Air conditioning device

Abstract

This air conditioning device comprises a heat source machine, a relay machine connected to the heat source machine, and a plurality of load devices connected to the relay machine. The heat source machine has a first refrigerant circuit in which a refrigerant circulates and a first intermediate heat exchanger in which a heat medium exchanges heat with the refrigerant flowing in the first refrigerant circuit. The relay machine has a second refrigerant circuit in which a refrigerant circulates and a second intermediate heat exchanger in which a heat medium exchanges heat with the refrigerant flowing in the second refrigerant circuit. The first intermediate heat exchanger, the second intermediate heat exchanger, and the plurality of load devices are connected by first heat medium piping, forming a first heat medium circuit in which the heat media circulate. The relay machine has bypass piping and a flow path switching mechanism for switching the flow directions of the heat media in the first heat medium circuit.

Description

air conditioning equipment

[0001] The present disclosure relates to an air conditioner equipped with an intermediate heat exchanger that exchanges heat between a refrigeration cycle and a transport heat medium.

[0002] In air conditioners in which multiple indoor units are connected to one outdoor unit, a water-based air conditioning system is known in which the outdoor unit and the indoor units are connected by a total of four pipes, including supply and return pipes for chilled water and hot water, and the multiple indoor units operate in simultaneous cooling and heating mode (see, for example, Patent Document 1). There are also systems in which a relay unit is installed and the outdoor unit and the relay unit are connected by two pipes, and chilled water and hot water are simultaneously produced within the relay unit.

[0003] Japanese Patent Application Publication No. 4-214134

[0004] However, chiller systems that use chilled or hot water to transport heat from one or more outdoor units to multiple indoor units require water to be cooled (or heated) when starting indoor cooling (or heating) operation, which means it takes longer to start up the indoor units than building air conditioners that use refrigerants to transport heat. Furthermore, when the outdoor unit's operating mode changes from cooling to heating (or vice versa), the heat capacity of the chilled water (hot water) in the water piping from the outdoor unit to the relay unit increases depending on the system size, making it time-consuming to switch operating modes. Thus, with conventional configurations, it can be difficult to quickly start up indoor cooling or heating when starting operation or switching operating modes in an air conditioning system.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an air conditioning apparatus that can start up indoor heating and cooling more quickly than conventional methods when starting operation or switching operation modes.

[0006] An air conditioning apparatus according to the present disclosure is an air conditioning apparatus including a heat source unit, a relay unit connected to the heat source unit, and a plurality of load devices connected to the relay unit, wherein the heat source unit has a first refrigerant circuit through which a refrigerant circulates, and a first intermediate heat exchanger through which a heat medium exchanges heat with the refrigerant flowing through the first refrigerant circuit, the relay unit has a second refrigerant circuit through which a refrigerant circulates, and a second intermediate heat exchanger through which the heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit, the first intermediate heat exchanger, the second intermediate heat exchanger, and the plurality of load devices are connected by a first heat medium piping to form a first heat medium circuit through which the heat medium circulates, and the relay unit has a bypass piping and a flow path switching mechanism that switches the flow direction of the heat medium in the first heat medium circuit.

[0007] According to the present disclosure, the relay unit includes a bypass pipe and a flow path switching mechanism that switches the flow direction of the heat medium in the first heat medium circuit. This allows the air conditioning apparatus to transition to steady operation through different flow directions when starting operation or switching operation modes, utilizing the heat capacity of the first heat medium circuit during this transition. As a result, indoor heating and cooling can be started up more quickly than in conventional systems.

[0008] 1 is a schematic configuration diagram of an air conditioner according to Embodiment 1.

[0023] FIG. 1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1, showing a state at the start of cooling operation.

[0024] FIG. 1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1, showing a state during steady operation of cooling operation.

[0025] FIG. 1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1, showing a state at the start of heating operation.

[0026] FIG. 1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1, showing a state during steady operation of heating operation.

[0027] FIG. 1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1, showing a state during steady operation of heating operation.

[0028] FIG. 1 is a refrigerant circuit diagram of an air conditioner according to a first modified example of Embodiment 1, showing a state at the start of cooling operation.

[0029] FIG. 2 is a schematic configuration diagram of an air conditioner according to a second modified example of Embodiment 1.

[0029] FIG. 2 is a refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a state during steady operation of cooling-dominated operation.

[0029] FIG. 3 is a refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a first state in the process of switching from cooling-dominated operation to heating-dominated operation in FIG. 8.

[0029] FIG. 3 is a refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a second state in the process of switching from cooling-dominated operation to heating-dominated operation in FIG. 8. 12. A refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a third state in the process of switching from cooling-dominant operation to heating-dominant operation in FIG. 8. A refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a state during steady operation of heating-dominant operation. A diagram showing a control sequence for switching the operation mode from cooling-dominant operation to heating-dominant operation in an air conditioner according to Embodiment 2. A refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a first state in the process of switching from heating-dominant operation to cooling-dominant operation in FIG. 12. A refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a second state in the process of switching from heating-dominant operation to cooling-dominant operation in FIG. 12. A refrigerant circuit diagram of an air conditioner according to Embodiment 2, showing a third state in the process of switching from heating-dominant operation to cooling-dominant operation in FIG. 12. A diagram showing a control sequence for switching the operation mode from heating-dominant operation to cooling-dominant operation in an air conditioner according to Embodiment 2. A refrigerant circuit diagram of an air conditioner according to Embodiment 3, showing a state at the start of cooling operation.22。 Refrigerant circuit diagram of an air conditioner according to Embodiment 3, showing a state during steady operation of cooling operation. Refrigerant circuit diagram of an air conditioner according to Embodiment 3, showing a state at the start of heating operation. Refrigerant circuit diagram of an air conditioner according to Embodiment 3, showing a state during steady operation of heating operation. Refrigerant circuit diagram of an air conditioner according to Embodiment 4, showing a state during steady operation of cooling-dominated operation. Refrigerant circuit diagram of an air conditioner according to Embodiment 4, showing a first state in the process of switching from cooling-dominated operation to heating-dominated operation of FIG. 22. Refrigerant circuit diagram of an air conditioner according to Embodiment 4, showing a second state in the process of switching from cooling-dominated operation to heating-dominated operation of FIG. 22. Refrigerant circuit diagram of an air conditioner according to Embodiment 4, showing a third state in the process of switching from cooling-dominated operation to heating-dominated operation of FIG. 22. Refrigerant circuit diagram of an air conditioner according to Embodiment 4, showing a state during steady operation of heating-dominated operation.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and their description will be omitted or simplified as appropriate. Furthermore, the shape, size, arrangement, etc. of the configurations shown in each drawing may be changed as appropriate.

[0010] Embodiment 1. FIG. 1 is a schematic diagram illustrating an air conditioning apparatus 100 according to Embodiment 1. FIG. 2 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 1, illustrating a state at the start of cooling operation. Note that the arrows in FIG. 2 indicate the flow of a heat medium (also referred to as a heat transfer medium). As shown in FIGS. 1 and 2 , the air conditioning apparatus 100 according to Embodiment 1 includes a heat source unit 1, a relay unit 2 connected to the heat source unit 1, and three load devices 3A, 3B, and 3C connected to the relay unit 2. The heat source unit 1 is, for example, an outdoor unit. The load devices 3A, 3B, and 3C are, for example, indoor units. Hereinafter, the load devices 3A, 3B, and 3C may be referred to as load devices 3 without distinction. The heat source unit 1 is installed, for example, on the roof of a building 200. The relay unit 2 and the load devices 3A, 3B, and 3C are installed, for example, inside the building 200. The components that make up the heat source unit 1, the relay unit 2, and the load units 3A, 3B, and 3C are controlled by a control unit 7.

[0011] 2 , the heat source unit 1 has a first refrigerant circuit 10 through which a refrigerant circulates, and a first intermediate heat exchanger 11 that exchanges heat with the first refrigerant circuit 10. The relay unit 2 has a second refrigerant circuit 20 through which a refrigerant circulates, a second intermediate heat exchanger 21 that exchanges heat with the second refrigerant circuit 20, and a third intermediate heat exchanger 22 that exchanges heat with the second refrigerant circuit 20. Each load device 3 has a load-side heat exchanger 30.

[0012] The first refrigerant circuit 10 contains, for example, R290, NH ３ The second refrigerant circuit 20 is filled with a non-flammable or slightly flammable refrigerant such as R410A, R32, olefin, or a mixture of these refrigerants. This is because the heat source unit 1 is mainly installed outdoors, and so a flammable refrigerant with a small global warming effect is used. The second refrigerant circuit 20 is filled with a non-flammable or slightly flammable refrigerant such as R410A, R32, olefin, or a mixture of these refrigerants. This is because the relay unit 2 is mainly installed indoors. The refrigerant filled in the first refrigerant circuit 10 and the second refrigerant circuit 20 is not limited to the above-mentioned refrigerants, and may be refrigerants commonly used in air conditioning at present, such as R410A or R32, R290, CO ２NH ３ For example, the refrigerant sealed in the second refrigerant circuit 20 may be, in consideration of safety, R290, NH ３ A flammable refrigerant such as olefin may be enclosed.

[0013] The amount of refrigerant circulating through the first refrigerant circuit 10 is greater than the amount of refrigerant circulating through the second refrigerant circuit 20. The amount of refrigerant charged in the first refrigerant circuit 10 is, for example, 5 kg or less. The amount of refrigerant charged in the second refrigerant circuit 20 is, for example, less than 1 kg, which is the standard for indoor use of a flammable refrigerant. The first refrigerant circuit 10 is primarily used for the load devices 3A, 3B, and 3C that operate with the greater of the cooling load ΣQc and the heating load ΣQh. In other words, to improve operating efficiency, the amount of refrigerant charged through the first refrigerant circuit 10 is greater than the amount of refrigerant circulating through the second refrigerant circuit 20.

[0014] In the air conditioning apparatus 100, the first intermediate heat exchanger 11, the load side heat exchanger 30, and the second intermediate heat exchanger 21 are connected by a first heat medium pipe 40 to form a first heat medium circuit 4 through which the heat medium circulates. In the air conditioning apparatus 100, the third intermediate heat exchanger 22 and the load side heat exchanger 30 are connected by a second heat medium pipe 50 to form a second heat medium circuit 5 through which the heat medium circulates. The first heat medium circuit 4 and the second heat medium circuit 5 are provided with a first flow path switching device 6 that switches the flow path of the heat medium flowing into the load devices 3A, 3B, and 3C between the first heat medium circuit 4 and the second heat medium circuit 5. The heat medium is, for example, water, brine, or a mixture of brine and water.

[0015] The first heat medium circuit 4 also has a switching mechanism for switching the flow direction of the heat medium. This switching mechanism includes a bypass pipe provided in the first heat medium pipe 40 and a flow path switching mechanism for switching the flow path in the first heat medium pipe 40 so that the heat medium flows into the bypass pipe. In the present embodiment, a load device bypass mechanism 8 is provided as the switching mechanism for switching the flow direction of the heat medium. The load device bypass mechanism 8 returns the heat medium to the heat source unit 1 without passing through the load devices 3A, 3B, and 3C. Specifically, the first heat medium circuit 4 includes a first bypass pipe 80 and a first bypass valve 81 (hereinafter also referred to as a first flow path switching mechanism) provided in the first bypass pipe 80 for adjusting the flow rate of the heat medium. The first bypass pipe 80 connects a point Pa, which is downstream of the first intermediate heat exchanger 11 and upstream of the load side heat exchanger 30, in the first heat medium pipe 40, to a point Pb, which is downstream of the load side heat exchanger 30 and upstream of the second intermediate heat exchanger 21. Point Pa is located on the first heat medium piping 40 upstream of the load-side heat exchanger 30, particularly upstream of the multiple branch pipes 40d branching into the load-side heat exchangers 30A, 30B, and 30C, i.e., upstream of the first flow switching device 6. Point Pb is located on the first heat medium piping 40 upstream of the second intermediate heat exchanger 21, particularly upstream of a first pump 41 (heat medium suction side) described below.

[0016] The first bypass valve 81 is configured, for example, as an on-off valve or a two-way valve whose valve opening (opening area) can be controlled. The first bypass valve 81 allows or blocks the flow of the heat medium into the first bypass piping 80 by opening or closing. When the first bypass valve 81 is opened, at least a portion of the heat medium can flow into the first bypass piping 80 and bypass the load devices 3A, 3B, and 3C. The first bypass valve 81 is controlled by the control device 7.

[0017] The first heat medium circuit 4 is provided with a temperature sensor 73 that detects the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2. The temperature sensor 73 is provided, for example, inside the relay unit 2, upstream of point Pa.

[0018] First, a description will be given of the configuration of the heat source unit 1. The heat source unit 1 has a first refrigerant circuit 10 through which a refrigerant circulates. The first refrigerant circuit 10 is configured such that a first compressor 12, a first flow switching valve 13, a heat source side heat exchanger 14, a first expansion mechanism 15, and a first intermediate heat exchanger 11 are connected in sequence by refrigerant piping. Note that the first refrigerant circuit 10 may include other components in addition to the above-described components, or may omit some components.

[0019] The first compressor 12 is, for example, an inverter compressor. When the first compressor 12 is an inverter compressor, the operating frequency may be changed arbitrarily by an inverter circuit or the like to change the refrigerant discharge capacity per unit time. In this case, the operation of the inverter circuit is controlled by the control device 7. The refrigerant discharged from the first compressor 12 flows into the heat source side heat exchanger 14 and the first intermediate heat exchanger 11 via the first flow path switching valve 13.

