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 including a plurality of heat source units.

Background Art

[0002] In a heat source system including a plurality of heat source units, when at least one heat source unit starts a defrost operation during a heating operation, the number of heat source units performing the heating operation decreases, resulting in a decrease in the total heating capacity of the heat source system. 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] In order to suppress a decrease in the temperature of the heat medium supplied to a load unit, for example, in the heat source system of Patent Document 1, when a decrease in the temperature of the heat medium due to a defrost operation is detected, it is proposed to increase the frequency of a pump and increase the flow rate of the heat medium.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the heating capacity is increased after detecting a decrease in the temperature of the heat medium supplied to a load unit as in Patent Document 1, the followability of the heat medium temperature with respect to the target temperature decreases. Therefore, a heat medium at a temperature lower than the target temperature is supplied to the load unit until the heating capacity increases, leading to a decrease in the comfort of the user.

[0006] The present disclosure solves the above problems and provides a heat source system capable of suppressing a decrease in the temperature of a heat medium during a defrost operation. [Means for solving the problem]

[0007] The heat source system according to this 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 connected to a compressor, an outdoor heat exchanger, an expansion valve, and a heat transfer medium heat exchanger, the heat transfer medium heat exchanger exchanges heat between the refrigerant flowing through the refrigerant circuit and the heat transfer 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 defrosting operation and, before the defrosting operation starts, performs a capacity increase operation to increase the total heating capacity of the heat source units other than the heat source unit scheduled for defrosting operation. [Effects of the Invention]

[0008] According to the heat source system of this disclosure, the system can detect when the heat source unit is scheduled to start defrosting operation and perform a capacity-increasing operation before the defrosting operation begins, thereby maintaining the heating capacity that was available before the prior detection, even during defrosting operation. This makes it possible to suppress the temperature drop of the heat transfer medium supplied to the load unit during defrosting operation. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the refrigeration cycle device according to Embodiment 1. [Figure 2] This is a schematic diagram of the heat source unit according to Embodiment 1. [Figure 3] This is a control block diagram of the heat source system according to Embodiment 1. [Figure 4] This flowchart shows the operation flow of the heat source system according to Embodiment 1. [Figure 5] This is a flowchart showing the flow of the capacity increase process in Embodiment 1. [Figure 6] This figure illustrates an example of a state transition of a heat source system according to Embodiment 1. [Figure 7]This figure shows the changes in heating capacity and outlet temperature during defrosting operation in a conventional heat source system. [Figure 8] This figure shows the changes in heating capacity and outlet temperature during defrosting operation in the heat source system according to Embodiment 1. [Figure 9] This is a flowchart showing the flow of the capacity increase process in Embodiment 2. [Figure 10] This figure shows the changes in heating capacity and outlet temperature during defrosting operation in the heat source system according to Embodiment 2. [Modes for carrying out the invention]

[0010] The embodiments will be described below with reference to the drawings. In each drawing, components with the same reference numerals are the same or equivalent components, and this is consistent throughout the entire specification. Furthermore, the forms of the components shown in the entire specification are merely examples and are not exhaustive. Additionally, the size relationships of the components in the following drawings may differ from those of the actual components.

[0011] Embodiment 1. Figure 1 is a schematic diagram of a refrigeration cycle device 100 according to Embodiment 1. The refrigeration cycle device 100 of Embodiment 1 is a heat pump chiller that performs air conditioning using a heat transfer medium flowing through a heat transfer medium circuit 40. As shown in Figure 1, the refrigeration cycle device 100 comprises a heat source system 1 and a plurality of load units 2. In the example in Figure 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 comprises 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 transfer medium circuit 40.

[0012] FIG. 2 is a schematic configuration diagram of the heat source unit 10A according to Embodiment 1. The heat source units 10B, 10C, and 10D have the same configuration as the heat source unit 10A. As shown in FIG. 2, the 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] As shown in FIG. 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 pipes 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 mixed refrigerant such as R-410A or R-404A, or a non-azeotropic mixed refrigerant such as R-407C. Also, a refrigerant or a mixture thereof having a relatively small global warming potential, such as CF3CF=CH2 which contains a double bond in its chemical formula, or a natural refrigerant such as CO2 or propane may be used.

