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

Heat Source System

[0001] The present disclosure relates to a heat source system including a plurality of heat source units.

[0002] In a heat source system equipped with multiple heat source units, if at least one heat source unit starts a defrosting operation during heating operation, the number of heat source units performing heating operation decreases, thereby reducing the total heating capacity of the heat source system. When the total heating capacity of the heat source system decreases, the temperature of the heat medium, such as water, supplied to the load units decreases.

[0003] In order to suppress a decrease in the temperature of the heat medium supplied to the load unit, for example, in the heat source system of Patent Document 1, it is proposed to increase the pump frequency and increase the flow rate of the heat medium when a decrease in the temperature of the heat medium due to defrosting operation is detected.

[0004] Patent No. 6896054

[0005] However, if the heating capacity is increased after detecting a temperature drop in the heat medium supplied to the load unit as in Patent Document 1, the ability of the heat medium temperature to follow the target temperature decreases. As a result, a heat medium at a temperature lower than the target temperature is supplied to the load unit until the heating capacity is increased, which can lead to a decrease in comfort for users.

[0006] The present disclosure is intended to solve the above-described problems and to provide a heat source system that can suppress a decrease in the temperature of a heat medium during a defrosting operation.

[0007] The heat source system according to the present disclosure comprises a plurality of heat source units and a control device that controls the plurality of heat source units, each of which comprises a refrigerant circuit to which a compressor, an outdoor heat exchanger, an expansion valve, and a heat medium heat exchanger are connected, and the heat medium heat exchanger exchanges heat between the refrigerant flowing through the refrigerant circuit and the heat medium supplied to the load unit, and the control device detects that at least one of the plurality of heat source units is scheduled to start a defrosting operation, and before the defrosting operation is started, performs a capacity increase operation that increases the total heating capacity of the heat source units other than the heat source unit that is scheduled to start the defrosting operation.

[0008] According to the heat source system of the present disclosure, the heat source unit detects that a defrosting operation is scheduled to start and performs a capacity increase operation before the defrosting operation starts, thereby maintaining the heating capacity before the advance detection even during the defrosting operation. This makes it possible to suppress a decrease in the temperature of the heat medium supplied to the load unit during the defrosting operation.

[0009] 1 is a schematic configuration diagram of a refrigeration cycle device according to embodiment 1. FIG. 2 is a schematic configuration diagram of a heat source unit according to embodiment 1. FIG. 3 is a control block diagram of a heat source system according to embodiment 1. FIG. 4 is a flowchart showing the operation flow of the heat source system according to embodiment 1. FIG. 5 is a flowchart showing the flow of a capacity increase process in embodiment 1. FIG. 6 is a diagram explaining an example of state transition of the heat source system according to embodiment 1. FIG. 7 is a diagram showing changes in heating capacity and outlet temperature during defrosting operation in a heat source system according to the prior art. FIG. 8 is a diagram showing changes in heating capacity and outlet temperature during defrosting operation in the heat source system according to embodiment 1. FIG. 9 is a flowchart showing the flow of a capacity increase process in embodiment 2. FIG. 10 is a diagram showing changes in heating capacity and outlet temperature during defrosting operation in the heat source system according to embodiment 2.

[0010] Hereinafter, embodiments will be described with reference to the drawings. In each drawing, the same reference numerals are used to denote the same or equivalent parts, and this applies throughout the entire specification. The shapes of the components shown in the entire specification are merely examples and are not intended to be limiting. Furthermore, the size relationships between the components in the drawings may differ from those in reality.

[0011] Embodiment 1. Fig. 1 is a schematic configuration diagram of a refrigeration cycle apparatus 100 according to Embodiment 1. The refrigeration cycle apparatus 100 of Embodiment 1 is a heat pump chiller that performs air conditioning using a heat medium flowing through a heat medium circuit 40. As shown in Fig. 1, the refrigeration cycle apparatus 100 includes a heat source system 1 and a plurality of load units 2. In the example of Fig. 1, two load units 2 are shown, but the number of load units 2 may be one, or three or more. The heat source system 1 includes a plurality of heat source units 10A, 10B, 10C, and 10D, and a control device 5. The plurality of heat source units 10A, 10B, 10C, and 10D are connected in parallel to each other with respect to the heat medium circuit 40.

[0012] Fig. 2 is a schematic configuration diagram of a heat source unit 10A according to embodiment 1. Heat source units 10B, 10C, and 10D have the same configuration as heat source unit 10A. As shown in Fig. 2, heat source unit 10A includes two refrigerant circuits 11, a heat medium heat exchanger 41 shared by the two refrigerant circuits 11, and a pump 42.

[0013] 2, each refrigerant circuit 11 of the heat source unit 10A includes a compressor 12, a flow path switching valve 13, an outdoor heat exchanger 14, an expansion valve 15, a heat medium heat exchanger 41, and an accumulator 16. The compressor 12, the flow path 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 piping to form the refrigerant circuit 11.

