JP5313774B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner including a heat source side heat exchanger using water as a heat source, and more particularly to an air conditioner having means for preventing freezing of water flowing in a heat source side heat exchanger.

  In recent years, environmental problems have become a global issue, and one solution is energy saving. In an air conditioner equipped with a heat source side heat exchanger that uses water as a heat source, water that is an unused heat source supplied from cooling tower equipment, boiler equipment, groundwater, etc. can be used. Since heat exchange is performed between the refrigerant and the refrigerant, its heat exchange efficiency is good, and it is more energy efficient than an air conditioner equipped with a heat source side heat exchanger that uses general air as a heat source. It can be said that the product has a low load. On the other hand, in an air conditioner equipped with a heat source side heat exchanger that uses water as a heat source, the heat source side heat exchanger exchanges heat between water and the refrigerant. Water flowing through the side heat exchanger may freeze and the frozen water may damage the heat exchanger.

  As a conventional anti-freezing technology for an air conditioner including a heat source side heat exchanger using water as a heat source, there is one disclosed in Japanese Patent Laid-Open No. 2003-294292 (Patent Document 1). In the air conditioner of Patent Document 1, whether or not sufficient water is supplied to the heat source side heat exchanger is detected by detecting the outlet gas temperature of the heat source side heat exchanger after a predetermined time has elapsed since the start of the compressor. When it is determined that water is not sufficiently supplied, the compressor is stopped to prevent water from freezing.

JP 2003-294292 A

  However, in the air conditioner of Patent Document 1, it is difficult to set a predetermined time and a predetermined temperature for preventing freezing of water, and if these settings are not appropriate, water for a specified flow flows at a specified temperature. Nevertheless, the compressor may be stopped to prevent freezing. If the compressor is stopped even when freezing prevention is not necessary, the heating operation cannot be performed during that time, causing a problem that indoor comfort cannot be ensured.

  In addition, in an air conditioner equipped with a heat source side heat exchanger that uses water as a heat source, it is desirable that the range of water flowing through the heat source side heat exchanger be as large as possible. It can be considered. In such a case, depending on the opening degree of the heat source side expansion valve, the installation conditions of the utilization unit, etc., it is understood that the compressor suction side pressure at the time of starting the compressor in the heating operation may decrease and the water may freeze. It was.

  An object of the present invention is to provide an air conditioner capable of improving indoor comfort by reliably preventing freezing of water flowing through a heat source side heat exchanger while increasing the use range of water flowing through the heat source side heat exchanger. There is to do.

In order to achieve the above-mentioned object, the present invention provides a compressor, a switching valve, a heat source side electric expansion valve, water provided with a refrigerant side flow path through which a refrigerant flows and a water side flow path through which water flows so that heat can be exchanged. Heat source unit having heat source side heat exchanger, liquid receiver, high pressure sensor and low pressure sensor as heat source, utilization unit having utilization side heat exchanger and utilization side electric expansion valve, heat source unit and utilization unit A gas connection pipe and a liquid connection pipe, and a control device, the compressor, the switching valve, the gas connection pipe, the use side heat exchanger, the use side electric expansion valve, and the liquid connection. Piping, the heat source side electric expansion valve, the refrigerant side flow path of the heat source side heat exchanger, the liquid receiver, the switching valve and the compressor are connected in order to constitute a refrigeration cycle, and heating operation and cooling operation are performed. In possible air conditioners, Serial refrigeration cycle includes a bypass circuit that communicates the low-pressure pipe of the suction side of the liquid receiver and the liquid connection pipe side of the liquid pipe of the heat-source-side electric expansion valve, the bypass circuit comprises a bypass electrically-operated expansion valve, wherein A refrigerant having a main circuit side flow path provided in the liquid pipe and a bypass side flow path provided downstream of the bypass circuit of the bypass electric expansion valve; the includes a refrigerant and heat exchange by-pass heat exchanger flows, wherein the control device, a part of the refrigerant to the bypass electrically-operated expansion valve when the compressor starts the heating operation to open have been flowing through the liquid pipe through the bypass circuit the flowing into the low-pressure pipe, the temperature of the refrigerant pressure of the low-pressure pipe flows through the refrigerant flow path of the heat source-side heat exchanger is controlled to be higher than freezing limit pressure becomes negative, the heating operation the compressor Control is performed to increase the heating capacity by increasing the operating frequency of the compressor until the low-pressure pressure of the low-pressure pipe reaches the freezing limit pressure while the bypass electric expansion valve is kept open even after transition from normal operation to normal operation It is in the structure to do.

