Heat source unit

Abstract

To restrain a decrease in the COP of a refrigeration cycle device.SOLUTION: A heat source unit of a refrigeration cycle device (1) cools water in a water circuit (30) flowing through a first water heat exchanger (14A) and a second water heat exchanger (14B) in this order, comprises a first refrigerant circuit (10A) comprising a first compressor (11A) and the first water heat exchanger (14A), and a second refrigerant circuit (10B) comprising a second compressor (11B) and the second water heat exchanger (14B), and comprises a control unit (100) for executing first control for controlling the first compressor (11A) and the second compressor (11B) so that the cooling capacity of the first refrigerant circuit (10A) approaches the cooling capacity of the second refrigerant circuit (10B) during cooling operation meeting required capacity for adjusting the water in the water circuit (30) to a target temperature.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a heat source unit. [Background technology]

[0002] The refrigeration system described in Patent Document 1 has multiple refrigerant circuits to which compressors are connected, and exchanges heat between the refrigerant and water flowing through two water heat exchangers connected in series. The two water heat exchangers are connected to independent refrigerant circuits as utilization heat exchangers. The capacity of the refrigeration system is controlled according to the operating load state so that the rotation speeds of the compressors connected to the two water heat exchangers are the same. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-206331 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in cooling operation to cool the water in the water circuit, the water flowing through the water circuit is cooled in the upstream water heat exchanger and then further cooled in the downstream water heat exchanger. Therefore, the water temperature in the upstream water heat exchanger is higher than that in the downstream water heat exchanger, and the evaporation temperature of the refrigerant in the upstream water heat exchanger is higher than that of the downstream water heat exchanger.

[0005] In the refrigeration system disclosed in Patent Document 1, for two water heat exchangers with different evaporation temperatures, the compressors of the refrigerant circuits connected to each water heat exchanger are capacity-controlled to the same rotation speed, so the refrigerant circuit connected to the upstream water heat exchanger has a higher heat exchange capacity with water than the refrigerant circuit connected to the downstream water heat exchanger.We have discovered that the COP of the refrigeration cycle system decreases due to a decrease in the balance of heat exchange capacity between the refrigerant circuit connected to the upstream water heat exchanger and the refrigerant circuit connected to the downstream water heat exchanger.

[0006] An object of the present disclosure is to suppress a decrease in the COP of a refrigeration cycle device. [Means for solving the problem]

[0007] The first aspect is A heat source unit of a refrigeration cycle device (1) that performs a cooling operation to cool water in a water circuit (30), a first refrigerant circuit (10A) including a first compressor (11A), a first air heat exchanger (12A), and a first water heat exchanger (14A) for exchanging heat between a refrigerant and water in the water circuit (30); a second refrigerant circuit (10B) including a second compressor (11B), a second air heat exchanger (12B), and a second water heat exchanger (14B) for exchanging heat between a refrigerant and water in the water circuit (30); In the cooling operation, the first water heat exchanger (14A) and the second water heat exchanger (14B) function as evaporators, and the first air heat exchanger (12A) and the second air heat exchanger (12B) function as condensers; the water circuit (30) is configured so that water flows through the first water heat exchanger (14A) and then the second water heat exchanger (14B); The cooling operation is an operation that satisfies the capacity required to adjust the water in the water circuit (30) to a target temperature, The cooling system includes a control unit (100) that performs first control to control the first compressor (11A) and the second compressor (11B) so that the cooling capacity of the first refrigerant circuit (10A) approaches the cooling capacity of the second refrigerant circuit (10B).

[0008] It has been found that the closer the capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) are to each other, the higher the COP of the refrigeration cycle apparatus (1), whereas the more the capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) are to each other, the worse the COP of the refrigeration cycle apparatus (1). Here, if the first refrigerant circuit (10A) and the second refrigerant circuit (10B) have the same configuration and the first compressor (11A) and the second compressor (11B) operate in the same manner, the evaporation temperature of the first water heat exchanger (14A) located upstream in the water circuit (30) is higher than the evaporation temperature of the second water heat exchanger (14B) located downstream in the water circuit (30) during cooling operation. This increases the cooling capacity of the first refrigerant circuit (10A). As a result, the balance of the cooling capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) is deteriorated.

[0009] Therefore, in the first mode, the first control brings the cooling capacity of the first refrigerant circuit (10A) closer to the cooling capacity of the second refrigerant circuit (10B), thereby suppressing a decrease in the cooling capacity balance and improving the COP of the refrigeration cycle device (1).

[0010] The second aspect is the first aspect, The first control is a control for making the rotation speed of the first compressor (11A) lower than the rotation speed of the second compressor (11B).

[0011] In the second aspect, the first control can be easily executed.

[0012] The third aspect is the first or second aspect, The control unit (100) performs the first control based on the state of refrigerant in the first refrigerant circuit (10A) or the second refrigerant circuit (10B).

[0013] In the third aspect, the first control can be easily performed simply by grasping the refrigerant state.

[0014] A fourth aspect is the first or second aspect, The control section (100) performs the first control based on the water temperature in the water circuit (30).

[0015] In the fourth aspect, the first control can be performed by detecting the water temperature in the water circuit (30).

[0016] A fifth aspect is any one of the first to fourth aspects, The refrigeration cycle device (1) performs a heating operation to heat water in the water circuit (30), In the heating operation, the first water heat exchanger (14A) and the second water heat exchanger (14B) function as condensers, and the first air heat exchanger (12A) and the second air heat exchanger (12B) function as evaporators; The heating operation is an operation that satisfies the capacity required to adjust the water in the water circuit (30) to a target temperature, The control unit (100) executes second control to control the first compressor (11A) and the second compressor (11B) so that the high pressures of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) approach each other.

