Refrigeration cycle device

Abstract

This refrigeration cycle device comprises: a heat source circuit that is equipped with a compressor, a heat source side heat exchanger, a decompression device, and an inter-heat medium heat exchanger and circulates a refrigerant therethrough; a load circuit that is equipped with an inter-heat medium heat exchanger, a load-side heat exchanger, and a pump and circulates a heat medium therethrough; and a control device. The inter-heat medium heat exchanger exchanges heat between the refrigerant and the heat medium. If the operating time after the compressor thermo-on is shorter than reference time, the control device sets the upper limit frequency of the compressor to be lower than the currently set upper limit frequency.

Description

Technical Field

[0001] The present disclosure relates to a refrigeration cycle device including a heat source circuit and a load circuit.

Background Art

[0002] Conventionally, for a large-capacity air-conditioning load such as air-conditioning of a large-scale building, a refrigeration cycle device that performs air-conditioning by supplying a heat medium cooled or heated by a heat source machine to the load is known. Such a refrigeration cycle device includes a heat source circuit in which a refrigerant circulates and a load circuit in which a heat medium different from the refrigerant circulates. Further, the heat source circuit is configured by connecting a compressor, a heat source-side heat exchanger, a heat medium-to-heat medium heat exchanger, and a throttling device with piping. The load circuit is configured by connecting a pump, a heat medium-to-heat medium heat exchanger, and a load-side heat exchanger with piping. And heat exchange between the refrigerant and the heat medium is performed by the heat medium-to-heat medium heat exchanger.

[0003] In a refrigeration cycle device including a heat source circuit and a load circuit, in order to reduce power consumption, Patent Document 1 proposes detecting a physical quantity related to the amount of heat involved in heat exchange of the load-side heat exchanger and controlling the operation of the heat source circuit using the data related to the detection.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the control described in Patent Document 1 requires detecting the physical quantity of the load-side heat exchanger provided in the indoor unit, and thus cannot be implemented when the physical quantity of the load-side heat exchanger cannot be detected.

[0006] The present disclosure is for solving the above problems, and an object thereof is to provide a refrigeration cycle device capable of reducing power consumption without detecting a physical quantity of a load-side device.

Means for Solving the Problems

[0007] The refrigeration cycle device according to the present disclosure includes a compressor, a heat source side heat exchanger, a decompression device, and a heat medium heat exchanger, a heat source circuit in which a refrigerant circulates, a heat medium heat exchanger, a load side heat exchanger, and a pump, a load circuit in which a heat medium circulates, a control device, an outlet temperature sensor that measures the outlet temperature of the heat medium at the outlet of the heat medium heat exchanger, and an inlet temperature sensor that measures the inlet temperature of the heat medium at the inlet of the heat medium heat exchanger. The heat medium heat exchanger exchanges heat between the refrigerant and the heat medium, and the control device Operation Rotation time During operation before the compressor stops with the thermo off, the operation time when it is shorter than a reference time, lowers the upper limit frequency of the compressor below the currently set upper limit frequency. The control device calculates the cooling load during the previous operation based on the outlet temperature and the inlet temperature, When the operation time is shorter than the reference time, and changes the upper limit frequency of the compressor based on the cooling load and the operation time.

Advantages of the Invention

[0008] According to the refrigeration cycle device of the present disclosure, when the operation time after the compressor thermally turns on is shorter than the reference time, by lowering the upper limit frequency of the compressor below the currently set upper limit frequency, it is possible to reduce power consumption without detecting the physical quantity of the load-side device.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described with reference to the drawings. In each figure, those with the same reference numerals are the same or corresponding ones, which is common throughout the entire specification. Also, the forms of the constituent elements shown throughout the specification are merely examples and are not limited to these descriptions. Furthermore, in the following drawings, the relationship of the sizes of each constituent member may be different from the actual ones.

[0011] Embodiment 1. The refrigeration cycle device 100 according to Embodiment 1 will be described. In this embodiment, a case where the refrigeration cycle device 100 is used as a cooling device for cooling a space such as a room will be described as an example. FIG. 1 is a schematic configuration diagram of the refrigeration cycle device 100 according to Embodiment 1. As shown in FIG. 1, the refrigeration cycle device 100 of this embodiment includes a heat source circuit 1, a load circuit 2, and a control device 5.

[0012] The heat source circuit 1 is a circuit through which a refrigerant circulates, and the load circuit 2 is a circuit through which a heat medium different from the refrigerant circulating in the heat source circuit 1 circulates. The heat source circuit 1 and the load circuit 2 commonly include a heat medium heat exchanger 14, and heat exchange is performed between the refrigerant circulating in the heat source circuit 1 and the heat medium circulating in the load circuit 2 by the heat medium heat exchanger 14.

[0013] The refrigerant circulating in the heat source circuit 1 is, for example, a single refrigerant such as R-22 or R-134a, a pseudo-azeotropic mixed refrigerant such as R-410A or R-404A, or a zeotropic mixed refrigerant such as R-407C. Further, the refrigerant may be a refrigerant or a mixture thereof having a relatively small global warming potential value such as CF3CF=CH2, which contains a double bond in its chemical formula, or a natural refrigerant such as CO2 or propane. Further, the heat medium circulating in the load circuit 2 is, for example, brine (antifreeze), water, a mixture of brine and water, or a mixture of water and an additive having a high anticorrosion effect.