[0015] The compressor 12 compresses and discharges the inhaled refrigerant. The compressor 12 is driven via an inverter drive device (not shown). The operating frequency of the compressor 12 is controlled by the control device 5. By controlling the operating frequency of the compressor 12, the capacity of the compressor 12, which is the amount of refrigerant sent out per unit time, can be changed.

[0016] The flow path switching valve 13 switches between the cooling operation and the defrosting operation in which the outdoor heat exchanger 14 functions as a condenser, and the 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 the switching is controlled by the control device 5. During the cooling operation or the defrosting operation, the flow path switching valve 13 is switched 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. Further, during the heating operation, the flow path switching valve 13 is switched so that the refrigerant discharged from the compressor 12 flows into the heat medium heat exchanger 41 as shown by the broken line in FIG. 1.

[0017] The outdoor heat exchanger 14 is, for example, a fin-tube type heat exchanger, and performs heat exchange between the refrigerant flowing through the inside of the heat transfer tube and the air supplied by the outdoor fan 17. In the heating operation (heating operation) for heating the heat medium, the outdoor heat exchanger 14 functions as an evaporator, performs heat exchange between the low-pressure refrigerant flowing in from the expansion valve 15 side and the air, and evaporates and vaporizes the refrigerant. Further, in the cooling operation or the defrosting operation (cooling operation) for cooling the heat medium, it functions as a condenser, performs heat exchange between the high-pressure refrigerant flowing in from the compressor 12 side and the air, and condenses and liquefies the refrigerant.

[0018] The expansion valve 15 expands and depressurizes the refrigerant. The expansion valve 15 of the present embodiment is an electronic expansion valve whose opening degree can be adjusted. The opening degree of the expansion valve 15 is controlled by the control device 5. Note that the expansion valve 15 may be a temperature-sensitive expansion valve whose opening degree changes based on the temperature of the refrigerant.

[0019] The accumulator 16 is provided on the suction side of the compressor 12 and stores the surplus refrigerant 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 supplies air to the outdoor heat exchanger 14, promoting 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 rotational speed of the outdoor fan 17 is controlled by the control device 5. The airflow can be changed by controlling the rotational speed of the outdoor fan 17. In Figure 2, the outdoor heat exchanger 14 and the outdoor fan 17 are shown in a one-to-one correspondence, but this is not the only option, and multiple outdoor fans 17 may be provided for a single outdoor heat exchanger 14.

[0021] The heat exchanger 41 performs heat exchange between the heat transfer medium flowing through the heat transfer circuit 40 and the refrigerant flowing through the refrigerant circuit 11. The heat transfer medium is water, brine (antifreeze), or a mixture of water and brine, and in this disclosure, it specifically refers to a heat transfer medium other than the refrigerant. In the following description, the case where the heat transfer medium is water will be used, but all instances of "water" should be replaced with "heat transfer medium". The heat exchanger 41 is the flow path for the two refrigerant circuits 11 and the flow path for the heat transfer circuit 40. Therefore, the heat exchanger 41 is a component of the refrigerant circuit 11 and a component of the heat transfer circuit 40. For example, during heating operation, the heat exchanger 41 functions as a condenser, performing heat exchange between the refrigerant flowing in from the compressor 12 and water, condensing the refrigerant into liquefaction or gas-liquid two-phase, and heating the water. On the other hand, during cooling operation, it functions as an evaporator, exchanging heat between the refrigerant flowing in from the expansion valve 15 and water, evaporating and vaporizing the refrigerant, and cooling the water.

