JP2017009269A - Air conditioning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioning system that can continue operation of a compressor in a refrigerant circuit longer while inhibiting freezing in a fluid circuit.SOLUTION: The air conditioning system normally controls a pump revolution speed so that a temperature difference ΔT between before and after passing of circulation fluid through a heat source-side heat exchanger becomes a normal target value and controls the pump revolution speed so as to be maintained at a predetermined lower limit flow rate when a flow rate equivalent to the pump revolution speed becomes equal to or lower than the predetermined lower limit flow rate.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an air conditioning system.

  Conventionally, for example, as in Patent Document 1 (Japanese Patent Application Laid-Open No. 8-210667), water cooled / heated by a cooling tower / boiler circulates in the water circuit by a pump, There is known an air conditioning system in which cold heat and / or warm heat is supplied to a heat source machine.

  Here, the flow rate of the water circulating through the water circuit can be controlled so that, for example, the temperature difference of the water at the entrance and exit of the heat source unit of the air conditioner is maintained at a certain temperature difference.

  In addition, when heating operation is performed in the air conditioner, in order to prevent freezing of water circulating in the water circuit even when the heat load in the air conditioner is small, 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 of the air conditioner is small, when trying to secure a certain temperature difference as the temperature difference of the water at the entrance and exit of the heat source unit of the air conditioner, the flow rate of the water circuit is less than the minimum flow rate In some cases, the flow rate may need to be controlled. In this case, the air conditioner is stopped to avoid freezing of water. When a certain temperature difference can be secured as the temperature difference of the water at the inlet / outlet of the heat source unit of the air conditioner and the flow rate of the water circuit can be increased from the minimum flow rate, the air conditioning is performed again. The operation of the apparatus will be started.

  Thus, when the heat load during the heating operation in the air conditioner is small, the water circuit is in a situation where a certain temperature difference can be ensured as the temperature difference of the water at the entrance and exit of the heat source unit of the air conditioner. The air flow system operation is likely to be stopped by reducing the flow rate of the air conditioner, and the air conditioner operation / stop is frequently repeated, resulting in not only poor energy efficiency but also frequent changes in the environment of the air conditioning target space. And lacks comfort.

  The subject of this invention is made | formed in view of the point mentioned above, and providing the air conditioning system which can continue the driving | running of the compressor in a refrigerant circuit for a long time, suppressing the freezing in a fluid circuit. is there.

  The air conditioning system according to the first aspect includes a fluid circuit, a boiler, a refrigerant circuit, a flow rate adjusting mechanism, and a control unit. In the fluid circuit, a circulating fluid circulates. The boiler heats the circulating fluid. The refrigerant circuit includes 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 exchanges heat 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 mechanism adjusts the flow rate of the circulating fluid sent to the heat source side heat exchanger. The control unit controls the flow rate adjusting mechanism. The control unit performs a 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. The control unit switches between the first control mode and the second control mode when performing the heating operation. When executing the first control mode, the control unit controls the flow rate adjusting mechanism so that the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes a predetermined target value. When executing the second control mode, the control unit executes one of the second control mode 1, the second control mode 2, and the second control mode 3. In the second control mode 1, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or lower than the predetermined flow rate, the control unit sets a predetermined temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger. The flow rate adjusting unit is controlled so as to fix the flow rate of the circulating fluid sent to the heat source side heat exchanger to a predetermined lower limit flow rate without performing control to the target value. In the second control mode 2, the control unit controls the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger when the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or lower than a predetermined flow rate. The target value is changed to an updated target value that is a smaller value, and the flow rate adjusting unit is controlled so that the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes the updated target value. In the second control mode 3, the control unit controls the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger when the capacity of the heat source ascertained from the rotational speed of the compressor is equal to or less than a predetermined capacity. The target value is changed to a target value corresponding to the number of revolutions obtained by dividing the heat source capacity obtained from the number of revolutions of the compressor by a predetermined lower limit flow rate, and before and after passing through the heat source side heat exchanger. The flow rate adjusting unit is controlled so that the temperature difference of the circulating fluid becomes the target value corresponding to the rotational speed.

  In this air conditioning system, the heat load is reduced when the flow rate of the circulating fluid sent to the heat source side heat exchanger is less than the predetermined flow rate, or when the heat source capacity grasped from the rotation speed of the compressor is less than the predetermined capacity. Even if it becomes difficult to secure a predetermined target value as the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger if the first control mode is continued as it is, the operation of the heat source unit is reduced. Without stopping the compressor (stopping the compressor), the control unit executes the second control mode, thereby suppressing the freezing in the fluid circuit and performing the operation according to the low load and continuing the operation state. It becomes possible.

  Specifically, in the second control mode 1, the circulating fluid that is sent to the heat source side heat exchanger without performing control to set the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger as a predetermined target value. As a result, 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, thereby controlling the low load. In addition, the flow rate of the circulating fluid sent to the heat source side heat exchanger is fixed at a predetermined lower limit flow rate, and a sufficient flow rate is kept, so that freezing of the circulation channel can be suppressed. It becomes possible.

  Further, in the second control mode 2, the control target value of the temperature difference between 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 then passed through the heat source side heat exchanger. By controlling the flow rate adjustment unit so that the temperature difference between the circulating fluid before and after it reaches the update target value, the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes smaller than the predetermined target value, and the load is low. The operation corresponding to is enabled. Furthermore, since the flow rate of the circulating fluid sent to the heat source side heat exchanger is controlled to a flow rate that realizes the temperature difference of the update target value, the flow rate is increased when switching from the first control mode to the second control mode. And freezing of the circulation channel can be suppressed.