[0014] The heat source circuit 1 includes a compressor 11, a heat source side heat exchanger 12, a decompression device 13, and a heat medium heat exchanger 14. The compressor 11, the heat source side heat exchanger 12, the decompression device 13, and the heat medium heat exchanger 14 are connected by piping in this order.

[0015] The compressor 11 is, for example, an inverter type compressor capable of capacity control. The compressor 11 sucks in the refrigerant, compresses it to a high temperature and high pressure state, and discharges it to circulate the refrigerant in the heat source circuit 1.

[0016] The heat source side heat exchanger 12 is, for example, a fin-tube type heat exchanger. In the present embodiment, the heat source side heat exchanger 12 functions as a condenser. The heat source side heat exchanger 12 performs heat exchange between air and the refrigerant, condensing and liquefying the refrigerant. The refrigeration cycle device 100 includes a first fan 15 for supplying air to the heat source side heat exchanger 12. The first fan 15 is, for example, a propeller fan or a cross-flow fan whose air volume can be adjusted. Note that the heat source side heat exchanger 12 may be, for example, a plate type heat exchanger that performs heat exchange between water or brine and the refrigerant. In this case, the first fan 15 may be omitted.

[0017] The pressure reducing device 13 is, for example, an electronic expansion valve whose opening can be controlled. The pressure reducing device 13 is connected to the heat source side heat exchanger 12, reducing the pressure and expanding the refrigerant flowing out from the heat source side heat exchanger 12. Note that the pressure reducing device 13 may be a capillary tube or a thermostatic expansion valve.

[0018] The heat medium heat exchanger 14 is, for example, a plate type heat exchanger. The heat medium heat exchanger 14 includes a refrigerant flow path 141 connected to the heat source circuit 1 and a heat medium flow path 142 connected to the load circuit 2, and performs heat exchange between the refrigerant flowing through the refrigerant flow path 141 and the heat medium flowing through the heat medium flow path 142. The refrigerant flow path 141 of the heat medium heat exchanger 14 functions as an evaporator, evaporating and gasifying the refrigerant. Also, in the heat medium flow path 142 of the heat medium heat exchanger 14, the heat medium is cooled by the refrigerant.

[0019] The load circuit 2 includes a pump 21, a heat medium heat exchanger 14, and a load side heat exchanger 22. The pump 21, the heat medium heat exchanger 14, and the load side heat exchanger 22 are connected by piping in this order.

[0020] The pump 21 circulates the heat medium in the load circuit 2. The pump 21 is an inverter type pump whose discharge flow rate can be adjusted. The operating frequency of the pump 21 is controlled by the control device 5.

[0021] The load-side heat exchanger 22 is, for example, a fin-tube type heat exchanger. The load-side heat exchanger 22 performs heat exchange between air and the heat medium. The refrigeration cycle apparatus 100 includes a second fan 25 for supplying air to the load-side heat exchanger 22. The second fan 25 is, for example, a propeller fan or a cross-flow fan whose air volume can be adjusted. Note that the load-side heat exchanger 22 may be, for example, a plate type heat exchanger. In this case, the second fan 25 may be omitted.

[0022] Further, the refrigeration cycle apparatus 100 includes an inlet temperature sensor 61 that measures the inlet temperature Tmi of the heat medium at the inlet of the heat medium-to-heat medium heat exchanger 14 in the load circuit 2. The inlet temperature sensor 61 is, for example, a thermistor, and is provided in a pipe connecting the heat medium flow path 142 of the heat medium-to-heat medium heat exchanger 14 and the pump 21. The inlet temperature Tmi measured by the inlet temperature sensor 61 is transmitted to the control device 5.

[0023] Note that the refrigeration cycle apparatus 100 may further include various sensors (not shown) such as an outside air temperature sensor that detects the outside air temperature, an indoor temperature sensor that detects the indoor temperature, and a sensor that detects the temperature or pressure of the refrigerant at an arbitrary location in the heat source circuit 1 and the load circuit 2.

[0024] The control device 5 controls the overall operation of the refrigeration cycle apparatus 100. The control device 5 is composed of a processing device including a memory that stores data and programs necessary for control and a CPU that executes the programs, or dedicated hardware such as an ASIC or an FPGA, or both. The control device 5 controls the operating frequencies of the compressor 11 and the pump 21, the opening degree of the decompression device 13, and the rotation speeds of the first fan 15 and the second fan 25 based on the information received from various sensors and the operation contents such as the set temperature instructed by the user.

[0025] In this embodiment, the heat source circuit 1, the pump 21 of the load circuit 2, the heat medium interchanger 14, the inlet temperature sensor 61, and the control device 5 are provided in a heat source machine installed outside the air-conditioned space. Further, the load-side heat exchanger 22 and the second fan 25 of the load circuit 2 are provided in an indoor unit installed in the indoor space which is the air-conditioned space. Note that the control device 5 may be provided in the indoor unit or may be provided separately from the heat source machine and the indoor unit.