[0014] The refrigerant flowing through the refrigerant circuit 11 is, for example, a single refrigerant such as R-22 or R-134a, a pseudo-azeotropic refrigerant mixture such as R-410A or R-404A, or a non-azeotropic refrigerant mixture such as R-407C. ３ CF=CH ２ Refrigerants with relatively low global warming potential, such as refrigerants or mixtures thereof, or CO ２ Alternatively, a natural refrigerant such as propane may be used.

[0015] The compressor 12 compresses the drawn refrigerant and discharges it. The compressor 12 is driven via an inverter drive device (not shown) or the like. The operating frequency of the compressor 12 is controlled by the control device 5. By controlling the operating frequency of the compressor 12, it is possible to change the capacity of the compressor 12, which is the amount of refrigerant discharged per unit time.

[0016] The flow path switching valve 13 switches between a cooling operation and a defrosting operation 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 path switching valve 13 is, for example, a four-way valve, and its switching is controlled by the control device 5. During the cooling operation or the defrosting operation, the flow path switching valve 13 switches so that the refrigerant discharged from the compressor 12 flows into the outdoor heat exchanger 14, as shown by the solid line in Fig. 1. During the heating operation, the flow path switching valve 13 switches so that the refrigerant discharged from the compressor 12 flows into the heat medium heat exchanger 41, as shown by the dashed line in Fig. 1.

[0017] The outdoor heat exchanger 14 is, for example, a fin-tube heat exchanger, and exchanges heat between the refrigerant flowing inside the heat transfer tubes and air supplied by the outdoor fan 17. In a heating operation (heating operation) in which the heat medium is heated, the outdoor heat exchanger 14 functions as an evaporator, exchanging heat between the low-pressure refrigerant flowing in from the expansion valve 15 side and the air, thereby evaporating and vaporizing the refrigerant. In a cooling operation or defrosting operation (cooling operation) in which the heat medium is cooled, the outdoor heat exchanger 14 functions as a condenser, exchanging heat between the high-pressure refrigerant flowing in from the compressor 12 side and the air, thereby condensing and liquefying the refrigerant.

[0018] The expansion valve 15 expands the refrigerant to reduce its pressure. In this embodiment, the expansion valve 15 is an electronic expansion valve with an adjustable opening. The opening of the expansion valve 15 is controlled by the control device 5. The expansion valve 15 may also be a temperature-sensitive expansion valve whose opening changes based on the temperature of the refrigerant.

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

[0020] The outdoor fan 17 sends air to the outdoor heat exchanger 14 to promote heat exchange between the refrigerant and the air. The outdoor fan 17 is driven via an inverter drive device (not shown) or the like. The rotation speed of the outdoor fan 17 is controlled by the control device 5. The air volume can be changed by controlling the rotation speed of the outdoor fan 17. In FIG. 2 , the outdoor heat exchanger 14 and the outdoor fan 17 are in one-to-one correspondence, but this is not limited thereto, and multiple outdoor fans 17 may be provided for one outdoor heat exchanger 14.

[0021] The heat medium heat exchanger 41 exchanges heat between the heat medium flowing through the heat medium circuit 40 and the refrigerant flowing through the refrigerant circuit 11. The heat medium may be water, brine (antifreeze), a mixture of water and brine, or the like. In this disclosure, the heat medium refers specifically to a heat medium other than the refrigerant. The following description will be given assuming that the heat medium is water, but all references to water should be replaced with the heat medium. The heat medium heat exchanger 41 serves as a flow path for the two refrigerant circuits 11 and the heat medium circuit 40. Therefore, the heat medium heat exchanger 41 serves as a component of the refrigerant circuit 11 and the heat medium circuit 40. For example, during heating operation, the heat medium heat exchanger 41 functions as a condenser, exchanging heat between the refrigerant flowing from the compressor 12 and water, condensing the refrigerant to liquefy or convert it into a two-phase gas-liquid mixture, and heating the water. Meanwhile, during cooling operation, the heat medium heat exchanger 41 functions as an evaporator, exchanging heat between the refrigerant flowing from the expansion valve 15 and water, evaporating the refrigerant to vaporize it, and cooling the water.

[0022] The pump 42 sucks water flowing through the heat medium circuit 40, applies pressure to it, and sends it out to circulate through the heat medium circuit 40. The pump 42 is driven via an inverter drive device (not shown) or the like. The operation frequency of the pump 42 is controlled by the control device 5. By controlling the operation frequency of the pump 42, the capacity of the pump 42 can be changed.