  Furthermore, in the second control mode 3, the control target value of the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger when the capacity of the heat source ascertained from the rotational speed of the compressor is equal to or less than a predetermined capacity. Is changed to a target value corresponding to the number of revolutions obtained by dividing the capacity of the heat source obtained from the number of revolutions of the compressor by a predetermined lower limit flow rate, and the circulating fluid before and after passing through the heat source side heat exchanger By controlling the flow rate adjustment unit so that the temperature difference of the engine reaches the target value corresponding to the rotation speed, 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, which corresponds to a low load. Driving becomes possible. Here, the target value corresponding to the rotational speed, which is a value obtained by dividing the capacity of the heat source by the predetermined lower limit flow rate, is necessary for maintaining the predetermined lower limit flow rate in the fluid circuit in the capacity of the heat source at that time. This is the target value of the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger. Furthermore, since the flow rate of the circulating fluid sent to the heat source side heat exchanger is also controlled to a flow rate that realizes 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 freezing of the circulation flow path.

  As described above, 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.

  The air conditioning system which concerns on a 2nd viewpoint is an air conditioning system which concerns on a 1st viewpoint, Comprising: In 2nd control mode, a control part is when the flow volume of the circulating fluid sent to a heat source side heat exchanger becomes below a predetermined flow volume. The flow rate of the circulating fluid sent to the heat source side heat exchanger is fixed to a predetermined lower limit flow rate without performing control to set the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger to a predetermined target value. The flow rate control unit is controlled (second control mode 1 is performed). When the second control mode is executed in the first control mode, when the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes larger than a return temperature difference that is a value larger than a predetermined target value, The second control mode 1 is switched to the first control mode.

  In this air conditioning system, when the load is low, the second control mode 1 is performed, and the load is large in a situation where the flow rate of the circulating fluid sent to the heat source side heat exchanger is fixed to a predetermined lower limit flow rate. Thus, when the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes larger than the return temperature difference, the control unit switches to the first control mode again. Here, since the return temperature difference is a value larger than the predetermined target value, hunting of control between the first control mode and the second control mode 1 can be suppressed.

  The air conditioning system which concerns on a 3rd viewpoint is an air conditioning system which concerns on a 1st viewpoint, Comprising: In 2nd control mode, a control part is when the flow volume of the circulating fluid sent to a heat source side heat exchanger becomes below a predetermined flow volume. The control target value of the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger is changed to a smaller updated target value, and the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger is changed. The flow rate adjustment unit is controlled so as to be the update target value (second control mode 2 is performed). When the second control mode is executed, the control unit causes the heat source when the flow rate of the circulating fluid sent to the heat source side heat exchanger becomes larger than a predetermined increased update flow rate that is a value larger than a predetermined lower limit flow rate. The control target value of the temperature difference between the circulating fluid before and after passing through the side heat exchanger is updated to an increased update target value that is larger than the update target value, and the flow rate is adjusted so that the temperature difference becomes the increased update target value. Control part.

  In this air conditioning system, the second control mode No. 2 is performed due to low load, and the control target value of the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger is an updated target value that is a smaller value. When the control is changed to, 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, the heat source side heat exchanger passes through the control with the update target value. The control target value of the temperature difference between the circulating fluid before and after the update is updated to a larger update target value that is a larger value. As a result, the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger can be increased to approach the predetermined target value.

  The air conditioning system which concerns on a 4th viewpoint is an air conditioning system which concerns on a 3rd viewpoint, Comprising: The temperature difference of the circulating fluid before and behind passing a heat-source side heat exchanger at the time of a control part performs 2nd control mode the 2nd Circulation before and after passing through the heat source side heat exchanger when the flow rate of the circulating fluid sent to the heat source side heat exchanger is less than or equal to the predetermined flow rate when controlling the flow rate adjustment unit so that it becomes the update target value The control target value of the fluid temperature difference is updated to a decrease update target value that is smaller than the update target value, and the flow rate adjusting unit is controlled so that the temperature difference becomes the decrease update target value.

  In this air conditioning system, the second control mode No. 2 is performed due to low load, and the control target value of the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger is an updated target value that is a smaller value. Even when the control is changed to, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is less than or equal to the predetermined flow rate, the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger is reduced. Control is performed to update the control target value to a decreasing 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, making it easier to secure 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 which concerns on a 5th viewpoint is an air conditioning system which concerns on a 3rd viewpoint or a 4th viewpoint, Comprising: A control part is the circulating fluid before and behind passing a heat source side heat exchanger at the time of 2nd control mode 2 execution. When the control target value of the temperature difference becomes the same value as the predetermined target value, the second control mode 2 is switched to the first control mode.

  In this air conditioning system, the second control mode No. 2 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 update target value. When the control target value of the temperature difference between 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 again enters the first control mode. Switch. Thereby, even when the load increases again after the load becomes low, it is possible to cope with the load by switching the control mode.

  The air conditioning system which concerns on a 6th viewpoint is an air conditioning system which concerns on a 1st viewpoint, Comprising: In 2nd control mode, a control part is when the capability of the heat source grasped | ascertained from the rotation speed of a compressor becomes below predetermined capability The number of revolutions is a value obtained by dividing the control target value of the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger by dividing the capacity of the heat source obtained from the number of revolutions of the compressor by a predetermined lower limit flow rate. By changing to the corresponding target value, the flow rate adjusting unit is controlled so that the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes the target value corresponding to the rotation speed (second control mode part 3 is performed). The control unit performs the second control mode when the ability of the heat source grasped from the rotation speed of the compressor becomes larger than a predetermined return ability that is a value larger than the predetermined ability at the time of executing the third control mode. Switch from 3 to the first control mode.

  In this air conditioning system, the second control mode No. 3 is performed due to the low load, and the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger is controlled to become the target value corresponding to the rotation speed. When the load becomes large and the heat source capacity ascertained from the rotation speed of the compressor becomes larger than the predetermined return capacity, the control unit switches to the first control mode again. Here, since the predetermined return ability is a value larger than the predetermined ability, hunting of control between the first control mode and the second control mode 3 can be suppressed.