[0026] The operation of the refrigeration cycle device 100 of this embodiment will be described. First, the operation of the heat source circuit 1 will be described. When the start of operation of the refrigeration cycle device 100 is instructed, the compressor 11 of the heat source circuit 1 sucks in the refrigerant, compresses it to a high temperature and high pressure state, and discharges it. The refrigerant discharged by the compressor 11 flows into the heat source-side heat exchanger 12. The heat source-side heat exchanger 12 performs heat exchange between the air supplied from the first fan 15 and the refrigerant, and condenses and liquefies the refrigerant.

[0027] The refrigerant condensed and liquefied by the heat source-side heat exchanger 12 passes through the decompression device 13. The decompression device 13 decompresses the condensed and liquefied refrigerant. The refrigerant decompressed by the decompression device 13 flows into the refrigerant flow path 141 of the heat medium interchanger 14. The refrigerant flowing into the refrigerant flow path 141 exchanges heat with the heat medium flowing through the heat medium flow path 142 of the heat medium interchanger 14 and evaporates and gasifies. The refrigerant evaporated and gasified by the heat medium interchanger 14 is sucked into the compressor 11 again.

[0028] Next, the operation of the load circuit 2 will be described. The pump 21 of the load circuit 2 supplies the heat medium to the heat medium interchanger 14. The heat medium flowing into the heat medium flow path 142 exchanges heat with the refrigerant flowing through the refrigerant flow path 141 of the heat medium interchanger 14 and is cooled.

[0029] The heat medium cooled by the heat medium interchanger 14 flows into the load-side heat exchanger 22. The load-side heat exchanger 22 performs heat exchange between the air supplied from the second fan 25 and the heat medium. At this time, the heat medium absorbs heat from the air, thereby cooling the room. The heat medium flowing out of the load-side heat exchanger 22 is supplied to the heat medium interchanger 14 again by the pump 21.

[0030] Next, the control of the compressor 11 by the control device 5 will be described. The control device 5 of the present embodiment changes the upper limit frequency Fmax (Hz), which is the upper limit of the operating frequency F (Hz) of the compressor 11, based on the operating time t1 of the compressor 11 during the previous operation and the stop time t2 at the time of thermo-off. FIG. 2 is a diagram showing an example of the time change of the inlet temperature Tmi of the heat medium and the operating frequency of the compressor 11.

[0031] As shown in FIG. 2, during the operation of the compressor 11, the inlet temperature Tmi of the heat medium decreases. When the inlet temperature Tmi becomes lower than a preset thermo-off temperature, the compressor 11 is stopped and thermo-off occurs. In thermo-off, the compressor 11, the first fan 15, and the second fan 25 are stopped, but the pump 21 continues to operate, and it is assumed that the heat medium circulates in the load circuit 2. Then, when the inlet temperature Tmi of the heat medium rises at the time of thermo-off and exceeds a preset thermo-on temperature, thermo-on occurs, and the operation of the compressor 111, the first fan 15, and the second fan 25 is restarted. Note that the temperature of the heat medium serving as the criterion for thermo-off and thermo-on is not limited to the inlet temperature Tmi, and the temperature of the heat medium at the outlet of the heat medium heat exchanger 14 may be used. The thermo-on temperature and the thermo-off temperature may be the same or different.

[0032] Here, the cooling capacity (Q1 - Q2) during operation is represented by the following formula (1). Q1 - Q2 = ρ × Cp × V × ΔTmi / t1 ···(1)

[0033] Also, the cooling capacity Q2 during stop is represented by the following formula (2). Q2 = ρ × Cp × V × ΔTmi / t2 ···(2) In formulas (1) and (2), Q1 is the cooling capacity of the compressor 11, ρ is the density of the heat medium (kg / m 3 ), V is the volume of the heat medium (m 3) Cp is the specific heat of the heat medium (kj / kgK), and ΔTmi is the change in the inlet temperature Tmi (K). Also, t1 is the operating time of the compressor 11 during the thermo-off period (sec), and t2 is the stopping time of the compressor 11 at the time of thermo-off (sec).

[0034] From equations (1) and (2), the cooling capacity Q2 at the time of stop can be expressed by the following equation (3). Q1 - Q2 = Q2 × t2 / t1 Q1 = Q2 × (t1 + t2) / t1 Q2 = Q1 × t1 / (t1 + t2) ··· (3)

[0035] Based on equation (3), the control device 5 changes the upper limit frequency Fmax of the compressor 11 according to the ratio of the operating time t1 of the compressor 11 (t1 / (t1 + t2)). Thereby, it is possible to suppress the compressor 11 from operating at a frequency higher than necessary and to increase the operating time t1.

[0036] Figure 3 is a flowchart showing the process of changing the upper limit frequency of the compressor 11 according to Embodiment 1. When the operation of the refrigeration cycle device 100 is started and the compressor 11 is driven, the control device 5 measures the operation time t1 (S1). The operation time t1 is the operation time of the compressor 11 during the thermo-off period, and is the time from when the compressor 11 starts operating until it is stopped by thermo-off. Then, the control device 5 determines whether to perform thermo-off (S2). Here, the control device 5 determines whether to perform thermo-off according to whether the inlet temperature Tmi has reached the thermo-off temperature.