In the present invention, a compressor, a switching valve, a heat source side electric expansion valve, a heat source side heat exchanger using water as a heat source, a receiver, a heat source unit having a high pressure sensor and a low pressure sensor, and a use side heat exchange And a use unit having a use side electric expansion valve, a gas connection pipe and a liquid connection pipe connecting the heat source unit and the use unit, and a control device, the compressor, the switching valve, the gas The connecting pipe, the use side heat exchanger, the use side electric expansion valve, the liquid connection pipe, the heat source side electric expansion valve, the heat source side heat exchanger, the liquid receiver, the switching valve, and the compressor in this order. In an air conditioner that is connected to form a refrigeration cycle and is capable of heating operation and cooling operation, the refrigeration cycle includes a liquid pipe on the liquid connection pipe side of the heat source side electric expansion valve and a low pressure on the suction side of the receiver Connect with piping The bypass circuit includes a bypass electric expansion valve, a main circuit side flow path provided in the liquid pipe, and a bypass side flow path provided downstream of the bypass circuit of the bypass electric expansion valve has the door, the refrigerant flowing through the refrigerant and the bypass-side flow path through the main circuit side flow path comprises a heat exchanger by-pass heat exchanger, the heat source unit detects the discharge superheat of the compressor the A high-pressure sensor, and a temperature sensor that detects an outlet superheat degree on the low-pressure piping side of the bypass circuit, and the control device opens the bypass electric expansion valve based on the high-pressure sensor and the temperature sensor. The upper limit of the degree is controlled so that the outlet temperature on the low-pressure piping side of the bypass circuit is equal to or lower than the saturation temperature of the refrigerant and the liquid refrigerant does not accumulate excessively in the receiver, and the bypass electric expansion Controlling the lower limit of the opening degree of the valve opening the low-pressure pipe side outlet superheat degree of the bypass circuit does not become and fully closed at a predetermined value or more.

  According to the air conditioner of the present invention, it is possible to improve indoor comfort by reliably preventing freezing of the water flowing through the heat source side heat exchanger while increasing the use range of the water flowing through the heat source side heat exchanger. .

The whole block diagram of the air conditioner of one Embodiment of this invention. The characteristic view which shows the relationship between the refrigerant | coolant pressure and water temperature in the heat source side heat exchanger of FIG. The figure which shows the change of the low voltage | pressure pressure at the time of starting of the compressor when not using the case where the bypass circuit of FIG. 1 is used. The figure which shows the change of the low pressure and the compressor frequency at the time of heating operation in this embodiment. The figure explaining the upper limit and lower limit opening degree of a bypass electric expansion valve in this embodiment. The control flowchart at the time of heating operation in this embodiment.

  Hereinafter, an air conditioner according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

  First, the overall configuration, functions, and the like of the air conditioner 50 of the present embodiment will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an air conditioner 50 according to the present embodiment.

  The air conditioner 50 includes a heat source unit 1 that is an outdoor unit, a plurality of (two in this embodiment) use units 23 that are indoor units, and a gas connection pipe that connects the heat source unit 1 and the use unit 23. 21 and a liquid connection pipe 22. The gas connection pipe 21 is provided so as to connect between the switching valve 3 of the heat source unit 1 and the use side heat exchanger 25 of the use unit 23. The liquid connection pipe 22 is provided so as to connect between the main circuit side flow path 7 a of the heat source unit 1 and the use side electric expansion valve 24 of the use unit 23.