[0023] The heat source unit 10A also includes an inlet temperature sensor 31, an outlet temperature sensor 32, a heat exchanger temperature sensor 33, and an outdoor air temperature sensor 34. The inlet temperature sensor 31 is located upstream of the heat medium heat exchanger 41 in the water flow direction and measures an inlet temperature Tin, which is the temperature of the water flowing into the heat medium heat exchanger 41. The outlet temperature sensor 32 is located downstream of the heat medium heat exchanger 41 in the water flow direction and measures an outlet temperature Tout, which is the temperature of the water flowing out of the heat medium heat exchanger 41. The heat exchanger temperature sensor 33 measures a refrigerant temperature Tr, which is the temperature of the refrigerant flowing through the outdoor heat exchanger 14 of each refrigerant circuit 11. The outdoor air temperature sensor 34 measures an outdoor air temperature Te, which is the temperature of the outdoor space in which the heat source unit 10A is installed. Each temperature sensor is, for example, a thermistor and outputs the measured temperature to the control device 5. In this embodiment, each heat source unit 10A to 10D is configured to have an outside air temperature sensor 34, but this is not limited to this, and it is sufficient that the heat source system 1 is configured to have at least one outside air temperature sensor 34.

[0024] Returning to Fig. 1 , the load unit 2 is a unit that sends conditioned air to an indoor space that is the target of air conditioning. As shown in Fig. 1 , each load unit 2 in this embodiment has an indoor heat exchanger 21, a flow rate adjustment valve 22, and an indoor fan 23. The indoor heat exchanger 21 and the flow rate adjustment valve 22 are devices that make up a heat medium circuit 40. In other words, the heat medium circuit 40 is configured by connecting the indoor heat exchanger 21 and the flow rate adjustment valve 22 of the load unit 2, the heat medium heat exchangers 41 of the heat source units 10A to 10D, and a pump 42 via piping.

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

[0026] The flow control valve 22 is, for example, a two-way valve whose valve opening (opening area) can be controlled. The flow control valve 22 controls the flow rate of water flowing into or out of the indoor heat exchanger 21 depending on its opening. Specifically, the flow control valve 22 adjusts the amount of water passing through the indoor heat exchanger 21 based on the temperatures of the water flowing into and out of the load unit 2, enabling the indoor heat exchanger 21 to exchange heat at a rate appropriate to the indoor heat load. When the indoor heat exchanger 21 does not need to exchange heat with the heat load, such as when the system is stopped or thermostat is turned off, the flow control valve 22 is fully closed, thereby stopping the supply of water to or from the indoor heat exchanger 21. In FIG. 1 , the flow control valve 22 is installed in the piping on the water inlet side of the indoor heat exchanger 21; however, the flow control valve 22 may also be installed on the water outlet side of the indoor heat exchanger 21.

[0027] The indoor fan 23 generates a flow of air that passes the air in the indoor space through the indoor heat exchanger 21 and returns it to the indoor space. The indoor fan 23 is driven via an inverter drive device (not shown) or the like. The rotation speed of the indoor fan 23 is controlled by the control device 5. The air volume can be changed by controlling the rotation speed of the indoor fan 23.

[0028] The control device 5 controls the operation of the heat source system 1. The control device 5 is composed of a computer including a memory for storing data and programs required for control and a processor such as a CPU for executing the programs, a dedicated processing circuit such as an ASIC or FPGA, or both. The control device 5 may also control the load units 2. Alternatively, although not shown in FIG. 1 , each load unit 2 may be equipped with a control device that controls each load unit 2.

[0029] FIG. 3 is a control block diagram of the heat source system 1 according to the first embodiment. The control device 5 of the heat source system 1 controls the heat source units 10A to 10D based on the measurement results of the temperature sensors provided in each of the heat source units 10A to 10D and instructions from a remote control (not shown). As shown in FIG. 3, the control device 5 includes an operation control unit 51, a pre-detection unit 52, a capacity increase unit 53, and a storage unit 54. The operation control unit 51, the pre-detection unit 52, and the capacity increase unit 53 are functional units realized by a processor provided in the control device 5 executing a program. Alternatively, at least one of the operation control unit 51, the pre-detection unit 52, and the capacity increase unit 53 may be realized by a processing circuit such as an ASIC or FPGA.

[0030] The operation control unit 51 controls each device of the heat source units 10A to 10D, and performs cooling operation, heating operation, and defrosting operation in the refrigeration cycle apparatus 100. Specifically, the operation control unit 51 controls the operation frequency of the compressor 12, the switching of the flow path switching valve 13, the opening degree of the expansion valve 15, the rotation speed of the outdoor fan 17, and the operation frequency of the pump 42, based on the operation mode setting and set temperature input by the user and the measurement results of each temperature sensor.

[0031] Specifically, the operation control unit 51 performs cooling or heating operation according to the operation mode setting and set temperature input by the user. In cooling or heating operation, the operation control unit 51 controls the compressor 12, the expansion valve 15, the outdoor fan 17, and the pump 42 so that the outlet temperature Tout measured by the outlet temperature sensor 32 becomes the target temperature Tm corresponding to the set temperature.