[0037] If it is determined to perform thermo-off (S2: YES), that is, if the inlet temperature Tmi has reached the thermo-off temperature, the control device 5 stops the compressor 11 and measures the stop time t2 (S3). The stop time t2 is the time when the compressor 11 is stopped by thermo-off. Subsequently, the control device 5 determines whether to perform thermo-on (S4). Here, the control device 5 determines whether to perform thermo-on according to whether the inlet temperature Tmi has reached the thermo-on temperature.

[0038] And when it is determined that thermo-on does not occur (S4: NO), that is, when the inlet temperature Tmi has not reached the thermo-on temperature, thermo-off is continued. On the other hand, when it is determined that thermo-on occurs (S4: YES), that is, when the inlet temperature Tmi has reached the thermo-on temperature, the control device 5 determines whether the operation time t1 is shorter than the reference time t0 (S5).

[0039] The reference time t0 is a threshold for determining whether it is necessary to change the upper limit frequency Fmax of the compressor 11. It is set according to the specifications and specification environment of the refrigeration cycle device 100 and stored in the memory of the control device 5. As an example, the reference time t0 is 10 to 15 minutes. Generally, for preventing freezing of the heat medium, the opening degree of the decompression device 13 at the start of the refrigeration cycle device 100 is set larger than the required amount. Therefore, at the start, a large amount of refrigerant returns from the high-pressure side to the low-pressure side. If the compressor 11 repeatedly starts and stops in a short time, there is a risk that the liquid will continue to migrate to the low-pressure side, leading to a failure of the compressor 11. Since the deviation of the refrigerant will be eliminated if the operation of the heat source circuit 1 continues for a certain period of time, that time is confirmed by actual machine tests or simulations and set as the reference time t0.

[0040] When the operation time t1 is shorter than the reference time t0 (S5: YES), the control device 5 determines that there is a margin in the current cooling capacity and changes the upper limit frequency Fmax of the compressor 11. Specifically, the control device 5 calculates the changed upper limit frequency Fmaxv (Hz) based on the current upper limit frequency Fmax of the compressor 11, the operation time t1 and the stop time t2 of the compressor 11 (S6). The changed upper limit frequency Fmaxv is obtained by the following formula (4). Fmaxv = Fmax × t1 / (t1 + t2) ···(4)

[0041] Then, the upper limit frequency Fmax of the compressor 11 is changed to the changed upper limit frequency Fmaxv (S7). As a result, the shorter the operation time t1 is, the lower the upper limit frequency Fmax of the compressor 11 is changed. Then, the control device 5 resets the operation time t1 (S8), resumes the operation of the compressor 11, and proceeds to step S12. Further, when the operation time t1 is equal to or longer than the reference time t0 (S5: NO), the control device 5 resets the operation time t1 without changing the upper limit frequency Fmax of the compressor 11 (S8), resumes the operation of the compressor 11, and proceeds to step S12.

[0042] On the other hand, when it is determined in step S2 that the thermo-off is not performed (S2: NO), that is, when the inlet temperature Tmi has not reached the thermo-off temperature, the control device 5 determines whether or not the current operation frequency F of the compressor 11 has reached the upper limit frequency Fmax (S9). When the current operation frequency F of the compressor 11 has reached the upper limit frequency Fmax (S9: YES), the control device 5 determines whether or not the inlet temperature Tmi is rising (S10).

[0043] When the inlet temperature Tmi is rising (S10: YES), the control device 5 determines that the current cooling capacity is insufficient, and returns the upper limit frequency Fmax of the compressor 11 to the initial value (S11). The initial value is the value at the initial setting before the refrigeration cycle device 100 starts operation. Here, when the cooling capacity is insufficient and the heat medium does not reach the set temperature by suppressing the upper limit frequency Fmax of the compressor 11, the shortage of the cooling capacity is eliminated by returning the upper limit frequency Fmax of the compressor 11 to the initial value.

[0044] On the one hand, when the current operating frequency F of the compressor 11 has not reached the upper limit frequency Fmax (S9: NO), or when the inlet temperature Tmi is not rising (S10: NO), the control device 5 proceeds to step S12 without resetting the upper limit frequency Fmax of the compressor 11 to its initial value. In step S12, the control device 5 determines whether to stop the refrigeration cycle device 100 (S12). If the control device 5 is instructed by a remote control (not shown) or the like from the user to stop the refrigeration cycle device 100, it determines to stop the refrigeration cycle device 100. If the refrigeration cycle device 100 is not to be stopped (S12: NO), it returns to step S1 and repeats the subsequent processing. When the refrigeration cycle device 100 is to be stopped (S12: YES), the control device 5 stops the compressor 11 and the pump 21 and ends the processing.

[0045] FIG. 4 is a diagram showing an example of the time change of the inlet temperature Tmi of the heat medium and the operating frequency of the compressor 11 after the upper limit frequency is changed. In the present embodiment, when the operating time t1 of the compressor 11 is shorter than the reference time t0, the upper limit frequency Fmax is lowered. Thereby, as shown in FIG. 4, the compressor 11 can be continuously operated, and the power consumption at startup can be reduced. Further, in the present embodiment, without using the physical quantity of the load side heat exchanger 22 provided in the indoor unit, the upper limit frequency Fmax of the compressor 11 is suppressed using the operating time t1 and the stop time t2, so that the power consumption can be reduced.

