Heat source system

Abstract

A heat source system comprising a plurality of heat source units and a control device for controlling the plurality of heat source units, wherein: the plurality of heat source units are each provided with a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve and a heat-medium heat exchanger are connected; the heat-medium heat exchanger exchanges heat between the refrigerant flowing through the refrigerant circuit and the heat medium supplied to the load unit; the control device detects that one or more of the plurality of heat source units are scheduled to start a defrosting operation, and before the defrosting operation starts, performs a capacity-increasing operation for increasing the total heating capacity of the heat source units other than the heat source units for which the defrosting operation is scheduled.

Description

Technical Field

[0001] The present disclosure relates to a heat source system provided with a plurality of heat source units. Background Art

[0002] In a heat source system provided with a plurality of heat source units, when at least one heat source unit starts a defrosting operation during a heating operation, with the number of heat source units that perform a heating operation reduced, the total heating capacity of the heat source system decreases. When the total heating capacity of the heat source system decreases, the temperature of a heat medium such as water supplied to a load unit decreases.

[0003] To inhibit a decrease in temperature of a heat medium supplied to a load unit, for example, in the heat source system of Patent Literature 1, in a case where a decrease in temperature of a heat medium due to a defrosting operation is detected, it is proposed to increase the frequency of a pump and to increase the flow rate of the heat medium. Citation List Patent Literature

[0004] Patent Literature 1: Japanese Patent No. 6896054 Summary of Invention Technical Problem

[0005] However, in a case where, as in Patent Literature 1, after a decrease in temperature of a heat medium supplied to a load unit is detected, a heating capacity is increased, the followability of the temperature of the heat medium to the target temperature decreases. Thus, until the heating capacity increases, a heat medium that has a temperature lower than the target temperature is supplied to the load unit, causing a disadvantage such as a decrease in user comfort.

[0006] The present disclosure solves such problems described above and provides a heat source system that inhibits a decrease in temperature of a heat medium during a defrosting operation. Solution to Problem

[0007] A heat source system according to an embodiment of the present disclosure includes a plurality of heat source units and a controller configured to control the plurality of heat source units. The plurality of heat source units are each provided with a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and a heat medium heat exchanger are connected. The heat medium heat exchanger exchanges heat between refrigerant that flows through the refrigerant circuit and a heat medium supplied to a load unit. The controller is configured to detect that at least one of the plurality of heat source units is to start a defrosting operation and is configured, before the defrosting operation is started, to perform a capacity enhancement operation that increases a total of heating capacities of remaining heat source units among the plurality of heat source units. The remaining heat source units are other than the at least one of the plurality of heat source units that is to start the defrosting operation. Advantageous Effects of Invention

[0008] A heat source system according to an embodiment of the present disclosure detects that a heat source unit is to start a defrosting operation, performs a capacity enhancement operation before the defrosting operation is started, and thereby maintains a heating capacity before a pre-detection even during the defrosting operation. Therefore, it is possible to inhibit a decrease in temperature of a heat medium supplied to a load unit during the defrosting operation. Brief Description of Drawings

[0009] [Fig. 1] Fig. 1 is a schematic diagram of the configuration of a refrigeration cycle apparatus according to Embodiment 1. [Fig. 2] Fig. 2 is a schematic diagram of the configuration of a heat source unit according to Embodiment 1. [Fig. 3] Fig. 3 is a control block diagram of a heat source system according to Embodiment 1. [Fig. 4] Fig. 4 is a flowchart that illustrates the flow of actions of the heat source system according to Embodiment 1. [Fig. 5] Fig. 5 is a flowchart that illustrates the flow of capacity enhancement processing according to Embodiment 1. [Fig. 6] Fig. 6 is a diagram that illustrates an example of the state transition of the heat source system according to Embodiment 1. [Fig. 7] Fig. 7 is a diagram that illustrates changes in heating capacity and outlet temperature during a defrosting operation in a heat source system according to prior art. [Fig. 8] Fig. 8 is a diagram that illustrates changes in heating capacity and outlet temperature during a defrosting operation in the heat source system according to Embodiment 1. [Fig. 9] Fig. 9 is a flowchart that illustrates the flow of capacity enhancement processing according to Embodiment 2. [Fig. 10] Fig. 10 is a diagram that illustrates changes in heating capacity and outlet temperature during a defrosting operation in a heat source system according to Embodiment 2. Description of Embodiments

[0010] Embodiments are described below with reference to drawings. Note that elements given the same reference signs in each drawing are the same or equivalent elements, and the same applies throughout the whole description of the specification. Also, the forms of components described throughout the whole description of the specification are illustrative only and are not limited to those described. Furthermore, the relationship in size among components illustrated in the following drawings may differ from the actual relationship.

[0011] Embodiment 1 Fig. 1 is a schematic diagram of the configuration of a refrigeration cycle apparatus 100 according to Embodiment 1. The refrigeration cycle apparatus 100 of the present Embodiment 1 is a heat pump chiller that conditions air by use of a heat medium that flows through a heat medium circuit 40. As illustrated in Fig. 1, the refrigeration cycle apparatus 100 includes a heat source system 1 and a plurality of load units 2. In the example in Fig. 1, two load units 2 are illustrated. However, the number of load units 2 may be one or may be three or more. The heat source system 1 includes a plurality of heat source units 10A, 10B, 10C, and 10D and a controller 5. The plurality of heat source units 10A, 10B, 10C, and 10D are connected in parallel with each other to the heat medium circuit 40.

[0012] Fig. 2 is a schematic diagram of the configuration of the heat source unit 10A according to Embodiment 1. The heat source units 10B, 10C, and 10D each have the same configuration as the heat source unit 10A. As illustrated in Fig. 2, the heat source unit 10A is provided with two systems of refrigerant circuits 11, a heat medium heat exchanger 41 through which the two systems of refrigerant circuits 11 pass, and a pump 42.

