GB2542301A

GB2542301A - Air conditioning device

Info

Publication number: GB2542301A
Application number: GB1621859.6A
Authority: GB
Inventors: Koge Hirofumi; Azuma Koji
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2014-05-21
Filing date: 2014-05-21
Publication date: 2017-03-15
Anticipated expiration: 2034-05-21
Also published as: JP6198945B2; WO2015177896A1; GB201621859D0; JPWO2015177896A1; GB2542301B

Abstract

The purpose of the present invention is to prevent the leakage of a refrigerant to the indoor unit side even if there occurs, on the indoor unit side, a crack in a pipe, etc. or loosening at a pipe connection section. An air conditioning device (1) is provided with a heat source device (A), indoor units (C, D), and a relay unit (B). The relay unit (B) is provided with: a first branch section (110) having second switching valves (108a, 108b) for connecting utilization-side heat exchangers (105c, 105d) so that the utilization-side heat exchangers (105c, 105d) can be switched to the cooling operation side or the heating operation side, the first branch section (110) connecting the second switching valves (108a, 108b) to first connection pipes (106c, 106d); and a second branch section (111) having third switching valves (124a, 124b) respectively connected to flow regulators (109d), the second branch section (111) connecting the third switching valves (124a, 124b) to second connection pipes (107c, 107d). The third switching valve (124a) connected to the second branch section (111) has a function for detecting a pressure higher than or equal to a predetermined value and release the pressure.

Description

DESCRIPTION Title of Invention AIR-CONDITIONING APPARATUS Technical Field [0001]

The present invention relates to an air-conditioning apparatus that supplies either or both of heating energy and cooling energy generated by a heat source unit to a plurality of load side units, and in particular, relates to a refrigerant circuit of the air-conditioning apparatus.

Background Art [0002]

Atypical air-conditioning apparatus using a refrigeration cycle (heat pump cycle) includes a heat source unit (heat source device or outdoor unit) including a compressor and a heat-source-unit heat exchanger and a load side unit (indoor unit) including a flow control device (e.g., an expansion valve) and an indoor-unit heat exchanger such that the heat source unit and the load side unit are connected by refrigerant pipes to form a refrigerant circuit that circulates refrigerant. In the indoor-unit heat exchanger, while evaporating or condensing, the refrigerant removes heat from or transfers heat to air, serving as a heat exchange target, in a space to be air-conditioned, or air-conditioned space.

Such a phenomenon is used to condition the air while changing, for example, pressure or temperature of the refrigerant in the refrigerant circuit. For example, a hydrofluorocarbon (FIFC)-based refrigerant is often used as refrigerant for such an air-conditioning apparatus. Furthermore, air-conditioning apparatuses using a natural refrigerant, such as carbon dioxide (CO2), have been developed.

[0003]

An air-conditioning apparatus has recently been developed which includes a plurality of indoor units and is capable of performing a cooling and heating simultaneous operation (cooling and heating mixed operation) in which for each of the indoor units it is automatically determines whether to perform cooling or heating based on, for example, a temperature set with a remote control provided for the indoor unit and an ambient temperature of the indoor unit, and the indoor unit performs cooling or heating based on the result of determination (see, for example, Patent Literature 1.) [0004] A refrigerant circuit has recently been developed which includes switching valves provided in pipes connecting to an indoor unit to prevent refrigerant from leaking from the refrigerant circuit due to a crack in, for example, any of the pipes on the indoor unit side or loosening of pipe connection part of the indoor unit. Citation List Patent Literature [0005]

Patent Literature 1: Japanese Patent No. 4076753 Summary of Invention Technical Problem [0006]

In the air-conditioning apparatus capable of performing the cooling and heating mixed operation disclosed in Patent Literature 1, a relay unit includes a first branch section including a valve unit that includes two valves connected in parallel. One of the valves is connected to a first connecting pipe and the other one of them is connected to a second connecting pipe. To increase energysaving performance in a heating operation, heat loss due to heat conduction in the valve unit has to be approximated to zero. However, for example, combining or integrating valves to increase connectivity with pipes or downsize the apparatus causes high temperature gas refrigerant to transfer heat to low temperature gas refrigerant, leading to a reduction in temperature of the refrigerant flowing into any indoor unit performing the heating operation. Unfortunately, this results in a reduction in comfort in an indoor space as well as a reduction in energy-saving performance.

[0007]

When the indoor unit switches from the heating operation to a cooling operation, the pressure balance of the refrigerant passing through a switching valve sharply changes upon switching of the valve connected to the first connecting pipe. Unfortunately, this causes a refrigerant flow sound.

[0008]

In the refrigerant circuit including the switching valves provided in the pipes connecting to or connected in the indoor unit, if the refrigerant leaks from the refrigerant circuit, the switching valves will be closed but the pressure of the refrigerant in the pipes will increase. Disadvantageously, the refrigerant may leak in the indoor unit side.

[0009]

The present invention has been made in view of the above-described problems. A first object of the present invention is to provide an air-conditioning apparatus capable of eliminating or reducing refrigerant leakage from an indoor unit if there is a crack in, for example, a pipe connecting to or connected in the indoor unit or loosening of pipe connection part of the indoor unit. A second object of the present invention is to provide an air-conditioning apparatus capable of eliminating or reducing a refrigerant flow sound by controlling a flow rate through a valve connected to a first connecting pipe when a heating operation is switched to a cooling operation. A third object of the present invention is to provide an air-conditioning apparatus that eliminates a reduction in performance in a cooling and heating simultaneous operation in which multiple use side heat exchangers each perform a cooling operation or a heating operation and that can be made using an inexpensive material.

