JP6672619B2 - Air conditioning system - Google Patents

Description

  The present invention relates to an air conditioning system.

  Conventionally, for example, as in Patent Document 1 (Japanese Patent Application Laid-Open No. Hei 8-210667), water cooled / heated by a cooling tower / boiler is circulated in a water circuit by a pump, and the water in the water circuit is used for the air conditioner. 2. Description of the Related Art An air conditioning system in which heat and / or heat is supplied to a heat source device is known.

  Here, the flow rate of the water circulating in the water circuit can be controlled, for example, such that the temperature difference between the inlet and outlet of the heat source unit of the air conditioner is maintained at a certain temperature difference.

  In addition, when the heating operation is performed in the air conditioner, even if the heat load in the air conditioner is small, in order to prevent freezing of the water circulating in the water circuit, the water circulating in the water circuit is required. It is required to control the flow rate to be equal to or higher than the minimum flow rate.

  However, when the heat load during the heating operation in the air conditioner is small, in order to secure a certain temperature difference as the temperature difference between the inlet and outlet of the heat source unit of the air conditioner, the flow rate of the water circuit is smaller than the minimum flow rate. In some cases, the flow rate must be controlled. In this case, the operation of the air conditioner is stopped to avoid freezing of water. Then, when a certain temperature difference can be secured as the temperature difference of the water at the entrance and exit of the heat source unit of the air conditioner, and the flow rate of the water circuit can be made larger than the minimum flow rate, the air conditioning is re-started. The operation of the device will be started.

  As described above, when the heat load during the heating operation in the air conditioner is small, the water circuit is maintained despite the fact that a certain temperature difference can be secured as the temperature difference of the water at the entrance and exit of the heat source unit of the air conditioner. When the flow rate of the air conditioner decreases, the operation of the air conditioner is likely to be stopped, and the operation / stop of the air conditioner is frequently repeated, which causes not only poor energy efficiency but also frequent changes in the environment of the air-conditioned space. And lacks comfort.

  An object of the present invention has been made in view of the above points, and it is an object of the present invention to provide an air conditioning system that can continue operation of a compressor in a refrigerant circuit for a longer time while suppressing freezing in a fluid circuit. is there.

  An air conditioning system according to a first aspect includes a fluid circuit, a heating unit, a refrigerant circuit, a flow control unit, and a control unit. In the fluid circuit, a circulating fluid circulates. The heating means heats the circulating fluid. The refrigerant circuit has a compressor, a use side heat exchanger, an expansion valve, and a heat source side heat exchanger, and the refrigerant circulates. The heat source side heat exchanger causes heat exchange between the heat of the circulating fluid and the heat of the refrigerant flowing inside the heat source side heat exchanger. The flow rate adjusting unit adjusts the flow rate of the circulating fluid sent to the heat source side heat exchanger. The control unit controls the flow rate adjusting unit. The control unit performs a heating operation in which the heat source side heat exchanger functions as a refrigerant evaporator and the use side heat exchanger functions as a refrigerant radiator in the refrigerant circuit. The control unit switches and executes the first control and the second control when performing the heating operation. When executing the first control, the control unit controls the flow rate adjusting unit such that the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger becomes a predetermined target value. In the second control, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or less than a predetermined flow rate, the control unit sets the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger. The flow rate adjusting unit is changed to a smaller update target value, and the flow rate adjustment unit is controlled so that the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger becomes the update target value.

  In this air conditioning system, the heat load is reduced as in the case where the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or less than a predetermined flow rate or in the case where the capacity of the heat source determined from the rotation speed of the compressor is equal to or less than the predetermined capacity. Even if it becomes difficult to secure a predetermined target value as the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger if the first control is kept as it is, the operation of the heat source unit is continued. By performing the second control without stopping (compressing the compressor), the control unit can perform the operation corresponding to the low load while suppressing the freezing in the fluid circuit and continue the operation state. Become.

  Specifically, in the second control, the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is changed to an updated target value that is a smaller value, and the control target value is passed through the heat source side heat exchanger. The temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger becomes smaller than a predetermined target value by controlling the flow rate adjustment unit so that the temperature difference of the circulating fluid before and after the heat treatment becomes the updated target value, thereby reducing the load. It becomes possible to operate in accordance with. Furthermore, since the flow rate of the circulating fluid sent to the heat source side heat exchanger is controlled to a flow rate that achieves the temperature difference of the update target value, the flow rate is increased when the first control is switched to the second control. And the freezing of the circulation channel can be suppressed.

  As described above, even when the load is low, the operation of the compressor in the refrigerant circuit can be continued for a longer time while the freezing in the fluid circuit is suppressed.

  The air-conditioning system according to the second aspect is the air-conditioning system according to the first aspect, wherein the control unit performs the second control so that a flow rate of the circulating fluid sent to the heat source side heat exchanger is lower than a predetermined lower limit flow rate. When it becomes larger than the predetermined increase update flow rate which is a large value, the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is increased to the increase update target value which is larger than the update target value. After updating, the flow rate controller is controlled so that the temperature difference becomes the increase update target value.

  In this air conditioning system, the second control is performed due to the low load, and the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is changed to a smaller updated target value. When the control is being performed, in the control by the update target value, when the flow rate of the circulating fluid sent to the heat source side heat exchanger becomes larger than the predetermined increased update flow rate, before and after passing through the heat source side heat exchanger Control is performed to update the control target value of the temperature difference of the circulating fluid to a larger increase target value. This makes it possible to increase the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger to approach a predetermined target value.

  The air conditioning system according to the third aspect is the air conditioning system according to the second aspect, wherein the control unit updates the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger when performing the second control 2. When the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or less than a predetermined flow rate while controlling the flow rate adjustment unit to be the target value, the circulating fluid before and after passing through the heat source side heat exchanger The control target value of the temperature difference is updated to a decrease update target value that is smaller than the update target value, and the flow rate controller is controlled such that the temperature difference becomes the decrease update target value.

  In this air conditioning system, the second control is performed due to the low load, and the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is changed to a smaller updated target value. Even when the control is performed, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or less than a predetermined flow rate, the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger Is updated to a reduced update target value that is smaller than the update target value. This further reduces the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger, thereby facilitating securing the flow rate of the circulating fluid sent to the heat source side heat exchanger and suppressing freezing of the circulation flow path. It becomes possible to do.

  The air-conditioning system according to a fourth aspect is the air-conditioning system according to the second aspect or the third aspect, wherein the control unit performs a second control to determine a temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger. Is switched from the second control to the first control when the control target value becomes the same value as the predetermined target value.

  In this air conditioning system, the second control is performed due to the low load, and in a situation where the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is controlled to be the updated target value, the load is reduced. Becomes larger, and the control target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger becomes the same value as the predetermined target value, the control unit switches to the first control again. Thereby, even if the load increases again after the load becomes low, it is possible to cope with the load by switching the control.

  The air-conditioning system according to the fifth aspect is the air-conditioning system according to any of the second to fourth aspects, wherein the update target value is obtained by changing the capacity of the heat source determined from the rotation speed of the compressor at a predetermined lower limit flow rate. This is a target value corresponding to the number of rotations, which is a value obtained by dividing the target.

