medium starts to decrease.

[0053] On the other hand, if the convergence value of the outlet temperature is equal to or greater than the specified threshold value (NO in step S302), the control device 10 controls the frequency of the compressor C1 based on the outlet temperature included in the stable data set (step S304), and ends the process. That is, the control device 10 feedback-controls the frequency of the compressor C1 using the outlet temperature.

[0054] <Transition of Outlet Temperature> Fig. 6 is a diagram for explaining the transition of the outlet temperature. From the top of Fig. 6, a waveform showing the transition of the heat medium flow rate, a waveform showing the transition of the inlet / outlet temperature and the frequency of the compressor C1 in the comparative example, and a waveform showing the transition of the inlet / outlet temperature and the frequency of the compressor C1 in the first embodiment are shown in this order. The horizontal axis in all the waveform diagrams indicates a common time.

[0055] The refrigeration cycle device of the comparative example does not predict the convergence value of the outlet temperature shown in Figure 5 and control the frequency of the compressor C1 based on the predicted convergence value, but always controls the frequency of the compressor C1 based on the value of the outlet temperature sensor Ex1.

[0056] Line Ln1 indicates the flow rate of the heat medium. In the first embodiment, line Ln1 is the detection value of the flow sensor PA1. Line Ln2 indicates the inlet temperature in the comparative example. Line Ln3 indicates the outlet temperature in the comparative example. Line Ln4 indicates the frequency of the compressor C1 in the comparative example. Line Ln5 indicates the inlet temperature in the first embodiment. Line Ln6 indicates the outlet temperature in the first embodiment. Line Ln7 indicates the convergence value of the outlet temperature predicted in the first embodiment. Line Ln8 indicates the frequency of the compressor C1 in the first embodiment.

[0057] In the refrigeration cycle apparatus of the comparative example, the control device 10 receives feedback of the outlet temperature indicated by line Ln3 and starts reducing the frequency of the compressor C1 at timing Tm2. As shown in FIG. 6 , the decrease in line Ln4 starts at timing Tm2. On the other hand, in the refrigeration cycle apparatus 100 of embodiment 1, the control device 10 starts reducing the frequency of the compressor C1 at timing Tm1 based on the convergence value of the predicted outlet temperature becoming less than threshold value T1. As shown in FIG. 6 , the decrease in line Ln8 starts at timing Tm1.

[0058] As described above, in the present embodiment, the frequency of the compressor C1 can be reduced earlier than in the comparative example. That is, in the present embodiment, the frequency of the compressor C1 is reduced in advance based on a decrease in the flow rate of the heat medium before the outlet temperature indicated by line Ln6 starts to decrease. As a result, as shown in FIG. 6 , the overshoot occurring on line Ln6 in the present embodiment is smaller than that on line Ln3 in the comparative example. That is, in the refrigeration cycle apparatus 100 of the present embodiment, an increase in the overshoot occurring during control of the temperature of the heat medium in the heat medium cycle circuit Cr1 can be suppressed. By suppressing the increase in the overshoot, for example, when the heat medium is water and the specified threshold is set based on the freezing point of water, freezing of the heat medium in the heat medium cycle circuit Cr1 can be suppressed.

[0059] Embodiment 2 In the first embodiment, a configuration in which the flow rate of the heat medium is acquired using the flow rate sensor PA1 has been described. In the second embodiment, a configuration in which the flow rate of the heat medium is estimated using the differential pressure in the heat medium cycle circuit Cr1 will be described. Note that in the second embodiment, the description of the configuration that overlaps with the air conditioning system 1000 of the first embodiment will not be repeated.

[0060] FIG. 7 is a diagram illustrating an air conditioning system 1000A according to a second embodiment. In the second embodiment, the air conditioning system 1000A has a bypass path Bp1 in a heat medium cycle circuit Cr1. A flow rate adjustment valve Ev1 capable of adjusting the flow rate and a differential pressure sensor PS1 are arranged in the bypass path Bp1. The differential pressure sensor PS1 is a sensor that detects the differential pressure between the pressure of the heat medium at one end of the flow rate adjustment valve Ev1 and the pressure of the heat medium at the other end of the flow rate adjustment valve Ev1. Note that the one end of the flow rate adjustment valve Ev1 may correspond to the "first position" in this disclosure. The other end of the flow rate adjustment valve Ev1 may correspond to the "second position" in this disclosure.