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

  In this air conditioning system, even if there are a plurality of refrigerant circuits, by controlling the circulation pump and the respective flow control valves according to the detection value of the flow sensor, the fluid circuit is directed toward each heat source side heat exchanger. It is possible to suppress frequent start and stop of the compressor in each refrigerant circuit while securing the flow rate of the circulating fluid to be sent and suppressing freezing in each heat source side heat exchanger.

  In the air conditioning system according to the first aspect, 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 even at a low load.

  In the air conditioning system according to the second aspect, even when the load increases again after becoming low load, it is possible to cope with the load by switching the control mode and to suppress hunting of control. .

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

  In the air conditioning system according to the fourth aspect, by further reducing the temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger, it becomes easier to secure the flow rate of the circulating fluid sent to the heat source side heat exchanger, and the circulation It is possible to suppress freezing of the flow path.

  In the air conditioning system according to the fifth aspect, even when the load increases again after the load becomes low, the load can be accommodated by switching the control mode.

  In the air conditioning system according to the sixth aspect, even when the load increases again after the load becomes low, the load can be dealt with by switching the control mode, and control hunting can be suppressed. .

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

1 is a schematic configuration diagram of an air conditioning system according to a first embodiment. It is a schematic block diagram which shows a part of air conditioning apparatus and a fluid circuit. It is a control flowchart of the pump which concerns on 1st Embodiment. It is a schematic block diagram of the air conditioning system which concerns on 2nd Embodiment. It is a schematic block diagram which shows a part of air conditioning apparatus and a fluid circuit. It is a control flowchart of the flow control valve concerning a 2nd embodiment. It is a control flowchart of the flow regulating valve concerning a modification (A).

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

In addition, the following description is an example and does not limit 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.

  As shown in FIG. 1, 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.

  The cooling tower 80 is installed on the rooftop of a building or the like where the air conditioning system 100 is installed, for example. Although the cooling tower 80 is not specifically limited, it cools the circulating fluid which flows through the fluid circuit 21 by making it contact directly or indirectly with air | atmosphere.

  The boiler 90 is installed in a machine room such as a building where the air conditioning system 100 is installed, for example. Although it does not specifically limit, the boiler 90 heats the circulating fluid which flows through the fluid circuit 21 with the heat obtained by burning a fuel.

  The fluid circuit 21 circulates a circulating fluid therein, and the circulating fluid cooled to a predetermined target cooling temperature by the cooling tower 80 or the circulating fluid heated to the predetermined target heating temperature by the boiler 90 is described later. It is configured to be able to carry to the heat source unit 40 of the device 30. The fluid circuit 21 is provided with a pump 20 capable of adjusting the flow rate (for example, volume flow rate) of the circulating fluid that circulates. By moving the pump 20, the circulating fluid circulates in the fluid circuit 21, and the circulating fluid goes back and forth between the cooling tower 80 or the boiler 90 and the heat source unit 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 toward the heat source unit 40, and a return pipe that sends a circulation channel from the heat source unit 40 toward 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 side of the forward pipe 22 opposite to the end portion on the heat source unit 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 the opposite side of the return pipe 23 from the heat source unit 40 side end. In the present embodiment, the pump 20 is provided in the middle of the forward pipe 22. Further, an upstream fluid temperature sensor 24 that detects the temperature of the circulating fluid before 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 forward pipe 22. . Further, a downstream fluid temperature sensor 25 for detecting the temperature of the circulating fluid after 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 return pipe 23. Yes. 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. The 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 stopped, and the first cooling valve 83 and the second cooling valve are stopped. 84 is fully open and the cooling tower 80 is in a driving state. The forward 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 configured 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 and the cooling tower 80 is stopped, and the first heating valve 93 and the second heating valve 94 is fully open and the boiler 90 is in a driving state. The forward 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. A 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 fluid controller 70 controls the opening and closing of the first heating valve 93, the second heating valve 94, the first cooling valve 83, and the second cooling valve 84. Further, 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 the present invention is not limited to this. For example, brine or the like may be used as the circulating fluid instead of water.

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

  As shown in FIG. 2, the refrigerant circuit 31 includes 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, and these are connected. A 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 an electric 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 device 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, for example, in a machine room on each floor such as a building where the air conditioning system 100 is installed. The indoor unit 50 is provided with an indoor fan 52 for sending air in the air-conditioning target space to the use side heat exchanger 51 and the use side heat exchanger 51. The indoor unit 50 is installed in the air conditioning target space.

  In the refrigerant circuit 31, the vapor compression refrigeration cycle is performed, whereby the air-conditioning target space is cooled or heated. During the cooling operation, the four-way switching valve 42 is connected as shown by a 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 to exchange heat on the heat source side. To the heat exchanger 43 and radiates heat in the heat source side heat exchanger 43. The refrigerant that has dissipated heat in the heat source side heat exchanger 43 is depressurized 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 is compressed by the compressor 41. Inhaled. During the heating operation, the four-way switching valve 42 is in the connection state indicated 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 side heat exchange. The heat is dissipated to the indoor air sent to the chamber 51 and sent from the indoor fan 52. The refrigerant that has dissipated heat in the use side heat exchanger 51 is depressurized 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 another connection port 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 device 40, heat exchange is performed between the refrigerant flowing through the refrigerant circuit 31 and the circulating fluid flowing through the fluid circuit 21. Thereby, 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 conditioner controller 49 controls the air conditioner 30 by the CPU reading and executing the 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 (for example, operation / stop of the indoor unit 50, operation mode (cooling / heating), set temperature, etc.) input to the remote controller, measurement values of various sensors of the air conditioner 30 (not shown), and the like. Thus, various configurations of the air conditioner 30 such as the indoor fan 52, the compressor 41, the four-way switching valve 42, and the expansion valve 44 are controlled.