[0013] As illustrated in Fig. 2, each of the refrigerant circuits 11 of the heat source unit 10A includes a compressor 12, a flow switching valve 13, an outdoor heat exchanger 14, an expansion valve 15, the heat medium heat exchanger 41, and an accumulator 16. The compressor 12, the flow switching valve 13, the outdoor heat exchanger 14, the expansion valve 15, the heat medium heat exchanger 41, and the accumulator 16 are connected by pipes, and the refrigerant circuit 11 is thereby formed.

[0014] Refrigerant that flows through the refrigerant circuit 11 is, for example, a singlecomponent refrigerant such as R-22 and R-134a, a near-azeotropic refrigerant mixture such as R-410A and R-404A, or a zeotropic refrigerant mixture such as R-407C. Also, a refrigerant or a mixture of the refrigerant, such as CF3CF=CH2, which contains a double bond in the chemical formula and is considered to have a relatively low global warming potential, or a natural refrigerant such as CO2 and propane may be used.

[0015] The compressor 12 draws in, compresses, and discharges refrigerant. The compressor 12 is driven by an inverter drive device (not illustrated) or another similar device. The operating frequency of the compressor 12 is controlled by the controller 5. By thus controlling the operating frequency of the compressor 12, the capacity of the compressor 12, which is the amount of refrigerant sent per unit time, is changed.

[0016] The flow switching valve 13 switches between a cooling operation and a defrosting operation both in which the outdoor heat exchanger 14 functions as a condenser and a heating operation in which the outdoor heat exchanger 14 functions as an evaporator. The flow switching valve 13 is, for example, a four-way valve, and its switching is controlled by the controller 5. The flow switching valve 13 is switched such that, in a cooling operation or a defrosting operation, as indicated by solid lines in Fig. 1, refrigerant discharged from the compressor 12 flows into the outdoor heat exchanger 14. Also, the flow switching valve 13 is switched such that, in a heating operation, as indicated by dashed lines in Fig. 1, refrigerant discharged from the compressor 12 flows into the heat medium heat exchanger 41.

[0017] The outdoor heat exchanger 14 is, for example, a fin-and-tube heat exchanger and exchanges heat between refrigerant that flows inside a heat transfer tube and air supplied by an outdoor fan 17. Ina heating operation (heating up operation) in which a heat medium is heated up, the outdoor heat exchanger 14 functions as an evaporator, exchanges heat between low-pressure refrigerant that has flowed in from the expansion valve 15 and air, and evaporates and gasifies the refrigerant. Also, in a cooling operation or a defrosting operation (cooling down operation) in which a heat medium is cooled down, the outdoor heat exchanger 14 functions as a condenser, exchanges heat between high-pressure refrigerant that has flowed in from the compressor 12 and air, and condenses and liquefies the refrigerant.

[0018] The expansion valve 15 expands refrigerant and reduces its pressure. The expansion valve 15 of the present embodiment is an electronic expansion valve that has an adjustable opening degree. The opening degree of the expansion valve 15 is controlled by the controller 5. Note that the expansion valve 15 may be, for example, a thermostatic expansion valve of which opening degree changes on the basis of the temperature of refrigerant.

[0019] The accumulator 16 is provided at the suction side of the compressor 12 and stores refrigerant that is in excess in the refrigerant circuit 11. The accumulator 16 is not an essential component in the refrigerant circuit 11 and may be omitted.

[0020] The outdoor fan 17 sends air to the outdoor heat exchanger 14 and promotes heat exchange between refrigerant and air. The outdoor fan 17 is driven by an inverter drive device (not illustrated) or another similar device. The rotational speed of the outdoor fan 17 is controlled by the controller 5. By thus controlling the rotational speed of the outdoor fan 17, the flow rate of air is changed. In Fig. 2, the outdoor heat exchanger 14 and the outdoor fan 17 correspond one-to-one. However, the configuration is not limited to this combination, and a plurality of outdoor fans 17 may be provided for one outdoor heat exchanger 14.

[0021] The heat medium heat exchanger 41 exchanges heat between a heat medium that flows through the heat medium circuit 40 and refrigerant that flows through the refrigerant circuit 11. The heat medium is water, brine (antifreeze), or a mixture of water and brine, and, in particular in the present disclosure, refers to a heat medium other than a refrigerant. Description is made below in a case where the heat medium is water; however, all portions described as water are replaceable with heat medium. The heat medium heat exchanger 41 serves as a portion of the flow passages of the two systems of refrigerant circuits 11 and as a portion of the flow passage of the heat medium circuit 40. Therefore, the heat medium heat exchanger 41 serves as a device that forms a portion of the refrigerant circuits 11 and as a device that forms a portion of the heat medium circuit 40. The heat medium heat exchanger 41, for example, functions as a condenser in a heating operation, exchanges heat between refrigerant that has flowed in from the compressor 12 and water, condenses the refrigerant into a liquid or a two-phase gas-liquid state, and heats the water. On the other hand, in a cooling operation, the heat medium heat exchanger 41 functions as an evaporator, exchanges heat between refrigerant that has flowed in from the expansion valve 15 and water, evaporates the refrigerant into a gas state, and cools the water.

[0022] The pump 42 draws in water that flows through the heat medium circuit 40, pressurizes and sends out the water, and circulates the water through the heat medium circuit 40. The pump 42 is driven by an inverter drive device (not illustrated) or another similar device. The operating frequency of the pump 42 is controlled by the controller 5. By thus controlling the operating frequency of the pump 42, the capacity of the pump 42 is changed.

[0023] Also, the heat source unit 10A is provided with an inlet temperature sensor 31, an outlet temperature sensor 32, heat exchange temperature sensors 33, and an outdoor air temperature sensor 34. The inlet temperature sensor 31 is provided upstream of the heat medium heat exchanger 41 in the direction in which water flows and measures an inlet temperature Tin, which is the temperature of water that flows into the heat medium heat exchanger 41. The outlet temperature sensor 32 is provided downstream of the heat medium heat exchanger 41 in the direction in which water flows and measures an outlet temperature Tout, which is the temperature of water that flows out from the heat medium heat exchanger 41. The heat exchange temperature sensors 33 each measure a refrigerant temperature Tr, which is the temperature of refrigerant that flows through the outdoor heat exchanger 14 in the corresponding one of the refrigerant circuits 11. The outdoor air temperature sensor 34 measures an outdoor air temperature Te, which is the temperature of an outdoor space in which the heat source unit 10A is installed. Each temperature sensor is formed by, for example, a thermistor and outputs the measured temperature to the controller 5. Note that, in the present embodiment, the heat source units 10Ato 10D are each provided with the outdoor air temperature sensor 34. However, the configuration is not limited to these combinations and need only be a configuration in which the heat source system 1 is provided with at least one outdoor air temperature sensor 34.