Solution to Problem [0010]

An air-conditioning apparatus according to an embodiment of a heat source unit including a compressor compressing and discharging refrigerant, a first switching valve switching between passages for the refrigerant discharged from the compressor, and a heat-source-unit heat exchanger exchanging heat between the refrigerant passing through the first switching valve and an ambient heat source medium; a plurality of indoor units each including a use side heat exchanger and a flow controller connected to the use side heat exchanger, the use side heat exchanger exchanging heat between the refrigerant passing through the first switching valve and an ambient use medium; and a relay unit disposed between the heat source unit and the indoor units, the relay unit connecting the heat source unit to each of the indoor units with first connecting pipes and second connecting pipes and having a function of switching at least one of the use side heat exchangers of the indoor units to a cooling operation side and switching at least one of the other use side heat exchangers to a heating operation side, the relay unit including a first branch section including second switching valves switchably connecting the use side heat exchangers to the cooling operation side or the heating operation side, the first branch section allowing the second switching valves to communicate to the first connecting pipes, and a second branch section including third switching valves connected to each of the flow controllers, the second branch section allowing the third switching valves to communicate to the second connecting pipes, the third switching valves, arranged in the second branch section, having a function of relieving pressure in response to detection of a predetermined or higher pressure.

Advantageous Effects of Invention [0011]

In this embodiment of the present invention, when the refrigerant leaks from any indoor unit, the corresponding switching valves arranged in the first and second branch sections are closed to stop movement of the refrigerant to the indoor unit. Since the switching valves arranged in the second branch section have the function of relieving pressure in response to detection of the predetermined or higher pressure, the switching valves reduce the pressure of the refrigerant in the corresponding indoor unit, thus minimizing the amount of refrigerant leaking into an indoor space.

Brief Description of Drawings [0012] [Fig. 1] Fig. 1 is a diagram illustrating an exemplary configuration of an air-conditioning apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a diagram illustrating an exemplary configuration of the air-conditioning apparatus of Fig. 1 in a cooling main operation state in a cooling and heating simultaneous operation.

[Fig. 3] Fig. 3 is a diagram illustrating an exemplary configuration of the air-conditioning apparatus of Fig. 1 in a heating main operation state in the cooling and heating simultaneous operation.

[Fig. 4] Fig. 4 is a graph illustrating an example of the relationship between a flow coefficient CV value of flow control valves in a first branch section and performance in a cooling operation in Fig. 1.

[Fig. 5] Fig. 5 is a diagram illustrating an example of switching valves provided with an air-tightness and evacuation mechanism in Fig. 1.

Description of Embodiments [0013]

Embodiment 1

Fig. 1 is a diagram illustrating an exemplary configuration of an air-conditioning apparatus. For example, a multi-air-conditioning apparatus for a building will be described as an example of the air-conditioning apparatus according to Embodiment 1. As illustrated in Fig. 1, an air-conditioning apparatus 1 includes a heat source unit A, a relay unit B, an indoor unit C, and an indoor unit D.

The relay unit B is disposed between the heat source unit A and the indoor units C and D. The relay unit B is connected to the heat source unit A by a first connecting pipe 106 and a second connecting pipe 107. The second connecting pipe 107 has a smaller diameter than the first connecting pipe 106.

The relay unit B is connected to the indoor unit C by first connecting pipes 106c and second connecting pipes 107c. The relay unit B is connected to the indoor unit D by first connecting pipes 106d and second connecting pipes 107d. With the above-described connection, the relay unit B relays refrigerant flowing between the heat source unit A and the indoor units C and D.

[0014]

The heat source unit A includes a compressor 101, a four-way valve 102, a heat-source-unit heat exchanger 103, and an accumulator 104. The heat source unit A further includes check valves 118, 119, 120, and 121.

[0015]

The compressor 101 is disposed between the four-way valve 102 and the accumulator 104. The compressor 101 sucks the refrigerant, compresses it, and discharges the compressed refrigerant. A suction side of the compressor 101 is connected to the accumulator 104 and a discharge side thereof is connected to the four-way valve 102.

[0016]

The four-way valve 102 has four ports. A first port of the four-way valve 102 is connected to the discharge side of the compressor 101, a second port thereof is connected to the heat-source-unit heat exchanger 103, a third port thereof is connected to the accumulator 104, and a fourth port thereof is connected to an outlet side of the check valve 119 and an inlet side of the check valve 120. The four-way valve 102 switches between refrigerant passages.

The four-way valve 102 corresponds to a first switching valve in the present invention.

[0017]

The heat-source-unit heat exchanger 103 is disposed between the fourway valve 102 and a point between the check valves 118 and 121. The heat-source-unit heat exchanger 103 is connected at one end to the four-way valve 102, and is connected at the other end to a pipe connecting to an inlet side of the check valve 118 and an outlet side of the check valve 121. The heat-source-unit heat exchanger 103 exchanges heat between the refrigerant flowing inside the heat-source-unit heat exchanger 103 and a medium flowing outside the heat-source-unit heat exchanger 103. Examples of the medium flowing outside the heat-source-unit heat exchanger 103 include water and brine.

[0018]

The accumulator 104 is connected between the four-way valve 102 and the suction side of the compressor 101. The accumulator 104 separates the refrigerant into liquid refrigerant and gas refrigerant, and supplies the gas refrigerant to the compressor 101.

[0019]

The compressor 101, the four-way valve 102, the heat-source-unit heat exchanger 103, and the accumulator 104 described above constitute part of a refrigerant circuit.

[0020] A flow switching valve of the refrigerant circuit including the check valves 118 to 121 will now be described.