[0046] Also, when the start / stop frequency of the compressor 11 increases during low load operation, liquid backflow in which liquid refrigerant is sucked in when the compressor 11 starts, an increase in bearing load due to a sudden increase in shaft torque at startup, or vibration may occur. In the present embodiment, by measuring the stop time t2 at the previous thermo-off, estimating the required capacity, and suppressing the upper limit frequency Fmax of the compressor 11, the start / stop frequency of the compressor 11 can be reduced even during low load operation. Therefore, in the refrigeration cycle device 100 of the present embodiment, in addition to reducing power consumption, a decrease in reliability associated with the startup of the compressor 11 can be suppressed.

[0047] Embodiment 2. Description will be given to Embodiment 2. FIG. 5 is a schematic configuration diagram of a refrigeration cycle apparatus 100A according to Embodiment 2. As shown in FIG. 5, the refrigeration cycle apparatus 100A of Embodiment 2 is different from that of Embodiment 1 in that it further includes an outlet temperature sensor 62. The configurations and operations of the other refrigeration cycle apparatus 100A are the same as those of Embodiment 1.

[0048] The outlet temperature sensor 62 detects the outlet temperature Tmo of the heat medium at the outlet of the heat medium-to-heat medium heat exchanger 14. The outlet temperature sensor 62 is, for example, a thermistor, and is provided in a pipe connecting the heat medium flow path 142 of the heat medium-to-heat medium heat exchanger 14 and the load-side heat exchanger 22. The outlet temperature Tmo detected by the outlet temperature sensor 62 is transmitted to the control device 5. Further, the outlet temperature sensor 62 is provided in the heat source machine.

[0049] In the present embodiment, the control device 5 obtains the cooling load during the previous operation from the temperature difference of the heat medium at the inlet and outlet of the heat medium-to-heat medium heat exchanger 14, and changes the upper limit frequency Fmax of the compressor 11 based on the obtained cooling load.

[0050] FIG. 6 is a flowchart showing the process of changing the upper limit frequency of the compressor 11 according to Embodiment 2. When the operation of the refrigeration cycle apparatus 100 is started and the compressor 11 is driven, the control device 5 measures the operation time t1 (S101). Then, the control device 5 calculates the cooling load Qa and records it in the memory of the control device 5 (S102). The cooling load Qa is obtained by the following formula (5). Qa = ρ × Cp × V × (Tmi - Tmo) ···(5)

[0051] Here, ρ is the density of the heat medium (kg / m 3 ), V is the volume of the heat medium (m 3 ), Cp is the specific heat of the heat medium (kj / kgK), Tmi is the inlet temperature of the heat medium (K), and Tmo is the outlet temperature of the heat medium (K). The volume V of the heat medium may be measured by providing a flow meter in the load circuit 2, or may be obtained by calculation from the rotation speed of the pump 21 or the like.

[0052] Then, the control device 5 determines whether to turn off the thermo (S103). If it is determined to turn off the thermo (S103: YES), the control device 5 stops the compressor 11 and determines whether the operation time t1 is shorter than the reference time t0 (S104).

[0053] If the operation time t1 is shorter than the reference time t0 (S104: YES), the control device 5 changes the upper limit frequency Fmax of the compressor 11. Specifically, the control device 5 obtains the required capacity Qn per unit time from the cooling load Qa and the operation time t1 during the previous operation. The previous operation refers to the operation before the compressor 11 turns off the thermo, and is the operation at the measured operation time t1. The required capacity Qn is obtained from the following formula (6). Qn = Qa / t1 ···(6)

[0054] Then, the control device 5 obtains the changed upper limit frequency Fmaxv of the compressor 11 from the required capacity Qn and the current inlet temperature Tmi of the heat medium (S106). Here, based on the performance curve of the compressor 11, the upper limit frequency Fmaxv corresponding to the required capacity Qn and the current inlet temperature Tmi of the heat medium is obtained.

[0055] FIG. 7 is an example of the performance curve of the compressor 11. FIG. 7 is a graph showing the COP ratio with respect to the frequency ratio of the compressor 11. The frequency ratio is the ratio of the operation frequency F to the upper limit frequency Fmax. As shown in FIG. 7, the COP ratio is maximized when the frequency ratio is around 50%. Therefore, the control device 5 obtains the upper limit frequency Fmaxv so that the COP ratio becomes as large as possible.

[0056] Returning to FIG. 6, the control device 5 changes the upper limit frequency Fmax of the compressor 11 to the changed upper limit frequency Fmaxv (S107). Subsequently, the control device 5 determines whether to turn on the thermo (S108). Note that when the operation time t1 is equal to or longer than the reference time t0 (S104: NO), the control device 5 proceeds to step S108 without changing the upper limit frequency Fmax of the compressor 11 and determines whether to turn on the thermo (S108).

[0057] And when it is determined that there is no thermo-on (S108: NO), the thermo-off is continued. On the other hand, when it is determined that there is thermo-on (S108: YES), the control device 5 resets the operation time t1 and the cooling load Qa (S109), resumes the operation of the compressor 11, and proceeds to step S113.