  In this air conditioning system, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or less than a predetermined flow rate or when the capacity of the heat source determined from the rotation speed of the compressor is equal to or less than the predetermined capacity, at a low load, The control target value of the temperature difference is changed to an updated target value that is a smaller value (a target value corresponding to a rotation speed that is a value obtained by dividing the capacity of the heat source determined from the rotation speed of the compressor by a predetermined lower flow rate). Then, the flow rate controller is controlled so that the temperature difference becomes the updated target value. Thereby, the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger becomes smaller than the predetermined target value, and the operation corresponding to the low load becomes possible. Here, the rotation speed corresponding target value, which is a value obtained by dividing the capacity of the heat source by the predetermined lower limit flow rate, is required to maintain the predetermined lower limit flow rate in the fluid circuit in the capacity of the heat source at that time, It becomes the target value of the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger. Further, since the flow rate of the circulating fluid sent to the heat source side heat exchanger is controlled to a flow rate that achieves the temperature difference of the target value corresponding to the rotation speed, a predetermined lower limit is set as the flow rate of the circulating fluid sent to the heat source side heat exchanger. It is possible to secure the flow rate and suppress the freezing of the circulation channel.

  As described above, even when the load is low, the operation of the compressor in the refrigerant circuit can be continued for a longer time while the freezing in the fluid circuit is suppressed.

The air-conditioning system according to Supplementary Note 1 is the air-conditioning system according to the fifth aspect, and in the second control, when the capacity of the heat source determined from the number of revolutions of the compressor is equal to or less than a predetermined capacity, The control target value of the difference is changed to the update target value, and the flow rate adjusting unit is controlled so that the temperature difference becomes the update target value. The control unit, when executing the second control, when the capability of the heat source grasped from the rotation speed of the compressor is larger than a predetermined return capability which is a value larger than the predetermined capability, the second control third to the third control. Switch to 1 control.

  In this air conditioning system, the second control is performed due to the low load, and the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is controlled to be the target value corresponding to the rotation speed. When the load increases and the capability of the heat source, which is determined from the rotation speed of the compressor, becomes greater than the predetermined return capability, the control unit switches to the first control again. Here, since the predetermined return ability is a value larger than the predetermined ability, hunting of the control between the first control and the second control can be suppressed.

An air conditioning system according to a sixth aspect is the air conditioning system according to any of the first to fifth aspects, and includes a plurality of refrigerant circuits and a plurality of flow sensors. The fluid circuit has a branch circuit that branches and flows a circulating fluid for each refrigerant circuit. The flow control unit has a circulation pump provided in a portion other than the branch circuit in the fluid circuit, and a flow control valve provided in each branch circuit. A plurality of flow sensors are provided for each branch circuit. Each flow sensor detects the flow rate of the circulating fluid flowing through the branch circuit in which the flow sensor is provided. The control unit controls the circulation pump and each of the flow control valves according to the detection value of the flow sensor.

  In this air conditioning system, even when a plurality of refrigerant circuits are provided, by controlling the circulation pump and the respective flow rate control valves according to the detection values of the flow rate sensors, the fluid circuit is directed toward each heat source side heat exchanger. Frequent start / stop of the compressor in each refrigerant circuit can be suppressed while securing the flow rate of the sent circulating fluid and suppressing freezing in each heat source side heat exchanger.

  In the air conditioning system according to the first aspect, even when the load is low, it is possible to continue the operation of the compressor in the refrigerant circuit for a longer time while suppressing freezing in the fluid circuit.

  In the air conditioning system according to the second aspect, it is possible to increase the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger to approach a predetermined target value.

  In the air conditioning system according to the third aspect, by further reducing the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger, the flow rate of the circulating fluid sent to the heat source side heat exchanger can be easily ensured, It is possible to suppress freezing of the flow path.

  In the air conditioning system according to the fourth aspect, even when the load increases again after the load becomes low, it is possible to cope with the load by switching the control.

  In the air conditioning system according to the fifth aspect, even when the load is low, the operation of the compressor in the refrigerant circuit can be continued for a longer time while the freezing in the fluid circuit is suppressed.

In the air conditioning system according to Supplementary Note 1 , even when the load increases again after the load becomes low, it is possible to cope with the load by switching the control and to suppress hunting of the control.

In the air conditioning system according to the sixth aspect, it is possible to suppress frequent start and stop of the compressor in each refrigerant circuit while suppressing freezing in each heat source side heat exchanger.

It is a schematic structure figure of an air-conditioning system concerning a 1st embodiment. It is a schematic structure figure showing a part of an air conditioner and a fluid circuit. 3 is a control flowchart of the pump according to the first embodiment. It is a schematic structure figure of an air-conditioning system concerning a 2nd embodiment. It is a schematic structure figure showing a part of an air conditioner and a fluid circuit. It is a control flow chart of the flow control valve concerning a 2nd embodiment. It is a control flowchart of a flow control valve concerning a modification (A).

  Hereinafter, an air conditioning system according to an embodiment will be described with reference to the drawings.

The following description is an example and does not limit the invention.
(1) First Embodiment (1-1) Overall Configuration The air conditioning system 100 according to the first embodiment is an air conditioning system installed in a building or the like. The air conditioning system 100 according to the present embodiment is used for cooling and heating of an installed building or the like.

  The air conditioning system 100 mainly includes a fluid circuit 21, a cooling tower 80, a boiler 90, a pump 20, a refrigerant circuit 31, an air conditioning controller 49, and a fluid controller 70, as shown in FIG.

  The cooling tower 80 is installed on a roof such as a building in which the air conditioning system 100 is installed, for example. Although not particularly limited, the cooling tower 80 cools the circulating fluid flowing through the fluid circuit 21 by bringing the circulating fluid into direct or indirect contact with the atmosphere.

  The boiler 90 is installed in a machine room such as a building where the air conditioning system 100 is installed. Although not particularly limited, the boiler 90 heats a circulating fluid flowing through the fluid circuit 21 by heat obtained by burning fuel.

  The fluid circuit 21 circulates a circulating fluid inside. The circulating fluid cooled to a predetermined target cooling temperature by the cooling tower 80 or the circulating fluid heated to a predetermined target heating temperature by the boiler 90 is air-conditioned, which will be described later. It is configured to be able to carry to the heat source device 40 of the device 30. The fluid circuit 21 is provided with a pump 20 that can adjust the flow rate (for example, volume flow rate) of the circulating fluid that circulates. When the pump 20 operates, the circulating fluid circulates in the fluid circuit 21, and the circulating fluid moves between the cooling tower 80 or the boiler 90 and the heat source device 40 of the air conditioner 30. Here, the fluid circuit 21 includes an outgoing pipe 22 that sends a circulating fluid from the cooling tower 80 or the boiler 90 to the heat source unit 40 and a return pipe that sends a circulating flow path from the heat source unit 40 to the cooling tower 80 or the boiler 90. 23. A first cooling pipe 81 extending to the cooling tower 80 and a first heating pipe 91 extending to the boiler 90 are connected to the end of the going pipe 22 opposite to the end on the heat source device 40 side. A second cooling pipe 82 extending to the cooling tower 80 and a second heating pipe 92 extending to the boiler 90 are connected to a side of the return pipe 23 opposite to the end of the heat source device 40. In the present embodiment, the pump 20 is provided in the middle of the going pipe 22. An upstream fluid temperature sensor 24 for detecting the temperature of the circulating fluid before the heat exchange with the refrigerant in the heat source side heat exchanger 43 in the heat source device 40 is provided in the middle of the going pipe 22. . Further, in the middle of the return pipe 23, a downstream fluid temperature sensor 25 for detecting the temperature of the circulating fluid after the heat exchange with the refrigerant in the heat source side heat exchanger 43 in the heat source device 40 is provided. I have. A first cooling valve 83 is provided in the middle of the first cooling pipe 81, a second cooling valve 84 is provided in the middle of the second cooling pipe 82, and a first heating valve 93 is provided in the middle of the first heating pipe 91. Is provided, and a second heating valve 94 is provided in the middle of the second heating pipe 92.