[0017] In the fifth aspect, the second control reduces the high pressure of the second refrigerant circuit (10B) connected to the second water heat exchanger (14B) having a high water temperature, thereby reducing the input power to the compressor and improving the COP. The required capacity can be ensured by matching the high pressures (condensation temperatures) of the first refrigerant circuit (10A) and the second refrigerant circuit (10B). [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a piping diagram of a refrigerant circuit of a heat source unit of this embodiment. [Figure 2] FIG. 2 is a block diagram showing the relationship between the control unit of the heat source unit and various devices. [Figure 3] FIG. 3 is a graph schematically showing the relationship between the ratio of the first cooling capacity to the second cooling capacity and the COP of the refrigeration cycle device. [Figure 4] FIG. 4 is a flowchart showing the operation of the control unit when the first control is executed. [Figure 5] FIG. 5 is a piping diagram of a refrigerant circuit of a heat source unit according to Modification 1. As shown in FIG. [Figure 6] FIG. 6 is a block diagram according to the first modification, which corresponds to FIG. [Figure 7] FIG. 7 is a flowchart showing the operation of the control unit when the second control is executed. [Figure 8] FIG. 8 is a partial piping diagram of a refrigerant circuit of a heat source unit according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses. Furthermore, each configuration of the embodiments, modifications, other examples, etc. described below can be combined or partially substituted within the scope of the present invention.

[0020] (1) Overview The heat source unit (U1) according to this embodiment is used as a heat source for a refrigeration cycle apparatus (1). For example, the refrigeration cycle apparatus (1) is an air conditioning apparatus that provides air conditioning for offices, shopping malls, factories, etc. The heat source unit (U1) is a chilling unit dedicated to cooling that produces chilled water. The heat source unit (U1) is an air-cooled chilling unit.

[0021] (2) Refrigerant circuit configuration The heat source unit (U1) of this embodiment has a plurality of refrigerant circuits (10A, 10B). The heat source unit (U1) has a first refrigerant circuit (10A) and a second refrigerant circuit (10B). The first refrigerant circuit (10A) and the second refrigerant circuit (10B) have the same basic configuration. Each refrigerant circuit (10A, 10B) is filled with refrigerant. Each refrigerant circuit (10A, 10B) performs a vapor compression refrigeration cycle by circulating the refrigerant.

[0022] The first refrigerant circuit (10A) includes a first compressor (11A), a first air heat exchanger (12A), a first expansion valve (13A), a first water heat exchanger (14A), a first four-way switching valve (15A), and a first accumulator (17A).

[0023] The first compressor (11A) compresses the sucked refrigerant and discharges the compressed refrigerant. The first compressor (11A) is, for example, a scroll compressor, but may be any other type of compressor, such as a screw type, a turbo type, or a rotary type.

[0024] The first air heat exchanger (12A) is an outdoor heat exchanger that exchanges heat between a refrigerant and outdoor air. The first air heat exchanger (12A) is a fin-and-tube heat exchanger. The heat source unit (U1) has a first fan (18A) that transfers air to the first air heat exchanger (12A). The first fan (18A) is a propeller fan.

[0025] The first expansion valve (13A) is provided on a refrigerant pipe between the first air heat exchanger (12A) and the first water heat exchanger (14A) near the first air heat exchanger (12A). The first expansion valve (13A) is an electronic expansion valve whose opening degree is variable.

[0026] The first water heat exchanger (14A) is, for example, a plate-type heat exchanger. The first water heat exchanger (14A) exchanges heat between the refrigerant and water. The first water heat exchanger (14A) is a counterflow heat exchanger. The first water heat exchanger (14A) has a first water flow path (14bA) and a first refrigerant flow path (14aA). The first water flow path (14bA) is connected to the water circuit (30), and the first refrigerant flow path (14aA) is connected to the first refrigerant circuit (10A). The first water heat exchanger (14A) exchanges heat between the water in the first water flow path (14bA) and the refrigerant in the first refrigerant circuit (10A).

[0027] The first four-way selector valve (15A) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first port (P1) is connected to the discharge side of the first compressor (11A) via a first discharge pipe (31A). The second port (P2) is connected to the suction side of the first compressor (11A) via a first suction pipe (32A). The third port (P3) is connected to the gas side end of the first air heat exchanger (12A) via a refrigerant piping. The fourth port (P4) is connected to the gas side end of the first refrigerant flow path (14aA) of the first water heat exchanger (14A) via a refrigerant piping.

[0028] The first four-way switching valve (15A) switches between a first state (state shown by solid lines in Figure 1) in which the first port (P1) and the third port (P3) communicate with each other and simultaneously the second port (P2) and the fourth port (P4) communicate with each other, and a second state (state shown by dashed lines in Figure 1) in which the first port (P1) and the fourth port (P4) communicate with each other and simultaneously the second port (P2) and the third port (P3) communicate with each other.

[0029] In the cooling operation of the refrigeration cycle apparatus (1), the first four-way switching valve (15A) is in the first state, and a refrigeration cycle (first refrigeration cycle) is performed in which the first air heat exchanger (12A) functions as a radiator and the first water heat exchanger (14A) functions as an evaporator. In the heating operation of the refrigeration cycle apparatus (1), the first four-way switching valve (15A) is in the second state, and a refrigeration cycle (second refrigeration cycle) is performed in which the first water heat exchanger (14A) functions as a radiator and the first air heat exchanger (12A) functions as an evaporator.

[0030] The first accumulator (17A) is connected to the first suction pipe (32A). The first accumulator (17A) is a sealed container that stores liquid refrigerant contained in the low-pressure refrigerant.