[0058] On the other hand, when it is determined in step S103 that there is no thermo-off (S103: NO), the control device 5 proceeds to step S110. The processes of steps S110 to S113 are the same as the processes of steps S9 to S12 in the first embodiment.

[0059] Also in this embodiment, similar to the first embodiment, when the operation time t1 of the compressor 11 is shorter than the reference time t0, the starting power consumption can be reduced by lowering the upper limit frequency Fmax. Further, in this embodiment, based on the inlet temperature Tmi and the outlet temperature Tmo of the heat medium heat exchanger 14 provided in the heat source machine, the upper limit frequency Fmax of the compressor 11 can be suppressed to reduce the power consumption. Furthermore, by obtaining the required capacity Qn according to the cooling load Qa during the previous operation and setting the upper limit frequency Fmax, the start / stop frequency of the compressor 11 can be reduced, and a decrease in reliability associated with the startup of the compressor 11 can be suppressed.

[0060] Embodiment 3. Embodiment 3 will be described. FIG. 8 is a schematic configuration diagram of the refrigeration cycle device 100B according to Embodiment 3. As shown in FIG. 8, the refrigeration cycle device 100B of Embodiment 3 is different from that of Embodiment 1 in that it further includes a first refrigerant temperature sensor 63, a second refrigerant temperature sensor 64, a discharge pressure sensor 65, and a suction pressure sensor 66. The configurations and operations of the other refrigeration cycle devices 100B are the same as those of Embodiment 1.

[0061] The first refrigerant temperature sensor 63 detects the outlet temperature Tro of the refrigerant at the outlet of the heat source side heat exchanger 12 that functions as a condenser. The first refrigerant temperature sensor 63 is, for example, a thermistor, and is provided in a pipe connecting the refrigerant outlet of the heat source side heat exchanger 12 and the decompression device 13. The outlet temperature Tro detected by the first refrigerant temperature sensor 63 is transmitted to the control device 5.

[0062] The second refrigerant temperature sensor 64 detects the suction temperature Trs of the refrigerant that flows out from the heat medium heat exchanger 14 and is sucked into the compressor 11. The second refrigerant temperature sensor 64 is, for example, a thermistor, and is provided in a pipe connecting the refrigerant outlet of the heat medium heat exchanger 14 and the suction port of the compressor 11. The suction temperature Trs detected by the second refrigerant temperature sensor 64 is transmitted to the control device 5.

[0063] The discharge pressure sensor 65 is provided at the discharge port of the compressor 11 and detects the discharge pressure Po of the refrigerant discharged from the compressor 11. The suction pressure sensor 66 is provided at the suction port of the compressor 11 and detects the suction pressure Ps of the refrigerant sucked into the compressor 11. The discharge pressure Po detected by the discharge pressure sensor 65 and the suction pressure Ps detected by the suction pressure sensor 66 are transmitted to the control device 5.

[0064] The control device 5 of the present embodiment obtains the cooling capacity of the heat source circuit 1 of the refrigeration cycle device 100B during the previous operation based on the temperatures and pressures detected by each temperature sensor and pressure sensor, and changes the upper limit frequency Fmax of the compressor 11 according to the obtained cooling capacity.

[0065] FIG. 9 is a flowchart showing the process of changing the upper limit frequency Fmax of the compressor 11 according to Embodiment 3. The process of changing the upper limit frequency Fmax in the present embodiment is the same as that in Embodiment 2 except for step S122. In step S122, the control device 5 obtains the cooling capacity Qb of the heat source circuit 1 during the previous operation. The cooling capacity Qb is obtained from the following formula (7). Qb = G × (h1 - h4) ··· (7)

[0066] Here, G is the circulation amount of the refrigerant and is obtained from the following formula (8). G = ρr × F × V × η ···(8) In formula (8), ρr is the suction refrigerant density, F is the operating frequency of the compressor 11, V is the volume of the compressor 11, and η is the volumetric efficiency. The suction refrigerant density ρr is determined from the suction temperature Trs and the suction pressure Ps of the compressor 11. The operating frequency F of the compressor 11 has a value in the control device 5. The volume V and the volumetric efficiency η of the compressor 11 are constants specific to the device and are input to the control device 5 in advance.

[0067] h1 in formula (7) is the specific enthalpy obtained from the suction temperature Trs and the suction pressure Ps, and h4 is the specific enthalpy obtained from the outlet temperature Tro and the discharge pressure Po.

[0068] In the subsequent processing, similar to the second embodiment, the required capacity Qn is obtained from the cooling capacity Qb (Qn = Qb / t1), and the upper limit frequency Fmax is changed based on the required capacity Qn and the inlet temperature Tmi of the heat medium.

[0069] Also in this embodiment, similar to the first embodiment, when the operating time t1 of the compressor 11 is shorter than the reference time t0, the power consumption at startup can be reduced by lowering the upper limit frequency Fmax. Further, in this embodiment, by calculating the cooling capacity Qb using the detection results of the temperature sensor and the force sensor provided only in the heat source circuit 1, the upper limit frequency Fmax of the compressor 11 can be suppressed without using the physical quantities of the load circuit 2, thereby reducing the power consumption. Furthermore, by obtaining the required capacity Qn according to the cooling capacity Qb of the heat source circuit 1 during the previous operation and setting the upper limit frequency Fmax, the start / stop frequency of the compressor 11 can be reduced, and the decrease in reliability associated with the startup of the compressor 11 can be suppressed.