The check valve 118 is disposed between a point between the heat-source-unit heat exchanger 103 and the outlet side of the check valve 121 and a point at which the second connecting pipe 107 is connected to an outlet side of the check valve 120. The inlet side of the check valve 118 is connected to a pipe connecting to the heat-source-unit heat exchanger 103 and the outlet side of the check valve 121. An outlet side of the check valve 118 is connected to a pipe connecting to the second connecting pipe 107 and the outlet side of the check valve 120. The check valve 118 permits the refrigerant to flow in only one direction from the heat-source-unit heat exchanger 103 to the second connecting pipe 107.

[0021]

The check valve 119 is disposed between a point between the four-way valve 102 and the inlet side of the check valve 120 and a point at which the first connecting pipe 106 is connected to an inlet side of the check valve 121. An inlet side of the check valve 119 is connected to a pipe connecting to the first connecting pipe 106 and the inlet side of the check valve 121. The outlet side of the check valve 119 is connected to a pipe connecting to the four-way valve 102 and the inlet side of the check valve 120. The check valve 119 permits the refrigerant to flow in only one direction from the first connecting pipe 106 to the four-way valve 102.

[0022]

The check valve 120 is disposed between the point between the four-way valve 102 and the outlet side of the check valve 119 and the point at which the second connecting pipe 107 is connected to the outlet side of the check valve 118. The inlet side of the check valve 120 is connected to a pipe connecting to the four-way valve 102 and the outlet side of the check valve 119. The outlet side of the check valve 120 is connected to a pipe connecting to the second connecting pipe 107 and the outlet side of the check valve 118. The check valve 120 permits the refrigerant to flow in only one direction from the four-way valve 102 to the second connecting pipe 107.

[0023]

The check valve 121 is disposed between the point at which the first connecting pipe 106 is connected to the inlet side of the check valve 119 and the point between the heat-source-unit heat exchanger 103 and the inlet side of the check valve 118. The inlet side of the check valve 121 is connected to a pipe connecting to the first connecting pipe 106 and the inlet side of the check valve 119. The outlet side of the check valve 121 is connected to a pipe connecting to the heat-source-unit heat exchanger 103 and the inlet side of the check valve 118. The check valve 121 permits the refrigerant to flow in only one direction from the first connecting pipe 106 to the heat-source-unit heat exchanger 103.

[0024]

The above-described check valves 118 to 121 constitute the flow switching valve of the refrigerant circuit. The flow switching valve, the relay unit B, and the indoor units C and D form a refrigeration cycle for a cooling operation and a refrigeration cycle for a heating operation in the refrigerant circuit in the cooling and heating simultaneous operation. The relay unit B and the indoor units C and D will be described in detail later.

[0025]

The refrigerant circuit including the relay unit B and the indoor units will now be described.

The relay unit B includes a first branch section 110, a second branch section 111, a gas-liquid separator 112, a second flow controller 113, a third flow controller 115, a first heat exchanger 116, a second heat exchanger 117, a first pressure detecting unit 122, a second pressure detecting unit 123, a temperature detecting unit 125, and a control unit 151.

The relay unit B is connected to the heat source unit A by the first connecting pipe 106 and the second connecting pipe 107. The relay unit B is connected to the indoor unit C via the first connecting pipes 106c and the second connecting pipes 107c. The relay unit B is connected to the indoor unit D via the first connecting pipes 106d and the second connecting pipes 107d.

[0026]

The refrigerant circuit including the first branch section 110 and the indoor units will now be described.

The first branch section 110 is connected to the indoor unit C via the first connecting pipes 106c and is connected to the indoor unit D via the first connecting pipes 106d.

The first branch section 110 includes flow control valves 108a and solenoid valves 108b. The flow control valves 108a are separated from the solenoid valves 108b in the first branch section 110.

[0027]

The configuration of the indoor unit C and that of the first branch section 110 will now be described.

The flow control valves 108a and the solenoid valves 108b for the indoor unit C are connected to the indoor unit C via the first connecting pipes 106c.

Each of the flow control valves 108a for the indoor unit C is connected at one end to the first connecting pipe 106 and is connected at the other end to the first connecting pipe 106c and one terminal of the solenoid valve 108b. The other terminal of the solenoid valve 108b is connected to the second connecting pipe 107. The flow control valve 108a for the indoor unit C is an openable and closable, and flow-controllable valve.

[0028]

Similarly, the configuration of the indoor unit D and that of the first branch section 110 will be described.

The flow control valves 108a and the solenoid valves 108b for the indoor unit D are connected to the indoor unit D via the first connecting pipes 106d.

Each of the flow control valves 108a for the indoor unit D is connected at one end to the first connecting pipe 106 and is connected at the other end to the first connecting pipe 106d and one terminal of the solenoid valve 108b. The other terminal of the solenoid valve 108b is connected to the second connecting pipe 107. The flow control valve 108a for the indoor unit D is an openable and closable, and flow-controllable valve.

[0029]

The refrigerant circuit including the first branch section 110 and the heat source unit A will now be described.

The first branch section 110 is connected to the heat source unit A by the first connecting pipe 106 and the second connecting pipe 107.

The first branch section 110 connects the first connecting pipes 106c to the first connecting pipe 106 or the second connecting pipe 107 with the flow control valves 108a and the solenoid valves 108b. Similarly, the first branch section 110 connects the first connecting pipes 106d to the first connecting pipe 106 or the second connecting pipe 107 with the flow control valves 108a and the solenoid valves 108b.

The flow control valves 108a and the solenoid valves 108b correspond to second switching valves in the present invention.

[0030]

The second branch section 111 will now be described.

The second branch section 111 includes pressure relief valves 124a each operating in response to detection of a predetermined or higher pressure (set at or below, for example, a design pressure so that the detected pressure exceeds the design pressure), and solenoid valves 124b. The pressure relief valves 124a are connected in antiparallel with the solenoid valves 124b.