[0022] Pump 42 draws water flowing through the heat transfer medium circuit 40, applies pressure, and sends it out to circulate the heat transfer medium circuit 40. Pump 42 is driven via an inverter drive device (not shown) or the like. The operating frequency of pump 42 is controlled by the control device 5. By controlling the operating frequency of pump 42, the capacity of 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 outside air temperature sensor 34. The inlet temperature sensor 31 is located upstream of the heat exchanger 41 in the direction of water flow and measures the inlet temperature Tin, which is the temperature of the water flowing into the heat exchanger 41. The outlet temperature sensor 32 is located downstream of the heat exchanger 41 in the direction of water flow and measures the outlet temperature Tout, which is the temperature of the water flowing out of the heat exchanger 41. The heat exchanger temperature sensor 33 measures the refrigerant temperature Tr, which is the temperature of the refrigerant flowing through the outdoor heat exchanger 14 of each refrigerant circuit 11. The outside air temperature sensor 34 measures the outside 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 equipped with an outside air temperature sensor 34, but the system is not limited to this configuration; any configuration in which the heat source system 1 is equipped with at least one outside air temperature sensor 34 is acceptable.

[0024] Returning to Figure 1, the load unit 2 is a unit that delivers conditioned air to the indoor space that is to be air-conditioned. As shown in Figure 1, each load unit 2 in this embodiment has an indoor heat exchanger 21, a flow control valve 22, and an indoor fan 23. The indoor heat exchanger 21 and the flow control valve 22 constitute the heat transfer medium circuit 40. That is, the heat transfer medium circuit 40 is composed of the indoor heat exchanger 21 of the load unit 2, the flow control valve 22, the heat transfer medium heat exchangers 41 of the heat source units 10A to 10D, and the pump 42 connected by piping.

[0025] The indoor heat exchanger 21 is, for example, a fin-tube type heat exchanger, which exchanges heat between the refrigerant circulating inside the heat transfer tubes and the air supplied by the outdoor fan 17. During cooling operation, water 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 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 that can control the valve opening (opening area). The flow control valve 22 controls the flow rate of water flowing into or out of the indoor heat exchanger 21 according to the opening. Specifically, the flow control valve 22 adjusts the amount of water that passes through the indoor heat exchanger 21 based on the temperature of the water flowing into and out of the load unit 2, so that the indoor heat exchanger 21 can perform heat exchange with a heat amount corresponding to the heat load in the room. Here, the flow control valve 22 can be fully closed when the indoor heat exchanger 21 does not need to exchange heat with the heat load, such as when the unit is stopped or the thermostat is turned off, thereby stopping the supply of water so that it does not flow into or out of the indoor heat exchanger 21. In Figure 1, the flow control valve 22 is installed in the piping on the water inlet side of the indoor heat exchanger 21, but 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 an airflow that passes air from 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 rotational speed of the indoor fan 23 is controlled by the control device 5. The airflow can be changed by controlling the rotational speed of the indoor fan 23.

[0028] The control device 5 controls the operation of the heat source system 1. The control device 5 consists of a computer equipped with a memory for storing data and programs necessary for control, and a processor such as a CPU for executing 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 Figure 1, each load unit 2 may be equipped with its own control device for controlling it.

[0029] Figure 3 is a control block diagram of the heat source system 1 according to Embodiment 1. The control device 5 of the heat source system 1 controls each heat source unit 10A to 10D based on the measurement results of the temperature sensors provided in each heat source unit 10A to 10D and instructions from a remote control (not shown). As shown in Figure 3, the control device 5 has 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 of the heat source units 10A to 10D to perform cooling, heating, and defrosting operations in the refrigeration cycle device 100. Specifically, the operation control unit 51 controls the operating 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 operating frequency of the pump 42 based on the operating mode setting and set temperature input by the user, as well as the measurement results of each temperature sensor.