  Here, when the air conditioner 30 performs the cooling operation, the first heating valve 93 and the second heating valve 94 are closed and the boiler 90 is in a stopped state, and the first cooling valve 83 and the second cooling valve 84 is fully opened and the cooling tower 80 is in a driving state, and the outgoing pipe 22, the heat source side heat exchanger 43, the return pipe 23, the second cooling pipe 82, the cooling tower 80, and the first cooling pipe 81 are connected in this order. The fluid circuit 21 is constituted by the closed circuit. Here, the circulating fluid flowing into the cooling tower 80 from the second cooling pipe 82 is cooled to a predetermined target cooling temperature, and then flows out through the first cooling pipe 81.

  When the air conditioner 30 performs the heating operation, the first cooling valve 83 and the second cooling valve 84 are closed, the cooling tower 80 is in a stopped state, and the first heating valve 93 and the second heating valve 94 is fully opened and the boiler 90 is in a driving state, and the closing pipe in which the going pipe 22, the heat source side heat exchanger 43, the return pipe 23, the second heating pipe 92, the boiler 90 and the first heating pipe 91 are connected in this order. The fluid circuit 21 is configured by the circuit. Here, the circulating fluid that has flowed into the boiler 90 from the second heating pipe 92 is heated to a predetermined target heating temperature, and then flows out through the first heating pipe 91.

  The fluid controller 70 can grasp the detected temperatures of the upstream fluid temperature sensor 24 and the downstream fluid temperature sensor 25. The opening and closing control of the first heating valve 93, the second heating valve 94, the first cooling valve 83, and the second cooling valve 84 is performed by the fluid controller 70. The drive control of the cooling tower 80 and the boiler 90 is also performed by the fluid controller 70.

  Here, water is used as the circulating fluid, but is not limited to this. For example, brine or the like may be used instead of water as the circulating fluid.

  The pump 20 is a variable capacity inverter pump. The pump 20 is configured to change the capacity (liquid sending amount) by controlling the rotation speed of a motor (not shown). The capacity of the pump 20, in other words, the rotation speed of the motor, is controlled by the fluid controller 70.

  As shown in FIG. 2, the refrigerant circuit 31 has a compressor 41, a four-way switching valve 42, a heat source side heat exchanger 43, an expansion valve 44, and a use side heat exchanger 51. The refrigerant is circulated inside. The compressor 41 is a variable capacity inverter type compressor. The type of the compressor 41 is not particularly limited, and a rotary compressor, a scroll compressor, or the like can be used. The expansion valve 44 is a motor-operated expansion valve with a variable opening.

  The refrigerant circuit is provided in the air conditioner 30. The air conditioner 30 is configured such that the heat source unit 40 and the indoor unit 50 are connected by a liquid-side communication pipe and a gas-side communication pipe that constitute a part of the refrigerant circuit 31. In the present embodiment, a compressor 41, a four-way switching valve 42, a heat source side heat exchanger 43, an expansion valve 44, and an air conditioning controller 49 are provided in the heat source device 40. The heat source device 40 is installed in a machine room on each floor of a building or the like in which the air conditioning system 100 is installed, for example. Further, the indoor unit 50 is provided with a use side heat exchanger 51 and an indoor fan 52 for sending air in a space to be air-conditioned to the use side heat exchanger 51. The indoor unit 50 is installed in a space to be air-conditioned.

  In the refrigerant circuit 31, cooling or heating of the air-conditioned space is performed by performing a vapor compression refrigeration cycle. During the cooling operation, the four-way switching valve 42 is in the connection state shown by the solid line in FIG. 2, and the refrigerant discharged from the compressor 41 passes through a part of the connection port of the four-way switching valve 42 and exchanges heat on the heat source side. The heat is sent to the heat exchanger 43 and radiated in the heat source side heat exchanger 43. The refrigerant radiated in the heat source side heat exchanger 43 is decompressed when passing through the expansion valve 44, and is sent to the use side heat exchanger 51. The refrigerant sent to the use side heat exchanger 51 evaporates due to the heat of the indoor air sent from the indoor fan 52, passes through some other connection ports of the four-way switching valve 42, and passes through the compressor 41. Inhaled. During the heating operation, the four-way switching valve 42 is in the connection state shown by the dotted line in FIG. 2, and the refrigerant discharged from the compressor 41 passes through a part of the connection port of the four-way switching valve 42 and is used for heat exchange on the use side. The heat is sent to the chamber 51 and is radiated to the indoor air sent from the indoor fan 52. The refrigerant that has radiated heat in the use side heat exchanger 51 is decompressed when passing through the expansion valve 44, and is sent to the heat source side heat exchanger 43. The refrigerant sent to the heat source side heat exchanger 43 evaporates, passes through some other connection ports of the four-way switching valve 42, and is sucked into the compressor 41.

  In the heat source side heat exchanger 43 provided in the heat source unit 40, heat exchange is performed between the refrigerant flowing through the refrigerant circuit 31 and the circulating fluid flowing through the fluid circuit 21. Accordingly, the refrigerant flowing through the refrigerant circuit 31 is cooled by the circulating fluid flowing through the fluid circuit 21 during the cooling operation, and is heated by the circulating fluid flowing through the fluid circuit 21 during the heating operation.

  The air conditioning controller 49 includes a CPU, a memory such as a RAM and a ROM, and the like. The air conditioning controller 49 is electrically connected to each component of the air conditioner 30, for example, the indoor fan 52, the compressor 41, the four-way switching valve 42, and the expansion valve 44. The air conditioning controller 49 is communicably connected to the fluid controller 70.

  The air conditioning controller 49 controls the air conditioner 30 by causing the CPU to read and execute a program stored in the memory. The air conditioning controller 49 exchanges control signals with a remote controller (not shown) for operating the indoor unit 50. The air-conditioning controller 49 is based on commands input to the remote controller (for example, operation / stop of the indoor unit 50, operation mode (cooling / heating), set temperature, and the like), measurement values of various sensors of the air conditioner 30 (not shown), and the like. Thus, it controls various components of the air conditioner 30, for example, the indoor fan 52, the compressor 41, the four-way switching valve 42, and the expansion valve 44.

  The air-conditioning controller 49 controls various components of the air-conditioning device 30 according to the air-conditioning load of the air-conditioning device 30 (capacity required for cooling / heating the space to be air-conditioned). Specifically, in the present embodiment, during the cooling operation of the air conditioner 30, the air conditioning controller 49 controls the rotation speed of the compressor 41 so that the rotation speed of the compressor 41 becomes a predetermined rotation speed according to the air conditioning load. The degree of opening of the expansion valve 44 is controlled such that the degree of superheating of the refrigerant flowing through the outlet of the vessel 51 becomes a predetermined degree of superheating. In the present embodiment, during the heating operation of the air conditioner 30, the air conditioning controller 49 controls the rotation speed of the compressor 41 so as to be a predetermined rotation speed according to the air conditioning load. The degree of opening of the expansion valve 44 is controlled so that the degree of supercooling of the refrigerant flowing through the outlet becomes a predetermined degree of supercooling.