  The air conditioning controller 49 controls various configurations of the air conditioner 30 according to the air conditioning load of the air conditioner 30 (capability necessary for cooling / heating the air conditioning target space). Specifically, in the present embodiment, 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 during the cooling operation of the air-conditioning apparatus 30, and uses-side heat exchange. The valve opening degree of the expansion valve 44 is controlled so that the degree of superheat of the refrigerant flowing through the outlet of the vessel 51 becomes a predetermined degree of superheat. Further, in the present embodiment, 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 during the heating operation of the air conditioner 30, and the use side heat exchanger 51. The valve opening degree 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 conditioner controller 49. The information regarding the operating status of the air conditioner 30 includes, for example, information regarding the operation / stop of the air conditioner 30, information regarding the air conditioning load of the air conditioner 30, information regarding the operation mode (heating / cooling mode) of the air conditioner 30, and the like.

  The fluid controller 70 reads and executes the program stored in the memory so that the first cooling valve 83, the second cooling valve 84, the first heating valve 93, and the second heating valve 94 are controlled to open and close, and the cooling tower. 80, drive control of the boiler 90 and the pump 20 is performed. Further, the fluid controller 70 controls the cooling tower 80, the boiler 90, and the pump 20 based on the information regarding the operation / stop of the air conditioner 30 and the information regarding the operation mode received from the air conditioning controller 49.

(1-2) Control of air conditioner 30 and pump 20 The air conditioner 30 is not particularly limited, and performs a cooling operation or a heating operation in response to an instruction such as a remote control operation by a user, for example. Here, in both the cooling operation and the heating operation, the air conditioner 30 is operated so that the temperature of the air-conditioning target space becomes the set temperature. The set temperature may be a temperature received by an input operation from the user, or may be a predetermined temperature.

  The air conditioner 30 is appropriately controlled so that the capacity according to the magnitude of the air conditioning load can be obtained. Specifically, the air conditioning controller 49 controls the rotation speed of the compressor 41 according to the difference between the set temperature of the air conditioning target space and the current temperature of the air conditioning target space. The air conditioner 30 continues this control at all times.

  The fluid controller 70 receives information indicating whether the air conditioner 30 is performing a cooling operation or a heating operation from the air conditioning controller 49. Here, during the cooling operation, the fluid controller 70 closes the first heating valve 93 and the second heating valve 94 to bring the boiler 90 into a stopped state, and fully opens the first cooling valve 83 and the second cooling valve 84 to perform cooling. 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 (although it is not particularly limited, at least the refrigerant flowing into the heat source side heat exchanger 43) It is cooled to a temperature lower than the temperature) and flows out to the first cooling pipe 81. 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 fully opens the first heating valve 93 and the second heating valve 94 to cause 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 (although not particularly limited, at least from the temperature of the refrigerant flowing into the heat source side heat exchanger 43). Is cooled to a higher temperature) and flows out to the first heating pipe 91.

  Below, control of the pump 20 at the time of heating operation is demonstrated, referring FIG.

  During the heating operation, unlike the cooling operation, control is performed so that the flow rate of the circulating fluid is 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, 50% of the predetermined rated flow rate of the pump 20 is predetermined as the predetermined minimum flow rate. Here, in order to more reliably suppress freezing, the predetermined lower limit flow rate is slightly higher than the predetermined minimum flow rate (50% of the predetermined rated flow rate of the pump 20) (the predetermined rating of the pump 20). 50% + α of the flow rate (α is, for example, 5% or less) is determined.

  In step S10, the fluid controller 70 rotates 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 a normal target value (predetermined target value) of 5 ° C. 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 unit 40 functions as a refrigerant evaporator. The circulating fluid flowing in 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 is configured so that 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 is normally 5 ° C. The rotational speed of the pump 20 is controlled. Therefore, when the temperature difference ΔT of the circulating fluid is smaller than 5 ° C., the rotational speed of the pump 20 is reduced in order to reduce 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 greater than 5 ° C., the rotational speed of the pump 20 is increased in order to increase the flow rate of the circulating fluid in the fluid circuit 21.

  In step S11, when the fluid controller 70 controls the rotation speed of the pump 20 so that the temperature difference ΔT of the circulating fluid becomes the normal target value of 5 ° C., the fluid circuit grasped from the rotation speed of the pump 20 It is determined whether or not the flow rate of the circulating fluid in 21 is equal to or lower than a predetermined lower limit flow rate. Here, when the flow rate is not less than the predetermined lower limit flow rate, the normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid, so the process returns to step S10 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 normal target value of 5 ° C. cannot be ensured as the temperature difference ΔT of the circulating fluid. Therefore, the process proceeds to step S12 and the low load control is performed.

  The air conditioner 30 stops the heating operation (stops the compressor 41) even when the fluid circuit 21 is in a state in which the normal target value of 5 ° C. cannot be secured as the temperature difference ΔT of the circulating fluid. Without stopping, 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 (control at low load) so that the flow rate of the circulating fluid in the fluid circuit 21 is fixed and maintained at a predetermined lower limit flow rate (circulation fluid control). The number of rotations of the pump 20 is not controlled so that the temperature difference ΔT is equal to the normal target value of 5 ° C.). Thereby, even when the air conditioning load of the air conditioner 30 is small during the heating operation, a predetermined lower limit flow rate can be secured as the flow rate of the circulating fluid in the fluid circuit 21, so that the circulating fluid flows in the fluid circuit 21. Freezing can be suppressed. Note that when the low load control is started from Step S11 to Step S12, the temperature difference ΔT of the circulating fluid is a value smaller than the normal target value of 5 ° C. Further, after that, when the air conditioning load in 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 a predetermined return temperature difference (5 + β) in which 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 value larger than the normal target value of 5 ° C. It is determined whether or not the temperature is higher than ° C (β is, for example, 0.5 ° C or higher and 2 ° C or lower). 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 to switch from the low load control to the normal control.

  In the cooling operation, the rotational 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 is normally set to 5 ° C. Since the problem of freezing of the circulating fluid in 21 is unlikely to occur, the processes in steps S11 to S13 described above are not performed.