[0032] Furthermore, when a defrosting condition is satisfied in any of the heat source units 10A to 10D during heating operation, the operation control unit 51 starts a defrosting operation of the heat source unit for which the defrosting condition is satisfied. The defrosting condition is that the difference ΔTf (=Te−Tr) between the refrigerant temperature Tr measured by the heat exchanger temperature sensor 33 of each of the heat source units 10A to 10D and the outside air temperature Te measured by the outside air temperature sensor 34 continues to be equal to or greater than a threshold value Tth for a predetermined first period of time (e.g., 10 minutes). Note that the defrosting condition is not limited to the above, and may be, for example, that the refrigerant temperature Tr measured by the heat exchanger temperature sensor 33 has fallen below a threshold temperature, or that the elapsed time since the end of the previous defrosting operation has exceeded a threshold time, or the like.

[0033] The operation control unit 51 performs defrosting by switching the flow path switching valve 13 of one of the heat source units 10A to 10D for which the defrosting conditions are satisfied in the same manner as during cooling operation and causing the outdoor heat exchanger 14 to function as a condenser. Note that the operation control unit 51 may start the defrosting operation of the heat source unit when both of the refrigerant temperatures Tr measured by the heat exchanger temperature sensors 33 of the two refrigerant circuits 11 provided in each of the heat source units 10A to 10D satisfy the defrosting conditions, or may start the defrosting operation of the heat source unit when either one of the refrigerant temperatures Tr satisfies the defrosting conditions.

[0034] The advance detection unit 52 advance detects defrosting operation in the heat source units 10A to 10D. "Advance detection of defrosting operation" means detecting that a defrosting operation is scheduled to start in any of the heat source units 10A to 10D before the defrosting operation actually starts. Here, "a defrosting operation is scheduled to start" includes not only cases where the start time of the defrosting operation has been set in advance, but also cases where the start of the defrosting operation is expected.

[0035] The pre-detection unit 52 pre-detects a defrosting operation, for example, when a state in which the difference ΔTf between the refrigerant temperature Tr of any of the heat source units 10A to 10D and the outside air temperature Te is equal to or greater than a threshold value Tth continues for a second time (e.g., 5 minutes) that is shorter than the first time, which is a defrosting condition. The second time is set in advance so that the difference between the second time and the first time for starting defrosting is equal to the time it takes for the outlet temperature Tout to reach the target temperature Tm after the stopped heat source unit is started, and is stored in the memory unit 54.

[0036] When a defrosting operation is detected in advance by the advance detection unit 52, the capacity increase unit 53 increases the heating capacity of the heat source unit that is not scheduled to start a defrosting operation, among the heat source units 10A to 10D. When any of the heat source units 10A to 10D that are in heating operation starts a defrosting operation, the total heating capacity of the heat source system 1 decreases, and the temperature of the water supplied to the load unit 2, i.e., the outlet temperature Tout, decreases. To compensate for the decrease in heating capacity due to the defrosting operation of any of the heat source units 10A to 10D, the capacity increase unit 53 increases the heating capacity of the heat source unit that is not scheduled to start a defrosting operation.

[0037] The storage unit 54 is, for example, a non-volatile semiconductor memory such as a ROM or a flash memory, a volatile semiconductor memory such as a RAM, an HDD, or an SSD, etc. The storage unit 54 stores programs executed by the control device 5 and various data such as thresholds used in executing the programs.

[0038] Next, the operation of the heat source system 1 will be described with reference to Fig. 4 to Fig. 6. Fig. 4 is a flowchart showing the flow of the operation of the heat source system 1 according to embodiment 1. Each process in the flowchart of Fig. 4 is performed by the control device 5 when the refrigeration cycle apparatus 100 is performing heating operation.

[0039] 4, first, the pre-detection unit 52 determines whether a defrosting operation of any of the heat source units 10A to 10D has been pre-detected (S1). If a defrosting operation of any of the heat source units 10A to 10D has not been pre-detected (S1: NO), the heating operation continues. On the other hand, if a defrosting operation of any of the heat source units 10A to 10D has been pre-detected (S1: YES), the capacity increase unit 53 performs a capacity increase process (S2).

[0040] 5 is a flowchart showing the flow of the capacity increasing process in embodiment 1. In this process, first, the capacity increasing unit 53 calculates the total heating capacity Qa of the heat source system 1 during the current heating operation and stores it in the memory unit 54 (S21). The total heating capacity Qa of the heat source system 1 is the sum of the heating capacities of the heat source units performing the heating operation. The heating capacity of each heat source unit performing the heating operation is determined by a known method based on the operating frequency of the compressor 12 of each heat source unit.

[0041] FIG. 6 is a diagram illustrating an example of state transitions in the heat source system 1 according to embodiment 1. (a) in FIG. 6 shows an example of the operating states of the heat source units 10A to 10D during heating operation. In state (a), the heat source units 10A, 10B, and 10D are performing heating operation, and the heat source unit 10C is stopped. In this case, if the heating capacity of each of the heat source units 10A, 10B, and 10D is A, the total heating capacity Qa of the heat source system 1 is 3A. At this time, the heating capacity Qa is balanced with the load of the load unit 2, and the temperature of the water supplied to the load unit 2 follows the target temperature Tm.