[0020] The first flow path switching valve 13 is, for example, a four-way valve and has a function of switching the flow path of the refrigerant. During cooling operation, the first flow path switching valve 13 connects the refrigerant discharge side of the first compressor 12 to the heat source side heat exchanger 14 and switches the refrigerant flow path to connect the refrigerant suction side of the first compressor 12 to the first intermediate heat exchanger 11. Meanwhile, during heating operation, the first flow path switching valve 13 connects the refrigerant discharge side of the first compressor 12 to the first intermediate heat exchanger 11 and switches the refrigerant flow path to connect the refrigerant suction side of the first compressor 12 to the heat source side heat exchanger 14. The first flow path switching valve 13 may be configured by combining two-way valves or three-way valves.

[0021] The heat source-side heat exchanger 14 functions as a condenser during cooling operation. The heat source-side heat exchanger 14 also functions as an evaporator during heating operation. The heat source-side heat exchanger 14 draws in outdoor air using the heat source-side blower 16, exchanges heat with the refrigerant flowing inside, and discharges the air to the outside.

[0022] The first expansion mechanism 15 reduces the pressure of the refrigerant flowing through the first refrigerant circuit 10 to expand it, and is configured, for example, by an electronic expansion valve whose opening degree is variably controlled.

[0023] The first intermediate heat exchanger 11 exchanges heat between the heat medium and the refrigerant. The first intermediate heat exchanger 11 is a flow path of the first refrigerant circuit 10 and a flow path of the first heat medium circuit 4. That is, the first intermediate heat exchanger 11 is a component of the first refrigerant circuit 10 and a component of the first heat medium circuit 4. The first intermediate heat exchanger 11 functions as an evaporator during cooling operation and exchanges heat between the refrigerant flowing out of the first expansion mechanism 15 and the heat medium, evaporating the refrigerant to vaporize it, and cooling the heat medium. The first intermediate heat exchanger 11 functions as a condenser during heating operation and exchanges heat between the refrigerant flowing in from the first compressor 12 and the heat medium, condensing the refrigerant to liquefy it or to form a two-phase gas-liquid state, and heating the heat medium.

[0024] The relay unit 2 includes a second refrigerant circuit 20 through which a refrigerant circulates, a second intermediate heat exchanger 21 that exchanges heat with the second refrigerant circuit 20, a third intermediate heat exchanger 22 that exchanges heat with the second refrigerant circuit 20, and a first flow switching device 6 that switches the flow path of the heat medium flowing into the load devices 3A, 3B, and 3C between the first heat medium circuit 4 and the second heat medium circuit 5. The second refrigerant circuit 20 is configured such that a second compressor 23, a second flow switching valve 24, the second intermediate heat exchanger 21, a second expansion mechanism 25, and the third intermediate heat exchanger 22 are connected in this order by refrigerant piping. Note that the second refrigerant circuit 20 may include other components in addition to the above-mentioned components, or some components may be omitted.

[0025] The second compressor 23 is, for example, an inverter compressor, and has basically the same configuration as the first compressor 12. The refrigerant discharged from the second compressor 23 flows into the second intermediate heat exchanger 21 or the third intermediate heat exchanger 22 via a second flow path switching valve 24.

[0026] The second flow path switching valve 24 is, for example, a four-way valve and has basically the same configuration as the first flow path switching valve 13. During cooling operation, the second flow path switching valve 24 switches the refrigerant flow path to connect the refrigerant discharge side of the second compressor 23 to the second intermediate heat exchanger 21 and to connect the refrigerant suction side of the second compressor 23 to the third intermediate heat exchanger 22. On the other hand, during heating operation, the second flow path switching valve 24 switches the refrigerant flow path to connect the refrigerant discharge side of the second compressor 23 to the third intermediate heat exchanger 22 and to connect the refrigerant suction side of the second compressor 23 to the second intermediate heat exchanger 21. The second flow path switching valve 24 may be configured by combining two-way valves or three-way valves.

[0027] The second refrigerant circuit 20 is stopped during steady cooling operation and steady heating operation. When the second refrigerant circuit 20 is stopped, the second flow switching valve 24 connects the refrigerant discharge side of the second compressor 23 to the third intermediate heat exchanger 22 and the refrigerant suction side of the second compressor 23 to the second intermediate heat exchanger 21.

[0028] The second expansion mechanism 25 reduces the pressure of the refrigerant circulating in the second refrigerant circuit 20 to expand it, and is configured, for example, by an electronic expansion valve whose opening degree is variably controlled.

[0029] The second intermediate heat exchanger 21 exchanges heat between the heat medium and the refrigerant. The second intermediate heat exchanger 21 serves as a flow path of the second refrigerant circuit 20 and a flow path of the first heat medium circuit 4. In other words, the second intermediate heat exchanger 21 serves as a component of the second refrigerant circuit 20 and a component of the first heat medium circuit 4. In the second intermediate heat exchanger 21 shown in FIG. 1 , particularly when functioning as a condenser, it is preferable to configure the piping so that the refrigerant circulating through the second refrigerant circuit 20 and the heat medium circulating through the first heat medium circuit 4 flow in counterflow directions to increase the heat exchange rate in the second intermediate heat exchanger 21.

[0030] When functioning as a condenser, the second intermediate heat exchanger 21 exchanges heat between the refrigerant flowing in from the second compressor 23 and the heat medium circulating through the first heat medium pipe 40, condenses the refrigerant to liquefy or convert it into a gas-liquid two-phase state, and heats the heat medium. When functioning as an evaporator, the second intermediate heat exchanger 21 exchanges heat between the refrigerant flowing out from the second expansion mechanism 25 and the heat medium circulating through the first heat medium pipe 40, evaporates the refrigerant to vaporize it, and cools the heat medium.

[0031] The third intermediate heat exchanger 22 exchanges heat between the heat medium and the refrigerant. The third intermediate heat exchanger 22 serves as a flow path of the second refrigerant circuit 20 and a flow path of the second heat medium circuit 5. That is, the third intermediate heat exchanger 22 serves as a component of the second refrigerant circuit 20 and a component of the second heat medium circuit 5. In the third intermediate heat exchanger 22 shown in FIG. 1 , particularly when functioning as a condenser, it is preferable to configure the piping so that the refrigerant circulating through the second refrigerant circuit 20 and the heat medium circulating through the second heat medium circuit 5 flow in counterflow directions to increase the heat exchange rate in the third intermediate heat exchanger 22.

[0032] When functioning as an evaporator, the third intermediate heat exchanger 22 exchanges heat between the refrigerant flowing out from the second expansion mechanism 25 and the heat medium circulating through the second heat medium pipe 50, evaporating the refrigerant and cooling the heat medium. When functioning as a condenser, the third intermediate heat exchanger 22 exchanges heat between the refrigerant flowing in from the second compressor 23 and the heat medium circulating through the second heat medium pipe 50, condensing the refrigerant to liquefy or convert it into a gas-liquid two-phase state, and heating the heat medium.

[0033] The first flow switching device 6 is provided on the inlet side and outlet side of the heat medium of the load-side heat exchanger 30 in the first heat medium circuit 4 and the second heat medium circuit 5, respectively. The first flow switching device 6 is configured as a three-way valve and is shared by the first heat medium circuit 4 and the second heat medium circuit 5. Hereinafter, switching the flow path of the heat medium flowing into the load devices 3A, 3B, and 3C to the first heat medium circuit 4 in the first flow switching device 6 will be referred to as "switching the first flow switching device 6 to the first heat medium circuit 4 side." Additionally, switching the flow path of the heat medium flowing into the load devices 3A, 3B, and 3C to the second heat medium circuit 5 in the first flow switching device 6 will be referred to as "switching the first flow switching device 6 to the second heat medium circuit 5 side."

[0034] The first flow path switching device 6 is not limited to the above configuration. For example, it may be configured by a two-way valve provided for each load device 3 in the first heat medium circuit 4 and a two-way valve provided for each load device 3 in the second heat medium circuit 5. The first flow path switching device 6 controls the heat medium flowing in and out of the load-side heat exchanger 30 by controlling the opening and closing thereof.

[0035] The first heat medium circuit 4 is provided with a first pump 41 that circulates the heat medium. The first pump 41 is one of the components that constitute the first heat medium circuit 4, and is provided in the first heat medium pipe 40 between the second intermediate heat exchanger 21 and point Pb, which is one end of the first bypass pipe 80. The first pump 41 is provided in the relay unit 2. The first pump 41 draws water in the first heat medium circuit 4, applies pressure to it, and sends it out to circulate. The capacity of the first pump 41 is changed by a pump inverter drive device (not shown). The pump inverter drive device changes the capacity of the first pump 41 by arbitrarily changing the drive frequency based on instructions from the control device 7.

[0036] In the first embodiment, the second intermediate heat exchanger 21 is provided in the return pipe 40b of the first heat medium pipe 40, through which the heat medium flows from the load device 3 to the heat source unit 1. Specifically, the second intermediate heat exchanger 21 is connected to the return main pipe 40mb, of the two main heat medium pipes 40m (the outward main pipe 40mo and the return main pipe 40mb) connecting the heat source unit 1 and the relay unit 2, through which the heat medium flows from the relay unit 2 to the heat source unit 1. The second intermediate heat exchanger 21 is also connected to the pipe in which the first pump 41 is provided, i.e., the pipe 40rb connected to the first flow path switching device 6 on the outflow side of the load devices 3A, 3B, and 3C.

[0037] The second heat medium circuit 5 is also provided with a second pump 51 for circulating the heat medium. The second pump 51 is one of the components constituting the second heat medium circuit 5. The second pump 51 draws water in the second heat medium circuit 5, applies pressure to it, and sends it out to circulate. The capacity of the second pump 51 is changed by a pump inverter drive device (not shown). The pump inverter drive device changes the capacity of the second pump 51 by arbitrarily changing the drive frequency based on instructions from the control device 7.

[0038] The second pump 51 has a smaller flow rate or head than the first pump 41. This is because the second heat medium circuit 5 connects the relay unit 2 and the load devices 3A, 3B, and 3C, and has shorter heat medium piping than the first heat medium circuit 4, so pressure loss is not as large. Making the second pump 51 smaller than the first pump 41 reduces costs and the burden of installation work. The second pump 51 may have the same flow rate or head as the first pump 41.

[0039] Each load device 3 includes a load-side heat exchanger 30 and a load-side blower 31. Each load device 3 generates an air flow that passes air from the indoor space through the load-side heat exchanger 30 and returns it to the indoor space. The load-side heat exchanger 30 is, for example, a fin-tube heat exchanger that exchanges heat between the indoor air in the indoor space supplied from the load-side blower 31 and a heat medium. During cooling operation, a heat medium that is colder than the indoor air passes through the heat transfer tubes of the load-side heat exchanger 30 to cool the indoor space. During heating operation, a heat medium that is warmer than the indoor air passes through the heat transfer tubes of the load-side heat exchanger 30 to heat the indoor space. Although not shown, each load device may include a flow rate control device that adjusts the flow rate of the heat medium flowing into the load-side heat exchanger 30.

[0040] The control device 7 controls the overall operation of the air conditioning apparatus 100. Specifically, the control device 7 controls the drive frequency of the compressor, the rotation speed of the blower, switching of the flow path switching device, the opening degree of the expansion mechanism, opening and closing of the first bypass valve 81, and the drive frequency of the pump. The control device 7 is composed of a computer equipped with a memory for storing data and programs required for control and a CPU for executing programs, dedicated hardware such as an ASIC or FPGA, or both.

[0041] Next, the operating behavior of the air conditioning apparatus 100 during various operations will be described. The operating behavior of the air conditioning apparatus 100 includes four modes: cooling operation, heating operation, cooling-dominated operation, and heating-dominated operation. FIG. 3 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 1, showing the state during steady-state cooling operation. FIG. 4 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 1, showing the state at the start of heating operation. FIG. 5 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 1, showing the state during steady-state heating operation. Note that the arrows in FIGS. 3 to 5 indicate the flow of the heat medium.

[0042] As shown in FIG. 3, cooling operation is an operation mode in which only cooling is possible in the load devices 3A, 3B, and 3C, and the load devices 3A, 3B, and 3C are either cooling or stopped. As shown in FIG. 5, heating operation is an operation mode in which only heating is possible in the load devices 3A, 3B, and 3C, and the load devices 3A, 3B, and 3C are either heating or stopped. Cooling-dominated operation is an operation mode in which cooling or heating can be selected for each load device 3A, 3B, and 3C, and in simultaneous cooling and heating operation in which the load devices 3A, 3B, or 3C performing cooling and the load devices 3A, 3B, or 3C performing heating are present simultaneously, the cooling load ΣQc is larger than the heating load ΣQh. Heating-dominated operation is an operation mode in which cooling or heating can be selected for each load device 3A, 3B, or 3C, and in simultaneous cooling and heating operation in which the load devices 3A, 3B, or 3C performing cooling and the load devices 3A, 3B, or 3C performing heating are present simultaneously, the heating load ΣQh is larger than the cooling load ΣQc.

[0043] Cooling operation and cooling-dominated operation are operation modes in which chilled water is produced by the heat source unit 1, and heating operation and heating-dominated operation are operation modes in which hot water is produced by the heat source unit 1. In this embodiment, the operation of the air conditioning apparatus 100 and the flow of the heat medium in heating operation and cooling operation will be described in detail.

[0044] (Cooling Operation) First, referring to Figure 3, cooling operation (particularly steady operation) of the air conditioning apparatus 100 will be described. Figure 3 shows the flow of refrigerant and heat medium when cooling is performed by two of the three load devices 3A, 3B, and 3C in the air conditioning apparatus 100, that is, the load devices 3B and 3C. Note that the load device 3A is not operating. In the air conditioning apparatus 100 according to the first embodiment, when cooling is performed by the load devices 3B and 3C as described above, the first flow switching device 6 for the load devices 3B and 3C is set to the first heat medium circuit 4 side, and the first flow switching device 6 for the load device 3A is set to the second heat medium circuit 5 side, the second refrigerant circuit 20 and the second heat medium circuit 5 are stopped, and only the first refrigerant circuit 10 and the first heat medium circuit 4 are operated.