(1-3) Features of the First Embodiment The air conditioning system 100 of the present embodiment is such 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. If the normal control for controlling the rotational speed of the pump 20 is continued as it is, it becomes difficult to ensure 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 it exists, without stopping the operation of the air conditioner 30 (without stopping the compressor 41), the fluid controller 70 performs the control by switching from the normal control to the low load control. In the low load control, a predetermined lower limit flow rate that is slightly higher than the predetermined minimum flow rate is ensured 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 if it is difficult to continue normal control, it is possible to avoid operation stop of the air conditioner 30 and to continue operation according to the air conditioning load by switching to low load control.

The predetermined return temperature difference (5 + β ° C.) is set to a value larger than the normal target value of 5 ° C. Therefore, if 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 does not become 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 air conditioner 30a, 30b, 30c. Below, it demonstrates centering on the difference with the example of 1st Embodiment.

  As shown in FIGS. 4 and 5, the air conditioning system 200 is provided with 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 configurations are indicated by corresponding numbers). Specifically, the 1st air conditioner 30a has the 1st refrigerant circuit 31a, the 1st heat source unit 40a, and the 1st indoor unit 50a, and is controlled by the 1st air conditioning controller 49a. The 2nd air conditioner 30b has the 2nd refrigerant circuit 31b, the 2nd heat source unit 40b, and the 2nd indoor unit 50b, and is controlled by the 2nd air conditioning controller 49b. The 3rd air conditioner 30c has the 3rd refrigerant circuit 31c, the 3rd heat source unit 40c, and the 3rd indoor unit 50c, and is controlled by the 3rd 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 heat source device 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 air conditioner 30a, 30b, 30c. The branch circuit includes a first forward pipe 22a, a second forward pipe 22b, a third forward pipe 22c, a first return pipe 23a, a second return pipe 23b, and a third return pipe 23c. The first forward pipe 22a, the second forward pipe 22b, and the third forward pipe 22c are respectively connected to the first air conditioner 30a side and the second air conditioner from the end of the forward pipe 22 opposite to the cooling tower 80 and the boiler 90 side. It extends so as to branch toward the device 30b side and the third air conditioner 30c side. 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 end 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 side and the third air conditioner 30c side.

  Here, the circulating fluid flowing through the first forward 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 forward 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 forward 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.

  A first flow rate adjustment valve 35a capable of adjusting the valve opening is provided in the middle of the first forward pipe 22a. A second flow rate adjustment valve 35b capable of adjusting the valve opening is provided in the middle of the second forward pipe 22b. A third flow rate adjustment valve 35c capable of adjusting the valve opening is provided in the middle of the third forward pipe 22c. The valve opening degree of each of the first flow rate adjustment valve 35a, the second flow rate adjustment valve 35b, and the third flow rate adjustment valve 35c is controlled by the fluid controller 70.

  A first upstream fluid temperature sensor 24a that detects the temperature of the circulating fluid passing therethrough is provided in the middle of the first forward pipe 22a and closer to the first heat source unit 40a than the first flow rate adjustment valve 35a. 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 that detects the temperature of the circulating fluid passing therethrough is provided in the middle of the second forward pipe 22b and closer to the second heat source device 40b than the second flow rate control valve 35b. A second downstream fluid temperature sensor 25b that detects the temperature of the circulating fluid passing therethrough is provided in the middle of the second return pipe 23b. A third upstream fluid temperature sensor 24c that detects the temperature of the circulating fluid passing therethrough is provided in the middle of the third forward pipe 22c and closer to the third heat source device 40c than the third flow rate control valve 35c. A third downstream fluid temperature sensor 25c that detects the temperature of the circulating fluid passing therethrough is provided in the middle of the third return pipe 23c. The first upstream fluid temperature sensor 24a, the first downstream fluid temperature sensor 25a, the second upstream fluid temperature sensor 24b, the second downstream fluid temperature sensor 25b, the third upstream fluid temperature sensor 24c, and the third downstream The fluid controller 70 can grasp the detected temperature of the side fluid temperature sensor 25c.

  A first flow rate 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 rate sensor 36b that detects the flow rate of the circulating fluid passing therethrough is provided in the middle of the second return pipe 23b. A third flow rate 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 all the flow rates detected by the first flow sensor 36a, the second flow sensor 36b, and the third flow sensor 36c.

(2-2) Control of 1st-3rd air conditioner 30a, 30b, 30c, pump 20, 1st-3rd flow control valve 35a, 35b, 35c The 1st-3rd air conditioner 30a, 30b, 30c is In response to the instruction from the user, the cooling operation or the heating operation is performed so that the temperature of the air-conditioning target space becomes the set temperature. The first to third air conditioners 30a, 30b, and 30c are controlled so as to be able to produce a capacity corresponding to the size of the air conditioning load based on the difference between the temperature of each air conditioning target space and the set temperature. Specifically, each air-conditioning controller 49a, 49b, 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. . In the first to third air conditioners 30a, 30b, and 30c, this control is always continued.

  The fluid controller 70 indicates information indicating which of the first to third air conditioning controllers 49a, 49b, and 49c is performing the cooling operation and the heating operation by the first to third air conditioning devices 30a, 30b, and 30c. 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 degree of each of the flow rate adjusting valves 35a, 35b, and 35c. Although not particularly limited, for example, the rotational speed of the pump 20 is controlled by the fluid controller 70 so as to be a predetermined rotational speed in accordance with the total value of the valve opening degrees of the flow rate adjusting valves 35a, 35b, and 35c. Also good. Here, the control of the rotation speed of the pump 20 by the fluid controller 70 always corresponds to the value of the valve opening degree of each flow rate adjustment valve 35a, 35b, 35c, or each flow rate adjustment valve 35a, 35b, 35c. Control is performed so as to correspond to the value of the valve opening at predetermined time intervals.