[0042] Next, the capacity increasing unit 53 calculates the temperature difference ΔTa (=Tout-Tin), which is the difference between the outlet temperature Tout and the inlet temperature Tin in the heat source system 1, and stores this in the memory unit 54 (S22). The temperature difference ΔTa is the difference between the outlet temperature Tout and the inlet temperature Tin of any of the heat source units 10A, 10B, and 10D that are performing heating operation, or the average value of the differences between the outlet temperature Tout and the inlet temperature Tin of each of the heat source units 10A, 10B, and 10D that are performing heating operation.

[0043] Then, the capacity increasing unit 53 calculates the target heating capacity Qb of the heat source system 1 (S23). The target heating capacity Qb is the heating capacity required to suppress a decrease in the temperature of the water supplied to the load unit 2 even when any of the heat source units 10A to 10D starts a defrosting operation. The target heating capacity Qb is calculated from the following formula (1): Qb = Qa + B (1)

[0044] Qa is the total heating capacity of the heat source system 1 at the time of advance detection stored in step S21, and in the example of Figure 6, it is 3A. B is the estimated amount of heat collected from the heat source unit scheduled to perform defrosting operation. The estimated amount of heat collected B is determined by the operating state of the compressor 12 of the heat source unit performing defrosting operation. If the operating frequency of the compressor 12 is constant, the amount of heat collected B can be calculated from conditions such as the operating frequency of the compressor 12 and the outside air temperature Te. If the operating frequency of the compressor 12 fluctuates, the amount of heat collected B from past defrosting operations is stored in the memory unit 54 and estimated from conditions such as the outside air temperature Te.

[0045] Then, the capacity increasing unit 53 calculates the target temperature difference ΔTb (S24). The target temperature difference ΔTb is calculated using the following formula (2): ΔTb=ΔTa×Qb / Qa (2)

[0046] Next, the capacity increasing unit 53 increases the capacity of the heat source units 10A to 10D that are not scheduled to start a defrosting operation. Specifically, the capacity increasing unit 53 determines whether any heat source units are currently stopped (S25). If any heat source units are currently stopped, the capacity increasing unit 53 activates the stopped heat source units (S26). Here, the capacity increasing unit 53 determines the number of heat source units to activate so that the number of heat source units performing heating operation after the start of defrosting operation will be the same as the number of heat source units currently performing heating operation. In other words, the capacity increasing unit 53 activates the same number of stopped heat source units as the number of heat source units scheduled to perform a defrosting operation. If the number of stopped heat source units is less than the number of heat source units scheduled to perform a defrosting operation, all stopped heat source units are activated. If no heat source units are currently stopped (S25: NO), i.e., if all heat source units in the heat source system 1 are performing heating operation, the processing of step S26 is skipped.

[0047] Then, the capacity increasing unit 53 controls the heat source units that are not scheduled to perform defrosting operation so that the temperature difference (Tout - Tin) between the outlet temperature Tout and the inlet temperature Tin of the heat source units that are not scheduled to perform defrosting operation satisfies the target temperature difference ΔTb (S27). The processing of steps S25 to S27 above is called "capacity increased operation." (b) of FIG. 6 shows a state in which the heat source system 1 is performing capacity increased operation. As shown in state (b), when the heat source unit 10B is scheduled to perform defrosting operation, the stopped heat source unit 10C is started first, and the heat source units 10A, 10C, and 10D other than the heat source unit 10B that is scheduled to perform defrosting operation are set to the target temperature difference ΔTb and controlled to satisfy the target temperature difference ΔTb. As a result, the heating capacities of the heat source units 10A, 10C, and 10D that are not scheduled to perform defrosting operation are increased to A １ where A １ >A, and Qb = 3A １ is.

[0048] 4 , the operation control unit 51 determines whether or not to start a defrosting operation in the heat source unit scheduled for defrosting operation (S3). If the defrosting operation is not to be started (S3: NO), the increased capacity operation continues until the defrosting operation is started. On the other hand, if the defrosting operation is to be started (S3: YES), the operation control unit 51 switches the flow path switching valve 13 of the heat source unit performing the defrosting operation to cause the outdoor heat exchanger 14 to function as a condenser, and performs the defrosting operation (S4).

[0049] 6(c) shows the state when the defrosting operation of the heat source unit 10B is started. As shown in state (c), even after the defrosting operation of the heat source unit 10B is started, the increased capacity operation continues in the heat source units 10A, 10C, and 10D that are in heating operation. As a result, even when the defrosting operation of the heat source unit 10B is started, the total heating capacity of the heat source system 1 becomes Qb-B=Qa, which is the same as state (a) before the defrosting operation. As a result, the decrease in the temperature of the water supplied to the load unit 2 can be suppressed.