  The fluid controller 70 includes a CPU, a memory such as a RAM and a ROM, and the like. The fluid controller 70 is electrically connected to the cooling tower 80, the boiler 90, and the pump 20. The fluid controller 70 is communicably connected to each air conditioning controller 49. The fluid controller 70 receives information on the operation status of each air conditioner 30 from each air conditioning controller 49. The information on the operation status of the air conditioner 30 includes, for example, information on the operation / stop of the air conditioner 30, information on the air conditioning load of the air conditioner 30, information on the operation mode (heating / cooling mode) of the air conditioner 30, and the like.

  The fluid controller 70 controls the opening and closing of the first cooling valve 83, the second cooling valve 84, the first heating valve 93, the second heating valve 94, and the cooling tower by reading and executing the program stored in the memory by the CPU. The drive control of the boiler 90, the boiler 90 and the pump 20 is performed. The fluid controller 70 controls the cooling tower 80, the boiler 90, and the pump 20 based on the information on the operation / stop of the air conditioner 30 and the information on the operation mode received from the air conditioning controller 49.

(1-2) Control of Air Conditioning Device 30 and Pump 20 The air conditioning device 30 performs, for example, a cooling operation or a heating operation in response to an instruction of a remote control operation or the like by a user. Here, in both the cooling operation and the heating operation, the air conditioner 30 is operated so that the temperature of the space to be air-conditioned becomes the set temperature. The set temperature may be a temperature received by an input operation from a user, or may be a predetermined temperature.

  The air conditioner 30 is appropriately controlled so as to be able to output a capacity corresponding to the magnitude of the air conditioning load. Specifically, the air conditioning controller 49 controls the rotation speed of the compressor 41 according to the magnitude of the difference between the set temperature of the air-conditioned space and the current temperature of the air-conditioned space. This control of the air conditioner 30 is always continued.

  The fluid controller 70 receives, from the air conditioning controller 49, information indicating whether the air conditioner 30 is performing a cooling operation or a heating operation. Here, during the cooling operation, the fluid controller 70 closes the first heating valve 93 and the second heating valve 94 to stop the boiler 90 while fully opening the first cooling valve 83 and the second cooling valve 84 to perform cooling. The tower 80 is driven. In the cooling tower 80, the temperature of the circulating fluid flowing into the cooling tower 80 from the second cooling pipe 82 is cooled to a predetermined target cooling temperature (not particularly limited, but at least the refrigerant flowing into the heat source side heat exchanger 43 is cooled). The liquid is allowed to flow out to the first cooling pipe 81 (to be cooled to a temperature lower than the temperature). Further, during the heating operation, the fluid controller 70 closes the first cooling valve 83 and the second cooling valve 84 to stop the cooling tower 80, and opens the first heating valve 93 and the second heating valve 94 fully to set the boiler. 90 is driven. In the boiler 90, the temperature of the circulating fluid flowing into the boiler 90 from the second heating pipe 92 is heated to a predetermined target heating temperature (not particularly limited, but at least the temperature of the refrigerant flowing into the heat source side heat exchanger 43 is higher than the temperature of the refrigerant flowing into the heat source side heat exchanger 43). After cooling to a higher temperature).

  Hereinafter, the control of the pump 20 during the heating operation will be described with reference to FIG.

  During the heating operation, unlike in the cooling operation, the flow rate of the circulating fluid is controlled to be maintained at a predetermined minimum flow rate or more so that the circulating fluid (water) is not easily frozen in the fluid circuit 21. In the present embodiment, a flow rate of 50% of a predetermined rated flow rate of the pump 20 is predetermined as a predetermined minimum flow rate. Here, as the predetermined lower limit flow rate, the flow rate (the predetermined rated flow rate of the pump 20) is slightly higher than the predetermined minimum flow rate (50% of the predetermined rated flow rate of the pump 20) so that freezing can be suppressed more reliably. 50% of flow rate + α (α is, for example, 5% or less) is defined.

  In step S10, the fluid controller 70 controls the rotation of the pump 20 so that the temperature difference ΔT of the circulating fluid before and after passing through the heat source side heat exchanger 43 in the heat source device 40 becomes 5 ° C. of the normal target value (predetermined target value). Control the number (normal control).

  Here, since the air conditioner 30 performs the heating operation, the heat source side heat exchanger 43 of the heat source device 40 functions as a refrigerant evaporator. The circulating fluid flowing through the fluid circuit 21 evaporates the refrigerant in the heat source side heat exchanger 43 of the heat source device 40, and the circulating fluid itself is cooled. Therefore, the temperature of the circulating fluid flowing through the fluid circuit 21 is such that the temperature detected by the downstream fluid temperature sensor 25 is lower than the temperature detected by the upstream fluid temperature sensor 24. Therefore, the fluid controller 70 sets the temperature difference ΔT of the circulating fluid obtained by subtracting the detected temperature of the downstream fluid temperature sensor 25 from the detected temperature of the upstream fluid temperature sensor 24 to be the normal target value of 5 ° C. The rotation speed of the pump 20 is controlled. Therefore, when the temperature difference ΔT of the circulating fluid is smaller than 5 ° C., the rotation speed of the pump 20 is reduced in order to decrease the flow rate of the circulating fluid in the fluid circuit 21. On the other hand, when the temperature difference ΔT of the circulating fluid is larger than 5 ° C., the rotation speed of the pump 20 is increased to increase the flow rate of the circulating fluid in the fluid circuit 21.

  In step S11, the fluid controller 70 controls the fluid circuit detected from the revolution speed of the pump 20 when controlling the revolution speed of the pump 20 so that the temperature difference ΔT of the circulating fluid becomes the normal target value of 5 ° C. It is determined whether or not the flow rate of the circulating fluid at 21 is equal to or less than a predetermined lower limit flow rate. If the flow rate is not lower than the predetermined lower limit flow rate, the flow returns to step S10 to continue the normal control since the normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid. On the other hand, if the flow rate is equal to or less than the predetermined lower limit flow rate, it is not possible to secure the normal target value of 5 ° C. as the temperature difference ΔT of the circulating fluid.

  Note that the air conditioner 30 stops the heating operation (stops the compressor 41) even in a case where the normal target value of 5 ° C. cannot be secured as the temperature difference ΔT of the circulating fluid in the fluid circuit 21. Without this, the operation according to the current air conditioning load is continued.

  In step S12, the fluid controller 70 controls the rotation speed of the pump 20 (low-load control) such that the flow rate of the circulating fluid in the fluid circuit 21 is fixed and maintained at a predetermined lower-limit flow rate (low-load control). The rotation speed of the pump 20 is not controlled so that the temperature difference ΔT becomes the normal target value of 5 ° C.). Accordingly, during the heating operation, even when the air conditioning load of the air conditioner 30 is small, a predetermined lower limit flow rate can be secured as the flow rate of the circulating fluid in the fluid circuit 21. Freezing can be suppressed. When the control is shifted from step S11 to step S12 to start the low load control, the temperature difference ΔT of the circulating fluid is smaller than the normal target value of 5 ° C. Further, if the air conditioning load on the air conditioner 30 increases after a while, the temperature difference ΔT of the circulating fluid gradually increases.