[0061] The control device 10 acquires the detection value of the differential pressure sensor PS1. The control device 10 controls the pump Pm1 and the flow rate control valve Ev1 so that the detection value of the differential pressure sensor PS1 becomes a target value. For example, when the detection value of the differential pressure sensor PS1 is smaller than the target value, the control device 10 reduces the opening of the flow rate control valve Ev1. Furthermore, when the detection value of the differential pressure sensor PS1 is larger than the target value, the control device 10 reduces the output of the pump Pm1.

[0062] When the detection value of the differential pressure sensor PS1 is large, a pressure difference occurs in the heat medium in the heat medium cycle circuit Cr1, and the flow rate of the heat medium increases. In the refrigeration cycle apparatus 100A, which performs control based on such differential pressure, the detection value of the differential pressure sensor PS1 can be used to estimate the flow rate in the heat medium cycle circuit Cr1. For example, the storage 14 of the control device 10 stores a table showing the relationship between the detection value of the differential pressure sensor PS1 obtained through experiments, simulations, etc. and the flow rate of the heat medium. The control device 10 uses this table to estimate the flow rate of the heat medium based on the detection value of the differential pressure sensor PS1.

[0063] Fig. 8 is a flowchart illustrating a flow rate acquisition process according to the second embodiment. In the second embodiment, the control device 10 executes the process of the flowchart shown in Fig. 8 in steps S102 and S107 of Fig. 3. The control device 10 acquires a detection value of the differential pressure sensor PS1 (step S201A). Thereafter, the control device 10 estimates the flow rate of the heat medium based on the detection value of the differential pressure sensor PS1 (step S202A).

[0064] That is, the control device 10 reads the relationship between the detection value of the differential pressure sensor PS1 and the heat medium flow rate from, for example, a table stored in the storage 14, and estimates the current heat medium flow rate. As such, in the second embodiment, the control device 10 can obtain the heat medium flow rate using the detection value of the differential pressure sensor PS1. Also, in the second embodiment, as in the first embodiment, the frequency of the compressor C1 can be reduced more quickly than in the comparative example, thereby suppressing an increase in overshoot that occurs when controlling the temperature of the heat medium in the heat medium cycle circuit Cr1.

[0065] Embodiment 3 In the first embodiment, a configuration in which the air conditioning system 1000 has one refrigerant circuit Rc1 has been described. In the third embodiment, a configuration in which the air conditioning system 1000 has a plurality of refrigerant circuits will be described. Note that in the third embodiment, the description of the configuration that overlaps with the air conditioning system 1000 of the first embodiment will not be repeated.

[0066] Fig. 9 is a diagram illustrating an air conditioning system 1000B according to a third embodiment. In the air conditioning system 1000B according to the third embodiment, a heat medium cycle circuit Cr1B has paths Pp1, Pp2, and Pp3 branching in parallel on the heat source side. As shown in Fig. 9, refrigerant circuits Rc1, Rc2, and Rc3 are arranged in the paths Pp1, Pp2, and Pp3, respectively. The refrigerant circuits Rc1, Rc2, and Rc3 cool the heat medium passing through the paths Pp1, Pp2, and Pp3, respectively.

[0067] The heat source side unit HS1 in the third embodiment has, as a configuration for cooling the heat medium passing through the path Pp2, a pump Pm2, an inlet temperature sensor In2, an outlet temperature sensor Ex2, and a control device 20. The heat source side unit HS1 also has, as a configuration for cooling the heat medium passing through the path Pp3, a pump Pm3, an inlet temperature sensor In3, an outlet temperature sensor Ex3, and a control device 30.

[0068] The refrigeration cycle apparatus 100B in the third embodiment includes a four-way valve Fw2, a compressor C2, heat exchangers Ha2 and Hb2, a fan Fa2, and a pressure reduction device Ea2 as components for cooling the heat medium passing through a path Pp2. The refrigeration cycle apparatus 100B further includes a four-way valve Fw3, a compressor C3, heat exchangers Ha3 and Hb3, a fan Fa3, and a pressure reduction device Ea3 as components for cooling the heat medium passing through a path Pp3.

[0069] The refrigerant circuit Rc2 may correspond to the "second refrigerant circuit" in this disclosure. The refrigerant circulating in the refrigerant circuit Rc2 may correspond to the "second refrigerant" in this disclosure. The compressor C2 may correspond to the "second compressor" in this disclosure.