[0045] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the heat source side heat exchanger 14, where it exchanges heat with air and condenses and liquefies. The condensed and liquefied refrigerant is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the first intermediate heat exchanger 11, where it exchanges heat with the heat medium flowing in the first heat medium circuit 4 and evaporates into gas. The gasified refrigerant passes through the first flow switching valve 13 and is drawn into the first compressor 12 via an accumulator.

[0046] On the other hand, the heat medium flowing through the first heat medium circuit 4 is cooled by the refrigerant flowing through the first intermediate heat exchanger 11 to become cold water, and then flows through the relay unit 2 to the load-side heat exchanger 30, where it is heated by heat exchange with the indoor air in the indoor space. The heated heat medium flows through the relay unit 2 and again into the first intermediate heat exchanger 11.

[0047] (Heating Operation) Next, heating operation (particularly steady operation) of the air conditioning apparatus 100 will be described with reference to Fig. 5. Fig. 5 shows the flow of refrigerant and heat medium when heating is performed by two of the three load devices 3A, 3B, and 3C in the air conditioning apparatus 100, that is, the load devices 3A and 3B. Note that the load device 3C is stopped. In the air conditioning apparatus 100 according to the first embodiment, when heating is performed by the load devices 3A and 3B as described above, the first flow switching device 6 for the load devices 3A and 3B is set to the side of the first heat medium circuit 4, and the first flow switching device 6 for the load device 3C is set to the side of the second heat medium circuit 5, the second refrigerant circuit 20 and the second heat medium circuit 5 are stopped, and only the first refrigerant circuit 10 and the first heat medium circuit 4 are operated.

[0048] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the first intermediate heat exchanger 11. The refrigerant that flows into the first intermediate heat exchanger 11 exchanges heat with the heat medium flowing through the first heat medium circuit 4, condenses, and liquefies, and is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the heat source side heat exchanger 14. The gas-liquid two-phase refrigerant that flows into the heat source side heat exchanger 14 exchanges heat with air and evaporates, passes through the first flow switching valve 13, and is drawn into the first compressor 12 via an accumulator.

[0049] On the other hand, the heat medium flowing through the first heat medium circuit 4 is heated by the refrigerant flowing through the first intermediate heat exchanger 11 to become hot water, and then flows through the relay unit 2 to the load-side heat exchanger 30, where it is cooled by heat exchange with the indoor air in the indoor space. The cooled heat medium flows through the relay unit 2 and again into the first intermediate heat exchanger 11.

[0050] (Operation at Start of Cooling Operation) Next, operation during startup of cooling operation and changes in the temperature of the heat medium at each location during startup of cooling operation and steady operation will be described with reference to Figures 2 and 3. Figures 2 and 3 show examples of the temperature of the heat medium at each location. Below, as in the case of steady operation described above, an example will be described in which two of the three load devices 3A, 3B, and 3C, 3B and 3C, are performing cooling, and one load device 3A is not operating.

[0051] As shown in FIG. 2 , in the air conditioning apparatus 100, when cooling operation is started, the first bypass valve 81 is opened, the first flow switching device 6 for the load devices 3B and 3C is set to the side of the second heat medium circuit 5, both the first refrigerant circuit 10 and the second refrigerant circuit 20 are operated (cooling), and both the first heat medium circuit 4 and the second heat medium circuit 5 are operated.

[0052] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the heat source side heat exchanger 14, where it exchanges heat with air and condenses and liquefies. The condensed and liquefied refrigerant is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the first intermediate heat exchanger 11, where it exchanges heat with the heat medium flowing in the first heat medium circuit 4 and evaporates into gas. The gasified refrigerant passes through the first flow switching valve 13 and is drawn into the first compressor 12 via an accumulator.

[0053] On the other hand, the heat medium flowing through the first heat medium circuit 4 is cooled by the refrigerant flowing through the first intermediate heat exchanger 11 to become chilled water, and then flows into the first bypass piping 80 in the relay unit 2 and flows from the first bypass piping 80 to the second intermediate heat exchanger 21 by the first pump 41. The heat medium flowing through the first heat medium circuit 4 is heated in the second intermediate heat exchanger 21 and returns to the first intermediate heat exchanger 11 of the heat source unit 1. In FIG. 2 , for ease of explanation, the portion of the first heat medium piping 40 through which the heat medium circulates is indicated by a dashed line. That is, when the cooling operation is started, the heat medium flowing through the first heat medium circuit 4 bypasses the load device 3 by the load device bypass mechanism 8 of the relay unit 2 and is returned to the heat source unit 1. In the example of FIG. 2 , the temperature of the heat medium cooled in the first intermediate heat exchanger 11 and before flowing into the second intermediate heat exchanger 21 of the relay unit 2 is 15°C. The temperature of the heat medium that is heated in the second intermediate heat exchanger 21 and returns to the first intermediate heat exchanger 11 is 20°C.

[0054] In the second refrigerant circuit 20, high-temperature, high-pressure gas refrigerant discharged from the second compressor 23 passes through the second flow switching valve 24 and flows to the second intermediate heat exchanger 21, where it condenses and liquefies through heat exchange with the heat medium flowing in the first heat medium circuit 4. The condensed and liquefied refrigerant is decompressed in the second expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant, flows to the third intermediate heat exchanger 22, and exchanges heat with the heat medium flowing in the second heat medium circuit 5 to evaporate and gasify. The gasified refrigerant passes through the second flow switching valve 24 and is drawn into the second compressor 23 via an accumulator.

[0055] On the other hand, the heat medium flowing through the second heat medium circuit 5 is cooled by the refrigerant flowing in the third intermediate heat exchanger 22 to become chilled water, and then flows into the load-side heat exchangers 30 of the load devices 3B and 3C, where it is heated by heat exchange with the indoor air in the indoor space. The heated heat medium flows into the third intermediate heat exchanger 22 again. In the example of Fig. 2 , the temperature of the heat medium cooled in the third intermediate heat exchanger 22 and before flowing into the load devices 3B and 3C that perform cooling is 7 [°C]. The temperature of the heat medium heated in the load device 3C and returning to the third intermediate heat exchanger 22 is 12 [°C].

[0056] Thereafter, when the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2 in the first heat medium circuit 4 reaches a predetermined temperature (for example, 7°C), that is, when the temperature of the heat medium supplied from the heat source unit 1 drops to a temperature sufficient for cooling, the first bypass valve 81 is closed and steady operation is performed. The operation during steady operation of cooling operation is as described using Figure 3.

[0057] (Operation at Start of Heating Operation) Next, operation during startup of heating operation and changes in the temperature of the heat medium at each location during startup of heating operation and steady operation will be described with reference to Figures 4 and 5. Figures 4 and 5 show examples of the temperature of the heat medium at each location. Below, as in the case of steady operation described above, an example will be described in which two of the three load devices 3A, 3B, and 3C, 3A and 3B, are performing heating and one load device 3C is not operating.

[0058] As shown in FIG. 4 , in the air conditioning apparatus 100, when the heating operation is started, the first bypass valve 81 is opened, the first flow switching device 6 for the load devices 3A and 3B is set to the side of the second heat medium circuit 5, both the first refrigerant circuit 10 and the second refrigerant circuit 20 are operated (heating), and both the first heat medium circuit 4 and the second heat medium circuit 5 are operated.

[0059] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the first intermediate heat exchanger 11. The refrigerant that flows into the first intermediate heat exchanger 11 exchanges heat with the heat medium flowing through the first heat medium circuit 4, condenses, and liquefies, and is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the heat source side heat exchanger 14. The gas-liquid two-phase refrigerant that flows into the heat source side heat exchanger 14 exchanges heat with air and evaporates, passes through the first flow switching valve 13, and is drawn into the first compressor 12 via an accumulator.

[0060] On the other hand, the heat medium flowing through the first heat medium circuit 4 is heated by the refrigerant flowing through the first intermediate heat exchanger 11 to become hot water, and then flows into the first bypass piping 80 in the relay unit 2 and flows from the first bypass piping 80 to the second intermediate heat exchanger 21 by the first pump 41. The heat medium flowing through the first heat medium circuit 4 is cooled in the second intermediate heat exchanger 21 and returns to the first intermediate heat exchanger 11 of the heat source unit 1. In FIG. 4 , for ease of explanation, the portion of the first heat medium piping 40 through which the heat medium circulates is indicated by a dashed line. That is, when the heating operation is started, the heat medium flowing through the first heat medium circuit 4 bypasses the load device 3 by the load device bypass mechanism 8 of the relay unit 2 and is returned to the heat source unit 1. In the example of FIG. 4 , the temperature of the heat medium heated in the first intermediate heat exchanger 11 and before flowing into the second intermediate heat exchanger 21 of the relay unit 2 is 20° C. The temperature of the heat medium cooled in the second intermediate heat exchanger 21 and returned to the first intermediate heat exchanger 11 is 15°C.

[0061] In the second refrigerant circuit 20, the high-temperature, high-pressure gas refrigerant discharged from the second compressor 23 passes through the second flow switching valve 24 and flows to the third intermediate heat exchanger 22, where it condenses and liquefies through heat exchange with the heat medium flowing in the second heat medium circuit 5. The condensed and liquefied refrigerant is decompressed by the second expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant, flows to the second intermediate heat exchanger 21, and exchanges heat with the heat medium flowing in the first heat medium circuit 4 to evaporate and gasify. The gasified refrigerant passes through the second flow switching valve 24 and is drawn into the second compressor 23 via an accumulator.

[0062] On the other hand, the heat medium flowing through the second heat medium circuit 5 is heated by the refrigerant flowing through the third intermediate heat exchanger 22 to become hot water, and then flows into the load-side heat exchangers 30 of the load devices 3A and 3B, where it is cooled by heat exchange with the indoor air in the indoor space. The cooled heat medium flows into the third intermediate heat exchanger 22 again. In the example of Fig. 4 , the temperature of the heat medium heated in the third intermediate heat exchanger 22 and before flowing into the load devices 3A and 3B that perform heating is 45 [°C]. The temperature of the heat medium cooled in the load devices 3A and 3B and returning to the third intermediate heat exchanger 22 is 40 [°C].

[0063] Thereafter, when the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2 in the first heat medium circuit 4 reaches a predetermined temperature (for example, 45°C), that is, when the temperature of the heat medium supplied from the heat source unit 1 rises to a temperature sufficient for heating, the first bypass valve 81 is closed and steady operation is performed. The operation during steady operation of the heating room operation is as described using Figure 5.

[0064] As explained using Figures 2 and 4, when the air conditioning apparatus 100 starts cooling or heating operation, the second refrigerant circuit 20 of the relay unit 2 cools or heats the room, and the load device bypass mechanism 8 causes the heat medium flowing through the first heat medium circuit 4 to return to the heat source unit 1 without passing through the load device 3. This allows the heat capacity of the heat medium between the heat source unit 1 and the relay unit 2 to be used to cool or heat the heat medium between the relay unit 2 and the load device 3 in the third intermediate heat exchanger 22. This allows the room to be cooled or heated quickly when the cooling or heating operation starts. In other words, the operation standby time until the load device 3 starts operating can be shortened compared to conventional cases.

[0065] In the first embodiment, the second intermediate heat exchanger 21 is provided in the return pipe 40b of the first heat medium pipe 40, and therefore, in particular, the return main pipe 40mb and the heat of the heat medium circulating through the return main pipe 40mb are utilized when the cooling operation or the heating operation is started.

[0066] (First Modification) FIG. 6 is a refrigerant circuit diagram of an air conditioning apparatus 100 according to a first modification of Embodiment 1, illustrating a state at the start of cooling operation. In the first modification, the location of the load device bypass mechanism 8a differs from that of the load device bypass mechanism 8 illustrated in FIG. 2. In the first modification, the first bypass piping 80a is provided at a branch point branching into multiple branch pipes 40d. Specifically, in the first heat medium circuit 4, the first bypass piping 80a is provided in parallel with multiple first flow switching devices 6 provided on the heat medium inlet side of the load-side heat exchanger 30. A first bypass valve 81a is provided in this first bypass piping 80a. For ease of explanation, FIG. 6 illustrates with dashed lines the portion of the first heat medium piping 40 through which the heat medium circulates at the start of cooling operation. As with the load device bypass mechanism 8 illustrated in FIG. 2, the load device bypass mechanism 8a of the first modification also allows the heat medium to bypass the load device 3 and return to the heat source unit 1.

[0067] Furthermore, by providing the load device bypass mechanism 8a at the branch point in the first heat medium circuit 4, the pipes and valves can be arranged together, facilitating maintenance.

[0068] FIG. 7 is a schematic diagram illustrating an air conditioning apparatus 100 according to a second modification of Embodiment 1. The numbers of heat source units 1, relay units 2, and load devices 3 in the air conditioning apparatus 100 are not limited to the above numbers. As shown in FIG. 7 , two or more heat source units 1 may be installed. When multiple heat source units 1 are installed, the heat source units 1 are connected to each other via the first heat medium piping 40. Also, as shown in FIG. 7 , two or more relay units 2 may be installed. When multiple relay units 2 are installed, the relay units 2 are connected to each other via the first heat medium piping 40. In this case, the number of load devices 3 connected to each relay unit 2 is not limited to three as described above. Also, some of the load devices 3 may be connected directly to the heat source unit 1 without going through the relay unit 2. However, the operating mode of the directly connected load devices 3 is the same as the operating mode of the heat source unit 1.