The pressure relief valves 124a and the solenoid valves 124b correspond to third switching valves in the present invention. Additionally, the pressure relief valves 124a correspond to a function of relieving pressure in response to detection of a predetermined or higher pressure in the present invention.

[0031]

The second branch section 111 is connected to the indoor unit C via the second connecting pipes 107c. Input sides of the pressure relief valves 124a and output sides of the solenoid valves 124b for the indoor unit C are connected to the indoor unit C via the second connecting pipes 107c.

In addition, the second branch section 111 is connected to the indoor unit D via the second connecting pipes 107d. Input sides of the pressure relief valves 124a and output sides of the solenoid valves 124b for the indoor unit D are connected to the indoor unit D via the second connecting pipes 107d.

[0032]

Output sides of the pressure relief valves 124a are connected to a merging portion 124a_all. Input sides of the solenoid valves 124b are connected to a merging portion 124b_all.

Furthermore, the second branch section 111 is connected to the second flow controller 113 and the second heat exchanger 117 by the merging portion 124a_all. In addition, the second branch section 111 is connected to the third flow controller 115 and the second heat exchanger 117 by the merging portion 124b_all.

[0033]

The components of the relay unit B will now be described.

The gas-liquid separator 112 is provided in the second connecting pipe 107. A gas phase portion of the gas-liquid separator 112 is connected to the solenoid valves 108b of the first branch section 110. A liquid phase portion of the gas-liquid separator 112 is connected to the second branch section 111 through the first heat exchanger 116, the second flow controller 113, the second heat exchanger 117, and the third flow controller 115.

[0034]

The second flow controller 113 is connected at a first end to the first heat exchanger 116, and is connected at a second end to a first end of the second heat exchanger 117 and the merging portion 124a_all of the second branch section 111. The first pressure detecting unit 122, which will be described in detail later, is provided in a pipe connecting the first heat exchanger 116 to the second flow controller 113. The second pressure detecting unit 123, which will be described in detail later, is provided in a pipe connecting the second flow controller 113 to the second heat exchanger 117 and the merging portion 124a_all.

The second flow controller 113 is a flow controller having a controllable opening degree. The opening degree of the second flow controller 113 is controlled so that the difference between a pressure detected by the first pressure detecting unit 122 and a pressure detected by the second pressure detecting unit 123 is constant.

[0035]

The third flow controller 115 is connected at a first end to a bypass pipe 114 extending through the second heat exchanger 117, and is connected at a second end to a pipe connecting the second heat exchanger 117 to the merging portion 124b_all.

The third flow controller 115 is a flow controller having a controllable opening degree. The opening degree of the third flow controller 115 is controlled by any one or a combination of the temperature detecting unit 125, the first pressure detecting unit 122, and the second pressure detecting unit 123.

The bypass pipe 114 is connected at one end to the first connecting pipe 106, and is connected at the other end to the third flow controller 115. The amount of refrigerant supplied to the heat source unit A accordingly depends on the opening degree of the third flow controller 115.

[0036]

The first heat exchanger 116 is disposed between the gas-liquid separator 112 and each of the second heat exchanger 117 and the second flow controller 113. The first heat exchanger 116 exchanges heat between the bypass pipe 114 and the pipe disposed between the gas-liquid separator 112 and the second flow controller 113.

[0037]

The second heat exchanger 117 is disposed between each of the first heat exchanger 116 and the second flow controller 113 and each of the first and second ends of the third flow controller 115. The second end of the third flow controller 115 is connected to the merging portion 124b_all. The second heat exchanger 117 exchanges heat between the bypass pipe 114 and a pipe disposed between the second flow controller 113 and the third flow controller 115.

[0038]

The temperature detecting unit 125 is, for example, a thermistor. The temperature detecting unit 125 measures the temperature of the refrigerant flowing from an outlet of the second heat exchanger 117, that is, the refrigerant flowing through the pipe disposed downstream of the second heat exchanger 117, and supplies the result of measurement to the control unit 151. The temperature detecting unit 125 may supply a measurement result as it is to the control unit 151. Alternatively, the temperature detecting unit 125 may accumulate measurement results for a predetermined period of time and supply the accumulated measurement results to the control unit 151 at predetermined time intervals.

In the above-described configuration, the temperature detecting unit 125 is a thermistor. The present invention is not limited to such a configuration.

[0039]

The first pressure detecting unit 122 measures the pressure of the refrigerant flowing through the pipe disposed between the first heat exchanger 116 and the second flow controller 113, and supplies the result of measurement to the control unit 151.

The second pressure detecting unit 123 measures the pressure of the refrigerant flowing through the pipe connecting the second flow controller 113 to the second heat exchanger 117 and the second branch section 111, and supplies the result of measurement to the control unit 151.

[0040]

The control unit 151 includes, as a main component, a microprocessor unit. The control unit 151 controls the whole of the relay unit B in a centralized manner, communicates with an external device, for example, the heat source unit A, and performs various arithmetic operations, for example.

[0041]

The indoor unit C includes use side heat exchangers 105c and first flow controllers 109c. The use side heat exchangers 105c are connected at one end to the first connecting pipes 106c, and are connected at the other end to the first flow controllers 109c. The first flow controllers 109c are connected at one end to the use side heat exchangers 105c, and are connected at the other end to the second connecting pipes 107c. The multiple use side heat exchangers 105C are arranged. The use side heat exchangers 105c and the first flow controllers 109c constitute part of the refrigerant circuit.