[0024] With reference back to Fig. 1, the load units 2 are each a unit that sends conditioned air into an indoor space, which is the target to be air-conditioned. As illustrated in Fig. 1, the load units 2 of the present embodiment each have an indoor heat exchanger 21, a flow control valve 22, and an indoor fan 23. The indoor heat exchangers 21 and the flow control valves 22 each serve as a device that forms a portion of the heat medium circuit 40. That is, the indoor heat exchangers 21 and the flow control valves 22 in the load units 2 and the heat medium heat exchangers 41 and the pumps 42 in the heat source units 10Ato 10D are connected by pipes, and the heat medium circuit 40 is thereby formed.

[0025] The indoor heat exchanger 21 is, for example, a fin-and-tube heat exchanger and exchanges heat between refrigerant that flows inside a heat transfer tube and air supplied by the outdoor fan 17. In a cooling operation, water colder than air flows through a heat transfer tube of the indoor heat exchanger 21, and an indoor space is cooled. On the other hand, in a heating operation, water warmer than air flows through the heat transfer tube of the indoor heat exchanger 21, and the indoor space is heated.

[0026] The flow control valve 22 is, for example, a two-way valve or another similar device that controls the opening degree (opening area) of the valve. The flow control valve 22 controls the flow rate of water that flows into the indoor heat exchanger 21 or that flows out from the indoor heat exchanger 21 according to the opening degree. In detail, the flow control valve 22 adjusts the amount of water that passes through the indoor heat exchanger 21 on the basis of the temperatures of the water that flows into and flows out from the load unit 2 such that the indoor heat exchanger 21 exchanges heat according to the amount of heat that corresponds to the thermal load of an indoor space. Here, when the indoor heat exchanger 21 does not need to exchange heat with the thermal load, such as when the operation is stopped or is in a thermo-off, the flow control valve 22 is in a fully closed state and stops water supply so that water does not flow into and flow out from the indoor heat exchanger 21. In Fig. 1, the flow control valve 22 is installed at a pipe at the water inlet side of the indoor heat exchanger 21. However, the flow control valve 22 may be installed at the water outlet side of the indoor heat exchanger 21.

[0027] The indoor fan 23 causes air in the indoor space to pass through the indoor heat exchanger 21 and generates a flow in which the air returns to the indoor space. The indoor fan 23 is driven by an inverter drive device (not illustrated) or another similar device. The rotational speed of the indoor fan 23 is controlled by the controller 5. By thus controlling the rotational speed of the indoor fan 23, the flow rate of air is changed.

[0028] The controller 5 controls the actions of the heat source system 1. The controller 5 is formed by a computer provided with a memory that stores data and a program required for control or a processor such as a CPU that executes the program and a dedicated processing circuit such as an ASIC and an FPGA, or both. Note that the controller 5 may be one that controls the load units 2. Alternatively, although no illustration is provided, the load units 2 may each be provided with a controller that controls the load unit 2.

[0029] Fig. 3 is a control block diagram of the heat source system 1 according to Embodiment 1. The controller 5 in the heat source system 1 controls the heat source units 10Ato 10D on the basis of measurement results by the respective temperature sensors provided in the heat source units 10Ato 10D and instructions from a remote control (not illustrated). As illustrated in Fig. 3, the controller 5 includes operation control circuitry 51, pre-detection circuitry 52, capacity enhancement circuitry 53, and memory circuitry 54. The operation control circuitry 51, the pre-detection circuitry 52, and the capacity enhancement circuitry 53 are functional units implemented by a processor provided in the controller 5 executing a program. Alternatively, at least one of the operation control circuitry 51, the predetection circuitry 52, and the capacity enhancement circuitry 53 may be implemented by a processing circuit such as an ASIC and an FPGA.

[0030] The operation control circuitry 51 controls each of the heat source units 10Ato 10D and performs a cooling operation, a heating operation, and a defrosting operation in the refrigeration cycle apparatus 100. Specifically, the operation control circuitry 51 controls the operating frequency of the compressor 12, the switching of the flow switching valve 13, the opening degree of the expansion valve 15, the rotational speed of the outdoor fan 17, and the operating frequency of the pump 42 on the basis of the settings of the operation mode and the set temperature input by a user and measurement results by the respective temperature sensors.

[0031] In detail, the operation control circuitry 51 performs a cooling operation or a heating operation according to the settings of the operation mode and the set temperature input by a user. In a cooling operation and a heating operation, the operation control circuitry 51 controls the compressor 12, the expansion valve 15, the outdoor fan 17, and the pump 42 such that the outlet temperature Tout measured by the outlet temperature sensor 32 becomes a target temperature Tm that corresponds to the set temperature.

[0032] Also, in a case where, in a heating operation, a defrosting condition is satisfied in any of the heat source units 10Ato 10D, the operation control circuitry 51 starts a defrosting operation in a heat source unit in which a defrosting condition is satisfied. The defrosting condition is that a state continues for a preset first period (for example, 10 minutes) in which a difference ATf (= Te - Tr) between the refrigerant temperature Tr measured by one of the heat exchange temperature sensors 33 and the outdoor air temperature Te measured by the outdoor air temperature sensor 34 of any of the heat source units 10A to 10D is higher than or equal to a threshold Tth. Note that the defrosting condition is not limited to the one described above, and may, for example, be that the refrigerant temperature Tr measured by one of the heat exchange temperature sensors 33 falls below a threshold temperature or that a time that has elapsed after the end of the previous defrosting operation exceeds a threshold time.