[0070] Also, when brine is used as the heat transfer medium circulating through the load circuit 2, since the brine is filled locally, it is not known at the time of designing the refrigeration cycle device 100B what physical properties of the brine will be used. Further, even if it is known in advance what the brine to be used is, the concentration of the brine may change during use, and the cooling capacity may change during operation. When the heat transfer medium is water, its physical properties are specified and there is no need to consider changes during use. Therefore, as in the present embodiment, obtaining the cooling capacity of the heat source circuit 1 and changing the upper limit frequency Fmax of the compressor 11 according to the obtained cooling capacity is particularly effective when the heat transfer medium is brine.

[0071] Embodiment 4. Embodiment 4 will be described. The configuration of the refrigeration cycle device 100 of Embodiment 4 is the same as that of Embodiment 1. The control device 5 of the present embodiment calculates the required load Qc from the volume, specific heat and density of the heat transfer medium and the inlet temperature Tmi of the heat transfer medium, and changes the upper limit frequency Fmax of the compressor 11.

[0072] FIG. 10 is a flowchart showing the process of changing the upper limit frequency Fmax of the compressor 11 according to Embodiment 4. When the operation of the refrigeration cycle device 100 is started and the compressor 11 is driven, the control device 5 measures the operation time t1 (S201). Then, the control device 5 determines whether to turn off the thermostat (S202).

[0073] If it is determined that the thermostat is to be turned off (S202: YES), the control device 5 stops the compressor 11 and determines whether the operation time t1 is shorter than the reference time t0 (S203). If the operation time t1 is shorter than the reference time t0 (S203: YES), the control device 5 changes the upper limit frequency Fmax of the compressor 11. Specifically, the control device 5 calculates the required load Qc based on the physical properties and amount of the heat transfer medium and the change amount of the inlet temperature Tmi of the heat transfer medium (S204). The required load Qc is obtained from the following formula (9). Qc = ρ × Cp × V × ΔTmi / t1 ···(9)

[0074] Here, ρ is the density of the heat transfer medium (kg / m 3)、V is the volume of the heat medium (m 3 )、Cp is the specific heat of the heat medium (kj / kgK), ΔTmi is the change in the inlet temperature Tmi (K), and t1 is the operating time of the compressor 11 (sec). The volume V of the heat medium may be measured by providing a flow meter in the load circuit 2, or may be obtained by calculation from the rotational speed of the pump 21 or the like. ΔTmi is the difference between the inlet temperature Tmi at the start of operation of the compressor 11 and the inlet temperature Tmi at the time of thermo-off.

[0075] And the control device 5 obtains the changed upper limit frequency Fmaxv of the compressor 11 from the required load Qc and the current inlet temperature Tmi of the heat medium (S205). Here, based on the performance curve of the compressor 11, the upper limit frequency Fmaxv corresponding to the required load Qc and the inlet temperature Tmi of the heat medium is obtained.

[0076] And the control device 5 changes the upper limit frequency Fmax of the compressor 11 to the changed upper limit frequency Fmaxv (S206). Subsequently, the control device 5 determines whether to turn on the thermo (S207). When the operation time t1 is less than the reference time t0 (S203: NO), the control device 5 proceeds to step S207 without changing the upper limit frequency Fmax of the compressor 11, and determines whether to turn on the thermo (S207).

[0077] And when it is determined not to turn on the thermo (S207: NO), the thermo-off is continued. On the other hand, when it is determined to turn on the thermo (S207: YES), the control device 5 resets the operation time t1 (S208), resumes the operation of the compressor 11, and proceeds to step S212.

[0078] On the other hand, when it is determined not to turn off the thermo in step S202 (S202: NO), the control device 5 proceeds to step S209. The processing from step S209 to step S212 is the same as the processing from step S9 to step S12 in the first embodiment.

[0079] Also in this embodiment, similar to Embodiment 1, when the operation time t1 of the compressor 11 is shorter than the reference time t0, the starting power consumption can be reduced by lowering the upper limit frequency Fmax. Further, in this embodiment, by calculating the required load Qc based on the physical properties and amount of the heat medium and the inlet temperature Tmi of the heat medium, the upper limit frequency Fmax of the compressor 11 is suppressed without using the physical quantities of the load-side heat exchanger 22, thereby reducing the power consumption. Further, by setting the upper limit frequency Fmax according to the required load Qc, the start / stop frequency of the compressor 11 can be reduced, and a decrease in reliability associated with the start-up of the compressor 11 can be suppressed.