  During the heating operation, unlike the cooling operation, the flow rate of the circulating fluid is maintained at a predetermined minimum flow rate or higher at any location so that the circulating fluid (water) is not easily frozen in the fluid circuit 21. Be controlled. Specifically, the flow rate of the circulating fluid flowing through the branch circuit (the first forward pipe 22a, the second forward pipe 22b, the third forward pipe 22c, the first return pipe 23a, the second return pipe 23b, and the third return pipe 23c). Is controlled to be maintained in a state of a predetermined minimum flow rate or more. In the present embodiment, 50% of the predetermined rated flow rate of the pump 20 is determined in advance as the predetermined minimum flow rate. Here, in order to more reliably suppress freezing, the predetermined lower limit flow rate is slightly higher than the predetermined minimum flow rate (50% of the predetermined rated flow rate of the pump 20) (the predetermined rating of the pump 20). 50% + α of the flow rate (α is, for example, 5% or less) is determined.

  Hereinafter, the individual control of the first to third flow rate adjusting 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 rate adjustment valve 35a will be described as an example. However, the control is independent of the control of the second flow rate adjustment valve 35b and the control of the third flow rate adjustment valve 35c. It is assumed that it is being 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 the normal target value (predetermined target value) of 5 ° C. The valve opening degree of the first flow rate adjustment 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 detected temperature of the first downstream fluid temperature sensor 25a from the detected temperature of the first upstream fluid temperature sensor 24a is the normal target value. The valve opening degree of the first flow rate adjustment 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 forward pipe 22a and the first return pipe 23a of the fluid circuit 21 is decreased. The valve opening degree of the 1 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., in order to increase the flow velocity of the circulating fluid flowing through the first forward pipe 22a and the first return pipe 23a in the fluid circuit 21. The valve opening degree of the first flow rate adjustment valve 35a is increased.

  In addition, since 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 degree of each flow rate adjusting valve 35a, 35b, 35c, the first flow rate here The number of rotations of the pump 20 is also adjusted according to the change in the control of the valve opening degree of the adjusting valve 35a.

  In step S21, the fluid controller 70 controls the first flow rate sensor 36a from the first flow rate sensor 36a when controlling the valve opening degree of the first flow rate adjustment valve 35a so that the temperature difference ΔT of the circulating fluid is a normal target value of 5 ° C. It is determined whether or not the flow rate of the circulating fluid flowing through the first forward pipe 22a and the first return pipe 23a to be grasped is equal to or lower than a predetermined lower limit flow rate. Here, when the flow rate is not less than the predetermined lower limit flow rate, the first flow rate adjustment valve 35a is in a state in which a normal target value of 5 ° C. can be secured as the temperature difference ΔT of the circulating fluid. Return to, and continue normal control. On the other hand, when the flow rate is equal to or lower than the predetermined lower limit flow rate, the first flow rate adjustment 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 therefore the process proceeds to step S22. Control at low load. Whether the flow rate of the circulating fluid flowing through the second forward pipe 22b and the second return pipe 23b ascertained from the second flow sensor 36b is less than or equal to a predetermined lower limit flow rate is ascertained from the third flow sensor 36c. It is similarly determined whether or not the flow rate of the circulating fluid flowing through the third forward pipe 22c and the third return pipe 23c is equal to or lower 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 the description thereof is omitted.

  In addition, the 1st air conditioner 30a which has the corresponding 1st heat-source equipment 40a cannot ensure 5 degreeC of normal target value as temperature difference (DELTA) T of circulating fluid in the 1st forward pipe 22a and the 1st return pipe 23a of the fluid circuit 21 Even in 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 sets a normal target value (predetermined target value) of 5 ° C. for the control target value of the circulating fluid temperature difference ΔT before and after passing through the first heat source side heat exchanger 43a of the first heat source device 40a. The valve opening degree of the first flow rate control valve 35a is controlled by updating to a value (update target value) decreased by a predetermined temperature (1 ° C. in the present embodiment) (control at low load). Thereby, even when the air conditioning load of the first air conditioner 30a is small during the heating operation, a predetermined lower limit flow rate is set as the flow rate of the circulating fluid in the first forward pipe 22a and the first return pipe 23a of the fluid circuit 21. Since it becomes easy to ensure, it is possible to prevent the circulating fluid from freezing in the first forward pipe 22a and the first return pipe 23a.

  In addition, since 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 degree of each flow rate adjusting valve 35a, 35b, 35c, the first flow rate here The number of rotations of the pump 20 is also adjusted according to the change in the control of the valve opening degree of the adjusting valve 35a.

  In step S22, the process proceeds to step S23 after waiting for a predetermined time to elapse for the first time when the valve opening degree of the first flow control valve 35a is controlled with the control target value updated.

  In step S23, the fluid controller 70 checks again whether or not the flow rate of the circulating fluid flowing through the first forward pipe 22a and the first return pipe 23a grasped from the first flow sensor 36a is equal to or lower than a predetermined lower limit flow rate. to decide. Here, even when the control target value of the first flow rate control valve 35a is updated, the control target value of the first flow rate control valve 35a is smaller when it is again below the predetermined lower limit flow rate. In order to update the value (decrease update target value), the process returns to step S22. Thus, 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 forward pipe 22a and the first return pipe 23a. On the other hand, when it is not less 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 forward pipe 22a and the first return pipe 23a grasped from the first flow sensor 36a is larger than a predetermined increased update flow rate. Here, when it is not larger than the predetermined increased update flow rate, the process returns to step S23. On the other hand, if the flow rate is larger than the predetermined increased update flow rate, there is room for increasing the flow rate in the control state of the first flow rate adjustment valve 35a, and the process proceeds to step S25.

  In step S25, the fluid controller 70 sets 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 to a predetermined temperature (this embodiment). Is updated to a value increased by 1 ° C. (increase update target value) to control the valve opening of the first flow rate control valve 35a (correction of the control target value during low load control).