[0031] The elements of the second refrigerant circuit (10B) are basically the same as those of the first refrigerant circuit (10A). The second refrigerant circuit (10B) includes a second compressor (11B), a second air heat exchanger (12B), a second expansion valve (13B), a second water heat exchanger (14B), a second four-way selector valve (15B), and a second accumulator (17B). The second water heat exchanger (14B) includes a second refrigerant flow path (14aB) and a second water flow path (14bB).

[0032] (3) Water circuit As shown in Fig. 1, the heat source unit (U1) has a water circuit (30) through which water flows. The water circuit (30) is configured so that water flows through the first water heat exchanger (14A) and the second water heat exchanger (14B) in this order. Specifically, the water circuit (30) is connected, in order from upstream to downstream of the water flow, to a pump (33), a first water flow path (14bA) of the first water heat exchanger (14A), and a second water flow path (14bB) of the second water heat exchanger (14B).

[0033] The pump (33) transports water in the water circuit (30). The water flowing through the water circuit (30) exchanges heat with the refrigerant in the first refrigerant flow path (14aA) in the first water flow path (14bA) of the first water heat exchanger (14A), and then exchanges heat with the refrigerant in the second refrigerant flow path (14aB) in the second water flow path (14bB) of the second water heat exchanger (14B).

[0034] (4) Sensor The heat source unit (U1) has a plurality of sensors. The first refrigerant circuit (10A) and the second refrigerant circuit (10B) are provided with the same types of sensors.

[0035] The first refrigerant circuit (10A) is provided with a first high-pressure pressure sensor (61A), a first low-pressure pressure sensor (62A), a first refrigerant temperature sensor (63A), and a second refrigerant temperature sensor (64A). The second refrigerant circuit (10B) is provided with a second high-pressure pressure sensor (61B), a second low-pressure pressure sensor (62B), a third refrigerant temperature sensor (63B), and a fourth refrigerant temperature sensor (64B). The water circuit (30) is provided with a first water temperature sensor (65).

[0036] The first high-pressure sensor (61A) is provided in the first discharge pipe (31A). The first high-pressure sensor (61A) detects the high-pressure (HP) of the first refrigerant circuit (10A), in other words, the discharge pressure of the first compressor (11A). The first high-pressure sensor (61A) detects the condensation pressure of the refrigerant when the first air heat exchanger (12A) or the first water heat exchanger (14A) functions as a condenser.

[0037] The first low-pressure pressure sensor (62A) is provided in the first suction pipe (32A). The first low-pressure pressure sensor (62A) is provided on the inlet side of the first accumulator (17A). The first low-pressure pressure sensor (62A) detects the low pressure (LP) of the first refrigerant circuit (10A), in other words, the suction pressure of the first compressor (11A). The first low-pressure pressure sensor (62A) detects the evaporation pressure of the refrigerant when the first water heat exchanger (14A) or the first air heat exchanger (12A) functions as an evaporator.

[0038] The first refrigerant temperature sensor (63A) is provided on a refrigerant pipe between the first air heat exchanger (12A) and the first expansion valve (13A). The first refrigerant temperature sensor (63A) detects the temperature of the refrigerant at the outlet side of the first air heat exchanger (12A), for example, when the first air heat exchanger (12A) functions as a condenser.

[0039] The second refrigerant temperature sensor (64A) is provided in the first suction pipe (32A). The second refrigerant temperature sensor (64A) is provided on the inlet side of the first accumulator (17A). The second refrigerant temperature sensor (64A) detects the refrigerant temperature on the outlet side of the first water heat exchanger (14A) functioning as an evaporator, for example.

[0040] The second high-pressure sensor (61B) is provided in the second discharge pipe (31B). The second high-pressure sensor (61B) detects the high-pressure (HP) of the second refrigerant circuit (10B), in other words, the discharge pressure of the second compressor (11B). The second high-pressure sensor (61B) detects the condensation pressure of the refrigerant when the second air heat exchanger (12B) or the second water heat exchanger (14B) functions as a condenser.

[0041] The second low-pressure sensor (62B) is provided in the second suction pipe (32B). The second low-pressure sensor (62B) detects the low-pressure (LP) of the second refrigerant circuit (10B), in other words, the suction pressure of the second compressor (11B). The second low-pressure sensor (62B) detects the evaporation pressure of the refrigerant when the second water heat exchanger (14B) or the second air heat exchanger (12B) functions as an evaporator.

[0042] The third refrigerant temperature sensor (63B) is provided on the refrigerant pipe between the second air heat exchanger (12B) and the second expansion valve (13B). The third refrigerant temperature sensor (63B) detects the refrigerant temperature on the outlet side of the second air heat exchanger (12B), for example, when the second air heat exchanger (12B) functions as a condenser.

[0043] The fourth refrigerant temperature sensor (64B) is provided in the second suction pipe (32B). The fourth refrigerant temperature sensor (64B) is provided on the inlet side of the second accumulator (17B). The fourth refrigerant temperature sensor (64B) detects the refrigerant temperature on the outlet side of the second water heat exchanger (14B) functioning as an evaporator, for example.

[0044] The first water temperature sensor (65) is provided downstream of the second water heat exchanger (14B) in the water circuit (30). The first water temperature sensor (65) detects the temperature of water at the outlet side of the second water flow path (14bB).

[0045] (3) Control Unit As shown in Fig. 2, the heat source unit (U1) has a control unit (100). The control unit (100) includes an MCU (Micro Control Unit), an electric circuit, and an electronic circuit. The MCU includes a CPU (Central Processing Unit), a memory, and a communication interface. The memory stores various programs to be executed by the CPU.