  In step S13, the fluid controller 70 determines that the temperature difference ΔT of the circulating fluid before and after passing through the heat source side heat exchanger 43 in the heat source device 40 is a predetermined return temperature difference (5 + β) that is larger than the normal target value of 5 ° C. It is determined whether the temperature is greater than C (β is, for example, 0.5 C or more and 2 C or less). Here, when the temperature difference ΔT of the circulating fluid is not larger than the return temperature difference (5 + β ° C.), the low load control in step S12 is continued. On the other hand, when the temperature difference ΔT of the circulating fluid is larger than the return temperature difference (5 + β ° C.), the process returns to step S10, and switches from the low load control to the normal control.

  In the cooling operation, the rotation speed of the pump 20 is controlled so that the temperature difference ΔT of the circulating fluid before and after passing through the heat source side heat exchanger 43 in the heat source device 40 becomes the normal target value of 5 ° C. Since the problem of freezing of the circulating fluid in 21 hardly occurs, the processing as in steps S11 to S13 described above is not performed.

(1-3) Features of First Embodiment In the air conditioning system 100 of the present embodiment, the temperature difference ΔT of the circulating fluid before and after passing through the heat source side heat exchanger 43 in the heat source device 40 is set to the normal target value of 5 ° C. If the normal control for controlling the rotation speed of the pump 20 is continued as it is, it becomes difficult to secure the normal target value of 5 ° C. as the temperature difference ΔT of the circulating fluid before and after passing through the heat source side heat exchanger 43. Even if there is, without stopping the operation of the air conditioner 30 (without stopping the compressor 41), the fluid controller 70 switches from the normal control to the low load control and executes the control. In the low load control, a predetermined lower limit flow rate slightly higher than the predetermined minimum flow rate is secured as the flow rate of the circulating fluid flowing through the fluid circuit 21, so that freezing of the circulating fluid in the fluid circuit 21 can be suppressed. . Moreover, even when it becomes difficult to continue the normal control, the operation is switched to the low-load control to avoid stopping the operation of the air conditioner 30 and to continue the operation according to the air-conditioning load.

  The predetermined return temperature difference (5 + β ° C.) is set as a value larger than the normal target value of 5 ° C. For this reason, unless the temperature difference ΔT of the circulating fluid before and after passing through the heat source side heat exchanger 43 in the heat source unit 40 becomes sufficiently large, switching from the low load control to the normal control is not performed. Can be suppressed.

(2) Second Embodiment (2-1) Overall Configuration An air conditioning system 200 according to a second embodiment is installed in a building or the like, and is used for cooling and heating of the installed building or the like. In the system of the embodiment, a plurality of air conditioners 30a, 30b, 30c are provided in parallel, and the fluid circuit 21 is branched for each of the air conditioners 30a, 30b, 30c. The following mainly describes differences from the example of the first embodiment.

  As shown in FIGS. 4 and 5, the air conditioning system 200 includes a first air conditioner 30a, a second air conditioner 30b, and a third air conditioner 30c. The configuration of each air conditioner is the same as that described in the first embodiment (corresponding components are indicated by corresponding numbers). Specifically, the first air conditioner 30a includes a first refrigerant circuit 31a, a first heat source unit 40a, and a first indoor unit 50a, and is controlled by a first air conditioning controller 49a. The second air conditioner 30b includes a second refrigerant circuit 31b, a second heat source unit 40b, and a second indoor unit 50b, and is controlled by a second air condition controller 49b. The third air conditioner 30c has a third refrigerant circuit 31c, a third heat source unit 40c, and a third indoor unit 50c, and is controlled by a third air conditioning controller 49c. Each branch circuit portion branched from the fluid circuit 21 passes through the heat source side heat exchangers 43a, 43b, and 43c of each of the heat source devices 40a, 40b, and 40c.

  The fluid circuit 21 has a branch circuit so as to correspond to each heat source side heat exchanger of each of the air conditioners 30a, 30b, 30c. The branch circuit includes a first going pipe 22a, a second going pipe 22b, a third going pipe 22c, a first returning pipe 23a, a second returning pipe 23b, and a third returning pipe 23c. The first outgoing pipe 22a, the second outgoing pipe 22b, and the third outgoing pipe 22c are respectively connected to the first air conditioner 30a side and the second air conditioner from the end of the outgoing pipe 22 opposite to the cooling tower 80 and the boiler 90 side. It extends so as to branch toward the device 30b and the third air conditioner 30c. The first return pipe 23a, the second return pipe 23b, and the third return pipe 23c are respectively connected to the first air conditioner 30a side and the second air conditioner from the ends of the return pipe 23 opposite to the cooling tower 80 and the boiler 90 side. It extends so as to branch toward the device 30b and the third air conditioner 30c.

  Here, the circulating fluid flowing through the first going pipe 22a exchanges heat with the refrigerant in the heat source side heat exchanger of the first air conditioner 30a, and is sent to the first return pipe 23a. The circulating fluid flowing through the second outgoing pipe 22b exchanges heat with the refrigerant in the heat source side heat exchanger of the second air conditioner 30b, and is sent to the second return pipe 23b. The circulating fluid flowing through the third going pipe 22c exchanges heat with the refrigerant in the heat source side heat exchanger of the third air conditioner 30c, and is sent to the third return pipe 23c.

  In the middle of the first going pipe 22a, a first flow control valve 35a capable of adjusting the valve opening is provided. A second flow control valve 35b capable of adjusting the valve opening is provided in the middle of the second going pipe 22b. A third flow control valve 35c capable of adjusting the valve opening is provided in the middle of the third going pipe 22c. The first controller 35a, the second controller 35b, and the third controller 35c all have their valve opening controlled by the fluid controller 70.

  A first upstream fluid temperature sensor 24a for detecting the temperature of the circulating fluid passing therethrough is provided on the first heat source device 40a side of the first flow control valve 35a in the middle of the first going pipe 22a. A first downstream fluid temperature sensor 25a for detecting the temperature of the circulating fluid passing therethrough is provided in the middle of the first return pipe 23a. A second upstream fluid temperature sensor 24b for detecting the temperature of the circulating fluid passing therethrough is provided in the middle of the second outflow pipe 22b and closer to the second heat source device 40b than the second flow control valve 35b. A second downstream fluid temperature sensor 25b for detecting the temperature of the passing circulating fluid is provided in the middle of the second return pipe 23b. A third upstream fluid temperature sensor 24c for detecting the temperature of the passing circulating fluid is provided on the third heat source device 40c side of the third flow control valve 35c in the middle of the third going pipe 22c. In the middle of the third return pipe 23c, there is provided a third downstream fluid temperature sensor 25c for detecting the temperature of the circulating fluid passing therethrough. These first upstream fluid temperature sensor 24a, first downstream fluid temperature sensor 25a, second upstream fluid temperature sensor 24b, second downstream fluid temperature sensor 25b, third upstream fluid temperature sensor 24c, and third downstream Any of the detected temperatures of the side fluid temperature sensor 25c can be grasped by the fluid controller 70.

  Further, a first flow sensor 36a for detecting the flow rate of the circulating fluid passing therethrough is provided in the middle of the first return pipe 23a. A second flow sensor 36b for detecting the flow rate of the circulating fluid passing therethrough is provided in the middle of the second return pipe 23b. A third flow sensor 36c for detecting the flow rate of the circulating fluid passing therethrough is provided in the middle of the third return pipe 23c. The fluid controller 70 can grasp the flow rates detected by the first flow rate sensor 36a, the second flow rate sensor 36b, and the third flow rate sensor 36c.