[0042]

The indoor unit D includes use side heat exchangers 105d and first flow controllers 109d. The use side heat exchangers 105d are connected at one end to the first connecting pipes 106d, and are connected at the other end to the first flow controllers 109d. The first flow controllers 109d are connected at one end to the use side heat exchangers 105d, and are connected at the other end to the second connecting pipes 107d. The multiple use side heat exchangers 105d are arranged. The use side heat exchangers 105d and the first flow controllers 109d constitute part of the refrigerant circuit.

[0043]

In the above-described configuration, the single heat source unit A, the two indoor units, and the single relay unit B are arranged. The present invention is not limited to such a configuration. For example, three or more indoor units may be arranged, and two or more heat source units A may be arranged. In addition, two or more relay units B may be arranged.

[0044]

Fig. 2 is a diagram illustrating an exemplary configuration of the air-conditioning apparatus 1 in a cooling main operation state in the cooling and heating simultaneous operation in Embodiment 1. It is assumed that the indoor unit C is set to perform the cooling operation, the indoor unit D is set to perform the heating operation, and the air-conditioning apparatus 1 is operated in a cooling main operation in Embodiment 1.

[0045]

The flow control valves 108a and the solenoid valves 124b for the indoor unit C are opened, and the solenoid valves 108b for the indoor unit C are closed. The flow control valves 108a and the solenoid valves 124b for the indoor unit D are closed, and the solenoid valves 108b for the indoor unit D are opened.

The opening degree of the second flow controller 113 is controlled so that the difference between a pressure detected by the first pressure detecting unit 122 and a pressure detected by the second pressure detecting unit 123 is a proper value.

[0046]

Refrigerant flows will now be described. The refrigerant is compressed into high temperature, high pressure gas refrigerant, and is then discharged by the compressor 101. As indicated by thick solid-line arrows in Fig. 2, the discharged refrigerant passes through the four-way valve 102 and then flows into the heat-source-unit heat exchanger 103.

The refrigerant passing through the heat-source-unit heat exchanger 103 exchanges heat with a heat source medium, such as water, so that the high temperature, high pressure gas refrigerant subjected to heat exchange turns into high temperature, high pressure, two-phase gas-liquid refrigerant. The high temperature, high pressure, two-phase gas-liquid refrigerant passes through the check valve 118 and the second connecting pipe 107, and is then supplied to the gas-liquid separator 112 in the relay unit B.

[0047]

The high temperature, high pressure, two-phase gas-liquid refrigerant is separated into gas refrigerant and liquid refrigerant by the gas-liquid separator 112. The separated gas refrigerant flows into the first branch section 110 as indicated by thick dashed-line arrows. The gas refrigerant having flowed into the first branch section 110 passes through opened ones of the solenoid valves 108b and the first connecting pipes 106d for the indoor unit D and is then supplied to the indoor unit D, which is set to perform the heating operation.

[0048]

In the indoor unit D, the use side heat exchangers 105d exchange heat between the refrigerant and a use medium, such as air, to condense and liquefy the supplied gas refrigerant. The refrigerant passing through the use side heat exchangers 105d are controlled based on the degree of subcooling at outlets of the use side heat exchangers 105d by the first flow controllers 109d.

The first flow controllers 109d reduce the pressure of the liquid refrigerant, condensed and liquefied in the use side heat exchangers 105d, so that the refrigerant turns into intermediate pressure refrigerant having an intermediate pressure between a high pressure and a low pressure. The intermediate pressure refrigerant passes through the pressure relief valves 124a and then flows into the second branch section 111.

[0049]

On the other hand, the liquid refrigerant, separated by the gas-liquid separator 112, passes through the second flow controller 113 controlling the difference between the high pressure and the intermediate pressure at a constant value, and then flows into the second branch section 111.

In the second branch section 111, the supplied liquid refrigerant passes through the solenoid valves 124b connected to the indoor unit C and then flows into the indoor unit C.

After that, the pressure of the liquid refrigerant having flowed into the indoor unit C is reduced to the low pressure by the first flow controllers 109c, which are controlled based on the degree of superheat at outlets of the use side heat exchangers 105c in the indoor unit C. The refrigerant is then supplied to the use side heat exchangers 105c.

[0050]

In the use side heat exchangers 105c, the supplied liquid refrigerant exchanges heat with the use medium, such as air, so that the refrigerant evaporates and gasifies. The gasified, or gas refrigerant passes through the first connecting pipes 106c and then flows into the first branch section 110.

In the first branch section 110, the flow control valves 108a connected to the indoor unit C are open. Thus, the gas refrigerant having flowed into the first branch section 110 passes through the flow control valves 108a connected to the indoor unit C and flows into the first connecting pipe 106.

Then, the gas refrigerant flows into the check valve 119, which is at a lower pressure than the check valve 121. After that, the gas refrigerant passes through the four-way valve 102 and the accumulator 104, and is then sucked into the compressor 101.

[0051]

In the cooling main operation, the first connecting pipe 106 is at the low pressure and the second connecting pipe 107 is at the high pressure. The difference in pressure between these pipes causes the refrigerant to flow through the check valves 118 and 119. The refrigerant does not flow through the check valves 120 and 121.

[0052]

Part of the liquid refrigerant, separated by the gas-liquid separator 112, flowing to the second branch section 111 does not flow to the indoor unit C.

This part of the liquid refrigerant passes through the second flow controller 113, flows through the second heat exchanger 117, and then flows into the third flow controller 115 without flowing into the second branch section 111.