[0033] The operation control circuitry 51 switches the flow switching valves 13 in a heat source unit among the heat source units 10Ato 10D in which the defrosting condition is satisfied to the same state as in a cooling operation, causes the corresponding outdoor heat exchangers 14 to function as condensers, and thereby performs defrosting. Note that, in a case where both refrigerant temperatures Tr measured by the heat exchange temperature sensors 33 in the two refrigerant circuits 11 provided in any of the heat source units 10A to 10D satisfy the defrosting condition, the operation control circuitry 51 may start a defrosting operation in the corresponding heat source unit. Alternatively, in a case where either of the refrigerant temperatures Tr satisfies the defrosting condition, the operation control circuitry 51 may start a defrosting operation in the corresponding heat source unit.

[0034] The pre-detection circuitry 52 pre-detects a defrosting operation in any of the heat source units 10A to 10D. "Pre-detects a defrosting operation" refers to detecting, before a defrosting operation is actually started, that the defrosting operation is to be started in any of the heat source units 10Ato 10D. Here, "the defrosting operation is to be started" includes not only a case where the start time or another set time of the defrosting operation is determined in advance, but also a case where the start of the defrosting operation is expected.

[0035] The pre-detection circuitry 52 pre-detects a defrosting operation, for example, in a case where a state in which the difference ATf between the refrigerant temperature Tr and the outdoor air temperature Te of any of the heat source units 10A to 10D is higher than or equal to the threshold Tth continues for a second period (for example, 5 minutes) that is shorter than the first period, which defines the defrosting condition. The second period is preset and stored in the memory circuitry 54 such that the difference from the first period, which defines the start of defrosting, corresponds to the time until a heat source unit that is stopped is activated and the outlet temperature Tout reaches the target temperature Tm.

[0036] In a case where a defrosting operation is pre-detected by the pre-detection circuitry 52, the capacity enhancement circuitry 53 increases the heating capacities of heat source units among the heat source units 10A to 10D that are not to start a defrosting operation. When any of the heat source units 10Ato 10D in a heating operation starts a defrosting operation, the total heating capacity of the heat source system 1 decreases, and the temperature of water supplied to the load units 2, that is, the outlet temperature Tout, decreases. To compensate for a decrease in the heating capacity caused by a defrosting operation of any of the heat source units 10A to 10D, the capacity enhancement circuitry 53 increases the heating capacities of the heat source units that are not to start a defrosting operation.

[0037] The memory circuitry 54 is, for example, a non-volatile semiconductor memory such as a ROM and a flash memory, a volatile semiconductor memory such as a RAM, an HDD, or an SSD. The memory circuitry 54 stores various data such as a program executed by the controller 5 and a threshold value used in the execution of a program.

[0038] Subsequently, actions of the heat source system 1 are described below with reference to Figs. 4 to 6. Fig. 4 is a flowchart that illustrates the flow of actions of the heat source system 1 according to Embodiment 1. Each processing illustrated in the flowchart of Fig. 4 is executed by the controller 5 when the refrigeration cycle apparatus 100 is performing a heating operation.

[0039] As illustrated in Fig. 4, first, it is determined whether a defrosting operation in any of the heat source units 10A to 10D is pre-detected by the pre-detection circuitry 52 (S1). In a case where a defrosting operation in any of the heat source units 10A to 10D is not pre-detected (NO in S1), the heating operation is continued. On the other hand, in a case where a defrosting operation in any of the heat source units 10A to 10D is pre-detected (YES in S1), capacity enhancement processing is executed by the capacity enhancement circuitry 53 (S2).

[0040] Fig. 5 is a flowchart that illustrates the flow of the capacity enhancement processing according to Embodiment 1. In the present processing, first, the capacity enhancement circuitry 53 calculates a total heating capacity Qa of the heat source system 1 in the current heating operation and stores it in the memory circuitry 54 (S21). The total heating capacity Qa of the heat source system 1 is a total of heating capacities of respective heat source units that are performing the heating operation. The heating capacity of each heat source unit that is performing the heating operation is obtained by a known method on the basis of the operating frequencies of the compressors 12 in the heat source unit.

[0041] Fig. 6 is a diagram that illustrates an example of the state transition of the heat source system 1 according to Embodiment 1. State (a) in Fig. 6 illustrates an example of the operation states of the heat source units WAto 10D in a heating operation. In state (a), the heat source units 10A, 10B, and 10D are performing a heating operation, and the heat source unit 10C is stopped. In this case, when a heating capacity of each of the heat source units 10A, 10B, and 10D is defined as A, the total heating capacity Qa of the heat source system 1 is 3A. The heating capacity Qa at this time is balanced with the loads of the load units 2 and the temperature of water supplied to the load units 2 follows the target temperature Tm.

[0042] Subsequently, the capacity enhancement circuitry 53 calculates a temperature difference ATa (= Tout - Tin), which is the difference between the outlet temperature Tout and the inlet temperature Tin of the heat source system 1 and stores it in the memory circuitry 54 (S22). The temperature difference ATa is the difference between the outlet temperature Tout and the inlet temperature Tin of any of the heat source units 10A, 10B, and 10D, which are performing the heating operation, or an average value of differences between the outlet temperatures Tout and the inlet temperatures Tin of the respective heat source units 10A, 10B, and 10D, which are performing the heating operation.

[0043] Then, the capacity enhancement circuitry 53 calculates a target heating capacity Qb of the heat source system 1 (S23). The target heating capacity Qb is a heating capacity required to inhibit a decrease in temperature of water supplied to the load units 2 also in a case where any of the heat source units 10A to 10D starts a defrosting operation. The target heating capacity Qb is obtained from mathematical formula (1) described below. Qb = Qa + B (1)

[0044] Qa is the total heating capacity of the heat source system 1 at the time of predetection stored in step S21 and, in a case of the example in Fig. 6, is 3A. B is estimated heat extraction amounts of heat source units that are to perform a defrosting operation. The estimated heat extraction amount B is determined by the operation states of the compressors 12 in a heat source unit that performs a defrosting operation. In a case where the operating frequencies of the compressors 12 are constant, the heat extraction amount B is calculated from conditions such as the operating frequencies of the compressors 12 and the outdoor air temperature Te. In a case where the operating frequencies of the compressors 12 vary, the heat extraction amounts B in prior defrosting operations are stored in the memory circuitry 54, and the heat extraction amount B is estimated from conditions such as the outdoor air temperature Te.