[0050] Next, the operation control unit 51 determines whether to terminate the defrosting operation (S5). If the defrosting operation is not to be terminated (S5: NO), the defrosting operation continues. On the other hand, if the defrosting operation is to be terminated (S5: YES), the operation control unit 51 determines whether the number of heat source units currently performing heating operation is the same as the number of units performing heating operation before the advance detection (S6). If the number of heat source units currently performing heating operation is the same as the number of units performing heating operation before the advance detection (S6: YES), the operation control unit 51 stops the heat source unit performing the defrosting operation (S7). On the other hand, if the number of heat source units currently performing heating operation is different from the number of units performing heating operation before the advance detection (S6: NO), the operation control unit 51 switches the flow path switching valve 13 of the heat source unit performing the defrosting operation to heating operation (S8).

[0051] That is, if the same number of stopped heat source units as the heat source units scheduled for defrosting operation are started during capacity increase operation, the number of heat source units currently performing heating operation is the same as the number of heat source units performing heating operation before advance detection, so the heat source units performing defrosting operation are stopped. On the other hand, if there are no stopped heat source units during capacity increase operation, or if the number of stopped heat source units is fewer than the number of heat source units scheduled for defrosting operation, the number of heat source units currently performing heating operation is fewer than the number of heat source units performing heating operation before advance detection, so the heat source units performing defrosting operation are switched to heating operation. In this way, by keeping the number of heat source units performing heating operation as constant as possible during heating operation, capacity increase operation, and defrosting operation, the heat source system 1 can be operated efficiently.

[0052] Then, the operation control unit 51 controls the heat source unit performing the heating operation so that the outlet temperature Tout of the heat source unit performing the heating operation satisfies the target temperature Tm (S9). As a result, the same heating operation as before the advance detection is performed. (d) of FIG. 6 shows the state after the defrosting operation of the heat source unit 10B has ended. In the example of FIG. 6, in state (b), when the defrosting operation of the heat source unit 10B has ended, the heat source unit 10B is stopped. Then, in the heat source units 10A, 10C, and 10D performing the heating operation, the outlet temperature Tout is controlled to satisfy the target temperature Tm, and the heating capacity of each heat source unit is increased to A. １ This reduces the total heating capacity Qa of the heat source system 1 to 3A.

[0053] Next, the effects of the heat source system 1 of this embodiment over the conventional technology will be described. First, the conventional technology will be described. FIG. 7 is a diagram showing changes in heating capacity and outlet temperature Tout during defrosting operation in a heat source system according to the conventional technology. As shown in FIG. 7, in the heat source system of the conventional technology, when any of a plurality of heat source units performing heating operation starts a defrosting operation at time t1, the total heating capacity of the heat source system decreases. To explain using the example of FIG. 6, if the total heating capacity Qa of the heat source system before starting the defrosting operation is 3A, when one heat source unit starts a defrosting operation, the total heating capacity of the heat source system becomes "2A - heat collection amount B by defrosting operation."

[0054] While the heating capacity required to maintain the target outlet temperature Tout is 3A, the defrosting operation reduces the heating capacity to 2A-B, causing the temperature of the water supplied to the load unit 2 to drop. Conventional heat source systems increase the capacity of the heat source unit during heating operation when they detect a drop in the temperature of the water supplied to the load unit. However, because the capacity of the heat source unit is increased after the supply water temperature drops, the supply water temperature continues to drop until the total heating capacity of the heat source system reaches the required heating capacity (3A). During this time, the temperature of the air supplied to the load unit 2 drops, reducing user comfort.

[0055] 8 is a diagram showing changes in heating capacity and outlet temperature Tout during defrosting operation in the heat source system 1 according to embodiment 1. As shown in FIG. 8, the heat source system 1 according to embodiment 1 detects a defrosting operation in advance at time t0, which is before time t1, when one of the plurality of heat source units performing a heating operation starts a defrosting operation, and performs a capacity increase operation. As a result, even if the heating capacity decreases due to the start of a defrosting operation, the total heating capacity of the heat source system 1 can be maintained at the total heating capacity Qa = 3A of the heat source system 1 before the start of the defrosting operation. This makes it possible to suppress a decrease in the heat medium temperature during defrosting operation, thereby maintaining user comfort.

[0056] Embodiment 2. Embodiment 2 will be described. The refrigeration cycle apparatus 100 of Embodiment 2 differs from Embodiment 1 in the timing of performing the capacity increase operation. The configuration of the refrigeration cycle apparatus 100 of Embodiment 2 is the same as that of Embodiment 1.

[0057] 9 is a flowchart showing the flow of the capacity increasing process in embodiment 2. The processes in steps S201 to S204 in this embodiment are the same as the processes in steps S21 to S24 in embodiment 1.