[0031] In detail, the operation control unit 51 performs cooling or heating operation according to the operating mode setting and set temperature input by the user. During cooling and heating operation, the operation control unit 51 controls the compressor 12, expansion valve 15, outdoor fan 17, and 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, during heating operation, the operation control unit 51 starts defrosting operation for any of the heat source units 10A to 10D if the defrosting conditions are met. The defrosting conditions are that the difference ΔTf (=Te-Tr) between the refrigerant temperature Tr measured by the heat exchanger temperature sensor 33 of the heat source units 10A to 10D and the outside air temperature Te measured by the outside air temperature sensor 34 is greater than or equal to a threshold Tth, and this condition continues for a preset first hour (for example, 10 minutes). Note that the defrosting conditions are not limited to the above, and may also be, for example, that the refrigerant temperature Tr measured by the heat exchanger temperature sensor 33 falls below the threshold temperature, or that the elapsed time since the end of the previous defrosting operation exceeds the threshold time.

[0033] The operation control unit 51 switches the flow path switching valve 13 of the heat source unit 10A to 10D whose defrosting conditions are met, in the same way as during cooling operation, and performs defrosting by making the outdoor heat exchanger 14 function as a condenser. The operation control unit 51 may start the defrosting operation of the heat source unit 10A to 10D when both of the refrigerant temperatures Tr measured by the heat exchanger temperature sensors 33 of the two refrigerant circuits 11 provided in each heat source unit 10A to 10D meet the defrosting conditions, or it may start the defrosting operation of the heat source unit when either one of them meets the defrosting conditions.

[0034] The pre-detection unit 52 pre-detects defrosting operations in the heat source units 10A to 10D. "Pre-detecting defrosting operations" 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 begins. Here, "scheduled to start defrosting operations" includes not only cases where the start time of the defrosting operation is predetermined, but also cases where it is anticipated that a defrosting operation will start.

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

[0036] The capacity increase unit 53 increases the heating capacity of the heat source units 10A to 10D that are not scheduled to start defrosting operation when the pre-detection unit 52 detects that defrosting operation is scheduled to start. If any of the heat source units 10A to 10D that are in heating operation start 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 units that are not scheduled to start defrosting operation.

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

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

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

[0040] Figure 5 is a flowchart showing the flow of the capacity increase process in Embodiment 1. In this process, first, the capacity increase unit 53 calculates the total heating capacity Qa of the heat source system 1 during the current heating operation and stores it in the storage unit 54 (S21). The total heating capacity Qa of the heat source system 1 is the sum of the heating capacities of each heat source unit 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] Figure 6 illustrates an example of the state transition of the heat source system 1 according to Embodiment 1. Figure 6(a) shows an example of the operating state of heat source units 10A to 10D during heating operation. In state (a), heat source units 10A, 10B, and 10D are performing heating operation, and heat source unit 10C is stopped. In this case, if the heating capacity of heat source units 10A, 10B, and 10D is A, then 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 load unit 2, and the temperature of the water supplied to load unit 2 follows the target temperature Tm.

[0042] Next, the capacity increase 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 it in the storage 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 difference 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 increase 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 the temperature drop of the water supplied to the load unit 2 even if any of the heat source units 10A to 10D starts defrosting operation. The target heating capacity Qb is calculated from the following equation (1). Qb = Qa + B ... (1)

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

[0045] Then, the capacity enhancement unit 53 calculates the target temperature difference ΔTb (S24). The target temperature difference ΔTb is obtained from the following equation (2). ΔTb = ΔTa × Qb / Qa ... (2)

[0046] Next, the capacity increase unit 53 increases the capacity of the heat source units 10A to 10D that are not scheduled to start defrosting operation. Specifically, the capacity increase unit 53 determines whether or not there are any heat source units that are currently stopped (S25). If there are any heat source units that are currently stopped, the capacity increase unit 53 starts them up (S26). Here, the capacity increase unit 53 determines the number of heat source units to start up so that the number of heat source units performing heating operation after the start of defrosting operation is the same as the number of heat source units currently performing heating operation. In other words, the capacity increase unit 53 starts up the same number of stopped heat source units as the number of heat source units scheduled for defrosting operation. If the number of stopped heat source units is less than the number of heat source units scheduled for defrosting operation, all stopped heat source units are started up. If there are no currently stopped heat source units (S25: NO), that is, if all heat source units in the heat source system 1 are performing heating operation, the process in step S26 is skipped.