[0045] Then, the capacity enhancement circuitry 53 calculates a target temperature difference ATb (S24). The target temperature difference ATb is obtained from mathematical formula (2) described below. ATb = ATa x Qb / Qa (2)

[0046] Subsequently, the capacity enhancement circuitry 53 increases the capacities of the heat source units among the heat source units 10Ato 10D that are not to start a defrosting operation. In detail, the capacity enhancement circuitry 53 determines whether any heat source unit is currently stopped (S25). Then, in a case where any heat source unit is currently stopped, the capacity enhancement circuitry 53 starts the stopped heat source unit (S26). Here, the capacity enhancement circuitry 53 determines the number of heat source units to be activated such that the number of heat source units that are performing a heating operation after the start of the defrosting operation is the same as the number of heat source units that are currently performing a heating operation. In other words, the capacity enhancement circuitry 53 activates the same number of heat source units that are currently stopped as the number of heat source units that are to perform a defrosting operation. In a case where the number of heat source units that are stopped is smaller than the number of heat source units that are to perform a defrosting operation, all the heat source units that are stopped are activated. In a case where no heat source unit is currently stopped (NO in S25), that is, in a case where all the heat source units in the heat source system 1 are performing a heating operation, the processing in step S26 is skipped.

[0047] Then, the capacity enhancement circuitry 53 controls the heat source units that are not to perform a defrosting operation such that the temperature difference (Tout -Tin) between the outlet temperature Tout and the inlet temperature Tin of each of the heat source units that are not to perform a defrosting operation satisfies the target temperature difference ATb (S27). The processing in steps S25 to S27 refers to "capacity enhancement operation". State (b) in Fig. 6 illustrates a state where the heat source system 1 is performing a capacity enhancement operation. As illustrated in state (b), in a case where the heat source unit 10B is to perform a defrosting operation, first, the heat source unit 10C, which has been stopped, is activated, and the heat source units 10A, 10C, and 10D, which are other than the heat source unit 10B, which is to perform a defrosting operation, are set to the target temperature difference ATb, and are controlled such that the target temperature difference ATb is satisfied. Therefore, the heating capacities of the heat source units 10A, 10C, and 10D, which are not to perform a defrosting operation, are increased to Ai. Here, the relationships Ai >A and Qb = 3Ai are satisfied.

[0048] With reference back to Fig. 4, the operation control circuitry 51 determines whether to start a defrosting operation in the heat source units that are to perform a defrosting operation (S3). In a case where a defrosting operation is not started (NO in S3), the capacity enhancement operation is continued until a defrosting operation is started. On the other hand, in a case where a defrosting operation is started (YES in S3), the operation control circuitry 51 switches the flow switching valves 13 in the heat source units that are to perform a defrosting operation, causes the corresponding outdoor heat exchangers 14 to function as condensers, and thereby performs a defrosting operation (S4).

[0049] State (c) in Fig. 6 illustrates a state where a defrosting operation is started in the heat source unit 10B. As illustrated in state (c), also after a defrosting operation is started in the heat source unit 10B, a capacity enhancement operation is continued in the heat source units 10A, 10C, and 10D, which are performing a heating operation. Therefore, in a case where a defrosting operation is started in the heat source unit 10B, the total heating capacity of the heat source system 1 is adjusted to Qb - B = Qa and is thus brought into the same state as state (a), which is before the defrosting operation is performed. As a result, a decrease in temperature of water supplied to the load units 2 is inhibited.

[0050] Subsequently, the operation control circuitry 51 determines whether to end the defrosting operation (S5). In a case where the defrosting operation is not ended (NO in S5), the defrosting operation is continued. On the other hand, in a case where the defrosting operation is ended (YES in S5), the operation control circuitry 51 determines whether the number of heat source units that are currently performing a heating operation is the same as the number of heat source units that are performing a heating operation before the pre-detection (S6). Then, in a case where the number of heat source units that are currently performing a heating operation is the same as the number of heat source units that are performing a heating operation before the pre-detection (YES in S6), the heat source units that are performing a defrosting operation are stopped (S7). On the other hand, in a case where the number of heat source units that are currently performing a heating operation differs from the number of heat source units that are performing a heating operation before the pre-detection (NO in S6), the operation control circuitry 51 switches the flow switching valves 13 of the heat source units that are performing a defrosting operation to a heating operation (S8).

[0051] That is, in a capacity enhancement operation, in a case where the same number of heat source units that are stopped as the number of heat source units that are to perform a defrosting operation are activated, the number of heat source units that are currently performing a heating operation is the same as the number of heat source units that are performing a heating operation before the pre-detection, and the heat source units that are performing a defrosting operation are thus stopped. On the other hand, in a capacity enhancement operation, in a case where no heat source unit is stopped or in a case where the number of heat source units that are stopped is smaller than the number of heat source units that are to perform a defrosting operation, the number of heat source units that are currently performing a heating operation is smaller than the number of heat source units that are performing a heating operation before the pre-detection, and the heat source units that are performing a defrosting operation are thus switched to a heating operation. As described above, in any of a heating operation, a capacity enhancement operation, and a defrosting operation, by maintaining the number of heat source units that perform a heating operation the same as possible, the heat source system 1 is operated efficiently.

[0052] Then, the operation control circuitry 51 controls the heat source units that are performing a heating operation such that the outlet temperatures Tout of the heat source units that are performing a heating operation satisfy the target temperature Tm (S9). Therefore, the same heating operation is performed as before the predetection. State (d) in Fig. 6 illustrates a state after the defrosting operation in the heat source unit 10B ends. In a case of the example in Fig. 6, in state (b), when the defrosting operation in the heat source unit 10B ends, the heat source unit 10B is stopped. Then, in the heat source units 10A, 10C, and 10D, which are performing a heating operation, the outlet temperatures Tout are controlled to satisfy the target temperature Tm, and the heating capacities of the respective heat source units are reduced from Ai to A. Therefore, the total heating capacity of the heat source system 1 is adjusted to Qa = 3A.