(2-2) Control of the first to third air conditioners 30a, 30b, 30c, the pump 20, and the first to third flow rate control valves 35a, 35b, 35c The first to third air conditioners 30a, 30b, 30c are: In response to an instruction from the user, a cooling operation or a heating operation is performed so that the temperature of the space to be air-conditioned becomes the set temperature. The first to third air conditioners 30a, 30b, and 30c are controlled based on the difference between the temperature of each air-conditioned space and the set temperature so that the air conditioner can output the capacity corresponding to the magnitude of the air-conditioning load. Specifically, each of the air conditioning controllers 49a, 49b, and 49c controls the rotation speed of each compressor according to the magnitude of the difference between the set temperature of the corresponding air conditioning target space and the current temperature of the air conditioning target space. . The first to third air conditioners 30a, 30b, and 30c always have this control continuously.

  The fluid controller 70 indicates from any one of the first to third air conditioning controllers 49a, 49b, 49c whether the first to third air conditioners 30a, 30b, 30c are performing a cooling operation or a heating operation. To receive.

  Here, the rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. Although not particularly limited, for example, the rotation speed of the pump 20 is controlled by the fluid controller 70 so as to be a predetermined rotation speed according to the total value of the valve opening degrees of the respective flow control valves 35a, 35b, 35c. Is also good. Here, the control of the rotation speed of the pump 20 by the fluid controller 70 is performed so as to always correspond to the value of the valve opening degree of each of the flow rate control valves 35a, 35b, 35c, or the control of the flow rate control valves 35a, 35b, 35c. Control is performed so as to correspond to the value of the valve opening at predetermined time intervals.

  In the heating operation, unlike the cooling operation, the flow rate of the circulating fluid is maintained at a predetermined minimum flow rate at any point so that freezing of the circulating fluid (water) does not easily occur in the fluid circuit 21. Controlled. Specifically, the flow rate of the circulating fluid flowing through the branch circuits (the first going pipe 22a, the second going pipe 22b, the third going pipe 22c, the first returning pipe 23a, the second returning pipe 23b, and the third returning pipe 23c) Is controlled so as to be maintained at or above a predetermined minimum flow rate. In the present embodiment, a flow rate of 50% of a predetermined rated flow rate of the pump 20 is predetermined as a predetermined minimum flow rate. Here, as the predetermined lower limit flow rate, the flow rate (the predetermined rated flow rate of the pump 20) is slightly higher than the predetermined minimum flow rate (50% of the predetermined rated flow rate of the pump 20) so that freezing can be suppressed more reliably. 50% of flow rate + α (α is, for example, 5% or less) is defined.

  Hereinafter, individual controls of the first to third flow control valves 35a, 35b, and 35c during the heating operation will be described with reference to FIG. In the following description, the control of the first flow control valve 35a will be described as an example. However, the control is independent of the control of the second flow control valve 35b and the control of the third flow control valve 35c. It is assumed that the processing is executed by the fluid controller 70.

  In step S20, the fluid controller 70 sets the temperature difference ΔT of the circulating fluid before and after passing through the first heat source side heat exchanger 43a of the first heat source device 40a to 5 ° C. of the normal target value (predetermined target value). Then, the valve opening of the first flow control valve 35a is controlled (normal control).

  Specifically, the fluid controller 70 determines that the temperature difference ΔT of the circulating fluid obtained by subtracting the temperature detected by the first downstream fluid temperature sensor 25a from the temperature detected by the first upstream fluid temperature sensor 24a is equal to the normal target value. The valve opening of the first flow control valve 35a is controlled so as to be 5 ° C. Therefore, when the temperature difference ΔT of the circulating fluid is smaller than the normal target value of 5 ° C., the flow rate of the circulating fluid flowing through the first going pipe 22a and the first return pipe 23a in the fluid circuit 21 is reduced. The valve opening of the one flow control valve 35a is reduced. On the other hand, when the temperature difference ΔT of the circulating fluid is larger than the normal target value of 5 ° C., the flow rate of the circulating fluid flowing through the first going pipe 22a and the first returning pipe 23a of the fluid circuit 21 is increased. The valve opening of the first flow control valve 35a is increased.

  The rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. The rotation speed of the pump 20 is also adjusted according to the change in the control of the valve opening of the control valve 35a.

  In step S21, when controlling the valve opening degree of the first flow control valve 35a so that the temperature difference ΔT of the circulating fluid becomes the normal target value of 5 ° C. It is determined whether the grasped flow rate of the circulating fluid flowing through the first going pipe 22a and the first return pipe 23a is equal to or less than a predetermined lower limit flow rate. Here, if the flow rate is not lower than the predetermined lower limit flow rate, since the first flow rate control valve 35a is in a state where the normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid, step S20 And the normal control is continued. On the other hand, when the flow rate is equal to or lower than the predetermined lower limit flow rate, the first flow rate control valve 35a is not in a state where the normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid. And control at low load. The third flow rate sensor 36c determines whether the flow rate of the circulating fluid flowing through the second going pipe 22b and the second return pipe 23b, which is determined from the second flow rate sensor 36b, is equal to or lower than a predetermined lower limit flow rate. It is similarly determined whether the flow rate of the circulating fluid flowing through the third going pipe 22c and the third return pipe 23c is equal to or less than a predetermined lower limit flow rate. Hereinafter, the same applies to the low-load control of each valve and the control of the corresponding air conditioner, and a description thereof will be omitted.

  Note that the first air conditioner 30a having the corresponding first heat source device 40a cannot secure the normal target value of 5 ° C. as the temperature difference ΔT of the circulating fluid in the first going pipe 22a and the first return pipe 23a of the fluid circuit 21. Even in the case of the state, the operation according to the current air conditioning load is continued without stopping the heating operation (stopping the compressor 41a).

  In step S22, the fluid controller 70 determines that the control target value of the temperature difference ΔT of the circulating fluid before and after passing through the first heat source side heat exchanger 43a of the first heat source device 40a is 5 ° C. of the normal target value (predetermined target value). The valve opening of the first flow control valve 35a is controlled by updating to a value (update target value) reduced by a predetermined temperature (1 ° C. in the present embodiment) (low load control). Thereby, even when the air conditioning load of the first air conditioner 30a is small during the heating operation, the predetermined lower limit flow rate is set as the flow rate of the circulating fluid in the first going pipe 22a and the first return pipe 23a of the fluid circuit 21. Since it is easy to secure the circulating fluid, the freezing of the circulating fluid in the first going pipe 22a and the first return pipe 23a can be suppressed.

  The rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. The rotation speed of the pump 20 is also adjusted according to the change in the control of the valve opening of the control valve 35a.

  Note that in step S22, the valve opening of the first flow rate control valve 35a is controlled in a state where the control target value is updated, and the process proceeds to step S23 after waiting for a predetermined time to elapse for the first time.

  In step S23, the fluid controller 70 determines again whether the flow rate of the circulating fluid flowing through the first going pipe 22a and the first return pipe 23a, which is grasped from the first flow rate sensor 36a, is equal to or less than a predetermined lower limit flow rate. to decide. Here, even if the control target value of the first flow control valve 35a is updated, the control target value of the first flow control valve 35a is smaller if the flow rate is again lower than the predetermined lower limit flow. The process returns to step S22 in order to update the value (reduction update target value). In this manner, by further reducing the control target value of the temperature difference, it becomes possible to easily secure the flow rate of the circulating fluid sent to the first going pipe 22a and the first return pipe 23a. On the other hand, when the flow rate is not lower than the predetermined lower limit flow rate, the process proceeds to step S24.