[0053]

The third flow controller 115 reduces the pressure of the liquid refrigerant, which has flowed into the third flow controller 115, to the low pressure, thus reducing the evaporating temperature of the refrigerant. In the second heat exchanger 117, the liquid refrigerant, reduced in evaporating temperature, passing through the bypass pipe 114 exchanges heat with the liquid refrigerant mainly supplied from the second flow controller 113, and thus turns into two-phase gas-liquid refrigerant. In the first heat exchanger 116, the two-phase gas-liquid refrigerant exchanges heat with the high temperature, high pressure liquid refrigerant supplied from the gas-liquid separator 112, so that the two-phase gas-liquid refrigerant turns into gas refrigerant. The gas refrigerant flows into the first connecting pipe 106. After that, the gas refrigerant passes through the fourway valve 102 and the accumulator 104 and is then sucked into the compressor 101.

The above-described operation forms the refrigeration cycles to perform the cooling main operation.

[0054]

Fig. 3 is a diagram illustrating an exemplary configuration of the air-conditioning apparatus 1 in a heating main operation state in the cooling and heating simultaneous operation in Embodiment 1. It is assumed that the indoor unit C is set to perform the heating operation, the indoor unit D is set to perform the cooling operation, and the air-conditioning apparatus 1 is operated in a heating main operation in Embodiment 1.

[0055]

The flow control valves 108a and the solenoid valves 124b for the indoor unit C are closed, and the solenoid valves 108b for the indoor unit C are opened. The flow control valves 108a and the solenoid valves 124b for the indoor unit D are opened, and the solenoid valves 108b for the indoor unit D are closed.

[0056]

Refrigerant flows will now be described. The refrigerant is compressed and discharged by the compressor 101. As indicated by the thick solid-line arrows in Fig. 3, the discharged, high temperature, high pressure gas refrigerant passes through the four-way valve 102, the check valve 120, and the second connecting pipe 107, and is then supplied to the gas-liquid separator 112 in the relay unit B.

The gas-liquid separator 112 supplies the high temperature, high pressure gas refrigerant to the first branch section 110. The gas refrigerant that has been supplied to the first branch section 110 passes through opened ones of the solenoid valves 108b and the first connecting pipes 106c for the indoor unit C, and is then supplied to the indoor unit C, which is set to perform the heating operation.

[0057]

In the indoor unit C, the use side heat exchangers 105c exchange heat between the refrigerant and the use medium, such as air, to condense and liquefy the supplied gas refrigerant. The refrigerant passing through the use side heat exchangers 105c is controlled based on the degree of subcooling at the outlets of the use side heat exchangers 105c by the first flow controllers 109c.

The first flow controllers 109c reduce the pressure of the liquid refrigerant, condensed and liquefied in the use side heat exchangers 105c, so that the refrigerant turns into intermediate pressure liquid refrigerant having the intermediate pressure between the high pressure and the low pressure. The intermediate pressure liquid refrigerant passes through the pressure relief valves 124a and flows into the second branch section 111.

[0058]

After that, two streams of the liquid refrigerant having flowed into the second branch section 111 merge into a single stream in the merging portion 124a_all. The liquid refrigerant resulting from the merging in the merging portion 124a_all passes through the second heat exchanger 117. At this time, part of the liquid refrigerant that has passed through the second heat exchanger 117 flows through the third flow controller 115. The liquid refrigerant passing through the third flow controller 115 is reduced in pressure by the third flow controller 115. The pressure-reduced refrigerant flows into the second heat exchanger 117.

[0059]

In the second heat exchanger 117, the low pressure liquid refrigerant exchanges heat with the intermediate pressure liquid refrigerant, so that the low pressure liquid refrigerant turns into gas refrigerant because the low pressure liquid refrigerant has a low evaporating temperature. The gas refrigerant passes through the bypass pipe 114 and then flows into the first connecting pipe 106. On the other hand, the intermediate pressure liquid refrigerant flows into the merging portion 124b_all, passes through the solenoid valves 124b connected to the indoor unit D, flows through the second connecting pipes 107d, and then flows into the indoor unit D.

[0060]

After that, the pressure of the liquid refrigerant having flowed into the indoor unit D is reduced to the low pressure by the first flow controllers 109d, which are controlled based on the degree of superheat at the outlets of the use side heat exchangers 105d in the indoor unit D. The liquid refrigerant in a low evaporating temperature state is supplied to the use side heat exchangers 105d.

In the use side heat exchangers 105d, the supplied liquid refrigerant having the low evaporating temperature exchanges heat with the use medium, such as air, and thus evaporates and gasifies.

[0061]

The gasified, or gas refrigerant passes through the first connecting pipes 106d and flows into the first branch section 110. In the first branch section 110, the flow control valves 108a connected to the indoor unit D are open. The gas refrigerant having flowed into the first branch section 110 passes through the flow control valves 108a connected to the indoor unit D and then flows into the first connecting pipe 106.

Then, the gas refrigerant flows to the check valve 121 at a lower pressure than the check valve 119 and flows into the heat-source-unit heat exchanger 103, where the refrigerant evaporates and gasifies. After that, the refrigerant passes through the four-way valve 102 and the accumulator 104 and is then sucked into the compressor 101.

[0062]

The first connecting pipe 106 is at the low pressure and the second connecting pipe 107 is at the high pressure. The difference in pressure between these pipes causes the refrigerant to flow through the check valves 120 and 121. The refrigerant does not flow through the check valves 118 and 119.

The above-described operation forms the refrigeration cycles to perform the heating main operation.

[0063]

Features of preventing the leakage of refrigerant, controlling the flow rate of refrigerant, and increasing the energy-saving performance at low cost by arranging the solenoid valves 108b, the solenoid valves 124b, the flow control valves 108a, and the pressure relief valves 124a will be described below.