  The heat source unit 1 includes a compressor 2, a switching valve 3, a liquid receiver 9, a heat source side heat exchanger 4, a heat source side electric expansion valve 5, a bypass circuit 6, a bypass heat exchanger 7, a bypass electric expansion valve 8, and the like. The refrigeration cycle component device and a control system component device including a high pressure sensor 10, a low pressure sensor 11, temperature sensors 12, 13 and a control unit 20 are provided. The heat source unit 1 uses water as a heat source.

  The compressor 2 is composed of a variable capacity compressor whose operating frequency is controlled by an inverter. The switching valve 3 is a switching valve that switches the flow direction of the refrigerant discharged from the compressor 2 and the flow direction of the refrigerant sucked into the compressor 2, and is constituted by a four-way valve in this embodiment. The liquid receiver 9 is provided in the low-pressure pipe 15 on the suction side of the compressor 2 so that only the gas refrigerant is sucked into the compressor 2.

  The low-pressure pipe 15 is a refrigerant pipe that connects the suction pipe of the compressor 2 and the switching valve 3. Further, the discharge pipe of the compressor 2 and the switching valve 3 are connected by a high-pressure pipe 31.

  The heat source side heat exchanger 4 is composed of a refrigerant / water heat exchanger, and has a refrigerant side flow path 4a through which the refrigerant flows and a water side flow path 4b through which water flows. The refrigerant side flow path 4a and the water side flow path 4b are provided so that heat exchange is possible, and heat is exchanged between the refrigerant flowing through the refrigerant side flow path 4a and the water flowing through the water side flow path 4b. The switching valve 3 and the refrigerant side flow path 4 a are connected via a gas / liquid pipe 32.

  Water is supplied from the outside of the heat source unit 1 to the water side flow path 4b of the heat source side heat exchanger 4. This water is sent by an external boiler or cold water equipment so that the temperature and flow rate are adjusted so as to be within the specified use range of the heat source unit.

  The heat source side electric expansion valve 5 is provided between the refrigerant side flow path 4a of the heat source side heat exchanger 4 and the liquid connection pipe 22, and depressurizes the flowing refrigerant. The heat source side electric expansion valve 5 is connected between the refrigerant side flow path 4a and the main circuit side flow path 7a. The heat source side electric expansion valve 5 and the liquid connection pipe 22 are connected by a liquid pipe 14.

  The bypass circuit 6 bypasses the refrigerant flowing through the liquid pipe 14 and returns it to the compressor 2 via the liquid receiver 9, and is connected so that the liquid pipe 14 and the low-pressure pipe 15 communicate with each other. The bypass circuit 6 is provided with a bypass electric expansion valve 8 and a bypass-side flow path 7 b of the bypass heat exchanger 7.

  The bypass electric expansion valve 8 is provided between the liquid pipe 14 and the bypass-side flow path 7 b and adjusts the bypass flow rate of the refrigerant to the bypass circuit 6.

  The bypass heat exchanger 7 includes a main circuit side flow path 7a provided in the liquid pipe 14 constituting the main circuit of the refrigeration cycle, and a bypass side flow path 7b provided in the bypass circuit 6, and the main circuit side Heat is exchanged between the refrigerant flowing through the flow path 7a and the refrigerant flowing through the bypass side flow path 7b. The bypass heat exchanger 7 is for evaporating the refrigerant bypassed from the liquid pipe 14 to the bypass circuit 6.

  The high pressure sensor 10 is provided in the high pressure pipe 31 on the discharge side of the compressor 2 and detects the discharge side pressure (high pressure) of the compressor 2. The low pressure sensor 11 is provided in the low pressure pipe 15 on the suction side of the compressor 2 and detects the suction side pressure (low pressure) of the compressor 2. The temperature sensor 12 is provided on the outlet side of the bypass side flow path 7b of the bypass circuit 6, and measures the refrigerant temperature evaporated in the main circuit side flow path 7a.