[0069] As described above, the air conditioning apparatus 100 according to Embodiment 1 is an air conditioning apparatus including a heat source unit 1, a relay unit 2 connected to the heat source unit 1, and a plurality of load devices 3A, 3B, and 3C connected to the relay unit 2. The heat source unit 1 has a first refrigerant circuit 10 through which a refrigerant circulates, and a first intermediate heat exchanger 11 through which a heat medium exchanges heat with the refrigerant flowing through the first refrigerant circuit 10. The relay unit 2 has a second refrigerant circuit 20 through which a refrigerant circulates, and a second intermediate heat exchanger 21 through which the heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit 20. The first intermediate heat exchanger 11, the second intermediate heat exchanger 21, and the plurality of load devices 3A, 3B, and 3C are connected by a first heat medium pipe 40, and a first heat medium circuit 4 through which the heat medium circulates is formed. The relay unit 2 has a bypass pipe (for example, a first bypass pipe 80 ) and a flow path switching mechanism (for example, a first bypass valve 81 ) that switch the flow direction of the heat medium in the first heat medium circuit 4 .

[0070] As described above, the relay unit 2 has a bypass pipe and a flow path switching mechanism that switches the flow direction of the heat medium in the first heat medium circuit 4. This allows the air conditioning apparatus 100 to transition to steady operation in stages, passing through states with different heat medium flow directions, when starting operation or switching operation modes. During this time, the heat capacity of the first heat medium circuit 4 can be utilized, allowing indoor heating and cooling to be started up more quickly than before.

[0071] The relay unit 2 also includes a first bypass pipe 80, 80a and a first flow path switching mechanism (first bypass valves 81, 81a) that switch the flow direction of the heat medium in the first heat medium circuit so that the heat medium returns to the heat source unit 1 without passing through the multiple load devices. This allows the flow direction of the heat medium in the first heat medium circuit 4 to be switched so that the heat medium returns to the heat source unit 1 without passing through the multiple load devices 3A, 3B, and 3C when starting heating and cooling operations. This allows the temperature of the main heat medium pipe 40m to be shifted to a temperature appropriate for the operating mode during startup, thereby heating or cooling the room. Furthermore, when transitioning to a steady state, the heat capacity of the main heat medium pipe 40m can be utilized, allowing room heating or cooling to be started up more quickly than before.

[0072] Furthermore, when the heat medium flows through the bypass pipe (the first bypass pipe 80 or the second bypass pipe 90), the second refrigerant circuit 20 is in operation.

[0073] Furthermore, the heat source unit 1 and the relay unit 2 are connected by two pipes through which the heat medium flows, which makes installation easier than in a configuration where they are connected by four pipes.

[0074] The relay unit 2 also has a third intermediate heat exchanger 22 in which the heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit 20. The third intermediate heat exchanger 22 and the plurality of load devices 3 are connected by second heat medium piping 50 to form a second heat medium circuit 5 in which the heat medium circulates. The second refrigerant circuit 20 generates the heat medium for the second heat medium circuit 5 so that the temperature range of the heat medium circulating through the first heat medium circuit 4 is different from that of the heat medium circulating through the first heat medium circuit 4.

[0075] The second refrigerant circuit 20 contains less than 1 kg of propane refrigerant.

[0076] Furthermore, a flammable refrigerant is sealed in the first refrigerant circuit 10, and a non-flammable or slightly flammable refrigerant is sealed in the second refrigerant circuit 20. This allows the amount of flammable refrigerant used throughout the air conditioning apparatus 100 to be reduced.

[0077] Furthermore, a plurality of heat source units 1 are installed in parallel, and two pipes are branched to the plurality of heat source units 1. This makes it possible to apply the system to large-scale facilities.

[0078] Furthermore, a plurality of relay units 2 are installed in parallel, and two pipes are branched to the plurality of relay units 2.

[0079] Embodiment 2 Next, an air conditioning apparatus 100 according to Embodiment 2 will be described with reference to FIGS. 8 to 17. FIG. 8 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 2, illustrating a state during steady operation in cooling-dominated operation. FIG. 9 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 2, illustrating a first state in the process of switching from cooling-dominated operation to heating-dominated operation in FIG. 8. FIG. 10 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 2, illustrating a second state in the process of switching from cooling-dominated operation to heating-dominated operation in FIG. 8. FIG. 11 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 2, illustrating a third state in the process of switching from cooling-dominated operation to heating-dominated operation in FIG. 8. FIG. 12 is a refrigerant circuit diagram of the air conditioning apparatus according to Embodiment 2, illustrating a state during steady operation in heating-dominated operation. Note that the same components as those in the air conditioning apparatus 100 described in Embodiment 1 are designated by the same reference numerals, and their description will be omitted as appropriate.

[0080] In the air conditioning apparatus 100 of the second embodiment, the first heat medium circuit 4 has, as a switching mechanism for switching the flow direction of the heat medium, in addition to the load device bypass mechanism 8 described in the first embodiment, a heat source unit bypass mechanism 9 that returns the heat medium to the load device 3 without passing through the heat source unit 1. Specifically, the first heat medium circuit 4 has a second bypass pipe 90 that connects a point Pc that is downstream of the first intermediate heat exchanger 11 and upstream of the load side heat exchanger 30 in the first heat medium pipe 40 to a point Pd that is upstream of the first intermediate heat exchanger 11 and downstream of the second intermediate heat exchanger 21, and a second bypass valve 91 (hereinafter also referred to as a second flow path switching mechanism) that is provided in the second bypass pipe 90 and adjusts the flow rate of the heat medium. Point Pc is located upstream of the load side heat exchanger 30 in the first heat medium piping 40, and in particular, upstream of the multiple branch pipes 40d that branch off to the load side heat exchangers 30A, 30B, and 30C, i.e., upstream of the first flow path switching device 6.

[0081] The first heat medium circuit 4 of the present embodiment includes the heat source unit bypass mechanism 9 in addition to the configuration of the first heat medium circuit 4 of the first embodiment. In FIG. 8 , the first heat medium piping 40 has a point Pa, which is a branch point to the first bypass piping 80, and a point Pc, which is a branch point to the second bypass piping 90, located upstream of the point Pc. Note that the first bypass piping 80 and the second bypass piping 90 are not used simultaneously, i.e., the heat medium does not flow through the first bypass piping 80 and the second bypass piping 90 simultaneously. Therefore, either the point Pa or the point Pc may be upstream. Furthermore, in the present embodiment, the configuration of the first heat medium circuit 4 is not limited to the above configuration. For example, the load device bypass mechanism 8 may be omitted from the first heat medium circuit 4.

[0082] The second bypass valve 91 is configured, for example, by a two-way valve or the like whose valve opening degree (opening area) can be controlled. The opening degree of the second bypass valve 91 is controlled to control the flow rate of the heat medium flowing into the second bypass piping 90. By opening the second bypass valve 91, at least a portion of the heat medium flowing out of the second intermediate heat exchanger 21 can be caused to flow into the second bypass piping 90 and bypass the heat source unit 1. The second bypass valve 91 is controlled by the control device 7.

[0083] The first heat medium circuit 4 is also provided with a temperature sensor 71 (see FIG. 9 ) that detects a temperature T1 of the heat medium returning from the relay unit 2 to the heat source unit 1. The temperature sensor 71 is provided, for example, at the heat medium outlet of the second intermediate heat exchanger 21. The first heat medium circuit 4 is also provided with a temperature sensor 72 (see FIG. 10 ) that detects a mixed temperature T2 of the heat medium supplied from the heat source unit 1 and the heat medium returned to the upstream side of the load device 3 via the second bypass piping 90. The temperature sensor 72 is provided on the first heat medium piping 40 downstream of point Pc and upstream of a plurality of branch pipes that branch off to the load side heat exchangers 30A, 30B, and 30C.

[0084] (Cooling-dominated operation) Next, steady-state operation of the cooling-dominated operation will be described with reference to Fig. 8. Here, the description will be made taking as an example a case where, of the three load devices 3A, 3B, and 3C, two load devices 3B and 3C perform cooling, one load device 3A performs heating, and the cooling load ΣQc is larger than the heating load ΣQh.

[0085] When the air conditioning apparatus 100 performs the cooling-dominant operation, the first refrigerant circuit 10, the first heat medium circuit 4, the second refrigerant circuit 20, and the second heat medium circuit 5 are operated. The operating mode of the heat source unit 1 is set to cooling, and the operating mode of the relay unit 2 is set to heating. Then, in order to connect the load-side heat exchangers 30 of the load devices 3B and 3C that perform cooling to the first heat medium circuit 4, the first flow switching devices 6 corresponding to the load devices 3B and 3C are set to the side of the first heat medium circuit 4. Furthermore, in order to connect the load-side heat exchanger 30 of the load device 3A that performs heating to the second heat medium circuit 5, the first flow switching device 6 corresponding to the load device 3A is set to the side of the second heat medium circuit 5.

[0086] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the heat source side heat exchanger 14, where it exchanges heat with air and condenses and liquefies. The condensed and liquefied refrigerant is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the first intermediate heat exchanger 11, where it exchanges heat with the heat medium flowing in the first heat medium circuit 4 and evaporates into gas. The gasified refrigerant passes through the first flow switching valve 13 and is drawn into the first compressor 12 via an accumulator.

[0087] Meanwhile, the heat medium flowing through the first heat medium circuit 4 is cooled by the refrigerant flowing through the first intermediate heat exchanger 11 to become chilled water, and then flows via the relay unit 2 to the load-side heat exchangers 30 of the load devices 3B and 3C, where it is heated through heat exchange with the indoor air in the indoor space. The heated heat medium flows to the second intermediate heat exchanger 21, where it is cooled through heat exchange with the refrigerant circulating through the second refrigerant circuit 20, and then flows into the first intermediate heat exchanger 11 again. In the example of FIG. 8 , the temperature of the heat medium cooled in the first intermediate heat exchanger 11 and before flowing into the load devices 3B and 3C that perform cooling is 7 [°C]. The temperature of the heat medium heated in the load devices 3B and 3C and before flowing into the second intermediate heat exchanger 21 is 12 [°C]. The temperature of the heat medium cooled in the second intermediate heat exchanger 21 and returning to the first intermediate heat exchanger 11 is 10 [°C].

[0088] In the second refrigerant circuit 20, the high-temperature, high-pressure gas refrigerant discharged from the second compressor 23 passes through the second flow switching valve 24 and flows to the third intermediate heat exchanger 22, where it condenses and liquefies through heat exchange with the heat medium flowing in the second heat medium circuit 5. The condensed and liquefied refrigerant is decompressed by the second expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant, flows to the second intermediate heat exchanger 21, and exchanges heat with the heat medium flowing in the first heat medium circuit 4 to evaporate and gasify. The gasified refrigerant passes through the second flow switching valve 24 and is drawn into the second compressor 23 via an accumulator.

[0089] On the other hand, the heat medium flowing through the second heat medium circuit 5 is heated by the refrigerant flowing through the third intermediate heat exchanger 22 to become hot water, and then flows into the load-side heat exchanger 30 of the load device 3A, where it is cooled by heat exchange with the indoor air in the indoor space. The cooled heat medium flows into the third intermediate heat exchanger 22 again. In the example of Fig. 8 , the temperature of the heat medium heated in the third intermediate heat exchanger 22 and before flowing into the load device 3A that performs heating is 45 [°C]. The temperature of the heat medium cooled in the load device 3A and returning to the third intermediate heat exchanger 22 is 40 [°C].

[0090] (Heating-dominated operation) Next, steady-state operation of the heating-dominated operation will be described with reference to Fig. 12. Here, the description will be made taking as an example a case where, of the three load devices 3A, 3B, and 3C, two load devices 3A and 3B perform heating, one load device 3C performs cooling, and the heating load ΣQh is larger than the cooling load ΣQc.

[0091] When the air conditioning apparatus 100 performs the heating-dominant operation, the first refrigerant circuit 10, the first heat medium circuit 4, the second refrigerant circuit 20, and the second heat medium circuit 5 are operated. The operation mode of the heat source unit 1 is set to heating, and the operation mode of the relay unit 2 is set to cooling. Then, in order to connect the load-side heat exchanger 30 of the load device 3C that performs cooling to the second heat medium circuit 5, the first flow switching device 6 corresponding to the load device 3C is set to the side of the second heat medium circuit 5. Furthermore, in order to connect the load-side heat exchangers 30 of the load devices 3A and 3B that perform heating to the first heat medium circuit 4, the first flow switching devices 6 corresponding to the load devices 3A and 3B are set to the side of the first heat medium circuit 4.

[0092] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the first intermediate heat exchanger 11. The refrigerant that flows into the first intermediate heat exchanger 11 exchanges heat with the heat medium flowing through the first heat medium circuit 4, condenses, and liquefies, and is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the heat source side heat exchanger 14. The gas-liquid two-phase refrigerant that flows into the heat source side heat exchanger 14 exchanges heat with air and evaporates, passes through the first flow switching valve 13, and is drawn into the first compressor 12 via an accumulator.

[0093] Meanwhile, the heat medium flowing through the first heat medium circuit 4 is heated by the refrigerant flowing through the first intermediate heat exchanger 11 to become hot water, and then flows via the relay unit 2 to the load-side heat exchangers 30 of the load devices 3A and 3B, where it is cooled by heat exchange with the indoor air in the indoor space. The cooled heat medium flows to the second intermediate heat exchanger 21, where it is heated by heat exchange with the refrigerant circulating through the second refrigerant circuit 20, and then flows into the first intermediate heat exchanger 11 again. In the example of FIG. 12 , the temperature of the heat medium heated in the first intermediate heat exchanger 11 and before flowing into the load devices 3A and 3B that perform heating is 45° C. The temperature of the heat medium cooled in the load devices 3A and 3B and before flowing into the second intermediate heat exchanger 21 is 40° C. The temperature of the heat medium heated in the second intermediate heat exchanger 21 and returning to the first intermediate heat exchanger 11 is 42° C.