[0064]

It is assumed that the refrigerant leaks from the indoor unit C or the indoor unit D in the cooling and heating simultaneous operation. If the refrigerant moves from the relay unit B to the indoor unit C or the indoor unit D and leaks from the indoor unit, the refrigerant would fall into a corresponding indoor space, or room. Stagnation of the refrigerant in the room would cause a shortage of oxygen in the room. Furthermore, the risk of combustion might increase depending on the refrigerant used. As a result, a user of the air-conditioning apparatus 1 would be affected physically as well as feeling uncomfortable.

[0065]

When the refrigerant leaks from the indoor unit C or the indoor unit D, the refrigerant leakage is detected by a refrigerant leakage sensor previously installed in the corresponding room. When the control unit receives a signal from the sensor, for example, solenoid valves have to be closed to interrupt the flow of refrigerant so that the refrigerant does not move from the relay unit B to the indoor unit C or the indoor unit D. Flowever, providing solenoid valves for each of the indoor units C and D requires a service space for the solenoid valves and a large amount of cost.

Furthermore, the closing of the solenoid valves would cause an increase in pressure of liquid refrigerant in the second connecting pipes 107c or 107d. Unfortunately, the refrigerant might leak from the indoor unit C or the indoor unit D.

[0066]

To prevent the refrigerant from moving from the relay unit B to the indoor unit C or the indoor unit D, the solenoid valves 108b are provided in the first connecting pipes 106c connected to the indoor unit C and the first connecting pipes 106d connected to the indoor unit D, the solenoid valves 124b are provided in the second connecting pipes 107c connected to the indoor unit C and the second connecting pipes 107d connected to the indoor unit D, and the flow control valves 108a are provided in the first connecting pipes 106c connected to the indoor unit C and the first connecting pipes 106d connected to the indoor unit D. This arrangement can eliminate or reduce an extra cost.

Additionally, the pressure relief valves 124a are provided in parallel with the respective solenoid valves 124b. This achieves a balance between suppressing an excessive increase in pressure and preventing the refrigerant leakage from the indoor unit C or the indoor unit D.

[0067]

In the above-described configuration, the solenoid valves 108b and 124b, the flow control valves 108a, and the pressure relief valves 124a are provided separately. The present invention is not limited to such a configuration. As each of these valves, a set of such valves may be provided.

[0068]

Refrigerant flow rate control by the flow control valves 108a will now be described.

Fig. 4 is a graph illustrating an example of the relationship between a flow coefficient CV value of the flow control valves 108a in the first branch section 110 and performance in the cooling operation. As illustrated in Fig. 4, a constant correlation is found between the flow coefficient CV value of the flow control valves 108a in the first branch section 110 in the relay unit B and the indoor unit performing the cooling operation. The axis of abscissas denotes the CV value of the flow control valves 108a and the axis of ordinates denotes the capacity of the cooling operation.

[0069]

As the flow coefficient CV value of the flow control valves 108a in the first branch section 110 increases in the cooling operation, the pressure loss of the flow control valves 108a decreases, causing an increase in cooling capacity. When the flow coefficient CV value of the flow control valves 108a in the first branch section 110 is greater than or equal to 4, the cooling capacity ratio is greater than or equal to 1. A target capacity can be thus achieved.

[0070]

In the heating operation, the flow coefficient CV value of the flow control valves 108a in the first branch section 110 is set to zero (closed), so that the flow bypassing the indoor unit disappears, thus eliminating a reduction in heating capacity.

If the refrigerant leaks in the indoor unit side, the cooling and heating simultaneous operation can be continued safely and stably without any reduction in performance.

[0071]

Furthermore, when the heating operation is switched to the cooling operation, the flow coefficient CV value of the flow control valves 108a in the first branch section 110 is set to a value at which each valve is slightly opened like an orifice (for example, the CV value is 0.005 to 0.15), thus preventing liquid expansion caused by liquid refrigerant accumulation in the first connecting pipes 106c or 106d. This results in pressure equalization, thus reducing pressure fluctuation in the cooling operation. This eliminates a refrigerant flow sound.

[0072]

The feature of increasing the energy-saving performance at low cost by providing the flow control valves 108a separately from the solenoid valves 108b will now be described.

If the pressure and temperature of gas refrigerant flowing into the indoor unit C or D performing the heating operation decrease, the temperature of the use medium, such as air, blown from the indoor unit would decrease. Consequently, the user of the air-conditioning apparatus 1 would feel uncomfortable.

[0073]

To prevent a reduction in temperature of the use medium, such as air, blown from the indoor unit C or D, the temperature of gas refrigerant flowing into the indoor unit has to be increased to a predetermined value or higher. If the flow control valves 108a and the solenoid valves 108b are combined or integrated in the first branch section 110, heat would transfer between the valves, thus reducing the temperature of the gas refrigerant flowing into the indoor unit performing the heating operation, or a heating operation side.

[0074]

Particularly, if the valves are molded of an inexpensive material having a thermal conductivity of 150 [W/mK] to 200 [W/mK], a significant reduction in heating capacity will result.

To maintain the heating capacity, the flow control valves 108a are arranged separately from the solenoid valves 108b. This arrangement eliminates heat transfer between the flow control valves 108a and the solenoid valves 108b, so that the temperature of gas refrigerant flowing into the heating operation side can be maintained. Although the first branch section 110 has been described above, similar advantages can be obtained in the second branch section 111.

[0075]

The above-described arrangement of the solenoid valves 108b and the flow control valves 108a in the first branch section 110 and the solenoid valves 124b and the pressure relief valves 124a in the second branch section 111 in the relay unit B offer the following advantages.

If the refrigerant leaks from the side of the indoor unit C or the side of the indoor unit D in the refrigerant circuit while the multiple use side heat exchangers, for example, the use side heat exchangers 105c, are performing the cooling operation or the heating operation in the cooling and heating simultaneous operation, the pressure relief valves 124a reduce the pressure of the refrigerant in the pipes, thus reducing the amount of refrigerant leaked. Advantageously, this suppresses a reduction in performance of the air-conditioning apparatus 1.