[0070] In the third embodiment, an integrated control device 50 is provided that integrally controls the control devices 10, 20, and 30. The integrated control device 50 acquires the detected value of the flow sensor PA1. The integrated control device 50 transmits the detected value of the flow sensor PA1 to each of the control devices 10, 20, and 30. Each of the control devices 10, 20, and 30 predicts a convergence value of the outlet temperature from the detected value of the flow sensor PA1 and a data set acquired from the corresponding configuration. Each of the control devices 10, 20, and 30 controls the frequency of each of the compressors C1, C2, and C3 based on the predicted convergence value of the outlet temperature.

[0071] In the third embodiment, the heat medium cycle circuit Cr1B has paths Pp4 and Pp5 branching in parallel on the load side. As shown in Fig. 9, the load side units NU1 and NU2 are arranged on the paths Pp4 and Pp5, respectively.

[0072] The load side unit NU2 in the third embodiment has a fan Fb2, a heat exchanger Hc2, and a flow rate adjustment valve Eb2. The load side units NU1 and NU2 each cool the space in which they are located. The room in which the load side unit NU1 is located may be different from the room in which the load side unit NU2 is located. In the third embodiment, as in the first embodiment, the frequencies of the compressors C1, C2, and C3 can be reduced more quickly than in the comparative example, thereby suppressing an increase in overshoot that occurs when controlling the temperature of the heat medium in the heat medium cycle circuit Cr1B.

[0073] <Modification> In the above example, in step S303, the control device 10 minimizes the frequency of the compressor C1 without stopping the refrigeration cycle apparatus 100. However, when reducing the frequency of the compressor C1, the control device 10 may reduce the frequency of the compressor C1 in accordance with the ratio of the temperature difference between the predicted outlet temperature and the current inlet temperature to the temperature difference between the target outlet temperature and the current inlet temperature. Alternatively, the control device 10 may perform proportional integral differential (PID) control to control the frequency of the compressor C1 using a convergence value of the predicted outlet temperature as a controlled variable and a difference between the target outlet temperature and the convergence value of the predicted outlet temperature as a control deviation.

[0074] In the above example, in the second embodiment, the differential pressure sensor PS1 is disposed on the bypass path Bp1. However, the location of the differential pressure sensor PS1 is not limited to the bypass path Bp1. For example, the differential pressure sensor PS1 may be a sensor that detects the differential pressure across the heat exchanger Hb1 or a sensor that detects the differential pressure across the pump Pm1. When the differential pressure sensor PS1 detects the differential pressure across the heat exchanger Hb1, the control device 10 estimates the heat medium flow rate using a coefficient that indicates the relationship between the detected value of the differential pressure sensor PS1 and the heat medium flow rate. When the differential pressure sensor PS1 detects the differential pressure across the pump Pm1, the control device 10 may estimate the heat medium flow rate using the output of the pump Pm1, the detected value of the differential pressure sensor PS1, and the pump performance curve.

[0075] In the above example, the heat medium is cooled in the heat exchanger Hb1. That is, the air conditioning system 1000 is in cooling operation. However, the heat medium may be heated in the heat exchanger Hb1. That is, the four-way valve Fw1 may be rotated and the air conditioning system 1000 may be in heating operation. In this case, the air conditioning system 1000 may be applied to, for example, a floor heating system.

[0076] In the above example, it has been described that the trigger for starting the processing of the flowchart in Fig. 5 is the update of the stable data set. However, the control device 10 may also start the processing of the flowchart in Fig. 5 based on, for example, the lapse of a predetermined period of time.

[0077] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0078] 10, 20, 30 control device, 11 processor, 12 communication interface, 13 memory, 14 storage, 15 program, 50 integrated control device, 100, 100A, 100B refrigeration cycle device, 1000, 1000A, 1000B air conditioning system, Bp1 bypass route, C1 to C3 compressor, Cr1, Cr1B heat medium cycle circuit, Ea1 to Ea3 pressure reducing device, Eb1, Eb2, Ev1 flow rate control valve, Ex1 to Ex3 outlet temperature sensor, Fa1 to Fa3, Fb1, Fb2 fan, Fw1 to Fw3 four-way valve, HS1 heat source side unit, Ha1 to Ha3, Hb1 to Hb3, Hc1, Hc2 heat exchanger, In1 to In3 inlet temperature sensor, Ln1 to Ln8 wire, NU1, NU2 Load side unit, PA1 flow sensor, PS1 differential pressure sensor, Pm1 to Pm3 pumps, Pp1 to Pp5 paths, Rc1 to Rc3 refrigerant circuits, T1 threshold, Tm1, Tm2 timing.