[0053] Subsequently, an effect of the heat source system 1 of the present embodiment over prior art is described. First, the prior art is described below. Fig. 7 is a diagram that illustrates changes in heating capacity and outlet temperature Tout during a defrosting operation in a heat source system according to prior art. As illustrated in Fig. 7, in the heat source system of the prior art, when any of a plurality of heat source units that are performing a heating operation starts a defrosting operation at time t1, the total heating capacity of the heat source system decreases. An explanation is given below with reference to the example in Fig. 6. In a case where the total heating capacity of the heat source system before a defrosting operation is started is expressed as Qa = 3A, when one heat source unit starts a defrosting operation, the total heating capacity of the heat source system is expressed as "2A - heat extraction amount B due to the defrosting operation".

[0054] Whereas the heating capacity required to maintain an outlet temperature Tout at a target temperature is 3A, the heating capacity is decreased to 2A - B due to the defrosting operation, and the temperature of water supplied to load units 2 is thus decreased. When the heat source system of the prior art detects a decrease in temperature of water supplied to the load units, the heat source system increases the capacities of the heat source units that are performing a heating operation. However, the capacities of the heat source units are thus increased after the temperature of supplied water decreases, and the temperature of supplied water continues decreasing until the total heating capacity of the heat source system reaches the required heating capacity (3A). During this time, the temperature of supplied air decreases at the load units 2, and user comfort is thus decreased.

[0055] Fig. 8 is a diagram that illustrates changes in heating capacity and outlet temperature Tout during a defrosting operation in the heat source system 1 according to Embodiment 1. As illustrated in Fig. 8, at time to, which is set before time t1, which is the time at which any of the plurality of heat source units that are performing a heating operation starts a defrosting operation, the heat source system 1 of Embodiment 1 pre-detects the defrosting operation and performs a capacity enhancement operation. Therefore, even when the heating capacity decreases due to the start of a defrosting operation, the total heating capacity of the heat source system 1 is maintained as Qa = 3A, which is the total heating capacity of the heat source system 1 before the defrosting operation is started. Therefore, it is possible to inhibit a decrease in temperature of a heat medium during a defrosting operation and to maintain user comfort.

[0056] Embodiment 2 Embodiment 2 is described below. A refrigeration cycle apparatus 100 of Embodiment 2 differs from Embodiment 1 in a timing at which a capacity enhancement operation is performed. The configuration of the refrigeration cycle apparatus 100 of Embodiment 2 is the same as that of Embodiment 1.

[0057] Fig. 9 is a flowchart that illustrates the flow of capacity enhancement processing according to Embodiment 2. The processing in steps S201 to S204 in the present embodiment is the same as the processing in steps S21 to S24 of Embodiment 1.

[0058] When capacity enhancement circuitry 53 calculates a target temperature difference ATb, the capacity enhancement circuitry 53 calculates a start time ta of a capacity enhancement operation (S205). Here, first, the capacity enhancement circuitry 53 calculates a required time At, which is a time required until the total heating capacity of a heat source system 1 reaches a target heating capacity Qb. The required time At is, in a case where any heat source unit is stopped, the time from a point at which the stopped heat source unit is activated to a point at which the target temperature difference ATb is satisfied. Also, in a case where no heat source unit is stopped, the required time At is the time until the heat source units other than the heat source units that are to perform a defrosting operation each satisfy the target temperature difference ATb. The required time At may be obtained in advance for each target temperature difference ATb and each operation state and may be stored in memory circuitry 54 and, alternatively, may be calculated by use of a function or another scheme with the target temperature difference ATb and the operation state serving as variables. Then, the capacity enhancement circuitry 53 defines the time obtained by subtracting the required time At from time t1 at which a defrosting operation is started as the start time ta of a capacity enhancement operation.

[0059] Subsequently, the capacity enhancement circuitry 53 determines whether the current time is the start time ta of a capacity enhancement operation (S206). In a case where the current time is not the start time ta of a capacity enhancement operation (NO in S206), the capacity enhancement circuitry 53 waits until the current time is the start time ta of a capacity enhancement operation.

[0060] On the other hand, in a case where the current time is the start time ta of a capacity enhancement operation (YES in S206), the capacity enhancement circuitry 53 performs the same capacity enhancement operation as that in Embodiment 1. The processing in steps S207 to S209 is the same as the processing in steps S25 to S27 of Embodiment 1. That is, in Embodiment 1, a capacity enhancement operation is started at a timing at which a defrosting operation is pre-detected. However, the present embodiment provides a configuration such that the timing of a capacity enhancement operation is determined separately from the timing of pre-detection.

[0061] An effect of the heat source system 1 of the present embodiment is described below. Fig. 10 is a diagram that illustrates changes in heating capacity and outlet temperature Tout during a defrosting operation in the heat source system 1 according to Embodiment 2. As illustrated in Fig. 10, at time to, which is set before time t1, which is the time at which any of the plurality of heat source units that are performing a heating operation starts a defrosting operation, the heat source system 1 of Embodiment 2 pre-detects the defrosting operation. Then, at the time ta, which is after the time to at which pre-detection is performed and before a start time t2 of a defrosting operation, a capacity enhancement operation is started.

[0062] Therefore, as in Embodiment 1, even when the heating capacity decreases due to the start of a defrosting operation, the total heating capacity of the heat source system 1 is maintained as Qa = 3A, which is the total heating capacity of the heat source system 1 before the defrosting operation is started. Therefore, it is possible to inhibit a decrease in temperature of a heat medium supplied to load units 2 and to maintain user comfort. Also, in the present embodiment, the timing at which a capacity enhancement operation is started is determined with the time required until the heating capacities of the heat source units that are not to perform a defrosting operation increase taken into consideration. It is thereby possible to shorten the time of a capacity enhancement operation, which would be performed with more heating capacity than necessary, as compared with Embodiment 1. Therefore, it is possible to inhibit an increase in consumed electric power due to a capacity enhancement operation.