  In addition, since 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 degree of each flow rate adjusting valve 35a, 35b, 35c, the first flow rate here The number of rotations of the pump 20 is also adjusted according to the change in the control of the valve opening degree of the adjusting valve 35a.

  In step S26, the fluid controller 70 determines whether or not the control target value of the first flow rate adjustment valve 35a has been returned to the normal target value (5 ° C.). If the target value has not been returned to the normal target value, the process returns to step S23 to continue the low load control using the control target value. On the other hand, when it is returned to the normal target value, the process returns to step S20 to switch from the low load control to the normal control. Thereby, about the 1st air conditioner 30a, even if it is a case where a load increases again after air-conditioning load becomes low load, it can respond to load by switching of a control mode.

  In the cooling operation, the valve of the first flow rate adjusting valve 35a is set so that 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 becomes the normal target value of 5 ° C. Although the opening degree is controlled, since the problem of freezing of the circulating fluid in the first forward pipe 22a and the first return pipe 23a of the fluid circuit 21 is unlikely to occur, the processes as in steps S21 to S26 described above are not performed.

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

(2-3) Features of the Second Embodiment The air conditioning system 200 of the present embodiment is a temperature difference of the circulating fluid before and after passing through the first heat source side heat exchangers 43a, 43b, 43c of the heat source devices 40a, 40b, 40c. If normal control for controlling the valve opening degree of each flow rate adjusting valve 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 set as the temperature difference ΔT of the circulating fluid. Even when it is difficult to ensure, the fluid controller 70 is controlled from the normal control to the low load control without stopping the operation of each air conditioner 30a, 30b, 30c (without stopping each compressor). Switch to and execute 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 that flows through each branch circuit portion of the fluid circuit 21 is slightly higher than a predetermined minimum flow rate. Since the lower limit flow rate is easily ensured, freezing of the circulating fluid in each branch circuit portion can be suppressed. Moreover, even if it is difficult to continue normal control, switching to low-load control avoids the shutdown of the air conditioners 30a, 30b, and 30c, and sets the rotation speed of the pump 20 to each 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) Modified Example In the above description, the 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 is low, the target value of the temperature difference ΔT, which is the control target value of the valve opening degree of each flow rate adjustment valve 35a, 35b, 35c, is changed 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 air conditioner 30a, 30b, 30c (value corresponding to the rotational speed of each compressor 41a, 41b, 41c). The flow rate regulating valves 35a, 35b, and 35c may be controlled by a target value that is determined in accordance with ().

  Hereinafter, as in the second embodiment, individual control of the first to third flow rate 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 rate adjustment valve 35a will be described as an example. However, the control is independent of the control of the second flow rate adjustment valve 35b and the control of the third flow rate adjustment valve 35c. It is assumed that it is being 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 degree of each flow rate adjusting valve 35a, 35b, 35c. Shall.

  In step S30, the fluid controller 70 adjusts 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 a normal target value (predetermined target value) of 5 ° C. The valve opening degree of the first flow rate adjustment valve 35a is controlled (normal control).

  In addition, since 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 degree of each flow rate adjusting valve 35a, 35b, 35c, the first flow rate here The number of rotations of the pump 20 is also adjusted according to the change in the control of the valve opening degree of the adjusting valve 35a.

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

  Here, the capacity Qr of the air conditioner is the refrigerant circulation amount Gr (= r × V ×) calculated from the rotational speed 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 pressure at the inlet / 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 adjustment valve 35b, and the third compressor 41c of the third air conditioner 30c corresponding to the third flow rate adjustment valve 35c. The same applies to the ability Qr obtained from the number of rotations. Hereinafter, the same applies to the low load control of each valve and the control of the corresponding air conditioner, and the description thereof is omitted.

  Here, when it is not less than the predetermined capacity, 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, and the process returns to step S30. Continue normal control. On the other hand, when the capacity is less 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. Performs on-load control.

  In addition, the 1st air conditioner 30a which has the corresponding 1st heat-source equipment 40a cannot ensure 5 degreeC of normal target value as temperature difference (DELTA) T of circulating fluid in the 1st forward pipe 22a and the 1st return pipe 23a of the fluid circuit 21 Even in 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 valve opening degree of the first flow rate control valve 35a is controlled by using a value obtained by dividing by the lower limit flow rate (temperature difference: a value corresponding to the capacity of the air conditioner) as a new control target value (target value corresponding to the rotation speed). (Control at low load). Thereby, even when the air conditioning load of the first air conditioner 30a is small during the heating operation, a predetermined lower limit flow rate is set as the flow rate of the circulating fluid in the first forward pipe 22a and the first return pipe 23a of the fluid circuit 21. Since it becomes easy to ensure, it is possible to prevent the circulating fluid from freezing in the first forward pipe 22a and the first return pipe 23a.

  In addition, since 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 degree of each flow rate adjusting valve 35a, 35b, 35c, the first flow rate here The number of rotations of the pump 20 is also adjusted according to the change in the control of the valve opening degree of the adjusting 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% + 2γ of the rated capacity of the first air conditioner 30a). It is determined whether or not this is the case. Here, the predetermined return ability is not particularly limited, but for example, is preferably a value slightly larger than the predetermined ability used for the determination in step S31. Here, if it is not equal to or greater than the predetermined return ability, the process returns to step S32 to continue the low load control. On the other hand, if it is equal to or greater than the predetermined return ability, the process returns to step S30 and the control is switched from the low load control to the normal control. Thereby, about the 1st air conditioner 30a, even if it is a case where a load increases again after air-conditioning load becomes low load, it can respond to load by switching of a control mode. Further, since the value of the predetermined return ability is set as a value larger than the value of the predetermined ability, it is possible to suppress hunting in the control.