[0094] In the second refrigerant circuit 20, high-temperature, high-pressure gas refrigerant discharged from the second compressor 23 passes through the second flow switching valve 24 and flows to the second intermediate heat exchanger 21, where it condenses and liquefies through heat exchange with the heat medium flowing in the first heat medium circuit 4. The condensed and liquefied refrigerant is decompressed in the second expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant, flows to the third intermediate heat exchanger 22, and exchanges heat with the heat medium flowing in the second heat medium circuit 5 to evaporate and gasify. The gasified refrigerant passes through the second flow switching valve 24 and is drawn into the second compressor 23 via an accumulator.

[0095] On the other hand, the heat medium flowing through the second heat medium circuit 5 is cooled by the refrigerant flowing in the third intermediate heat exchanger 22 to become chilled water, and then flows into the load-side heat exchanger 30 of the load device 3C, where it is heated by heat exchange with the indoor air in the indoor space. The heated heat medium flows into the third intermediate heat exchanger 22 again. In the example of Fig. 12 , the temperature of the heat medium cooled in the third intermediate heat exchanger 22 and before flowing into the load device 3C that performs cooling is 7 [°C]. The temperature of the heat medium heated in the load device 3C and returning to the third intermediate heat exchanger 22 is 12 [°C].

[0096] (Switching from cooling-dominated operation to heating-dominated operation) Figure 13 is a diagram showing the control sequence for switching the operation mode from cooling-dominated operation to heating-dominated operation in the air conditioning apparatus 100 according to Embodiment 2. Below, the operation when switching from cooling-dominated operation (Figure 8) to heating-dominated operation (Figure 12) will be explained step by step with reference to Figures 8 to 13. Each figure illustrates the temperature of the heat medium at each location.

[0097] Here, as shown in Figure 8, the state is defined as a state in which two load devices 3B and 3C are performing cooling and one load device 3A is performing heating, but then load device 3B is switched from cooling to heating, and the state is changed to one in which two load devices 3A and 3B are performing heating and one load device 3C is performing cooling.

[0098] As shown in Fig. 13, during cooling-dominated operation (see Fig. 8), the control device 7 determines whether the heating load ΣQh is greater than the cooling load ΣQc (step S1). If it is determined that the heating load ΣQh is greater than the cooling load ΣQc (step S1; YES), the control device 7 switches the operation mode of the heat source unit 1 from cooling to heating (step S2). On the other hand, if it is determined that the heating load ΣQh is equal to or less than the cooling load ΣQc (step S1; NO), the control device 7 continues the cooling-dominated operation shown in Fig. 8. During cooling-dominated operation, the control device 7 performs the determination in step S1 every time a predetermined time elapses.

[0099] Here, the cooling load ΣQc is the sum of the required capacities Qc of the load devices 3 that perform cooling (load devices 3B and 3C in FIG. 8), and the heating load ΣQh is the sum of the required capacities Qh of the load devices 3 that perform heating (load device 3A in FIG. 8). The determination in step S1 is a determination of whether the heat source unit 1 should heat or cool the heat medium. This determination may be made based on whether the temperature of the heat medium returning to the heat source unit 1 is higher than the temperature of the heat medium supplied to the load devices 3, instead of being made based on the load of the load devices 3 or the number of operating units as described above.

[0100] In step S2, the operation mode of the heat source unit 1 is switched from cooling to heating by switching the first flow path switching valve 13 of the first refrigerant circuit 10, as shown in Fig. 9. At this stage, only the operation mode of the heat source unit 1 is switched, and the relay unit 2 is maintained in a state during cooling-dominated operation, i.e., heating. Hereinafter, this state in which only the operation mode of the heat source unit 1 is switched is referred to as the first state.

[0101] In the first state, the operation mode of the relay unit 2 remains heating, and the heat medium returning from the load device 3C performing cooling is cooled in the second intermediate heat exchanger 21 of the relay unit 2 and returns to the first intermediate heat exchanger 11 of the heat source unit 1. Then, the heat medium is heated in the first intermediate heat exchanger 11 of the heat source unit 1 that has been switched to the heating mode, and is supplied to the load device 3C.

[0102] 9 shows the temperatures of each part immediately after the first state is reached. In the example of FIG. 9 , the temperature of the heat medium heated by the load device 3C performing cooling and before flowing into the second intermediate heat exchanger 21 is 12 [°C]. The temperature of the heat medium cooled by the second intermediate heat exchanger 21 and returning to the first intermediate heat exchanger 11 is 6 [°C]. The temperature of the heat medium heated by the first intermediate heat exchanger 11 and before flowing into the load device 3C is 7 [°C]. Furthermore, the temperature of the heat medium heated by the third intermediate heat exchanger 22 and before flowing into the load devices 3A, 3B performing heating is 45 [°C]. The temperature of the heat medium cooled by the load devices 3A, 3B and returning to the third intermediate heat exchanger 22 is 40 [°C]. Thus, immediately after the first state is reached, the temperature of the heat medium in the main heat medium pipe 40m is still low (6 [°C] in FIG. 9 ).

[0103] After switching the operation mode of the heat source unit 1 from cooling to heating in step S2, the control device 7 determines whether the temperature T1 of the heat medium returning from the relay unit 2 to the heat source unit 1 is lower than a predetermined temperature Ta (e.g., 5°C) (step S3). If it is determined that the temperature T1 is lower than the temperature Ta (step S3; YES), the control device 7 opens the second bypass valve 91 and transitions to an operation mode transition state (hereinafter also referred to as the second state) as shown in FIG. 10 (step S4). At this stage, the relay unit 2 remains in a cooling-dominated operation state, i.e., heating. On the other hand, if it is determined that the temperature T1 is equal to or higher than the temperature Ta (step S3; NO), the control device 7 continues the first state shown in FIG. 9 . In the first state, the control device 7 performs the determination in step S3 every time a predetermined time elapses.

[0104] The second state is a transition state for smoothly switching the operation mode of the relay unit 2 because heat balance was not achieved in the first state. In the first state, the operation mode of the heat source unit 1 is switched to heating, causing the temperature of the heat medium supplied from the heat source unit 1 to rise (for example, to 20°C). Therefore, in the second state, the second bypass valve 91 is opened, and a portion of the heat medium (for example, chilled water with a temperature of 5°C) from the second intermediate heat exchanger 21 of the relay unit 2 is merged with the heat medium supplied from the heat source unit 1 and then supplied to the load device 3C performing cooling. The temperature of the heat medium after this merger, i.e., the mixed temperature T2, is 7°C in the example of FIG. 10. In the second state, the opening degree of the second bypass valve 91 is adjusted so that the mixed temperature T2 becomes the desired temperature (here, 7°C).

[0105] In the second state, the control device 7 determines whether the second bypass valve 91 is fully open (step S5). If it is determined that the second bypass valve 91 is fully open (step S5; YES), the control device 7 closes the second bypass valve 91, switches the operation mode of the relay unit 2 from heating to cooling, and temporarily turns off all load devices 3A, 3B, and 3C to exchange the water temperature (step S6). This state will be referred to as the third state hereinafter. On the other hand, if it is determined that the second bypass valve 91 is not fully open (step S5; NO), the control device 7 continues the second state shown in FIG. 10 . In the second state, the control device 7 performs the determination in step S5 every time a predetermined time elapses.

[0106]

[0063] In this way, even in the second state, if the temperature of the heat medium supplied from the heat source unit 1 rises, the system transitions to the third state. In step S6, the operation mode of the relay unit 2 is switched from heating to cooling by switching the second flow path switching valve 24 of the second refrigerant circuit 20, as shown in Fig. 11. Accordingly, the first flow path switching device 6 corresponding to the load devices 3A and 3B performing heating is switched to the first heat medium circuit 4 side, and the first flow path switching device 6 corresponding to the load device 3C performing cooling is switched to the second heat medium circuit 5 side. In the third state, the heat medium from the heat source unit 1 is supplied to the load devices 3A and 3B performing heating, and chilled water generated by the relay unit 2 is supplied to the load device 3C performing cooling, but the heating and cooling of the load devices 3A, 3B, and 3C is temporarily stopped.

[0107] In the example of Fig. 11 , the temperature of the heat medium heated in the first intermediate heat exchanger 11 and before flowing into the load devices 3A and 3B is 35°C, which is lower than the 45°C during steady operation shown in Fig. 12 . In the third state, the load devices 3 are stopped, and therefore the temperature of the heat medium before flowing from the load devices 3A and 3B into the second intermediate heat exchanger 21 is 35°C, the same as the temperature of the heat medium before flowing into the load devices 3A and 3B. The temperature of the heat medium heated in the second intermediate heat exchanger 21 and flowing out of the relay unit 2 is 37°C, and the temperature of the heat medium flowing into the heat source unit 1 after passing through the main heat medium pipe 40 m is 30°C, which is lower than that.

[0108] 11, the temperature of the heat medium cooled in the third intermediate heat exchanger 22 and before flowing into the load device 3C is 10°C, which is higher than 7°C during steady operation shown in Fig. 12. Note that in the third state, the load device 3 is stopped from operating, and therefore the temperature of the heat medium returning from the load device 3C to the third intermediate heat exchanger 22 is 10°C, the same as the temperature of the heat medium before flowing into the load device 3C.

[0109] The third state is a standby time for the load devices 3 to adjust the temperature of the heat medium. During this time, the air conditioning apparatus 100 needs to reheat the first heat medium circuit 4 by an amount equivalent to the heat capacity of the main heat medium pipe 40 m, and needs to recool the second heat medium circuit 5 by an amount equivalent to the heat capacity of the heat medium pipes arranged in the relay unit 2. However, by shifting operation in stages as described above, the time during which the operation of the load devices 3 is stopped and the temperature of the heat medium is adjusted (the time in the third state) can be shortened compared to the standby time for operation in the conventional configuration.

[0110] In the third state, the control device 7 determines whether the temperature of the water supplied to the load device 3 is sufficient for cooling or heating (step S7). If it is determined that the temperature of the water supplied to the load device 3 is sufficient for cooling or heating (step S7; YES), the control device 7 turns on the load device 3 that was stopped (step S8), and steady-state operation with heating as the main operation is performed as shown in FIG. 12 (step S9).

[0111] (Switching from heating-dominant operation to cooling-dominant operation) Fig. 14 is a refrigerant circuit diagram of an air conditioning apparatus according to Embodiment 2, and is a diagram showing a first state in the process of switching from the heating-dominant operation of Fig. 12 to the cooling-dominant operation. Fig. 15 is a refrigerant circuit diagram of an air conditioning apparatus according to Embodiment 2, and is a diagram showing a second state in the process of switching from the heating-dominant operation of Fig. 12 to the cooling-dominant operation. Fig. 16 is a refrigerant circuit diagram of an air conditioning apparatus according to Embodiment 2, and is a diagram showing a third state in the process of switching from the heating-dominant operation of Fig. 12 to the cooling-dominant operation. Fig. 17 is a diagram showing a control sequence for switching the operation mode from heating-dominant operation to cooling-dominant operation in an air conditioning apparatus according to Embodiment 2.

[0112] In the cooling-dominant operation of FIG. 14, the load device 3B switches from heating to cooling from the heating-dominant operation state shown in FIG. 12, and two load devices 3B and 3C perform cooling, while one load device 3A performs heating. FIGS. 12, 14 to 16, and 8 show the gradual changes that occur when switching from heating-dominant operation to cooling-dominant operation. Each figure illustrates the temperature of the heat medium at each location. Below, the operation and control sequence when switching from heating-dominant operation to cooling-dominant operation will be described with reference to FIGS. 8, 12, and 14 to 17.

[0113] As shown in Fig. 17, during heating-dominated operation (see Fig. 12), the control device 7 determines whether the cooling load ΣQc is greater than the heating load ΣQh (step S11). If it is determined that the cooling load ΣQc is greater than the heating load ΣQh (step S11; YES), the control device 7 switches the operation mode of the heat source unit 1 from heating to cooling (step S12). On the other hand, if it is determined that the cooling load ΣQc is equal to or less than the heating load ΣQh (step S11; NO), the control device 7 continues the heating-dominated operation shown in Fig. 12. During heating-dominated operation, the control device 7 performs the determination in step S11 every time a predetermined time elapses.

[0114] In step S12, the operation mode of the heat source unit 1 is switched from heating to cooling by switching the first flow path switching valve 13 of the first refrigerant circuit 10, as shown in Fig. 14. At this stage, only the operation mode of the heat source unit 1 is switched, and the relay unit 2 is maintained in a state during heating-dominated operation, i.e., cooling. Hereinafter, this state in which only the operation mode of the heat source unit 1 is switched will be referred to as the first state.

[0115] In the first state, the operation mode of the relay unit 2 remains the cooling mode, and the heat medium returning from the load device 3A performing heating is heated in the second intermediate heat exchanger 21 of the relay unit 2 and returns to the first intermediate heat exchanger 11 of the heat source unit 1. Then, the heat medium is cooled in the first intermediate heat exchanger 11 of the heat source unit 1, which has been switched to the cooling mode, and is supplied to the load device 3A.

[0116] 14 shows the temperatures of each part immediately after the first state is reached. In the example of FIG. 14 , the temperature of the heat medium cooled by the load device 3A performing heating and before flowing into the second intermediate heat exchanger 21 is 40° C. The temperature of the heat medium heated by the second intermediate heat exchanger 21 and returning to the first intermediate heat exchanger 11 is 46° C. The temperature of the heat medium cooled by the first intermediate heat exchanger 11 and before flowing into the load device 3A is 45° C. The temperature of the heat medium cooled by the third intermediate heat exchanger 22 and before flowing into the load devices 3B and 3C performing cooling is 7° C. The temperature of the heat medium heated by the load devices 3B and 3C and returning to the third intermediate heat exchanger 22 is 12° C. Thus, immediately after the first state is reached, the temperature of the heat medium in the main heat medium pipe 40 m is still high (46° C. in FIG. 14 ).