[0063] The embodiments are as described above. The present disclosure is not limited to the embodiments described above and may be variously modified or combined without departing from the spirit of the present disclosure. For example, in the embodiments described above, a case is described where the refrigeration cycle apparatus 100 is a heat pump chiller. However, the refrigeration cycle apparatus 100 may be a heating-only unit provided with no heating and cooling switcher unit, a water heater device, or another similar device. In a case where the refrigeration cycle apparatus 100 is a heating-only unit, the flow switching valves 13 are omitted.

[0064] Also, the embodiments described above provide a configuration in which the heat source system 1 is provided with the four heat source units 10Ato 10D; however, the number of heat source units need only be two or more. Also, the embodiments described above provide a configuration in which each of the heat source units 10Ato 10D has the two systems of refrigerant circuits 11; however, each of the heat source units 10Ato 10D may have one system or three or more systems of refrigerant circuits 11.

[0065] Also, the embodiments described above provide a configuration in which the controller 5 provided separately from each of the heat source units 10Ato 10D controls the heat source system 1. However, the configuration is not limited to this arrangement. For example, the heat source units 10Ato 10D may each have a controller, and the functional units of the controller 5 of the heat source system 1 may each be shared by the controllers of the heat source units 10A to 10D. Specifically, the controllers of the heat source units 10Ato 10D may each have the operation control circuitry 51 and the pre-detection circuitry 52, and any one of the heat source units 10Ato 10D may be defined as a master unit of which controller has the capacity enhancement circuitry 53. In this case, each of the heat source units 10Ato 10D pre-detects that the unit itself is to start a defrosting operation and notifies the master unit of the pre-detection. When the master unit is notified of the pre-detection, the master unit calculates the target temperature difference ATb and notifies each of the heat source units 10Ato 10D of the calculated difference, and it is thereby possible to perform a capacity enhancement operation before the start of a defrosting operation.

[0066] Furthermore, in the embodiments described above, a defrosting operation is pre-detected in a case where a state where the difference ATf between the refrigerant temperature Tr and the outdoor air temperature Te of any of the heat source units 10A to 10D is higher than or equal to the threshold Tth continues for the second period. However, the method of pre-detection is not limited to this condition. The predetection circuitry 52 need only estimate a defrosting start time at which a defrosting condition is satisfied and pre-detect a defrosting operation at the preset second period (for example, 5 minutes) before the defrosting start time. For example, the pre-detection circuitry 52 may estimate a time at which the defrosting condition is reached on the basis of the rate of increase of the difference ATf between the refrigerant temperature Tr and the outdoor air temperature Te of any of the heat source units 10Ato 10D and may pre-detect a defrosting operation at the second period before the time at which the defrosting condition is reached. Alternatively, the pre-detection circuitry 52 may estimate a time at which the defrosting condition is reached on the basis of the rate of decrease of the refrigerant temperature Tr measured by one of the heat exchange temperature sensors 33 and may pre-detect a defrosting operation at the second period before the time at which the defrosting condition is reached. Alternatively, the pre-detection circuitry 52 may pre-detect a defrosting operation in a case where the elapsed time from the end of the previous defrosting operation reaches (threshold time - the second period).

[0067] Also, in a case where, even when a preset time (for example, 10 minutes) elapses after the start of a capacity enhancement operation, a defrosting operation is not started, the heat source system 1 may end the capacity enhancement operation and return to a heating operation. In this case, the operation control circuitry 51 determines whether the number of heat source units that are currently performing a heating operation is the same as the number of heat source units that are performing a heating operation before the pre-detection. Then, in a case where the number of heat source units that are currently performing a heating operation is the same as the number of heat source units that are performing a heating operation before the predetection, the heat source units are controlled such that the outlet temperatures Tout of the heat source units that are performing a heating operation satisfy the target temperature Tm. On the other hand, in a case where the number of heat source units that are currently performing a heating operation differs from the number of heat source units that are performing a heating operation before the pre-detection, that is, in a case where the stopped heat source units are activated to perform a capacity enhancement operation, the operation control circuitry 51 stops the heat source units that are to perform a defrosting operation and controls the heat source units such that the outlet temperatures Tout of the heat source units that are performing a heating operation satisfy the target temperature Tm. Therefore, it is possible to inhibit a capacity enhancement operation from being continued unintentionally for a long time. Reference Signs List

[0068] 1: heat source system, 2: load unit, 5: controller, 10A, 10B, 10C, 10D: heat source unit, 11: refrigerant circuit, 12: compressor, 13: flow switching valve, 14: outdoor heat exchanger, 15: expansion valve, 16: accumulator, 17: outdoor fan, 21: 5 indoor heat exchanger, 22: flow control valve, 23: indoor fan, 31: inlet temperature sensor, 32: outlet temperature sensor, 33: heat exchange temperature sensor, 34: outdoor air temperature sensor, 40: heat medium circuit, 41: heat medium heat exchanger, 42: pump, 51: operation control circuitry, 52: pre-detection circuitry, 53: capacity enhancement circuitry, 54: memory circuitry, 100: refrigeration cycle 10 apparatus

Claims

1. A heat source system comprising:a plurality of heat source units; anda controller configured to control the plurality of heat source units,the plurality of heat source units being each provided with a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and a heat medium heat exchanger are connected,the heat medium heat exchanger being configured to exchange heat between refrigerant that flows through the refrigerant circuit and a heat medium supplied to a load unit,the controller being configured to detect that at least one of the plurality of heat source units is to start a defrosting operation and being configured, before the defrosting operation is started, to perform a capacity enhancement operation that increases a total of heating capacities of remaining heat source units among the plurality of heat source units, the remaining heat source units being other than the at least one of the plurality of heat source units that is to start the defrosting operation.