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

  Even in the control according to the modification A described above, it is possible to continue the operation according to the air conditioning load while suppressing freezing of the circulating fluid in the fluid circuit 21 as in the above 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 having 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, the case where the flow rate of the circulating fluid in each branch circuit portion is grasped by using the flow rate sensors of the first flow rate sensor 36a, the second flow rate sensor 36b, and the third flow rate sensor 36c is taken as an example. explained.

  On the other hand, the circulating fluid that passes through the heat source side heat exchangers 43a, 43b, and 43c of the heat source devices 40a, 40b, and 40c from the rotational speed of the pump 20 and the valve opening degrees of the flow rate adjustment valves 35a, 35b, and 35c You may make it obtain | require flow volume of. In this case, it is not necessary to provide 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 heat from the circulating fluid circulated by the pump to the heat source device of the air conditioner is heated. Can be used as an air conditioning system.

20 Pump (Flow rate adjustment mechanism)
21 Fluid circuit 22a First forward pipe (branch circuit)
22b Second forward pipe (branch circuit)
22c Third forward pipe (branch circuit)
23a First return pipe (branch circuit)
23b Second return pipe (branch circuit)
23c Third return pipe (branch circuit)
30 Air Conditioner 31, 31a, 31b, 31c Refrigerant Circuit 35 Flow Control Valve (Flow Control Mechanism)
36a First flow sensor (flow sensor)
36b Second flow sensor (flow sensor)
36c Third flow sensor (flow sensor)
40 heat source machine 41 compressor 43 heat source side heat exchanger 44 expansion valve 49 air conditioning controller (flow rate variable mechanism adjustment unit)
51 User-side heat exchanger 70 Controller (pump adjustment part)
80 Cooling tower 90 Boiler 100 Air conditioning system 200 Air conditioning system

JP-A-8-210667

Claims (7)

A fluid circuit (21) through which the circulating fluid circulates;
A boiler (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 that exchanges heat 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 mechanism (20, 35a, 35b, 35c) for adjusting the 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 adjusting mechanism;
With
In the case where 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,
A first control mode for controlling the flow rate adjusting mechanism so that a temperature difference between the circulating fluid before and after passing through the heat source side heat exchanger becomes a predetermined target value;
When the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or lower than a predetermined flow rate, the circulation sent to the heat source side heat exchanger without performing control to set the temperature difference as the predetermined target value. Controlling the flow rate controller to fix the flow rate of the fluid at a predetermined lower limit flow rate,
When the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or lower than a predetermined flow rate, the control target value of the temperature difference is changed to an update target value that is a smaller value, and the temperature difference is updated. Controlling the flow rate adjusting unit to achieve a target value, or
When the capacity of the heat source ascertained from the rotational speed of the compressor is less than or equal to a predetermined capacity, the control target value for the temperature difference is set to the capacity of the heat source as determined from the rotational speed of the compressor at a predetermined lower limit flow rate. Change to the target value corresponding to the rotational speed, which is a value obtained by dividing, or control the flow rate adjustment unit so that the temperature difference becomes the target value corresponding to the rotational speed,
A second control mode which is either
Switch to execute,
Air conditioning system (100, 200). In the second control mode, when the flow rate of the circulating fluid sent to the heat source side heat exchanger is equal to or lower than a predetermined flow rate, the control unit performs control without setting the temperature difference as the predetermined target value. And controlling the flow rate adjusting unit so as to fix the flow rate of the circulating fluid sent to the heat source side heat exchanger to a predetermined lower limit flow rate,
When the second control mode is executed, the control unit changes from the second control mode to the first control mode when the temperature difference becomes larger than a return temperature difference that is larger than the predetermined target value. Switch to
The air conditioning system according to claim 1. In the second control mode, 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 updates the update target that is a smaller control target value of the temperature difference. Change to a value, control the flow rate adjustment unit so that the temperature difference becomes the update target value,
The control unit, when executing the second control mode, when the flow rate of the circulating fluid sent to the heat source side heat exchanger becomes larger than a predetermined increased update flow rate that is a value larger than a predetermined lower limit flow rate. The temperature difference control target value is updated to an increase update target value that is larger than the update target value, and the flow rate control unit is controlled so that the temperature difference becomes the increase update target value.
The air conditioning system according to claim 1. The control unit, when executing the second control mode, controls the flow rate adjusting unit so that the temperature difference becomes the update target value, and the circulating fluid sent to the heat source side heat exchanger When the flow rate is less than or equal to 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, and the temperature difference becomes the decrease update target value. So as to control the flow rate regulator,
The air conditioning system according to claim 3. The control unit switches from the second control mode to the first control mode 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 mode.
The air conditioning system according to claim 3 or 4. In the second control mode, the control unit determines the control target value of the temperature difference from the rotational speed of the compressor when the capacity of the heat source ascertained from the rotational speed of the compressor is equal to or less than a predetermined capacity. The flow rate adjusting unit is controlled so that the temperature difference becomes the rotation speed target value by changing the grasped heat source capacity to the rotation speed target value that is a value obtained by dividing the heat source capacity by the predetermined lower limit flow rate. And
The controller, when executing the second control mode, when the capacity of the heat source ascertained from the rotation speed of the compressor is greater than a predetermined return capacity that is larger than the predetermined capacity. Switching from the 2 control mode to the first control mode,
The air conditioning system according to claim 1. A plurality of the refrigerant circuits (31a, 31b, 31c);
The fluid circuit has a branch circuit (22a, 23a, 22b, 23b, 22c, 23c) that branches into each refrigerant circuit and flows the circulating fluid,
The flow rate adjusting mechanism includes a circulation pump (20) provided in a portion of the fluid circuit other than the branch circuit, and a flow rate control valve (35a, 35b, 35c) provided for each branch circuit. And
A flow sensor (36a, 36b, 36c) for detecting the flow rate of the circulating fluid flowing through the branch circuit is provided for each branch circuit;
The control unit controls the circulation pump and each of the flow control valves according to a detection value of the flow sensor.
The air conditioning system (200) according to any one of claims 1 to 6.

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