[0058] After calculating the target temperature difference ΔTb, the capacity increasing unit 53 calculates the start time ta of the capacity increase operation (S205). Here, the capacity increasing unit 53 first calculates the required time Δt until the total heating capacity of the heat source system 1 reaches the target heating capacity Qb. If there are any stopped heat source units, the required time Δt is the time until the stopped heat source units are started and the target temperature difference ΔTb is satisfied. Furthermore, if there are no stopped heat source units, the required time Δt is the time until the heat source units other than the heat source unit scheduled for defrosting operation satisfy the target temperature difference ΔTb. The required time Δt may be calculated in advance for each target temperature difference ΔTb and operating state and stored in the memory unit 54, or may be calculated using a function or the like that uses the target temperature difference ΔTb and the operating state as variables. The capacity increasing unit 53 then determines the time obtained by subtracting the required time Δt from the defrosting operation start time t1 as the start time ta of the capacity increase operation.

[0059] Next, the capacity increasing unit 53 determines whether the current time is the start time ta of the capacity increase operation (S206). If the current time is not the start time ta of the capacity increase operation (S206: NO), the capacity increasing unit 53 waits until the current time becomes the start time ta of the capacity increase operation.

[0060] On the other hand, if the current time is the start time ta of the increased capacity operation (S206: YES), the capacity increasing unit 53 performs the increased capacity operation similar to that of Embodiment 1. The processing of steps S207 to S209 is the same as the processing of steps S25 to S27 in Embodiment 1. That is, in Embodiment 1, the increased capacity operation is started at the timing when advance detection of the defrosting operation is performed, but in this embodiment, the timing of the increased capacity operation is determined separately from the timing of advance detection.

[0061] The effects of the heat source system 1 of this embodiment will be described. Fig. 10 is a diagram showing changes in heating capacity and outlet temperature Tout during defrosting operation in the heat source system 1 according to embodiment 2. As shown in Fig. 10, the heat source system 1 of embodiment 2 detects a defrosting operation in advance at time t0, which is before time t1, when one of the plurality of heat source units performing heating operation starts a defrosting operation. Then, at time ta, which is after the advance detection time t0 and before the start time t2 of the defrosting operation, a capacity increase operation is started.

[0062] As a result, similar to the first embodiment, even if the heating capacity decreases due to the start of a defrosting operation, the total heating capacity of the heat source system 1 can be maintained at the total heating capacity Qa = 3A of the heat source system 1 before the start of the defrosting operation. Therefore, a decrease in the temperature of the heat medium supplied to the load unit 2 can be suppressed, and user comfort can be maintained. Furthermore, in this embodiment, the timing to start the capacity increase operation is determined taking into account the time required for the heating capacity of the heat source units not scheduled for a defrosting operation to increase, so that the time for the capacity increase operation, in which the heat source units are operated at a heating capacity greater than necessary, can be shortened compared to the first embodiment. This makes it possible to suppress an increase in power consumption due to the capacity increase operation.

[0063] Although the above is a description of the embodiment, the present disclosure is not limited to the above embodiment and various modifications and combinations are possible within the scope of the gist of the present disclosure. For example, in the above embodiment, the refrigeration cycle apparatus 100 is described as a heat pump chiller, but the refrigeration cycle apparatus 100 may be a dedicated heating apparatus that does not have a switchable cooling / heating function, or a hot water supply apparatus. If the refrigeration cycle apparatus 100 is a dedicated heating apparatus, the flow path switching valve 13 is omitted.

[0064] In the above embodiment, the heat source system 1 is configured to include four heat source units 10A to 10D, but the number of heat source units may be two or more. In the above embodiment, each of the heat source units 10A to 10D is configured to include two refrigerant circuits 11, but each of the heat source units 10A to 10D may include one refrigerant circuit 11, or three or more refrigerant circuits 11.

[0065] Furthermore, in the above embodiment, the heat source system 1 is controlled by a control device 5 provided separately from each of the heat source units 10A to 10D. However, this is not limiting. For example, each of the heat source units 10A to 10D may have a control device, and the functional units of the control device 5 of the heat source system 1 may be shared by the control devices of the heat source units 10A to 10D. Specifically, the control devices of the heat source units 10A to 10D may have an operation control unit 51 and a pre-detection unit 52, and one of the heat source units 10A to 10D may be designated as a parent unit, with the parent unit's control device having a capacity increase unit 53. In this case, each of the heat source units 10A to 10D may detect in advance that it plans to start a defrosting operation and notify the parent unit. When notified of the pre-detection, the parent unit may calculate a target temperature difference ΔTb and notify each of the heat source units 10A to 10D, thereby enabling capacity increase operation before the start of defrosting operation.