[0047] Then, the capacity increase unit 53 controls the heat source units that are not scheduled for defrosting operation so that the temperature difference (Tout-Tin) between the outlet temperature Tout and the inlet temperature Tin of those heat source units that are not scheduled for defrosting operation satisfies the target temperature difference ΔTb (S27). The process described in steps S25 to S27 above is called "capacity increase operation". Figure 6(b) shows the state in which the heat source system 1 is in capacity increase operation. As shown in state (b), when heat source unit 10B is scheduled for defrosting operation, the previously stopped heat source unit 10C is started first, and the heat source units 10A, 10C and 10D other than the heat source unit 10B scheduled for defrosting operation are set to the target temperature difference ΔTb and controlled to satisfy the target temperature difference ΔTb. As a result, the heating capacity of the heat source units 10A, 10C and 10D that are not scheduled for defrosting operation increases to A1. Here, A1 > A and Qb = 3A1.

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

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

[0050] Next, the operation control unit 51 determines whether or not 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 prior 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 prior detection (S6: YES), the heat source unit that was performing defrosting operation is stopped (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 prior detection (S6: NO), the operation control unit 51 switches the flow path switching valve 13 of the heat source unit that was performing defrosting operation to heating operation (S8).

[0051] In other words, during capacity-increasing operation, if the same number of stopped heat source units as the heat source units scheduled for defrosting are activated, the number of heat source units currently performing heating operation is the same as the number of heat source units performing heating operation before the prior detection, so the heat source units performing defrosting operation are stopped. On the other hand, during capacity-increasing operation, if there are no stopped heat source units, or if the number of stopped heat source units is less than the number of heat source units scheduled for defrosting operation, the number of heat source units currently performing heating operation is less than the number of heat source units performing heating operation before the prior 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 similar as possible during heating operation, capacity-increasing 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 meets the target temperature Tm (S9). As a result, the same heating operation as before the prior detection is performed. Figure 6(d) shows the state after the defrosting operation of heat source unit 10B is completed. In the example of Figure 6, in state (b), when the defrosting operation of heat source unit 10B is completed, heat source unit 10B is stopped. Then, the outlet temperatures Tout of heat source units 10A, 10C, and 10D that are performing the heating operation are controlled to meet the target temperature Tm, thereby reducing the heating capacity of each heat source unit from A1 to A. As a result, the total heating capacity Qa of the heat source system 1 becomes Qa = 3A.

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

[0054] While the required heating capacity 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 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 has dropped, 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 load unit 2 drops, reducing user comfort.

[0055] Figure 8 shows the changes in heating capacity and outlet temperature Tout during defrosting operation in the heat source system 1 according to Embodiment 1. As shown in Figure 8, in the heat source system 1 of Embodiment 1, defrosting operation is detected in advance at time t0, before time t1 when any of the multiple heat source units performing heating operation starts defrosting operation, and capacity increase operation is performed. As a result, even if the heating capacity decreases when defrosting operation starts, the total heating capacity of the heat source system 1 can maintain the total heating capacity Qa = 3A of the heat source system 1 before defrosting operation started. This makes it possible to suppress the decrease in the temperature of the heat medium during defrosting operation and maintain user comfort.

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

[0057] Figure 9 is a flowchart showing the flow of the capacity increase 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] The capacity increase unit 53 calculates the target temperature difference ΔTb and then calculates the start time ta for the capacity increase operation (S205). Here, the capacity increase unit 53 first calculates the time Δt required for the total heating capacity of the heat source system 1 to reach the target heating capacity Qb. The required time Δt is the time it takes for any stopped heat source units to start up and satisfy the target temperature difference ΔTb. If there are no stopped heat source units, the required time Δt is the time it takes for all heat source units other than the one scheduled for defrosting to satisfy the target temperature difference ΔTb. The required time Δt may be determined in advance for each target temperature difference ΔTb and operating state and stored in the memory unit 54, or it may be calculated using a function with the target temperature difference ΔTb and operating state as variables. The capacity increase unit 53 then subtracts the required time Δt from the defrosting start time t1 and sets this time as the start time ta for the capacity increase operation.