[0046] The control unit (100) controls the heat source unit (U1). Specifically, the control unit (100) controls ON / OFF switching of the first compressor (11A) and the second compressor (11B), the rotation speeds of the first compressor (11A) and the second compressor (11B), ON / OFF switching of the first fan (18A) and the second fan (18B), the rotation speeds of the first fan (18A) and the second fan (18B), ON / OFF switching of the pump (33), the rotation speed of the pump (33), the opening degree of the first expansion valve (13A), and the opening degree of the second expansion valve (13B).

[0047] The control unit (100) receives the detection values ​​of the various sensors described above. The control unit (100) detects the rotation speed of each compressor (11A, 11B). The rotation speed of the compressors (11A, 11B) can be detected based on, for example, the value of a current flowing through a motor (not shown) of the compressor (11A, 11B).

[0048] The control unit (100) calculates a predetermined index based on the received detected value and controls each device based on the detected value. The control unit (100) controls the rotation speed of each compressor (11A, 11B) so that the water temperature detected by the first water temperature sensor (65) approaches a target temperature.

[0049] (4) Driving behavior The operation of the heat source unit (U1) will be described. The heat source unit (U1) performs a cooling operation and a heating operation as normal operation. In FIG. 1, the flow of refrigerant during the cooling operation is indicated by solid arrows, and the flow of refrigerant during the heating operation is indicated by dashed arrows. In the following description, since the operation of the first refrigerant circuit (10A) and the operation of the second refrigerant circuit (10B) are the same, only the operation of the first refrigerant circuit (10A) will be described, and the operation of the second refrigerant circuit (10B) will be omitted.

[0050] (4-1) Cooling operation In the cooling operation, the control unit (100) operates the first compressor (11A), the first fan (18A), and the pump (33), sets the first four-way switching valve (15A) to the first state, and appropriately adjusts the opening of the first expansion valve (13A).

[0051] The refrigerant compressed by the first compressor (11A) flows through the first air heat exchanger (12A). In the first air heat exchanger (12A), the refrigerant dissipates heat to the outdoor air and is condensed. The condensed high-pressure liquid refrigerant is reduced in pressure to a low pressure when passing through the first expansion valve (13A). The reduced-pressure refrigerant flows through a first refrigerant flow path (14aA) of the first water heat exchanger (14A).

[0052] In the first water heat exchanger (14A), the refrigerant in the first refrigerant flow path (14aA) evaporates and the water in the first water flow path (14bA) is cooled. The water cooled in the first water flow path (14bA) is supplied to the utilization units.

[0053] The refrigerant evaporated in the first water heat exchanger (14A) passes through the first accumulator (17A), and is then sucked into the first compressor (11A) and compressed again. In this way, in the cooling operation, the first water heat exchanger (14A) functions as an evaporator, and the first air heat exchanger (12A) functions as a condenser.

[0054] (4-2) Heating operation In the heating operation, the control unit (100) operates the first compressor (11A), the first fan (18A), and the pump (33), sets the first four-way switching valve (15A) to the second state, and appropriately adjusts the opening of the first expansion valve (13A).

[0055] The refrigerant compressed by the first compressor (11A) flows through the first refrigerant flow path (14aA) of the first water heat exchanger (14A). In the first water heat exchanger (14A), the refrigerant dissipates heat to the water in the first water flow path (14bA) and is condensed, and the water in the first water flow path (14bA) is heated. The heated water is supplied to the utilization units.

[0056] The condensed high-pressure liquid refrigerant is reduced in pressure to a low pressure when passing through the first expansion valve (13A). The reduced-pressure refrigerant flows into the first air heat exchanger (12A). In the first air heat exchanger (12A), the refrigerant absorbs heat from the outdoor air and evaporates.

[0057] The refrigerant evaporated in the first air heat exchanger (12A) passes through the first accumulator (17A), and is then sucked into the first compressor (11A) and compressed again. In this way, in the heating operation, the first water heat exchanger (14A) functions as a condenser, and the first air heat exchanger (12A) functions as an evaporator.

[0058] (5) Issues In a water circuit having a plurality of water heat exchangers as in this embodiment, water flowing through the water circuit exchanges heat with a refrigerant in an upstream water heat exchanger and then exchanges heat with a refrigerant in a downstream water heat exchanger. For example, during cooling operation, the water in the water circuit (30) is cooled in the upstream first water heat exchanger (14A) and then further cooled in the downstream second water heat exchanger (14B). Therefore, the water temperature in the first water flow path (14bA) is higher than the water temperature in the second water flow path (14bB). Therefore, the evaporation temperature of the refrigerant in the first water heat exchanger (14A) is higher than the evaporation temperature of the refrigerant in the second water heat exchanger (14B). In other words, the evaporation pressure in the first water heat exchanger (14A) is higher than the evaporation pressure in the second water heat exchanger (14B). That is, the suction density of the refrigerant drawn by the first compressor (11A) is higher than the suction density of the refrigerant drawn by the second compressor (11B).

[0059] In the heat source unit (U1) of this embodiment, the first refrigerant circuit (10A) and the second refrigerant circuit (10B) have the same configuration. That is, the first water heat exchanger (14A) and the second water heat exchanger (14B) have the same configuration, the first air heat exchanger (12A) and the second air heat exchanger (12B) have the same configuration, and the first compressor (11A) and the second compressor (11B) have the same configuration.

[0060] Therefore, the suction density of the refrigerant flowing into the first compressor (11A) in the first refrigerant circuit (10A) is higher than the suction density of the refrigerant flowing into the second compressor (11B) in the second refrigerant circuit (10B). Therefore, when the first compressor (11A) and the second compressor (11B) are controlled so that the rotation speeds of the first compressor (11A) and the second compressor (11B) are the same while satisfying a predetermined required capacity, the cooling capacity of the first refrigerant circuit (10A) becomes higher than the cooling capacity of the second refrigerant circuit (10B). Therefore, when the required capacity of the heat source unit (U1) for raising the water in the water circuit (30) to a target temperature is 100%, the ratio of the cooling capacity of the first refrigerant circuit (10A) becomes higher than the ratio of the cooling capacity of the second refrigerant circuit (10B).