  In Step S24, the fluid controller 70 determines whether or not the flow rate of the circulating fluid flowing through the first going pipe 22a and the first return pipe 23a, which is grasped from the first flow rate sensor 36a, is larger than a predetermined increase update flow rate. Here, when it is not larger than the predetermined increase update flow rate, the process returns to step S23. On the other hand, if the flow rate is larger than the predetermined increase update flow rate, the flow proceeds to step S25 because there is room for increasing the flow rate in the control state of the first flow rate control valve 35a.

  In step S25, the fluid controller 70 sets the control target value of the temperature difference ΔT of the circulating fluid before and after the first heat source device 40a passes through the first heat source side heat exchanger 43a at a predetermined temperature (present embodiment). In this case, the value is increased by 1 ° C. (increased update target value) to control the valve opening of the first flow control valve 35a (correction of the control target value during low load control).

  The rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. The rotation speed of the pump 20 is also adjusted according to the change in the control of the valve opening of the control valve 35a.

  In step S26, the fluid controller 70 determines whether the control target value of the first flow control valve 35a has been returned to the normal target value (5 ° C.). Here, if it has not been returned to the normal target value, the process returns to step S23, and the low load control based on the control target value is continued. On the other hand, if it has been returned to the normal target value, the process returns to step S20, and switches from the low load control to the normal control. Thus, even if the load of the first air conditioner 30a increases again after the air conditioning load becomes low, the load can be handled by switching the control mode.

  In the cooling operation, the valve of the first flow control valve 35a is controlled so that the temperature difference ΔT of the circulating fluid before and after the passage of the first heat source unit 40a through the first heat source side heat exchanger 43a becomes the normal target value of 5 ° C. Although the degree of opening is controlled, the problem of freezing of the circulating fluid in the first going pipe 22a and the first return pipe 23a of the fluid circuit 21 is unlikely to occur, so that the above-described processing in steps S21 to S26 is not performed.

  The control of the second flow control valve 35b and the control of the third flow control valve 35c are the same as the above-described control of the first flow control valve 35a, and these controls are simultaneously executed by the fluid controller 70.

(2-3) Features of Second Embodiment The air conditioning system 200 of the present embodiment has a temperature difference of the circulating fluid before and after the heat source devices 40a, 40b, 40c pass through the first heat source side heat exchangers 43a, 43b, 43c. If the normal control for controlling the valve opening of each of the flow rate control valves 35a, 35b, 35c is continued as it is so that ΔT becomes the normal target value of 5 ° C., the normal target value of 5 ° C. is used as the temperature difference ΔT of the circulating fluid. Even if it becomes difficult to secure the air conditioner, the fluid controller 70 switches from the normal control to the low load control without stopping the operation of each air conditioner 30a, 30b, 30c (without stopping each compressor). To execute the control. In the low load control, the control target value of the temperature difference is lowered from the normal target value, so that the flow rate of the circulating fluid flowing through each branch circuit portion of the fluid circuit 21 is a predetermined flow rate slightly larger than the predetermined minimum flow rate. Since the lower limit flow rate is easily secured, the freezing of the circulating fluid in each branch circuit portion can be suppressed. Moreover, even when it becomes difficult to continue the normal control, the air conditioners 30a, 30b, and 30c can be prevented from being stopped by switching to the low load control, and the rotation speed of the pump 20 can be reduced by the flow control valve. By controlling according to the valve opening degree of 35a, 35b, 35c, it becomes possible to continue the operation according to the air conditioning load.

(3) Modifications In the above description, an example of the air conditioning system has been described. However, the air conditioning system may be appropriately modified as described below.

(3-1) Modification A
In the air conditioning system 200 of the second embodiment, when the load becomes low, the target value of the temperature difference ΔT, which is the control target value of the valve opening of each of the flow control valves 35a, 35b, 35c, is updated to a smaller value. The case where the control is performed is described as an example.

  However, the control is not limited to this. For example, as described below, the capacity of each of the air conditioners 30a, 30b, and 30c (a value corresponding to the number of rotations of each of the compressors 41a, 41b, and 41c). ), The flow rate control valves 35a, 35b, 35c may be controlled by a target value determined according to the above.

  Hereinafter, individual controls of the first to third flow rate control valves 35a, 35b, and 35c during the heating operation will be described with reference to FIG. 7, as in the second embodiment. In the following description, the control of the first flow control valve 35a will be described as an example. However, the control is independent of the control of the second flow control valve 35b and the control of the third flow control valve 35c. It is assumed that the processing is executed by the fluid controller 70. Further, similarly to the second embodiment, the rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. Shall be.

  In step S30, the fluid controller 70 sets the temperature difference ΔT of the circulating fluid before and after passing through the first heat source side heat exchanger 43a of the first heat source device 40a to 5 ° C., which is the normal target value (predetermined target value). Then, the valve opening of the first flow control valve 35a is controlled (normal control).

  The rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. The rotation speed of the pump 20 is also adjusted according to the change in the control of the valve opening of the control valve 35a.

  In step S31, the fluid controller 70 controls the valve opening of the first flow control valve 35a such that the temperature difference ΔT of the circulating fluid becomes the normal target value of 5 ° C. Whether the capacity Qr obtained from the rotation speed of the first compressor 41a of the first air conditioner 30a is equal to or less than a predetermined capacity (here, 50% of the rated capacity of the first air conditioner 30a + γ (γ is, for example, 5% or less)) or not. to decide. Here, the predetermined capacity is not particularly limited. For example, when the circulating fluid having a predetermined lower flow rate slightly larger than the predetermined minimum flow rate is passed through the first heat source side heat exchanger 43a, the circulation before and after the passage is performed. An ability to ensure a temperature difference ΔT of the fluid of 5 ° C. can be achieved.

  Here, the capacity Qr of the air conditioner is a refrigerant circulation amount Gr (= r × V ×) calculated from the number of rotations r of the compressor, the discharge volume V of the compressor, and the density ρs obtained from the temperature and pressure of the suction refrigerant gas. ρs) and the specific enthalpy difference Δh calculated from the refrigerant temperature and the pressure at the inlet and outlet of the heat exchanger can be expressed as Qr = Δh × Gr.

  The capacity Qr obtained from the rotation speed of the second compressor 41b of the second air conditioner 30b corresponding to the second flow rate control valve 35b, and the third compressor 41c of the third air conditioner 30c corresponding to the third flow rate control valve 35c The same applies to the ability Qr obtained from the rotation speed of Hereinafter, the same applies to the low-load control of each valve and the control of the corresponding air conditioner, and a description thereof will be omitted.

  Here, when the capacity is not lower than the predetermined capacity, since the first flow rate control valve 35a is in a state where the normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid, the process returns to step S30. Then, the normal control is continued. On the other hand, when the capacity is lower than the predetermined capacity, the first flow rate control valve 35a is not in a state where the normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid. Perform load control.

  Note that the first air conditioner 30a having the corresponding first heat source device 40a cannot secure the normal target value of 5 ° C. as the temperature difference ΔT of the circulating fluid in the first going pipe 22a and the first return pipe 23a of the fluid circuit 21. Even in the case of the state, the operation according to the current air conditioning load is continued without stopping the heating operation (stopping the compressor 41a).