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

[0060] On the other hand, if the current time becomes the start time ta for capacity increase operation (S206: YES), the capacity increase unit 53 performs capacity increase operation in the same manner as in Embodiment 1. The processing in steps S207 to S209 is the same as the processing in steps S25 to S27 of Embodiment 1. In other words, in Embodiment 1, capacity increase operation was started at the timing of pre-detection of defrost operation, but in this embodiment, the timing of capacity increase operation is determined separately from the timing of pre-detection.

[0061] The effects of the heat source system 1 of this embodiment will now be explained. Figure 10 shows the changes in heating capacity and outlet temperature Tout during defrosting operation in the heat source system 1 according to Embodiment 2. As shown in Figure 10, in the heat source system 1 of Embodiment 2, defrosting operation is detected in advance at time t0, which is before time t1, when any of the multiple heat source units performing heating operation starts defrosting operation. Then, at time ta, which is after the time of pre-detection t0 but before the start time t2 of defrosting operation, capacity increase operation is started.

[0062] As a result, similar to Embodiment 1, even if the heating capacity decreases when defrosting operation is started, the total heating capacity of the heat source system 1 can maintain the total heating capacity Qa = 3A of the heat source system 1 before defrosting operation was started. Therefore, the temperature drop of the heat medium supplied to the load unit 2 can be suppressed, and user comfort can be maintained. In addition, in this embodiment, by determining the timing of starting the capacity increase operation considering the time required for the heating capacity of heat source units that are not scheduled for defrosting operation to increase, the time of capacity increase operation, which operates with more heating capacity than necessary, can be shortened compared to Embodiment 1. This makes it possible to suppress the increase in power consumption due to capacity increase operation.

[0063] The above describes the embodiments, but this disclosure is not limited to the above embodiments, and can be modified or combined in various ways without departing from the spirit of this disclosure. For example, in the above embodiments, the case in which the refrigeration cycle device 100 is a heat pump chiller was described, but the refrigeration cycle device 100 may be a heating-only device without a heating / cooling switch, or a hot water supply device, etc. If the refrigeration cycle device 100 is a heating-only device, the flow path switching valve 13 is omitted.

[0064] Furthermore, 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 can be two or more. Also, in the above embodiment, each heat source unit 10A to 10D is configured to have two refrigerant circuits 11, but each heat source unit 10A to 10D may have one 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 heat source unit 10A to 10D, but the system is not limited to this. For example, each heat source unit 10A to 10D may have its own control device, and the functional parts of the control device 5 of the heat source system 1 may be shared among the control devices of each heat source unit 10A to 10D. Specifically, the control devices of 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 heat source unit 10A to 10D pre-detects that it is scheduled to start defrosting operation and notifies the parent unit. When the parent unit is notified of the pre-detection, it calculates the target temperature difference ΔTb and notifies each heat source unit 10A to 10D, thereby enabling the parent unit to perform capacity increase operation before the start of defrosting operation.

[0066] Furthermore, in the above embodiment, defrosting operation is pre-detected when the difference ΔTf between the refrigerant temperature Tr of any of the heat source units 10A to 10D and the outside air temperature Te continues to be greater than or equal to a threshold Tth for a second time. However, the method of pre-detection is not limited to this. The pre-detection unit 52 may estimate the defrosting start time when the defrosting conditions are met and pre-detect the defrosting operation two hours (for example, 5 minutes) before the defrosting start time. For example, the pre-detection unit 52 may estimate the time when the defrosting conditions are reached from the rate of increase of the difference ΔTf between the refrigerant temperature Tr of any 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 conditions are reached. Alternatively, the pre-detection unit 52 may estimate the time when the defrosting conditions are reached 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 conditions are reached. Alternatively, the pre-detection unit 52 may pre-detect a defrosting operation when the elapsed time since the end of the previous defrosting operation reaches (threshold time - 2nd hour).