Claims

1. A refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium, comprising: a first compressor that can compress a first refrigerant circulating in a first refrigerant circuit; a first heat exchanger that exchanges heat between the first refrigerant and the heat medium in the heat medium cycle circuit; and a control device that controls the first compressor, wherein the control device obtains flow rate information that indicates the flow rate of the heat medium circulating in the heat medium cycle circuit, and controls the frequency of the first compressor based on the flow rate information.

2. The refrigeration cycle device according to claim 1, wherein the control device predicts a convergence temperature of the heat medium based on the flow rate information and the frequency of the first compressor, and controls the frequency of the first compressor based on the convergence temperature of the heat medium.

3. A refrigeration cycle device as described in claim 2, further comprising an outlet temperature sensor that measures the temperature of the heat medium flowing out of the first heat exchanger, wherein the control device reduces the frequency of the first compressor when the convergence value of the temperature of the heat medium is less than a specified threshold, and controls the frequency of the first compressor based on the detection value of the outlet temperature sensor when the convergence value of the temperature of the heat medium is equal to or greater than the specified threshold.

4. The refrigeration cycle device according to claim 3, wherein the specified threshold value is determined according to the freezing point of the heat medium.

5. A refrigeration cycle device according to any one of claims 1 to 4, further comprising a flow rate sensor disposed in the heat medium cycle circuit and detecting a flow rate of the heat medium, wherein the control device acquires the detected value of the flow rate sensor as the flow rate information.

6. The refrigeration cycle device according to any one of claims 1 to 4, further comprising a differential pressure sensor disposed in the heat medium cycle circuit and detecting a differential pressure between a first pressure of the heat medium at a first position and a second pressure of the heat medium at a second position, wherein the control device estimates the flow rate information based on the differential pressure.

7. A refrigeration cycle device according to any one of claims 1 to 6, further comprising: a second compressor that compresses a second refrigerant circulating in a second refrigerant circuit different from the first refrigerant circuit; and a second heat exchanger that exchanges heat between the second refrigerant and the heat medium, wherein the control device acquires flow rate information that indicates the flow rate of the heat medium in the heat medium cycle circuit, predicts a convergence value of the temperature of the heat medium based on the flow rate information and the frequency of the second compressor, and controls the frequency of the second compressor based on the convergence value of the temperature of the heat medium.

8. A control device that controls the circulation of refrigerant in a refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium, wherein the refrigeration cycle device comprises: a first compressor that can compress a first refrigerant circulating in a first refrigerant circuit; and a heat exchanger that exchanges heat between the first refrigerant and the heat medium in the heat medium cycle circuit, the control device comprising: a storage device; and a control unit that controls the first compressor, wherein the control unit acquires flow rate information that indicates the flow rate of the heat medium in the heat medium cycle circuit, and controls the frequency of the first compressor based on the flow rate information.

9. A control method for controlling the circulation of refrigerant in a refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium, wherein the refrigeration cycle device comprises: a first compressor that can compress a first refrigerant circulating in a first refrigerant circuit; and a heat exchanger that exchanges heat between the first refrigerant and the heat medium in the heat medium cycle circuit, and the control method includes, as processing to be executed by a computer, a step of acquiring flow rate information that indicates the flow rate of the heat medium in the heat medium cycle circuit; and a step of controlling the frequency of the first compressor based on the flow rate information.

10. A control program for controlling the circulation of refrigerant in a refrigeration cycle device that exchanges heat with a heat medium cycle circuit that circulates a heat medium, wherein the refrigeration cycle device comprises: a first compressor capable of compressing a first refrigerant circulating in a first refrigerant circuit; and a heat exchanger that exchanges heat between the first refrigerant and the heat medium in the heat medium cycle circuit, the control program causing a computer to execute the steps of: acquiring flow rate information indicating the flow rate of the heat medium in the heat medium cycle circuit; and controlling the frequency of the first compressor based on the flow rate information.

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