[0117] After switching the operation mode of the heat source unit 1 from heating to cooling in step S12, the control device 7 determines whether the temperature T1 of the heat medium returning from the relay unit 2 to the heat source unit 1 is greater than a predetermined temperature Tb (e.g., 50°C) (step S13). If it is determined that the temperature T1 is greater than the temperature Tb (step S13; YES), the control device 7 opens the second bypass valve 91 and transitions to an operation mode transition state (hereinafter also referred to as the second state) as shown in FIG. 15 (step S14). At this stage, the relay unit 2 remains in a heating-dominated operation state, i.e., cooling. On the other hand, if it is determined that the temperature T1 is equal to or less than the temperature Tb (step S13; NO), the control device 7 continues the first state shown in FIG. 14. In the first state, the control device 7 performs the determination of step S13 every time a predetermined time elapses.

[0118] In the first state described above, the operation mode of the heat source unit 1 is switched to cooling, and the temperature of the heat medium supplied from the heat source unit 1 drops (for example, to 20° C.). Therefore, in the second state, the second bypass valve 91 is opened, and a portion of the hot water (for example, having a temperature of 40° C.) from the second intermediate heat exchanger 21 of the relay unit 2 is merged with the heat medium supplied from the heat source unit 1, and then supplied to the load device 3A that performs heating.

[0119] In the second state, the control device 7 determines whether the second bypass valve 91 is fully open (step S15). If it is determined that the second bypass valve 91 is fully open (step S15; YES), the control device 7 closes the second bypass valve 91, switches the operation mode of the relay unit 2 from cooling to heating, and temporarily turns off all load devices 3 to exchange the water temperature (step S16). This state will be referred to as the third state hereinafter. On the other hand, if it is determined that the second bypass valve 91 is not fully open (step S15; NO), the control device 7 continues the second state shown in FIG. 15 . In the second state, the control device 7 performs the determination in step S15 every time a predetermined time elapses.

[0120] 16 , the operation mode of the relay unit 2 is switched from cooling to heating by switching the second flow path switching valve 24 of the second refrigerant circuit 20. Accordingly, the first flow path switching device 6 corresponding to the load devices 3B and 3C performing cooling is switched to the first heat medium circuit 4, and the first flow path switching device 6 corresponding to the load device 3A performing heating is switched to the second heat medium circuit 5. In the third state, the heat medium from the heat source unit 1 is supplied to the load devices 3B and 3C performing heating, and hot water produced by the relay unit 2 is supplied to the load device 3A performing heating, but the cooling and heating of the load devices 3A, 3B, and 3C is temporarily stopped.

[0121] In the example of Fig. 16, the temperature of the heat medium cooled in the first intermediate heat exchanger 11 and before flowing into the load devices 3B and 3C is 20°C, which is higher than the 7°C during steady operation shown in Fig. 8. In the third state, the load devices 3 are stopped, and therefore the temperature of the heat medium before flowing from the load devices 3B and 3C into the second intermediate heat exchanger 21 is 20°C, the same as the temperature of the heat medium before flowing into the load devices 3B and 3C. The temperature of the heat medium cooled in the second intermediate heat exchanger 21 and flowing out of the relay unit 2 is 17°C, and the temperature of the heat medium flowing into the heat source unit 1 after passing through the main heat medium pipe 40m is 25°C, which is higher than that.

[0122] 16, the temperature of the heat medium heated in the third intermediate heat exchanger 22 and before flowing into the load device 3A is 35°C, which is lower than 45°C during steady operation shown in Fig. 8. In the third state, the load device 3 is stopped from operating, and therefore the temperature of the heat medium returning from the load device 3A to the third intermediate heat exchanger 22 is 35°C, the same as the temperature of the heat medium before flowing into the load device 3A.

[0123] The third state is a standby time for the load devices 3 to regulate the temperature of the heat medium. During this time, the air conditioning apparatus 100 needs to recool the first heat medium circuit 4 by an amount corresponding to the heat capacity of the main heat medium piping 40m (the first heat medium piping 40 from the heat source unit 1 to the relay unit 2), and it also needs to reheat the second heat medium circuit 5 by an amount corresponding to the heat capacity of the heat medium piping arranged in the relay unit 2. However, by shifting the operation in stages as described above, the time during which the operation of the load devices 3 is stopped and the temperature of the heat medium is regulated (the period of the third state) can be shortened compared to the standby time for operation in the conventional configuration.

[0124] In the second embodiment, the second intermediate heat exchanger 21 is provided in the return pipe 40b of the first heat medium pipe 40, and therefore, in particular, the return main pipe 40mb and the heat of the heat medium circulating through the return main pipe 40mb are utilized when switching between cooling-dominated operation and heating-dominated operation.

[0125] In the third state, the control device 7 determines whether the temperature of the water supplied to the load device 3 is sufficient for cooling or heating (step S17). If it is determined that the temperature of the water supplied to the load device 3 is sufficient for cooling or heating (step S17; YES), the control device 7 turns on the load device 3 that was stopped (step S18), and the steady-state operation of the cooling-dominated operation as shown in FIG. 8 is performed (step S19).

[0126] As described above, the air conditioning apparatus 100 according to Embodiment 2 is an air conditioning apparatus including a heat source unit 1, a relay unit 2 connected to the heat source unit 1, and a plurality of load devices 3A, 3B, and 3C connected to the relay unit 2. The heat source unit 1 has a first refrigerant circuit 10 through which a refrigerant circulates, and a first intermediate heat exchanger 11 through which a heat medium exchanges heat with the refrigerant flowing through the first refrigerant circuit 10. The relay unit 2 has a second refrigerant circuit 20 through which a refrigerant circulates, and a second intermediate heat exchanger 21 through which the heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit 20. The first intermediate heat exchanger 11, the second intermediate heat exchanger 21, and the plurality of load devices 3A, 3B, and 3C are connected by a first heat medium pipe 40, and a first heat medium circuit 4 through which the heat medium circulates is formed. The relay unit 2 has a second bypass pipe 90 and a second flow path switching mechanism (second bypass valve 91) that switch the flow direction of the heat medium in the first heat medium circuit 4 so that the heat medium returns to the multiple load devices 3A, 3B, and 3C without passing through the heat source unit 1. This allows for indoor heating and cooling by switching the flow direction of the heat medium in the first heat medium circuit 4 so that the heat medium returns to the multiple load devices 3 without passing through the heat source unit 1 when switching between heating-dominated operation and cooling-dominated operation, thereby shifting the temperature of the main heat medium pipe 40m to a value appropriate for the switched-to operating mode. When transitioning to a steady state, the heat capacity of the main heat medium pipe 40m can be utilized, allowing for faster start-up of indoor heating and cooling than before.

[0127] Third Embodiment Next, an air conditioning apparatus 100 according to a third embodiment will be described with reference to FIGS. 18 to 21 . FIG. 18 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to the third embodiment, illustrating the state at the start of cooling operation. FIG. 19 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to the third embodiment, illustrating the state during steady cooling operation. FIG. 20 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to the third embodiment, illustrating the state at the start of heating operation. FIG. 21 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to the third embodiment, illustrating the state during steady heating operation. Arrows shown in FIGS. 18 to 21 indicate the flow of heat medium. In the air conditioning apparatus 100 according to the third embodiment, the configuration of the first heat medium circuit 4 differs from that in the first embodiment. Note that components that are the same as or correspond to those in the air conditioning apparatus 100 described in the first embodiment are denoted by the same reference numerals, and repeated description may be omitted.

[0128] In the first embodiment, the first intermediate heat exchanger 11, the load side heat exchanger 30, and the second intermediate heat exchanger 21 are connected in this order by the first heat medium piping 40, but in the third embodiment, the first intermediate heat exchanger 11, the second intermediate heat exchanger 21, and the load side heat exchanger 30 are connected in this order by the first heat medium piping 40. That is, the second intermediate heat exchanger 21 is provided in the forward piping 40o of the first heat medium piping 40, through which the heat medium flows from the heat source unit 1 to the load device 3. Specifically, the second intermediate heat exchanger 21 is connected to the forward main piping 40mo, through which the heat medium flows from the heat source unit 1 to the relay unit 2, of the two main heat medium piping 40m (the forward main piping 40mo and the return main piping 40mb) that connect the heat source unit 1 and the relay unit 2. The second intermediate heat exchanger 21 is connected to a pipe 40ro that is connected to the first flow switching device 6 on the inflow side of the load devices 3A, 3B, and 3C within the relay unit 2.

[0129] The first pump 41 is provided in the relay unit 2. The first pump 41 is provided in the first heat medium piping 40 downstream of the load side heat exchanger 30 and upstream of the first intermediate heat exchanger 11.

[0130] In the third embodiment, as in the first embodiment, a load device bypass mechanism 8 is provided that returns the heat medium to the heat source unit 1 without passing through the load devices 3A, 3B, and 3C. In the third embodiment, the first bypass piping 80 connects a point Pa1 in the first heat medium piping 40 that is downstream of the second intermediate heat exchanger 21 and upstream of the load side heat exchanger 30, to a point Pb1 that is downstream of the load side heat exchanger 30 and upstream of the first intermediate heat exchanger 11. The point Pa1 is upstream of the load side heat exchanger 30 in the first heat medium piping 40, and in particular, is upstream of the multiple branch pipes 40d that branch into the load side heat exchangers 30A, 30B, and 30C, i.e., is upstream of the first flow switching device 6. The point Pb1 is also within the relay unit 2 in the first heat medium piping 40, and is upstream of the first pump 41 (the heat medium suction side).

[0131] Also in the third embodiment, as in the first embodiment, the first heat medium circuit 4 is provided with a temperature sensor 73 that detects the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2. In the third embodiment, the temperature sensor 73 is provided, for example, at the heat medium inlet of the second intermediate heat exchanger 21.

[0132] The air conditioning apparatus 100 of embodiment 3 also has four modes: cooling operation, heating operation, cooling-dominated operation, and heating-dominated operation, as in embodiment 1. The operation of the air conditioning apparatus 100 and the flow of the heat medium in heating operation and cooling operation will be described in detail.

[0133] First, the operation during startup of cooling operation, the operation during steady operation of cooling operation, and the change in the temperature of the heat medium at each location during startup and steady operation of cooling operation will be described with reference to Figures 18 and 19. Figures 18 and 19 illustrate the temperature of the heat medium at each location. Below, an example will be described in which, of the three load devices 3A, 3B, and 3C, two load devices 3B and 3C are performing cooling, and one load device 3A is not operating.

[0134] As shown in FIG. 18 , in the air conditioning apparatus 100, when cooling operation is started, the first bypass valve 81 is opened, the first flow switching device 6 for the load devices 3B and 3C is set to the side of the second heat medium circuit 5, both the first refrigerant circuit 10 and the second refrigerant circuit 20 are operated (cooling), and both the first heat medium circuit 4 and the second heat medium circuit 5 are operated.

[0135] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the heat source side heat exchanger 14, where it exchanges heat with air and condenses and liquefies. The condensed and liquefied refrigerant is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the first intermediate heat exchanger 11, where it exchanges heat with the heat medium flowing in the first heat medium circuit 4 and evaporates into gas. The gasified refrigerant passes through the first flow switching valve 13 and is drawn into the first compressor 12 via an accumulator.

[0136] On the other hand, the heat medium flowing through the first heat medium circuit 4 is cooled by the refrigerant flowing through the first intermediate heat exchanger 11 to become chilled water, and then flows to the second intermediate heat exchanger 21 in the relay unit 2. The heat medium flowing through the first heat medium circuit 4 is heated in the second intermediate heat exchanger 21, flows into the first bypass piping 80, and is returned to the first intermediate heat exchanger 11 of the heat source unit 1 from the first bypass piping 80 by the first pump 41. In FIG. 18 , for ease of explanation, the portion of the first heat medium piping 40 through which the heat medium circulates is indicated by a dashed line. That is, when cooling operation is started, the heat medium flowing through the first heat medium circuit 4 bypasses the load device 3 by the load device bypass mechanism 8 of the relay unit 2 and is returned to the heat source unit 1. In the example of FIG. 18 , the temperature of the heat medium cooled in the first intermediate heat exchanger 11 and before flowing into the second intermediate heat exchanger 21 of the relay unit 2 is 15° C. The temperature of the heat medium that is heated in the second intermediate heat exchanger 21 and returns to the first intermediate heat exchanger 11 is 20°C.

[0137] In the second refrigerant circuit 20, high-temperature, high-pressure gas refrigerant discharged from the second compressor 23 passes through the second flow switching valve 24 and flows to the second intermediate heat exchanger 21, where it condenses and liquefies through heat exchange with the heat medium flowing in the first heat medium circuit 4. The condensed and liquefied refrigerant is decompressed in the second expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant, flows to the third intermediate heat exchanger 22, and exchanges heat with the heat medium flowing in the second heat medium circuit 5 to evaporate and gasify. The gasified refrigerant passes through the second flow switching valve 24 and is drawn into the second compressor 23 via an accumulator.

[0138] On the other hand, the heat medium flowing through the second heat medium circuit 5 is cooled by the refrigerant flowing in the third intermediate heat exchanger 22 to become chilled water, and then flows into the load-side heat exchangers 30 of the load devices 3B and 3C, where it is heated by heat exchange with the indoor air in the indoor space. The heated heat medium flows into the third intermediate heat exchanger 22 again. In the example of Fig. 18 , the temperature of the heat medium cooled in the third intermediate heat exchanger 22 and before flowing into the load devices 3B and 3C that perform cooling is 7 [°C]. The temperature of the heat medium heated in the load device 3C and returning to the third intermediate heat exchanger 22 is 12 [°C].