[0067] Furthermore, if defrosting operation does not start after a preset time (e.g., 10 minutes) has elapsed since the start of capacity-increasing operation, the heat source system 1 may terminate the capacity-increasing 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 of units performing heating operation before the prior detection. If the number of heat source units currently performing heating operation is the same as the number of units performing heating operation before the prior 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 of units performing heating operation before the prior detection, that is, if a heat source unit that was stopped for capacity-increasing operation is started, the operation control unit 51 stops the heat source unit scheduled for defrosting operation and controls the heat source units so that the outlet temperature Tout of the heat source units performing heating operation meets the target temperature Tm. This prevents the capacity-increasing operation from continuing unintentionally for a long period of time. [Explanation of Symbols]

[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 transfer medium circuit, 41 Heat transfer medium heat exchanger, 42 Pump, 51 Operation control unit, 52 Pre-detection unit, 53 Capacity increase unit, 54 Memory unit, 100 Refrigeration cycle device.

Claims

1. Multiple heat source units, The system includes a control device for controlling a plurality of the heat source units, Each of the aforementioned heat source units is equipped with a refrigerant circuit to which a compressor, an outdoor heat exchanger, an expansion valve, and a heat transfer medium heat exchanger are connected. The heat exchanger in the heat transfer medium exchanges heat between the refrigerant flowing through the refrigerant circuit and the heat transfer medium supplied to the load unit. The control device is The system detects that at least one of the multiple heat source units is scheduled to start defrosting operation. A heat source system that performs a capacity-boosting operation to increase the total heating capacity of the heat source units other than the heat source unit scheduled for defrosting operation, before the defrosting operation is started.

2. In the capacity-increasing operation, the control device The heat source system according to claim 1, wherein if at least one of the multiple heat source units is stopped, the same number of stopped heat source units as the number of heat source units scheduled for defrosting operation are started.

3. In the capacity-increasing operation, the control device The system controls the heat source units other than the heat source unit scheduled for defrosting so that the total heating capacity of the heat source units other than the heat source unit scheduled for defrosting reaches the target heating capacity. The heat source system according to claim 1 or 2, wherein the target heating capacity is the sum of the heating capacity of the multiple heat source units at the time of detection and the amount of heat collected during the defrosting operation of the heat source unit scheduled for defrosting operation.

4. In the capacity-increasing operation, the control device This system controls the temperature difference between the heat source units other than the heat source unit scheduled for defrosting operation to reach the target temperature difference. The aforementioned temperature difference is the difference between the outlet temperature of the heat medium downstream of the heat exchanger and the inlet temperature of the heat medium upstream, in the flow direction of the heat medium. The heat source system according to claim 3, wherein the target temperature difference is determined based on the target heating capacity and the temperature difference at the time of detection.

5. The control device is When the defrosting conditions are met, the defrosting operation of the heat source unit scheduled for defrosting operation is started. The capacity-increasing operation is also performed during the defrosting operation of the heat source unit scheduled for defrosting. The heat source system according to claim 1 or 2, wherein the capacity increase operation is terminated when the defrosting operation is completed.

6. The defrosting condition is that the difference between the outside air temperature and the temperature of the refrigerant flowing through at least one of the outdoor heat exchangers of the multiple heat source units remains above a threshold for a first hour. The heat source system according to 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 at least one of the multiple heat source units' outdoor heat exchangers is greater than or equal to the threshold for a second time that is shorter than the first time.

7. The control device is The start time of the capacity increase operation is determined from the time required for the total heating capacity of the heat source units other than the heat source unit scheduled for defrosting operation to reach the target heating capacity. The heat source system according to claim 1 or 2, wherein the capacity-increasing operation is started at the aforementioned start time.

Images