[0061] In the present embodiment, when the upstream first water heat exchanger (14A) and the downstream second water heat exchanger (14B) connected in series to the water circuit (30) function as evaporators, the relationship between the ratio of the capacities of the first water heat exchanger (14A) and the second water heat exchanger (14B) and the COP of the refrigeration cycle apparatus (1) can be represented schematically as shown in Fig. 3. It has been found that the COP is highest when the ratio of the cooling capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) is 1:1, i.e., 50%:50%. Therefore, if the first compressor (11A) and the second compressor (11B) are controlled to have the same rotation speed as in the conventional technique, the ratio of the cooling capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) is not 1:1, and the COP cannot be said to be highest.

[0062] Based on this knowledge, the heat source unit (U1) of this embodiment executes a first control to suppress a decrease in the balance of the capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) during the cooling operation. The first control will be described in detail below.

[0063] (6) First control The control unit (100) of the heat source unit (U1) of this embodiment executes a first control for controlling the first compressor (11A) and the second compressor (11B) so that the cooling capacity of the first refrigerant circuit (10A) approaches the cooling capacity of the second refrigerant circuit (10B). The first control is executed when the ratio between the cooling capacity of the first refrigerant circuit (10A) and the cooling capacity of the second refrigerant circuit (10B) deviates from 1:1. The flow of the first control of this embodiment will be described below with reference to FIG. 4.

[0064] In step S01, the control unit (100) starts the cooling operation. The control unit (100) increases the rotation speed of each of the first compressor (11A) and the second compressor (11B) by a predetermined number of rotations so that the rotation speeds of the first compressor (11A) and the second compressor (11B) become the same.

[0065] In step S02, the control unit (100) determines whether the water temperature detected by the first water temperature sensor (65) has reached the target temperature. If it is determined that the water temperature has reached the target temperature (YES in step S02), step S03 is executed. If it is determined that the water temperature has not reached the target temperature (NO in step S02), step S02 is executed again.

[0066] In step S03, the control section (100) determines the cooling capacity of each of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) based on the refrigerant states in the first refrigerant circuit (10A) and the second refrigerant circuit (10B).

[0067] Specifically, the control unit (100) determines a first enthalpy on the inlet side of the first water heat exchanger (14A) based on the condensation pressure of the refrigerant in the first air heat exchanger (12A) and the refrigerant temperature on the outlet side of the first air heat exchanger (12A). The control unit (100) also determines a second enthalpy on the outlet side of the first water heat exchanger (14A) based on the evaporation pressure of the refrigerant in the first water heat exchanger (14A) and the refrigerant temperature on the outlet side of the first water heat exchanger (14A). In this way, the control unit (100) determines the difference between the first enthalpy and the second enthalpy (the enthalpy difference between the outlet side and the inlet side of the first water heat exchanger (14A)). Next, the control unit (100) calculates the amount of refrigerant circulating in the first refrigerant circuit (10A) based on the condensation pressure of the refrigerant in the first air heat exchanger (12A), the evaporation pressure of the refrigerant in the first water heat exchanger (14A), and the rotation speed of the first compressor (11A).The control unit (100) calculates a first cooling capacity, which is the cooling capacity of the first refrigerant circuit (10A), from the enthalpy difference between the outlet and inlet sides of the first water heat exchanger (14A) and the amount of refrigerant circulating.Similarly, the control unit (100) calculates a second cooling capacity, which is the cooling capacity of the second refrigerant circuit (10B).

[0068] In step S04, the control unit (100) determines whether the ratio between the first cooling capacity and the second cooling capacity is 1:1. If the ratio between the first cooling capacity and the second cooling capacity is 1:1 (YES in step S04), step S05 is executed. If the ratio between the first cooling capacity and the second cooling capacity is not 1:1 (NO in step S04), step S06 is executed.

[0069] In step S05, the control unit (100) determines whether or not a command to stop the cooling operation has been received. If it is determined that a command to stop the cooling operation has been received (YES in step S05), the operation of the heat source unit (U1) is stopped. If it is determined that a command to stop the cooling operation has not been received (NO in step S05), step S03 is executed again.

[0070] In step S06, the control unit (100) executes the first control. The first control is executed based on the refrigerant states of the first refrigerant circuit (10A) and the second refrigerant circuit (10B). Specifically, it is assumed that the ratio between the first cooling capacity and the second cooling capacity calculated based on the refrigerant states of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) in step S03 is 60%:40%. In this case, the control unit (100) controls the first compressor (11A) to reduce the first cooling capacity so that the first cooling capacity approaches the second cooling capacity. Since the sum of the ratios between the first cooling capacity and the second cooling capacity is 100%, the control unit (100) increases the second cooling capacity by an amount corresponding to the reduction in the first cooling capacity.

[0071] In this embodiment, the first compressor (11A) and the second compressor (11B) are controlled so that the ratio between the first cooling capacity and the second cooling capacity becomes 1:1. Specifically, the control unit (100) reduces the rotation speed of the first compressor (11A) to adjust the ratio of the first cooling capacity from 60% to 50%. The control unit (100) increases the rotation speed of the second compressor (11B) to adjust the ratio of the second cooling capacity from 40% to 50%. After the first control is performed, step S04 is performed again.