  In step S32, the fluid controller 70 sets the capacity Qr of the first air conditioner 30a to a predetermined value for the control target value of the temperature difference ΔT of the circulating fluid before and after passing through the first heat source side heat exchanger 43a of the first heat source device 40a. The value obtained by dividing by the lower limit flow rate (temperature difference: a value according to the capacity of the air conditioner) is used as a new control target value (rotation speed target value) to control the valve opening of the first flow control valve 35a. (Low load control). Thereby, even when the air conditioning load of the first air conditioner 30a is small during the heating operation, the predetermined lower limit flow rate is set as the flow rate of the circulating fluid in the first going pipe 22a and the first return pipe 23a of the fluid circuit 21. Since it is easy to secure the circulating fluid, the freezing of the circulating fluid in the first going pipe 22a and the first return pipe 23a can be suppressed.

  The rotation speed of the pump 20 is controlled by the fluid controller 70 so as to satisfy a predetermined relationship according to the valve opening of each of the flow control valves 35a, 35b, 35c. The rotation speed of the pump 20 is also adjusted according to the change in the control of the valve opening of the control valve 35a.

  In step S33, the fluid controller 70 determines that the capacity Qr obtained from the rotation speed of the first compressor 41 of the corresponding first air conditioner 30a is a predetermined return capacity (here, 50% of the rated capacity of the first air conditioner 30a + 2γ). It is determined whether or not this is the case. Here, the predetermined return ability is not particularly limited, but is preferably, for example, a value slightly larger than the predetermined ability used for the determination in step S31. If it is not equal to or greater than the predetermined return capability, the process returns to step S32 to continue the low load control. On the other hand, if it is equal to or higher than the predetermined return capability, the process returns to step S30, and the control is switched from the low load control to the normal control. Thus, even when the load of the first air conditioner 30a increases again after the air conditioning load becomes low, the load can be handled by switching the control mode. Further, since the value of the predetermined return ability is set to a value larger than the value of the predetermined ability, hunting in control can be suppressed.

  The control of the second flow control valve 35b and the control of the third flow control valve 35c are the same as the above-described control of the first flow control valve 35a, and these controls are simultaneously executed by the fluid controller 70.

  Even in the control according to Modification A described above, it is possible to continue the operation according to the air conditioning load while suppressing the freezing of the circulating fluid in the fluid circuit 21 as in the above-described embodiment.

(3-2) Modification B
In the above example, the case where the cooling tower 80 and the boiler 90 are provided has been described as an example.

  However, the air conditioning system is not limited to this, and may have the boiler 90 without the cooling tower 80. For example, when the air conditioner 30 performs the heating operation without performing the cooling operation, the air conditioning system 100 may include the boiler 90 without including the cooling tower 80.

(3-3) Modification C
In the second embodiment, an example in which the flow rate of the circulating fluid in each branch circuit portion is grasped using each of the first flow rate sensor 36a, the second flow rate sensor 36b, and the third flow rate sensor 36c is described. explained.

  On the other hand, the circulating fluid passing through the heat source side heat exchangers 43a, 43b, 43c of the heat source devices 40a, 40b, 40c is determined from the rotation speed of the pump 20 and the valve opening of each of the flow rate control valves 35a, 35b, 35c. May be obtained. In this case, it is not necessary to provide each flow sensor of the first flow sensor 36a, the second flow sensor 36b, and the third flow sensor 36c.

  By using the present invention, it is possible to continue the operation of the compressor in the refrigerant circuit for a longer time while suppressing freezing in the fluid circuit, so that the circulating fluid circulated by the pump circulates heat to the heat source device of the air conditioner. Can be used as an air conditioning system.

20 pump (flow rate adjustment part)
21 fluid circuit 22a first going pipe (branch circuit)
22b Second outgoing pipe (branch circuit)
22c Third outgoing pipe (branch circuit)
23a 1st return pipe (branch circuit)
23b 2nd return pipe (branch circuit)
23c 3rd return pipe (branch circuit)
Reference Signs List 30 air conditioner 31, 31a, 31b, 31c refrigerant circuit 35 flow control valve (flow control unit)
36a First flow sensor (flow sensor)
36b 2nd flow sensor (flow sensor)
36c 3rd flow sensor (flow sensor)
Reference Signs List 40 heat source unit 41 compressor 43 heat source side heat exchanger 44 expansion valve 49 air conditioning controller (flow rate variable mechanism adjustment unit)
51 Use side heat exchanger 70 Controller (pump adjustment unit)
80 cooling tower 90 boiler (heating means)
100 air conditioning system 200 air conditioning system

JP-A-8-210667

Claims (6)

A fluid circuit (21) in which a circulating fluid circulates;
Heating means (90) for heating the circulating fluid;
A compressor (41), a use side heat exchanger (51), an expansion valve (44), and a heat source side heat exchanger for performing heat exchange between the heat of the circulating fluid and the heat of the refrigerant flowing inside. (43), and a refrigerant circuit (31) in which the refrigerant circulates;
A flow rate adjusting unit (20, 35a, 35b, 35c) for adjusting a flow rate of the circulating fluid sent to the heat source side heat exchanger;
A control unit (70, 49, 49a, 49b, 49c) for controlling the flow rate adjustment unit;
With
In the case where the control unit performs the heating operation in which the heat source side heat exchanger functions as a refrigerant evaporator in the refrigerant circuit and the use side heat exchanger functions as a refrigerant radiator,
First control for controlling the flow rate adjusting unit such that the temperature difference of the circulating fluid before and after passing through the heat source side heat exchanger is a predetermined target value;
When the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or less than a predetermined flow rate, the control target value of the temperature difference is changed to an updated target value that is a smaller value, and the temperature difference is updated. A second control for controlling the flow rate adjusting unit to be a target value;
Switch and execute
Air conditioning system (100, 200). The control unit, at the time of performing the second control, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is larger than a predetermined increase update flow rate which is a value larger than a predetermined lower limit flow rate, The control target value of the temperature difference is updated to an increase update target value that is a value larger than the update target value, and the flow rate adjustment unit is controlled such that the temperature difference becomes the increase update target value.
The air conditioning system according to claim 1. The control unit is configured to control the flow rate of the circulating fluid sent to the heat source side heat exchanger when controlling the flow rate adjusting unit such that the temperature difference becomes the update target value during the second control. When the flow rate is equal to or less than the predetermined flow rate, the control target value of the temperature difference is updated to a decrease update target value that is smaller than the update target value, so that the temperature difference becomes the decrease update target value. Controlling the flow rate adjustment unit to
The air conditioning system according to claim 2. The control unit switches from the second control to the first control when the control target value of the temperature difference becomes the same value as the predetermined target value during the execution of the second control.
The air conditioning system according to claim 2. The update target value is a rotation speed corresponding target value which is a value obtained by dividing the capacity of the heat source determined from the rotation speed of the compressor by a predetermined lower limit flow rate,
The air conditioning system according to any one of claims 2 to 4. A plurality of refrigerant circuits (31a, 31b, 31c);
The fluid circuit has a branch circuit (22a, 23a, 22b, 23b, 22c, 23c) that branches and flows the circulating fluid for each refrigerant circuit,
The flow control unit includes a circulation pump (20) provided in a portion of the fluid circuit other than the branch circuit, and a flow control valve (35a, 35b, 35c) provided for each branch circuit. And
A flow sensor (36a, 36b, 36c) for detecting a flow rate of the circulating fluid flowing through the branch circuit, for each of the branch circuits;
The control unit controls the circulation pump and each of the flow rate control valves according to a detection value of the flow rate sensor,
Air conditioning system as claimed in any one of claims 1 to 5 (200).

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