[0066] Furthermore, in the above embodiment, a defrosting operation is pre-detected when the difference ΔTf between the refrigerant temperature Tr of any one of the heat source units 10A to 10D and the outside air temperature Te remains equal to or greater than the threshold value Tth for a second period of time. However, the pre-detection method is not limited to this. The pre-detection unit 52 may estimate the defrosting start time when the defrosting condition is satisfied and pre-detect the defrosting operation a predetermined second period (e.g., 5 minutes) before the defrosting start time. For example, the pre-detection unit 52 may estimate the time when the defrosting condition will be met from the rate of increase of the difference ΔTf between the refrigerant temperature Tr of any one of the heat source units 10A to 10D and the outside air temperature Te, and pre-detect the defrosting operation two hours before the time when the defrosting condition will be met. Alternatively, the pre-detection unit 52 may estimate the time when the defrosting condition will be met from the rate of decrease of the refrigerant temperature Tr measured by the heat exchanger temperature sensor 33 and pre-detect the defrosting operation two hours before the time when the defrosting condition will be met. Alternatively, the pre-detection unit 52 may pre-detect the defrosting operation when the time elapsed since the end of the previous defrosting operation becomes (threshold time - second time).

[0067] Furthermore, if a defrosting operation is not initiated within a predetermined time (e.g., 10 minutes) after the start of the increased capacity operation, the heat source system 1 may terminate the increased capacity operation and return to heating operation. In this case, the operation control unit 51 determines whether the number of heat source units currently performing heating operation is the same as the number performing heating operation before the advance detection. If the number of heat source units currently performing heating operation is the same as the number performing heating operation before the advance detection, the operation control unit 51 controls the heat source units so that the outlet temperature Tout of the heat source units performing heating operation meets the target temperature Tm. On the other hand, if the number of heat source units currently performing heating operation is different from the number performing heating operation before the advance detection, i.e., if a heat source unit that was stopped for the increased capacity operation is started, the operation control unit 51 stops the heat source unit scheduled to perform the defrosting operation and controls the heat source units so that the outlet temperature Tout of the heat source unit performing heating operation meets the target temperature Tm. This prevents the increased capacity operation from being unintentionally continued for a long period of time.

[0068] 1 Heat source system, 2 Load unit, 5 Control device, 10A, 10B, 10C, 10D Heat source unit, 11 Refrigerant circuit, 12 Compressor, 13 Flow path switching valve, 14 Outdoor heat exchanger, 15 Expansion valve, 16 Accumulator, 17 Outdoor fan, 21 Indoor heat exchanger, 22 Flow control valve, 23 Indoor fan, 31 Inlet temperature sensor, 32 Outlet temperature sensor, 33 Heat exchanger temperature sensor, 34 Outdoor air temperature sensor, 40 Heat medium circuit, 41 Heat medium heat exchanger, 42 Pump, 51 Operation control unit, 52 Advance detection unit, 53 Capacity increase unit, 54 Memory unit, 100 Refrigeration cycle device.

Claims

1. A plurality of heat source units; a control device that controls the plurality of heat source units, Each of the heat source units includes a refrigerant circuit to 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 Detecting that at least one of the plurality of heat source units is scheduled to start a defrosting operation, A heat source system that performs a capacity increase operation to increase the total heating capacity of the heat source units other than the heat source unit scheduled to perform the defrosting operation before the defrosting operation is started.

2. The control device, in the capacity increase operation, The heat source system according to claim 1, wherein when at least one of the plurality of heat source units is stopped, the same number of stopped heat source units as the number of heat source units scheduled to perform defrosting operation are started.

3. The control device, in the capacity increase operation, The heat source units other than the heat source unit scheduled for defrosting operation are controlled so that the total heating capacity of the heat source units other than the heat source unit scheduled for defrosting operation becomes a target heating capacity, The heat source system according to claim 1 or 2, wherein the target heating capacity is the sum of the total heating capacity of the heat source units at the time of detection and the amount of heat extracted during defrosting operation of the heat source unit scheduled to perform defrosting operation.

4. The control device, in the capacity increase operation, The temperature difference in the heat source unit other than the heat source unit scheduled to perform the defrosting operation is controlled to be 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 flow direction of the heat medium, The heat source system according to claim 3 , wherein the target temperature difference is calculated based on the target heating capacity and the temperature difference at the time of detection.

5. The control device When the defrosting conditions are satisfied, a defrosting operation is started for the heat source unit scheduled to undergo the defrosting operation; The increased capacity operation is performed even during the defrosting operation of the heat source unit that is scheduled to perform the defrosting operation, The heat source system according to claim 1 or 2, wherein the capacity increase operation is terminated when the defrosting operation is terminated.

6. the defrosting condition is that a state in which a difference between an outdoor air temperature and a temperature of the refrigerant flowing through the outdoor heat exchanger of at least one of the plurality of heat source units is equal to or greater than a threshold continues for a first time; The heat source system described in claim 5, wherein the control device detects that the heat source unit is scheduled to start defrosting operation when the difference between the outside air temperature and the temperature of the refrigerant flowing through the outdoor heat exchanger of at least one of the plurality of heat source units remains above the threshold for a second time period that is shorter than the first time period.

7. The control device determining a start time of the capacity increase operation from a required time until the total heating capacity of the heat source units other than the heat source unit scheduled to perform the defrosting operation reaches a target heating capacity; The heat source system according to claim 1 or 2, wherein the increased capacity operation is started at the start time.