[0139] Thereafter, when the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2 in the first heat medium circuit 4 reaches a predetermined temperature (for example, 7°C), that is, when the temperature of the heat medium supplied from the heat source unit 1 drops to a temperature sufficient for cooling, the first bypass valve 81 is closed and steady-state operation is performed.

[0140] As shown in Figure 19, during steady-state operation of the cooling operation, the first flow path switching device 6 for the load devices 3B and 3C is set to the side of the first heat medium circuit 4, and the first flow path switching device 6 for the load device 3A is set to the side of the second heat medium circuit 5, the second refrigerant circuit 20 and the second heat medium circuit 5 are stopped, and only the first refrigerant circuit 10 and the first heat medium circuit 4 are operated.

[0141] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the heat source side heat exchanger 14, where it exchanges heat with air and condenses and liquefies. The condensed and liquefied refrigerant is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the first intermediate heat exchanger 11, where it exchanges heat with the heat medium flowing in the first heat medium circuit 4 and evaporates into gas. The gasified refrigerant passes through the first flow switching valve 13 and is drawn into the first compressor 12 via an accumulator.

[0142] On the other hand, the heat medium flowing through the first heat medium circuit 4 is cooled by the refrigerant flowing through the first intermediate heat exchanger 11 to become cold water, and then flows through the relay unit 2 to the load-side heat exchanger 30, where it is heated by heat exchange with the indoor air in the indoor space. The heated heat medium flows through the relay unit 2 and again into the first intermediate heat exchanger 11.

[0143] 19 , the temperature of the heat medium cooled in the first intermediate heat exchanger 11 and flowing into the relay unit 2 is 7°C, which is lower than at startup. During steady-state operation, the second refrigerant circuit 20 and the second heat medium circuit 5 are stopped, so the heat medium at 7°C flows from the relay unit 2 to the load devices 3B and 3C that perform cooling. The temperature of the heat medium after being heated in the load devices 3B and 3C is 12°C. The temperature of the heat medium returning from the load devices 3B and 3C to the first intermediate heat exchanger 11 via the relay unit 2 is also 12°C.

[0144] Next, the operation during startup of the heating operation, the operation during steady operation of the heating operation, and the change in the temperature of the heat medium at each part during startup and steady operation of the heating operation will be described with reference to Figures 20 and 21. Figures 20 and 21 show examples of the temperature of the heat medium at each part. Below, an example will be described in which two of the three load devices 3A, 3B, and 3C, 3A and 3B, are performing heating and one load device 3C is not operating.

[0145] As shown in FIG. 20 , in the air conditioning apparatus 100, when heating operation is started, the first bypass valve 81 is opened, the first flow switching device 6 for the load devices 3A and 3B is set to the side of the second heat medium circuit 5, both the first refrigerant circuit 10 and the second refrigerant circuit 20 are operated (heating), and both the first heat medium circuit 4 and the second heat medium circuit 5 are operated.

[0146] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the first intermediate heat exchanger 11. The refrigerant that flows into the first intermediate heat exchanger 11 exchanges heat with the heat medium flowing through the first heat medium circuit 4, condenses, and liquefies, and is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the heat source side heat exchanger 14. The gas-liquid two-phase refrigerant that flows into the heat source side heat exchanger 14 exchanges heat with air and evaporates, passes through the first flow switching valve 13, and is drawn into the first compressor 12 via an accumulator.

[0147] On the other hand, the heat medium flowing through the first heat medium circuit 4 is heated by the refrigerant flowing through the first intermediate heat exchanger 11 to become hot water, and then flows to the second intermediate heat exchanger 21 in the relay unit 2. The heat medium flowing through the first heat medium circuit 4 is cooled in the second intermediate heat exchanger 21, flows into the first bypass piping 80, and is returned to the first intermediate heat exchanger 11 of the heat source unit 1 from the first bypass piping 80 by the first pump 41. In FIG. 20 , for ease of explanation, the portion of the first heat medium piping 40 through which the heat medium circulates is indicated by a dashed line. That is, when the heating operation is started, the heat medium flowing through the first heat medium circuit 4 bypasses the load device 3 by the load device bypass mechanism 8 of the relay unit 2 and is returned to the heat source unit 1. In the example of FIG. 20 , the temperature of the heat medium heated in the first intermediate heat exchanger 11 and before flowing into the second intermediate heat exchanger 21 of the relay unit 2 is 20° C. The temperature of the heat medium cooled in the second intermediate heat exchanger 21 and returned to the first intermediate heat exchanger 11 is 15°C.

[0148] In the second refrigerant circuit 20, the high-temperature, high-pressure gas refrigerant discharged from the second compressor 23 passes through the second flow switching valve 24 and flows to the third intermediate heat exchanger 22, where it condenses and liquefies through heat exchange with the heat medium flowing in the second heat medium circuit 5. The condensed and liquefied refrigerant is decompressed by the second expansion mechanism 25 to become a low-pressure gas-liquid two-phase refrigerant, flows to the second intermediate heat exchanger 21, and exchanges heat with the heat medium flowing in the first heat medium circuit 4 to evaporate and gasify. The gasified refrigerant passes through the second flow switching valve 24 and is drawn into the second compressor 23 via an accumulator.

[0149] On the other hand, the heat medium flowing through the second heat medium circuit 5 is heated by the refrigerant flowing through the third intermediate heat exchanger 22 to become hot water, and then flows into the load-side heat exchangers 30 of the load devices 3A and 3B, where it is cooled by heat exchange with the indoor air in the indoor space. The cooled heat medium flows into the third intermediate heat exchanger 22 again. In the example of Fig. 20 , the temperature of the heat medium heated in the third intermediate heat exchanger 22 and before flowing into the load devices 3A and 3B that perform heating is 45 [°C]. The temperature of the heat medium cooled in the load devices 3A and 3B and returning to the third intermediate heat exchanger 22 is 40 [°C].

[0150] Thereafter, when the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2 in the first heat medium circuit 4 reaches a predetermined temperature (for example, 45°C), that is, when the temperature of the heat medium supplied from the heat source unit 1 rises to a temperature sufficient for heating, the first bypass valve 81 is closed and steady-state operation is performed.

[0151] As shown in FIG. 21 , during steady-state heating operation, the first flow path switching device 6 for the load devices 3A and 3B is set to the side of the first heat medium circuit 4, and the first flow path switching device 6 for the load device 3C is set to the side of the second heat medium circuit 5, the second refrigerant circuit 20 and the second heat medium circuit 5 are stopped, and only the first refrigerant circuit 10 and the first heat medium circuit 4 are operated.

[0152] In the first refrigerant circuit 10, high-temperature, high-pressure gas refrigerant discharged from the first compressor 12 passes through the first flow switching valve 13 and flows to the first intermediate heat exchanger 11. The refrigerant that flows into the first intermediate heat exchanger 11 exchanges heat with the heat medium flowing through the first heat medium circuit 4, condenses, and liquefies, and is reduced in pressure by the first expansion mechanism 15 to become a low-pressure gas-liquid two-phase refrigerant, and flows to the heat source side heat exchanger 14. The gas-liquid two-phase refrigerant that flows into the heat source side heat exchanger 14 exchanges heat with air and evaporates, passes through the first flow switching valve 13, and is drawn into the first compressor 12 via an accumulator.

[0153] On the other hand, the heat medium flowing through the first heat medium circuit 4 is heated by the refrigerant flowing through the first intermediate heat exchanger 11 to become hot water, and then flows through the relay unit 2 to the load-side heat exchanger 30, where it is cooled by heat exchange with the indoor air in the indoor space. The cooled heat medium flows through the relay unit 2 and again into the first intermediate heat exchanger 11.

[0154] 21 , the temperature of the heat medium heated in the first intermediate heat exchanger 11 and flowing into the relay unit 2 is 45° C., which is higher than the temperature at startup. During steady-state operation, the second refrigerant circuit 20 and the second heat medium circuit 5 are stopped, so the heat medium at 45° C. flows from the relay unit 2 to the load devices 3A and 3B that perform heating. The temperature of the heat medium after being cooled in the load devices 3A and 3B is 40° C. The temperature of the heat medium returning from the load devices 3A and 3B to the first intermediate heat exchanger 11 via the relay unit 2 is also 40° C.

[0155] As explained using FIGS. 18 and 20 , in the air conditioning apparatus 100 of embodiment 3, as in embodiment 1, when cooling or heating operation is started, the second refrigerant circuit 20 of the relay unit 2 cools or heats the room, and the load device bypass mechanism 8 causes the heat medium flowing through the first heat medium circuit 4 to return to the heat source unit 1 without passing through the load device 3. This allows the heat capacity of the heat medium between the heat source unit 1 and the relay unit 2 to be used to cool or heat the heat medium between the relay unit 2 and the load device 3 in the third intermediate heat exchanger 22. This allows the room to be cooled or heated quickly when cooling or heating operation is started. In other words, the operation standby time until the load device 3 starts operating can be shortened compared to the conventional case.

[0156] In the third embodiment, the second intermediate heat exchanger 21 is provided in the supply pipe 40o of the first heat medium pipe 40, and therefore, in particular, the heat of the supply main pipe 40mo and the heat of the heat medium circulating through the supply main pipe 40mo are utilized when the cooling operation or the heating operation is started.

[0157] Also in the third embodiment, as in the first embodiment, the relay unit 2 has a third intermediate heat exchanger 22 in which a heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit 20. The third intermediate heat exchanger 22 and the plurality of load devices 3 are connected by second heat medium pipes 50 to form a second heat medium circuit 5 in which the heat medium circulates. The second refrigerant circuit 20 generates the heat medium for the second heat medium circuit 5 so that the temperature range of the heat medium circulating through the first heat medium circuit 4 is different from that of the heat medium circulating through the first heat medium circuit 4.

[0158] In the third embodiment, the first intermediate heat exchanger 11, the second intermediate heat exchanger 21, and the plurality of load devices 3A, 3B, and 3C in the first heat medium circuit 4 are connected by a first heat medium pipe 40 so that the heat medium circulates in the order of the first intermediate heat exchanger 11, the second intermediate heat exchanger 21, the plurality of load devices 3A, 3B, and 3C, and the first intermediate heat exchanger 11.

[0159] As a result, in the third embodiment, the heat of the heat medium circulating through the supply pipe 40o in the first heat medium pipe 40 and the supply pipe 40o can be taken away (or given) by the second refrigerant circuit 20 for heating and cooling.

[0160] Embodiment 4 Next, an air conditioning apparatus 100 according to Embodiment 4 will be described with reference to Figures 22 to 26. Figure 22 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 4, illustrating a state during steady operation of cooling-dominated operation. Figure 23 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 4, illustrating a first state during the process of switching from cooling-dominated operation to heating-dominated operation in Figure 22. Figure 24 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 4, illustrating a second state during the process of switching from cooling-dominated operation to heating-dominated operation in Figure 22. Figure 25 is a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 4, illustrating a third state during the process of switching from cooling-dominated operation to heating-dominated operation in Figure 22. Figure 26 is a refrigerant circuit diagram of the air conditioning apparatus according to Embodiment 4, illustrating a state during steady operation of heating-dominated operation. Arrows in Figures 22 to 26 indicate the flow of heat medium. Note that components that are the same as or correspond to those of the air conditioning apparatus 100 described in the third embodiment are denoted by the same reference numerals, and repetition of similar descriptions may be omitted.

[0161] In the air conditioning apparatus 100 of the fourth embodiment, the first heat medium circuit 4 has, as a switching mechanism for switching the flow direction of the heat medium, a heat source unit bypass mechanism 9 that returns the heat medium to the load device 3 without passing through the heat source unit 1, in addition to the load device bypass mechanism 8 described in the third embodiment. Specifically, the first heat medium circuit 4 has a second bypass pipe 90 that connects a point Pc1 in the first heat medium piping 40 that is downstream of the first intermediate heat exchanger 11 and upstream of the second intermediate heat exchanger 21, to a point Pd1 that is downstream of the load side heat exchanger 30 and upstream of the first intermediate heat exchanger 11, and a second bypass valve 91 (hereinafter also referred to as a second flow path switching mechanism) that is provided in the second bypass piping 90 and adjusts the flow rate of the heat medium. In FIG. 22 , the point Pd1 is downstream of the load side heat exchanger 30 in the first heat medium piping 40, and in particular, downstream of the first pump 41. The opening degree of the second bypass valve 91 is controlled by the control device 7, and at least a portion of the heat medium flowing from the load device 3 to the heat source unit 1 can be flowed into the second bypass piping 90, thereby bypassing the heat source unit 1.

[0162] The first heat medium circuit 4 is also provided with a temperature sensor 74 that detects a temperature T4 of the heat medium flowing out of the second intermediate heat exchanger 21 and heading toward the load device 3. The temperature sensor 74 is provided, for example, at the heat medium outlet of the second intermediate heat exchanger 21.

[0163] The operation of each device in the cooling-dominated steady operation and the heating-dominated steady operation is the same as in the third embodiment. A brief explanation will be given below. In the cooling-dominated operation shown in Fig. 22, it is defined that, of the three load devices 3A, 3B, and 3C, two load devices 3B and 3C are performing cooling, and one load device 3A is performing heating. In the heating-dominated operation shown in Fig. 26, it is defined that, of the three load devices 3A, 3B, and 3C, two load devices 3A and 3B are performing heating, and one load device 3C is performing cooling.