When the heating operation is switched to the cooling operation, the flow coefficient CV value of the flow control valves 108a in the first branch section 110 is set to a value at which each valve is slightly opened like an orifice, thus preventing liquid expansion caused by liquid refrigerant stagnation in the first connecting pipes 106c or 106d. This results in pressure equalization, thus reducing pressure fluctuation in the cooling operation. Advantageously, a refrigerant flow sound can be eliminated or reduced.

In addition, the flow control valves 108a are arranged separately from the solenoid valves 108b, and the pressure relief valves 124a are arranged separately from the solenoid valves 124b, thus eliminating heat transfer between the valves. The temperature of gas refrigerant flowing into the heating operation side can be maintained. Advantageously, the safe and stable cooling and heating simultaneous operation can be easily controlled, and comfort can be maintained at low cost.

[0076]

Although the multi-air-conditioning apparatus for a building has been described as an example of the air-conditioning apparatus 1 according to Embodiment 1, the present invention is not limited to this example.

[0077]

After installation or pipe connection of an air-conditioning apparatus, a refrigerant circuit is typically subjected to an air-tightness test and is then evacuated to remove gas used for the tightness test from the refrigerant circuit. The switching valves (the flow control valve 108a and the solenoid valve 108b) in the first branch section 110 or the switching valves (the pressure relief valve 124a and the solenoid valve 124b) in the second branch section 111 may be provided with an air-tightness and evacuation mechanism for the above-described tightness test and evacuation. This eliminates the need for providing a separate tightness and evaluation mechanism.

[0078]

Fig. 5 is a diagram illustrating an example of switching valves provided with the tightness and evacuation mechanism.

As illustrated in Fig. 5, the switching valves (the flow control valve 108a and the solenoid valve 108b) arranged in the first branch section 110 are provided with an air-tightness and evacuation port 140.

The tightness and evacuation port 140 corresponds to an air-tightness and evacuation mechanism in the present invention.

Reference Signs List [0079] A: heat source unit; B: relay unit; C: indoor unit; D: indoor unit; 1: air-conditioning apparatus; 101: compressor; 102: four-way valve; 103: heat-source-unit heat exchanger; 104: accumulator; 105c: use side heat exchanger; 105d: use side heat exchanger; 106: first connecting pipe; 106c: first connecting pipe; 106d: first connecting pipe; 107: second connecting pipe; 107c: second connecting pipe; 107d: second connecting pipe; 108a: flow control valve; 108b: solenoid valve; 109c: first flow controller; 109d: first flow controller; 110: first branch section; 111: second branch section; 112: gas-liquid separator; 113: second flow controller; 114: bypass pipe; 115: third flow controller; 116: first heat exchanger; 117: second heat exchanger; 118: check valve; 119: check valve; 120: check valve; 121: check valve; 122: first pressure detecting unit; 123: second pressure detecting unit; 124a: pressure relief valve; 124b: solenoid valve; 124a_all: merging portion; 124b_all: merging portion; 125: temperature detecting unit; 140: tightness and evacuation port; and 151: control unit.

Claims

CLAIMS [Claim 1] An air-conditioning apparatus comprising: a heat source unit including a compressor compressing and discharging refrigerant, a first switching valve switching between passages for the refrigerant discharged from the compressor, and a heat-source-unit heat exchanger exchanging heat between the refrigerant passing through the first switching valve and an ambient heat source medium; a plurality of indoor units each including a use side heat exchanger and a flow controller connected to the use side heat exchanger, the use side heat exchanger exchanging heat between the refrigerant passing through the first switching valve and an ambient use medium; and a relay unit disposed between the heat source unit and the indoor units, the relay unit connecting the heat source unit to each of the indoor units with first connecting pipes and second connecting pipes and having a function of switching at least one of the use side heat exchangers of the indoor units to a cooling operation side and switching at least one of the other use side heat exchangers to a heating operation side, the relay unit including a first branch section including second switching valves switchably connecting the use side heat exchangers to the cooling operation side or the heating operation side, the first branch section allowing the second switching valves to communicate to the first connecting pipes, and a second branch section including third switching valves connected to each of the flow controllers, the second branch section allowing the third switching valves to communicate to the second connecting pipes, the third switching valves, arranged in the second branch section, having a function of relieving pressure in response to detection of a predetermined or higher pressure. [Claim 2] The air-conditioning apparatus of claim 1, wherein the second switching valves, arranged in the first branch section, include a valve connected to the cooling operation side and a valve connected to the heating operation side, and the valve connected to the cooling operation side is a flow control valve. [Claim 3] The air-conditioning apparatus of claim 1 or 2, wherein the flow control valve is configured to open to a predetermined opening degree when a heating operation is switched to a cooling operation. [Claim 4] The air-conditioning apparatus of any one of claims 1 to 3, wherein the second switching valves, arranged in the first branch section, include a valve connected to the cooling operation side and a valve connected to the heating operation side such that the valves are separate from each other. [Claim 5] The air-conditioning apparatus of claim 2, wherein the flow control valve allows flow rate control at or below a flow coefficient CV value of 4.0. [Claim 6] The air-conditioning apparatus of any one of claims 1 to 5, wherein at least either the second switching valves of the first branch section or the third switching valves of the second branch section is molded of a material having a thermal conductivity of 150 [W/mK] to 200 [W/mK], [Claim 7] The air-conditioning apparatus of any one of claims 1 to 6, wherein either the second switching valves of the first branch section or the third switching valves of the second branch section includes an air-tightness and evacuation mechanism for the indoor unit or the connecting pipes.