2. The heat source system of claim 1, wherein, in the capacity enhancement operation, in a case where at least one of the plurality of heat source units is stopped, the controller is configured to activate the same number of heat source units among the plurality of heat source units that are stopped as the number of the at least one of the plurality of heat source units that is to start the defrosting operation.

3. The heat source system of claim 1 or 2, wherein,in the capacity enhancement operation,the controller is configured to control the remaining heat source units other than the at least one of the plurality of heat source units that is to start the defrosting operation such that a total of heating capacities of the remaining heat source units other than the at least one of the plurality of heat source units that is to start thedefrosting operation reaches a target heating capacity, andthe target heating capacity is obtained by adding a total of heating capacities of the plurality of heat source units at a time of the detection and a heat extraction amount at a time of the defrosting operation of the at least one of the plurality of heat source units that is to start the defrosting operation.

4. The heat source system of claim 3, wherein,in the capacity enhancement operation,the controller is configured to control the remaining heat source units other than the at least one of the plurality of heat source units that is to start the defrosting operation such that a temperature difference in each of the remaining heat source units other than the at least one of the plurality of heat source units reaches a target temperature difference,the temperature difference is a difference between an outlet temperature of the heat medium downstream of the heat medium heat exchanger and an inlet temperature of the heat medium upstream of the heat medium heat exchanger in a direction in which the heat medium flows, andthe target temperature difference is obtained based on the target heating capacity and the temperature difference at the time of the detection.

5. The heat source system of any one of claims 1 to 4, wherein, the controller is configuredto start the defrosting operation in the at least one of the plurality of heat source units that is to start the defrosting operation in a case where a defrosting condition is satisfied,to perform the capacity enhancement operation also while the at least one of the plurality of heat source units that is to start the defrosting operation is performing the defrosting operation, andto end the capacity enhancement operation in a case where the defrosting operation ends.

6. The heat source system of claim 5, wherein,the defrosting condition is that a state where a difference between an outdoor air temperature and a temperature of the refrigerant that flows through the outdoor heat exchanger in at least one of the plurality of heat source units is higher than or equal to a threshold continues for a first period, andthe controller is configured to detect that the at least one of the plurality of heat source units is to start the defrosting operation, in a case where the state where the difference between the outdoor air temperature and the temperature of the refrigerant that flows through the outdoor heat exchanger in the at least one of the plurality of heat source units is higher than or equal to the threshold continues for a second period that is shorter than the first period.

7. The heat source system of any one of claims 1 to 6, wherein, the controller is configuredto obtain a start time of the capacity enhancement operation from a required time until a total of heating capacities of the remaining heat source units other than the at least one of the plurality of heat source units that is to start the defrosting operation reaches a target heating capacity, andto start the capacity enhancement operation at the start time.INTERNATIONAL SEARCH REPORT International application No. PCT / J1’2023 / 026225 A. CLASSIFICATION OF SUBJECT MATTER F25B 47 / 02(2006.01)1 FI: F25B47 / 02 570W; F25B47 / 02 570A; F25B47 / 02 570R According to International Patent Classification (IPC) or to both national classification ar id IPC B. FIELDS SEARCHEDMinimum documentation searched (classification system followed by classification symbols) F25B47 / 02Documentation searched other than minimum documentation to the extent that such documents are included in the fields searchedPublished examined utility model applications of Japan 1922-1996Published unexamined utility model applications of Japan 1971-2023Registered utility model specifications of Japan 1996-2023Published registered utility model applications of Japan 1994-2023Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)C. DOCUMENTS CONSIDERED TO BE RELEVANTCategory* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. A JP 5-322265 A (KABUSHIKI KAISHA TOSHIBA) 07 December 1993 (1993-12-07) entire text, all drawings 1-7 A JP 2013-108732 A (MITSUBISHI HEAVY INDUSTRIES, LTD.) 06 June 2013 (2013-06-06) entire text, all drawings 1-7 A JP 2005-090785 A (MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.) 07 April 2005 (2005-04-07) entire text, all drawings 1-7 A WO 2018 / 042611 Al (MITSUBISHI ELECTRIC CORPORATION) 08 March 2018 (2018-03-08) entire text, all drawings 1-7 A WO 2021 / 001969 Al (MITSUBISHI ELECTRIC CORPORATION) 07 January 2021 (2021-01-07) fig- 6 3 A JP 6-265244 A (KABUSHIKI KAISHA TOSHIBA) 20 September 1994 (1994-09-20) paragraphs [0055]-[0056] 6| | Further documents are listed in the continuation of Box C.annex.* Special categories of cited documents:■‘A” document defining the general state of the art which is not considered to be of particular relevance■SE” earlier application or patent but published on or after the international filing date•SL” document which may throw doubts on priority claim(s) or which is cited to establish die publication date of another citation or other special reason (as specified)“O” document referring to an oral disclosure, use, exhibition or other means“P” document published prior to the international filing date but later than the priority date claimed“T” later document published after the international filing date or priority date and not in conflict with the application but cited to understand the principle or theory underlying the invention“X” document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone“Y” document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the artdocument member of the same patent familyDate of the actual completion of the international searchDate of mailing of the international search report19 September 2023Name and mailing address of the ISA / JPJapan Patent Office (ISA / JP)3-4-3 Kasumigaseki, Chiyoda-ku, Tokyo 100-8915JapanAuthorized officer03 October 2023Telephone No.INTERNATIONAL SEARCH REPORT Information on patent family members International application No. PCT / JP2023 / 026225Patent document cited in search report Publication date (day / month / year) Patent family member) s) Publication date (day / month / year) JP 5-322265 A 07 December 1993 (Family: none) JP 2013-108732 A 06 June 2013 EP 2784414 Al CN 103906984 A KR 10-2014-0066773 A JP 2005-090785 A 07 April 2005 (Family: none) WO 2018 / 042611 Al 08 March 2018 US 2019 / 0203994 Al GB 2568404 A WO 2021 / 001969 Al 07 January 2021 EP 3995763 Al fig- 6 CN 114026373 A JP 6-265244 A 20 September 1994 (Family: none)

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