[0072] (7) Features (7-1) Feature 1 The heat source unit (U1) of this embodiment has a control unit (100) that performs first control to control the first compressor (11A) and the second compressor (11B) so that the cooling capacity of the first refrigerant circuit (10A) approaches the cooling capacity of the second refrigerant circuit (10B) during cooling operation.

[0073] In the cooling operation, the evaporation temperature in the first water heat exchanger (14A) is higher than the evaporation temperature in the second water heat exchanger (14B), and the cooling capacity of the first refrigerant circuit (10A) increases, resulting in an imbalance between the cooling capacities of the first refrigerant circuit (10A). However, in the present embodiment, the first control is performed to bring the cooling capacity of the first refrigerant circuit (10A) closer to the cooling capacity of the second refrigerant circuit (10B). This prevents the imbalance between the cooling capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) from worsening, and improves the COP of the refrigeration cycle apparatus (1).

[0074] (7-2) Feature 2 In the cooling operation, the control section (100) of this embodiment performs a first control based on the refrigerant states in the first refrigerant circuit (10A) and the second refrigerant circuit (10B).

[0075] The refrigerant state includes the amount of refrigerant circulating in the refrigerant circuits (10A, 10B), the condensation pressure of the air heat exchangers (12A, 12B), the refrigerant temperature on the outlet side of the air heat exchangers (12A, 12B), the evaporation pressure of the water heat exchangers (14A, 14B), and the refrigerant temperature on the outlet side of the water heat exchangers (14A, 14B). By detecting these, the ratio of the cooling capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) can be determined. This allows the first control to be easily performed.

[0076] (8) Variations In the following modifications, configurations different from the above embodiment will be described.

[0077] (8-1) Variation 1 The control unit (100) of the first modification executes a first control based on the water temperature of the water circuit (30). Specifically, the heat source unit (U1) of the first modification shown in Fig. 5 includes a first water pressure sensor (68), a second water pressure sensor (69), a third water pressure sensor (70), an intermediate water temperature sensor (67), and a second water temperature sensor (66) connected to the water circuit (30).

[0078] The first water pressure sensor (68) detects the pressure of water before it flows into the first water heat exchanger (14A). The first water pressure sensor (68) is located closer to the water inlet side than the first water flow path (14bA).

[0079] The second water pressure sensor (69) detects the water pressure between the first water heat exchanger (14A) and the second water heat exchanger (14B). The second water pressure sensor (69) is provided between the first water flow path (14bA) and the second water flow path (14bB).

[0080] The third water pressure sensor (70) detects the pressure of the water after it has flowed out from the second water heat exchanger (14B). The third water pressure sensor (70) is located closer to the water outlet side than the second water flow path (14bB).

[0081] The intermediate water temperature sensor (67) detects the temperature of water between the first water heat exchanger (14A) and the second water heat exchanger (14B). The intermediate water temperature sensor (67) is provided between the first water flow path (14bA) and the second water flow path (14bB).

[0082] The second water temperature sensor (66) detects the temperature of the water before it flows into the first water heat exchanger (14A). The second water temperature sensor (66) is located closer to the water inlet side than the first water flow path (14bA).

[0083] As shown in FIG. 6, each sensor is connected to the control unit (100) by wire or wirelessly.

[0084] The first control flow of the first modification differs from the first control flow of the above embodiment in step S04. Specifically, in step S03 of the first modification, the control unit (100) determines the cooling capacity of the first refrigerant circuit (10A) and the cooling capacity of the second refrigerant circuit (10B) based on the water temperature and water pressure of the water circuit (30). First, a method for determining the cooling capacity of the first refrigerant circuit (10A) will be described. The flow rate of water flowing through the first water heat exchanger (14A) is determined based on the difference between the water pressure detected by the first water pressure sensor (68) and the water pressure detected by the second water pressure sensor (69), i.e., the difference between the water pressure on the inlet side and the water pressure on the outlet side of the first water flow path (14bA). The control unit (100) also determines the difference between the water temperature detected by the second water temperature sensor (66) and the water temperature detected by the intermediate water temperature sensor (67), i.e., the difference between the water temperature on the inlet side and the water temperature on the outlet side of the first water flow path (14bA). Next, the cooling capacity of the first refrigerant circuit (10A) is calculated based on the calculated water flow rate and water temperature difference.

[0085] The method for determining the cooling capacity of the second refrigerant circuit (10B) will be described. The flow rate of water flowing through the second water heat exchanger (14B) is determined based on the difference between the water pressure detected by the second water pressure sensor (69) and the water pressure detected by the third water pressure sensor (70), i.e., the difference between the water pressure on the inlet side and the water pressure on the outlet side of the second water flow path (14bB). Also, the difference between the water temperature detected by the intermediate water temperature sensor (67) and the water temperature detected by the first water temperature sensor (65), i.e., the difference between the water temperature on the inlet side and the water temperature on the outlet side of the second water flow path (14bB), is determined. Next, the cooling capacity of the second unit () is determined based on the determined water flow rate and water temperature difference.

[0086] Based on the cooling capacities of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) thus determined, the steps from step S05 onwards are executed, which are the same as those in the above embodiment.

[0087] (8-2) Variation 2 In the heating operation of the heat source unit (U1) of this embodiment, the first air heat exchanger (12A) and the second air heat exchanger (12B) function as evaporators. Since the temperature of the air (outside air) exchanging heat with the refrigerant in each air heat exchanger (12A, 12B) is the same, there is no difference in heat exchange capacity between the first air heat exchanger (12A) and the second air heat exchanger (12B) in the heating operation.

[0088] On the other hand, the water in the water circuit (30) is heated in the first water heat exchanger (14A) and then in the second water heat exchanger (14B). That is, the water temperature in the second water flow path (14bB) is higher than the water temperature in the first water flow path (14bA), and therefore the condensation temperature of the refrigerant in the second water heat exchanger (14B) is higher than the condensation temperature of the refrigerant in the first water heat exchanger (14A).