[0080] The above is the description of the embodiment. However, the present disclosure is not limited to the above-described embodiment, and various modifications or combinations can be made without departing from the gist of the present disclosure. For example, in the above embodiment, an air conditioner is described as an example of the refrigeration cycle device. However, the refrigeration cycle device may be an air conditioner or a hot water supply device that performs cooling and heating operations. Even when performing heating or hot water supply, similar to the above embodiment, the upper limit frequency Fmax of the compressor 11 is changed according to the operation time t1 between thermo-off, the stop time t2 at the time of thermo-off, the heating load at the previous operation, or the heating capacity. Thereby, reduction of power consumption and suppression of start / stop frequency can be realized.

[0081] Also, in the above embodiment, the refrigeration cycle device 100 is configured to have one heat source circuit 1. However, the process of changing the upper limit frequency Fmax of the compressor 11 described in the above embodiment can also be applied to a configuration in which a plurality of heat source circuits 1 cool the same heat medium. By controlling the compressors 11 of the plurality of heat source circuits 1 with the same frequency command and commanding each heat source circuit 1 with the frequency at which the COP of the compressor 11 is optimal, the COP of the system can be improved.

Explanation of Reference Numerals

[0082] 1 Heat source circuit, 2 Load circuit, 5 Control device, 11 Compressor, 12 Heat source side heat exchanger, 13 Pressure reducing device, 14 Heat medium-to-heat medium heat exchanger, 15 First fan, 21 Pump, 22 Load side heat exchanger, 25 Second fan, 61 Inlet temperature sensor, 62 Outlet temperature sensor, 63 First refrigerant temperature sensor, 64 Second refrigerant temperature sensor, 65 Discharge pressure sensor, 66 Suction pressure sensor, 100, 100A, 100B Refrigeration cycle device, 141 Refrigerant flow path, 142 Heat medium flow path.

Claims

1. A refrigeration cycle apparatus comprising a compressor, a heat source side heat exchanger, an expansion device, and a heat medium heat exchanger, a heat source circuit in which a refrigerant circulates, a load circuit including the heat medium heat exchanger, a load side heat exchanger, and a pump, in which a heat medium circulates, a control device, an outlet temperature sensor that measures an outlet temperature of the heat medium at an outlet of the heat medium heat exchanger, an inlet temperature sensor that measures an inlet temperature of the heat medium at an inlet of the heat medium heat exchanger, and the heat medium heat exchanger exchanges heat between the refrigerant and the heat medium, the control device, when an operation time of the compressor, which is an operation time before the compressor stops with thermo-off, is shorter than a reference time, makes an upper limit frequency of the compressor lower than a currently set upper limit frequency, the control device, calculates a cooling load during a previous operation based on the outlet temperature and the inlet temperature, and when the operation time is shorter than the reference time, changes the upper limit frequency of the compressor based on the cooling load and the operation time.

2. A refrigeration cycle apparatus comprising a compressor, a heat source side heat exchanger, an expansion device, and a heat medium heat exchanger, a heat source circuit in which a refrigerant circulates, a load circuit including the heat medium heat exchanger, a load side heat exchanger, and a pump, in which a heat medium circulates, a control device, a first refrigerant temperature sensor that measures an outlet temperature of the refrigerant at an outlet of the heat source side heat exchanger, a second refrigerant temperature sensor that measures an inlet temperature of the refrigerant sucked into the compressor, a discharge pressure sensor that measures a discharge pressure of the compressor, a suction pressure sensor that measures a suction pressure of the compressor, and the heat medium heat exchanger exchanges heat between the refrigerant and the heat medium, When the operation time of the compressor, which is the operation time during operation before the compressor stops due to thermo-off, is shorter than the reference time, the control device lowers the upper limit frequency of the compressor below the currently set upper limit frequency. The control device calculates the cooling capacity of the heat source circuit during the previous operation based on the discharge pressure, the suction pressure, the suction temperature, and the outlet temperature. A refrigeration cycle device that changes the upper limit frequency of the compressor based on the cooling capacity and the operation time when the operation time is shorter than the reference time.

3. A heat source circuit in which a compressor, a heat source side heat exchanger, a decompression device, and a heat medium heat exchanger are provided and a refrigerant circulates, A load circuit in which the heat medium heat exchanger, a load side heat exchanger, and a pump are provided and a heat medium circulates, A control device, and an inlet temperature sensor that measures the inlet temperature of the heat medium at the inlet of the heat medium heat exchanger. The heat medium heat exchanger exchanges heat between the refrigerant and the heat medium. When the operation time of the compressor, which is the operation time during operation before the compressor stops due to thermo-off, is shorter than the reference time, the control device lowers the upper limit frequency of the compressor below the currently set upper limit frequency. The control device A refrigeration cycle device that returns the upper limit frequency to the initial value when the operation frequency of the compressor reaches the upper limit frequency and the inlet temperature has not reached the set temperature and is rising.

4. The control device controls the compressor to thermo-off when the temperature of the heat medium becomes lower than a predetermined temperature and to thermo-on when the temperature of the heat medium exceeds the predetermined temperature, according to any one of claims 1 to 3.

5. The control device measures the stop time during which the compressor has stopped due to thermo-off. The refrigeration cycle apparatus according to claim 3, wherein an upper limit frequency of the compressor is changed based on the operation time and the stop time.

6. The control device calculates a required load based on the inlet temperature and the operation time, and changes an upper limit frequency of the compressor based on the required load, the refrigeration cycle apparatus according to claim 3.

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