[0164] 22 , in cooling-dominated operation, the air conditioning apparatus 100 operates the first refrigerant circuit 10, the first heat medium circuit 4, the second refrigerant circuit 20, and the second heat medium circuit 5. The operating mode of the heat source unit 1 is cooling, and the operating mode of the relay unit 2 is heating. In order to connect the load-side heat exchangers 30 of the load devices 3B and 3C that perform cooling to the first heat medium circuit 4, the first flow switching devices 6 corresponding to the load devices 3B and 3C are set to the side of the first heat medium circuit 4. Furthermore, in order to connect the load-side heat exchanger 30 of the load device 3A that performs heating to the second heat medium circuit 5, the first flow switching device 6 corresponding to the load device 3A is set to the side of the second heat medium circuit 5.

[0165] In the example of Fig. 22 , the temperature of the heat medium cooled in the first intermediate heat exchanger 11 and flowing into the second intermediate heat exchanger 21 is 9 [°C]. The temperature of the heat medium cooled in the second intermediate heat exchanger 21 and before flowing into the load devices 3B and 3C that perform cooling is 7 [°C]. The temperature of the heat medium heated in the load devices 3B and 3C and returning to the first intermediate heat exchanger 11 is 12 [°C]. The temperature of the heat medium heated in the third intermediate heat exchanger 22 and before flowing into the load device 3A that performs heating is 45 [°C]. The temperature of the heat medium cooled in the load device 3A and returning to the third intermediate heat exchanger 22 is 40 [°C].

[0166] 26 , in heating-dominated operation, the air conditioning apparatus 100 operates the first refrigerant circuit 10, the first heat medium circuit 4, the second refrigerant circuit 20, and the second heat medium circuit 5. The operating mode of the heat source unit 1 is heating, and the operating mode of the relay unit 2 is cooling. In order to connect the load-side heat exchanger 30 of the load device 3C that performs cooling to the second heat medium circuit 5, the first flow switching device 6 corresponding to the load device 3C is set to the side of the second heat medium circuit 5. Furthermore, in order to connect the load-side heat exchangers 30 of the load devices 3A and 3B that perform heating to the first heat medium circuit 4, the first flow switching devices 6 corresponding to the load devices 3A and 3B are set to the side of the first heat medium circuit 4.

[0167] In the example of Fig. 26, the temperature of the heat medium heated in the first intermediate heat exchanger 11 and flowing into the second intermediate heat exchanger 21 is 43 [°C]. The temperature of the heat medium heated in the second intermediate heat exchanger 21 and before flowing into the load devices 3A and 3B that perform heating is 45 [°C]. The temperature of the heat medium cooled in the load devices 3A and 3B and returning to the first intermediate heat exchanger 11 is 40 [°C]. The temperature of the heat medium cooled in the third intermediate heat exchanger 22 and before flowing into the load device 3C that performs cooling is 7 [°C]. The temperature of the heat medium heated in the load device 3C and returning to the third intermediate heat exchanger 22 is 12 [°C].

[0168] The operation of each device when switching from cooling-dominant operation to heating-dominant operation and when switching from heating-dominant operation to cooling-dominant operation is the same as in the third embodiment. That is, the operation mode is switched while shifting stepwise from state 1 to state 2 to state 3. Below, with reference to Figures 22 to 26, the operation when switching from cooling-dominant operation to heating-dominant operation is briefly described. Here, it is defined as a change from a state in which two load devices 3B and 3C are performing cooling and one load device 3A is performing heating, as shown in Figure 22, to a state in which load device 3B is switched from cooling to heating, and two load devices 3A and 3B are performing heating and one load device 3C is performing cooling.

[0169] (Switching from cooling-dominated operation to heating-dominated operation) When the load device 3B is switched from cooling to heating and the heating load ΣQh becomes larger than the cooling load ΣQc, the operation mode of the heat source unit 1 is switched from cooling to heating, as shown in Fig. 23. The operation mode of the heat source unit 1 is switched from cooling to heating, for example, when the temperature T4 of the heat medium flowing from the second intermediate heat exchanger 21 to the load device 3 becomes lower than the required supply water temperature (7 [°C] in Fig. 23).

[0170] At this stage, only the operation mode of the heat source unit 1 is switched, and the relay unit 2 is maintained in a cooling-dominated operation state, i.e., heating. Hereinafter, this state in which only the operation mode of the heat source unit 1 is switched will be referred to as the first state.

[0171] In the first state, the operation mode of the relay unit 2 remains in heating mode, and therefore the heat medium cooled in the second intermediate heat exchanger 21 flows into the load device 3C that performs cooling, is heated in the load device 3C, and returns to the first intermediate heat exchanger 11 of the heat source unit 1. Then, the heat medium is heated in the first intermediate heat exchanger 11 of the heat source unit 1 that has been switched to the heating mode, and is sent to the relay unit 2.

[0172] 23 , the temperature of the heat medium cooled in the second intermediate heat exchanger 21 and before flowing into the load device 3C is 7 [°C]. The temperature of the heat medium heated in the load device 3C and returning to the first intermediate heat exchanger 11 is 12 [°C]. The temperature of the heat medium heated in the first intermediate heat exchanger 11 and before flowing into the second intermediate heat exchanger 21 is 13 [°C].

[0173] The temperature of the heat medium heated in the third intermediate heat exchanger 22 before flowing into the load devices 3A and 3B that perform heating is 45°C. The temperature of the heat medium cooled in the load devices 3A and 3B and returning to the third intermediate heat exchanger 22 is 40°C.

[0174] In the first state, if the temperature of the heat medium flowing from the heat source unit 1 to the relay unit 2 rises and the temperature of the heat medium flowing into the load device 3C performing the air conditioning does not reach the desired temperature (e.g., 7°C) even after being cooled in the second intermediate heat exchanger 21, the second bypass valve 91 is opened, as shown in Figure 24, and the system transitions to a second state in which the temperature of the heat medium is adjusted by the opening degree of the second bypass valve 91.

[0175] In the second state, part of the heat medium in the return pipe 40b (for example, having a temperature of 12°C) is merged with the heat medium (for example, having a temperature of 20°C) supplied from the heat source unit 1 via the second bypass valve 91 to be cooled to a lower temperature (for example, having a temperature of 15°C), and then the cooled heat medium is allowed to flow into the second intermediate heat exchanger 21. In the example of FIG. 24 , the temperature T4 of the heat medium flowing out of the second intermediate heat exchanger 21 and heading toward the load device 3C is 7°C. In the second state, the opening of the second bypass valve 91 is adjusted so that this temperature T4 becomes a desired temperature (here, 7°C).

[0176] In the second state, when the second bypass valve 91 is fully opened, the second bypass valve 91 is closed, the operation mode of the relay unit 2 is switched from heating to cooling, and all the load devices 3A, 3B, and 3C are temporarily turned off, as shown in Fig. 25. This state will be referred to as the third state hereinafter.

[0177] In the third state, as the operating mode of the relay unit 2 is switched from heating to cooling, the first flow path switching device 6 corresponding to the load devices 3A and 3B that perform heating is switched to the side of the first heat medium circuit 4, and the first flow path switching device 6 corresponding to the load device 3C that performs cooling is switched to the side of the second heat medium circuit 5.

[0178] The third state is a standby time for the load devices 3 to adjust the temperature of the heat medium. During this time, the air conditioning apparatus 100 needs to reheat the first heat medium circuit 4 by an amount equivalent to the heat capacity of the main heat medium pipe 40 m, and needs to recool the second heat medium circuit 5 by an amount equivalent to the heat capacity of the heat medium pipes arranged in the relay unit 2. However, by shifting operation in stages as described above, the time during which the operation of the load devices 3 is stopped and the temperature of the heat medium is adjusted (the time in the third state) can be shortened compared to the standby time for operation in the conventional configuration.

[0179] In the fourth embodiment, the second intermediate heat exchanger 21 is provided in the supply pipe 40o of the first heat medium pipe 40, and therefore, in particular, the supply main pipe 40mo and the heat of the heat medium circulating through the supply main pipe 40mo are utilized when switching between cooling-dominated operation and heating-dominated operation.

[0180] In the third state, when the temperature of the water supplied to the load device 3 becomes sufficient for cooling or heating, the load device 3 that was stopped is turned on, and steady-state operation with heating as the main operation is performed as shown in Figure 26.

[0181] Although the operation when switching from heating-dominated operation to cooling-dominated operation will not be described here, even in this case, the operation standby time can be shortened compared to conventional methods by gradually shifting the operation mode, such as by switching the operation mode of the heat source unit 1, adjusting the temperature using the second bypass valve 91, and switching the operation mode of the relay unit 2.

[0182] Although the air conditioning apparatus 100 has been described above based on Embodiments 1 and 2, the air conditioning apparatus 100 is not limited to the configuration of the above-described embodiments. The configuration of the air conditioning apparatus 100 described above is an example, and other components may be included, or some components may be omitted. In short, the air conditioning apparatus 100 includes a range of design modifications and application variations that are normally made by a person skilled in the art, as long as they do not deviate from the technical concept of the air conditioning apparatus 100.

[0183] 1 Heat source unit, 2 Relay unit, 3 Load device, 3A Load device, 3A Load device, 3B Load device, 3B Load device, 3C Load device, 4 First heat medium circuit, 5 Second heat medium circuit, 6 First flow switching device, 7 Control device, 8 Load device bypass mechanism, 8a Load device bypass mechanism, 9 Heat source unit bypass mechanism, 10 First refrigerant circuit, 11 First intermediate heat exchanger, 12 First compressor, 13 First flow switching valve, 14 Heat source side heat exchanger, 15 First expansion mechanism, 16 Heat source side blower, 20 Second refrigerant circuit, 21 Second intermediate heat exchanger, 22 Third intermediate heat exchanger, 23 Second compressor, 24 Second flow switching valve, 25 Second expansion mechanism, 30 Load side heat exchanger, 30A Load side heat exchanger, 30B Load side heat exchanger, 30C Load side heat exchanger, 31 Load side blower, 40 First heat medium pipe, 40b Return pipe, 40d Branch pipe, 40m Main heat medium pipe, 40mb Main return pipe, 40mo Main forward pipe, 40o Forward pipe, 40rb Pipe, 40ro Pipe, 41 First pump, 50 Second heat medium pipe, 51 Second pump, 71 Temperature sensor, 72 Temperature sensor, 73 Temperature sensor, 74 Temperature sensor, 80 First bypass pipe, 80a First bypass pipe, 80a First bypass pipe, 81 First bypass valve, 81a First bypass valve, 81a First bypass valve, 90 Second bypass pipe, 91 Second bypass valve, 100 Air conditioning apparatus, 200 Building, 401 First pump, Pa Point, Pb Point, Pc Point, Pd Point, Qc Required capacity, Qh Required capacity, T1 Temperature, T2 Mixed temperature, Ta temperature, Tb temperature, ΣQc cooling load, ΣQh heating load.

Claims

1. An air conditioning apparatus comprising a heat source unit, a relay unit connected to the heat source unit, and a plurality of load devices connected to the relay unit, wherein the heat source unit has a first refrigerant circuit through which a refrigerant circulates, and a first intermediate heat exchanger in which the heat medium exchanges heat with the refrigerant flowing through the first refrigerant circuit, the relay unit has a second refrigerant circuit through which a refrigerant circulates, and a second intermediate heat exchanger in which the heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit, the first intermediate heat exchanger, the second intermediate heat exchanger, and the plurality of load devices are connected by a first heat medium piping to form a first heat medium circuit through which the heat medium circulates, and the relay unit has a bypass piping and a flow path switching mechanism that switches the flow direction of the heat medium in the first heat medium circuit.

2. The air conditioning apparatus of claim 1, wherein the bypass piping and the flow path switching mechanism switch the flow direction of the heat medium in the first heat medium circuit so that the heat medium flowing in from the heat source unit returns to the heat source unit without passing through the multiple load devices.

3. The air conditioning apparatus of claim 1, wherein the bypass piping and the flow path switching mechanism switch the flow direction of the heat medium in the first heat medium circuit so that a portion of the heat medium flowing in from the plurality of load devices returns to the plurality of load devices without passing through the heat source machine.

4. The air conditioner according to any one of claims 1 to 3, wherein the second refrigerant circuit is in operation when the heat medium is flowing through the bypass pipe.

5. The air conditioning apparatus according to any one of claims 1 to 4, wherein the heat source unit and the relay unit are connected by two pipes through which the heat medium flows.

6. The air conditioning apparatus according to any one of claims 1 to 5, wherein the relay unit has a third intermediate heat exchanger in which a heat medium exchanges heat with the refrigerant flowing through the second refrigerant circuit, the third intermediate heat exchanger and the plurality of load devices are connected by second heat medium piping to form a second heat medium circuit in which the heat medium circulates, and the second refrigerant circuit generates the heat medium of the second heat medium circuit so that the temperature range of the heat medium circulating in the first heat medium circuit is different.

7. The air conditioning apparatus according to claim 6, wherein in the first heat medium circuit, the first intermediate heat exchanger, the second intermediate heat exchanger, and the plurality of load devices are connected by the first heat medium piping so that the heat medium circulates through the first intermediate heat exchanger, the second intermediate heat exchanger, the plurality of load devices, and the first intermediate heat exchanger in that order.

8. The air conditioner according to any one of claims 1 to 7, wherein the second refrigerant circuit contains less than 1 kg of propane refrigerant.

9. An air conditioning apparatus according to any one of claims 1 to 8, wherein the first refrigerant circuit is filled with a flammable refrigerant, and the second refrigerant circuit is filled with a non-flammable or slightly flammable refrigerant.

10. The air conditioning apparatus according to any one of claims 1 to 9, wherein a plurality of the heat source units are installed in parallel, and two pipes are branched to the plurality of heat source units.

11. The air conditioning apparatus according to any one of claims 1 to 10, wherein a plurality of the relay units are installed in parallel, and two pipes are branched to the plurality of the relay units.

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