[0089] For this reason, when the first compressor (11A) and the second compressor (11B) are operated at the same rotation speed, the high pressure of the first refrigerant circuit (10A) becomes lower than the high pressure of the second refrigerant circuit (10B). In other words, the high pressure of the second refrigerant circuit (10B) becomes higher than the high pressure of the first refrigerant circuit (10A). When the refrigeration cycle apparatus (1) is operated under such conditions, the power consumption of the second compressor (11B) becomes high, and as a result, the COP of the refrigeration cycle apparatus (1) cannot be said to be good.

[0090] Therefore, the control unit (100) of Modification 2 executes the second control during the heating operation. In the second control, the control unit (100) controls the first compressor (11A) and the second compressor (11B) so that the high pressures of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) approach each other. The flow of the second control will be described below with reference to FIG. 7.

[0091] In step S11, the control section (100) starts the heating operation. The control section (100) adjusts the rotation speeds of the first compressor (11A) and the second compressor (11B) to predetermined rotation speeds.

[0092] In step S12, the control section (100) determines whether the water temperature detected by the first water temperature sensor (65) has reached the target temperature. If it is determined that the water temperature has reached the target temperature (YES in step S12), step S13 is executed. If it is determined that the water temperature has not reached the target temperature (NO in step S12), step S12 is executed again.

[0093] In step S13, the control unit (100) determines whether the difference between the condensing temperature of the first refrigerant circuit (10A) and the condensing temperature of the second refrigerant circuit (10B) is within a predetermined range. The smaller the predetermined range, the better. When the difference between the condensing temperature of the first refrigerant circuit (10A) and the condensing temperature of the second refrigerant circuit (10B) is within the predetermined range, the high pressures of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) are approximately equal. In this state, it can be said that the COP of the heat source unit is good. The condensing temperature of the first refrigerant circuit (10A) is based on the detection value of the first high-pressure pressure sensor (61A). The condensing temperature of the second refrigerant circuit (10B) is based on the detection value of the second high-pressure pressure sensor (61B). When it is determined that the difference between the condensing temperature of the first refrigerant circuit (10A) and the condensing temperature of the second refrigerant circuit (10B) is within the predetermined range (YES in step S13), step S14 is executed. If it is determined that the difference between the condensing temperature of the first refrigerant circuit (10A) and the condensing temperature of the second refrigerant circuit (10B) is outside the predetermined range (NO in step S13), step S15 is executed. The predetermined range may be a range based on the difference in high pressure between the first refrigerant circuit (10A) and the second refrigerant circuit (10B). That is, the predetermined range may be a range based on the difference in detected values ​​between the first high-pressure sensor (61A) and the second high-pressure sensor (61B).

[0094] In step S14, the control unit (100) determines whether a predetermined condition is met. The predetermined condition is a condition under which the COP of the heat source unit (U1) decreases when the difference in condensation temperature between the first refrigerant circuit (10A) and the second refrigerant circuit (10B) is within a predetermined range in step S13. Specifically, the predetermined condition is met when the rotation speed of the first compressor (11A) is equal to or greater than a first rotation speed and the rotation speed of the second compressor (11B) is equal to or greater than a second rotation speed. The first rotation speed and the second rotation speed are determined based on the characteristics of the COP of the heat source unit (U1). For example, the first rotation speed and the second rotation speed are set to values ​​that cause the COP to decrease when the rotation speed of the first compressor (11A) is equal to or greater than the first rotation speed and the rotation speed of the second compressor (11B) is equal to or greater than the second rotation speed.

[0095] If it is determined that the predetermined condition is met (YES in step S14), step S15 is executed. If it is determined that the predetermined condition is not met (NO in step S14), step S16 is executed.

[0096] In step S15, the control unit (100) executes the second control. In this modification, the control unit (100) reduces the rotation speed of the second compressor (11B) so as to lower the condensing temperature of the second refrigerant circuit (10B). Here, the heating operation is an operation that satisfies the capacity required to bring the water in the water circuit (30) to a set temperature, and therefore the heating operation is executed so that when the required capacity is 100%, the sum of the capacity ratios of the first heating capacity and the second heating capacity is 100%.

[0097] Therefore, when the capacity ratio of the second refrigerant circuit (10B) is reduced by reducing the rotation speed of the second compressor (11B), the control unit (100) increases the rotation speed of the first compressor (11A) to increase the capacity ratio of the first refrigerant circuit (10A) accordingly. In this case, the control unit (100) increases the rotation speed of the first compressor (11A) and decreases the rotation speed of the second compressor (11B) so that the high pressures of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) approach each other. Thereafter, step S13 is executed again.

[0098] In step S16, the control section (100) controls the rotation speeds of the first compressor (11A) and the second compressor (11B). Specifically, the control section (100) controls the first compressor (11A) and the second compressor (11B) so that the rotation speed of the first compressor (11A) is equal to or less than a first rotation speed and so that the rotation speed of the second compressor (11B) is equal to or less than a second rotation speed. Thereafter, step S13 is executed again.

[0099] In step S17, the control unit (100) determines whether a command to stop the heating operation has been received. If it is determined that a command to stop the heating operation has been received (YES in step S17), this control flow ends. If it is determined that a command to stop the heating operation has not been received (NO in step S17), step S12 is executed again.

[0100] In this way, by using the second control, the rotation speeds of the first compressor (11A) and the second compressor (11B) are controlled so that the evaporation temperature of the first refrigerant circuit (10A) and the evaporation temperature of the second refrigerant circuit (10B) approach each other, thereby improving the COP of the heat source unit (U1). On the other hand, when attempting to make the evaporation temperature of the first refrigerant circuit (10A) and the evaporation temperature of the second refrigerant circuit (10B) equal, the rotation speeds of the first compressor (11A) and the second compressor (11B) increase, which may result in a decrease in the COP. Therefore, even if the evaporation temperatures of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) are within a predetermined range, if the rotation speed of the first compressor (11A) exceeds the first rotation speed or the rotation speed of the second compressor (11B) exceeds the second rotation speed in step S13, the COP cannot be said to be the highest. Therefore, by adjusting the rotation speed of the first compressor (11A) or the rotation speed of the second compressor (11B) in steps S14 and S16, the COP can be maximized.

[0101] (9) Other embodiments The above embodiment may be configured as follows.

[0102] The first control may be a control to make the rotation speed of the first compressor (11A) lower than the rotation speed of the second compressor (11B). For example, in the above embodiment, if YES is determined in step S04, the control unit (100) may increase the rotation speed of the first compressor (11A) by a predetermined rotation speed and decrease the rotation speed of the second compressor (11B) by a predetermined rotation speed. The predetermined rotation speed may be a preset value.

[0103] The first refrigerant circuit (10A) and the second refrigerant circuit (10B) may each be configured such that a plurality of refrigerant circuits (10A, 10B) share one water heat exchanger (14A, 14B). For example, as shown in Fig. 8, the first refrigerant circuit (10A) and the second refrigerant circuit (10B) may each include two independent refrigerant circuits excluding the water heat exchangers (14A, 14B), and heat exchange between water and refrigerant may occur in one water heat exchanger (14A, 14B).

[0104] In the first control flow of the above embodiment, step S04 may be determined as YES as long as the ratio between the first cooling capacity and the second cooling capacity is approximately equal, even if it is not strictly 1:1. For example, the difference between the ratio of the first cooling capacity and the ratio of the second cooling capacity is preferably less than 10%, more preferably less than 5%, even more preferably less than 2.5%, and most preferably less than 1%.

[0105] The first control of the above embodiment may be performed based on the refrigerant state of the first refrigerant circuit (10A) or the second refrigerant circuit (10B). For example, the second cooling capacity can be calculated based on the difference between the cooling capacity of the entire heat source unit (U1) and the first cooling capacity. Therefore, the second cooling capacity can be calculated by calculating the cooling capacity of the entire heat source unit (U1) based on the water temperature and water pressure of the water flowing through the water circuit (30) and calculating the first cooling capacity based on the refrigerant state of the first refrigerant circuit (10A). The cooling capacity of the entire heat source unit (U1) is calculated based on the details of Modification 1.

[0106] In the second modification, the predetermined condition in step S14 of the second control may be satisfied when the rotation speed of the first compressor (11A) is equal to or greater than the first rotation speed, or when the rotation speed of the second compressor (11B) is equal to or greater than the second rotation speed.

[0107] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be combined or substituted as appropriate as long as the functionality of the subject matter of this disclosure is not impaired. The terms "first," "second," etc., described above, are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0108] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for heat source units. [Explanation of symbols]

[0109] 1 Refrigeration cycle device 10A First refrigerant circuit 10B 2nd refrigerant circuit 11A First compressor 11B Second compressor 12A First air heat exchanger 12B Second air heat exchanger 14A 1st water heat exchanger 14B 2nd water heat exchanger 30 water circuit 100 control section U1 Heat source unit

Claims

1. A heat source unit of a refrigeration cycle apparatus (1) that performs a cooling operation to cool water in a water circuit (30), a first refrigerant circuit (10A) having a first compressor (11A), a first air heat exchanger (12A), and a first water heat exchanger (14A) for exchanging heat between a refrigerant and water in the water circuit (30); a second refrigerant circuit (10B) including a second compressor (11B), a second air heat exchanger (12B), and a second water heat exchanger (14B) for exchanging heat between a refrigerant and water in the water circuit (30); In the cooling operation, the first water heat exchanger (14A) and the second water heat exchanger (14B) function as evaporators, and the first air heat exchanger (12A) and the second air heat exchanger (12B) function as condensers; the water circuit (30) is configured so that water flows through the first water heat exchanger (14A) and then the second water heat exchanger (14B); The cooling operation is an operation that satisfies the capacity required to adjust the water temperature in the water circuit (30) to a target temperature, a control unit (100) that performs first control to control the first compressor (11A) and the second compressor (11B) so that the cooling capacity of the first refrigerant circuit (10A) approaches the cooling capacity of the second refrigerant circuit (10B). Heat source unit.

2. The first control is a control for making the rotation speed of the first compressor (11A) lower than the rotation speed of the second compressor (11B). The heat source unit according to claim 1 .

3. The control unit (100) performs the first control based on the state of refrigerant in the first refrigerant circuit (10A) or the second refrigerant circuit (10B). The heat source unit according to claim 1 or 2.

4. The control section (100) executes the first control based on the water temperature of the water circuit (30). The heat source unit according to claim 1 or 2.

5. The refrigeration cycle apparatus (1) performs a heating operation to heat water in the water circuit (30), In the heating operation, the first water heat exchanger (14A) and the second water heat exchanger (14B) function as condensers, and the first air heat exchanger (12A) and the second air heat exchanger (12B) function as evaporators; The heating operation is an operation that satisfies the capacity required to adjust the water temperature in the water circuit (30) to a target temperature, The control unit (100) performs second control to control the first compressor (11A) and the second compressor (11B) so that the high pressures of the first refrigerant circuit (10A) and the second refrigerant circuit (10B) approach each other. The heat source unit according to claim 1 or 2.

Images