  The control part 20 controls the apparatus which comprises the air conditioner 50 based on sensors, such as the high pressure sensor 10, the low pressure sensor 11, and the temperature sensor 12, and an operation switch. In the present embodiment, the control unit 20 is provided only in the heat source unit 1, but may cooperate with a control device provided in the utilization unit 23.

  The two usage units 23 are connected in parallel. Each usage unit 23 includes a component device of a refrigeration cycle including a usage-side heat exchanger 25, a usage-side electric expansion valve 24, and the like, and a usage-side blower 26 that vents usage-side air to the usage-side heat exchanger 25. ing. The use side heat exchanger 25 and the use side electric expansion valve 24 are connected in series between the gas connection pipe 21 and the liquid connection pipe 22.

  During the heating operation, the switching valve 3 is switched as shown by a solid line, the use-side electric expansion valve 24 is fully opened, and the heat source-side electric expansion valve 5 is set to a predetermined throttle opening, so that the refrigerant is the main refrigeration cycle. The circuit is circulated as shown by solid arrows.

  That is, the refrigerant compressed to high temperature and high pressure by the compressor 2 passes through the switching valve 3 and the gas connection pipe 21, reaches the use side heat exchanger 25 of the use unit 23, and condenses in the use side heat exchanger 25. Then, heat is released to the room air to heat the room. The condensed and liquefied refrigerant passes through the use side electric expansion valve 24, the liquid connection pipe 22 and the main circuit side flow path 7a, reaches the heat source side electric expansion valve 5, and is depressurized by the heat source side electric expansion valve 5, and the heat source The refrigerant is evaporated by absorbing heat from the water in the water side channel 4b in the refrigerant side channel 4a of the side heat exchanger 4. The evaporated refrigerant is returned to the compressor 2 through the gas / liquid pipe 32, the switching valve 3, the low pressure pipe 15 and the liquid receiver 9.

  Next, freezing of water in the water side flow path 4b of the heat source side heat exchanger 4 during heating operation will be described with reference to FIGS. FIG. 2 is a characteristic diagram showing the relationship between the refrigerant pressure and the water temperature in the heat source side heat exchanger 4 of FIG.

  During the heating operation, the refrigerant side flow path 4a of the heat source side heat exchanger 4 serves as an evaporator, and low-pressure and low-temperature refrigerant flows in. The refrigerant that has flowed into the refrigerant side flow path 4a evaporates by removing heat from the water supplied from the external equipment. As a result, the temperature of the water flowing in the water side flow path 4b of the heat source side heat exchanger 4 is lowered.

  The refrigerant temperature (refrigerant saturation temperature) at the inlet of the refrigerant side flow path 4 a of the heat source side heat exchanger 4 depends on the pressure, and the pressure is almost the same as the low pressure of the compressor 2. Since the minimum temperature of the water in the water side flow path 4b of the heat source side heat exchanger 4 is considered to be substantially equal to the refrigerant temperature, the relationship between the water temperature and the low pressure is as shown in FIG. The pressure at which the refrigerant temperature becomes negative is represented as P1.

  As a general anti-freezing method, there is a method in which the compressor frequency is controlled by the control unit 20 so that the low-pressure pressure is maintained at the pressure P1 or more during heating operation. For example, when the low pressure of the compressor 2 falls below the pressure P1, the compressor frequency is lowered to reduce the refrigerant circulation rate, and control is performed so that the low pressure is restored to the pressure P1 or higher (slightly higher than the pressure P1).

  When the temperature of the water flowing through the water-side flow path 4b of the heat source side heat exchanger 4 is high and the flow rate is large, the possibility of water freezing is low, but the water temperature is low (for example, the water temperature after heat exchange is 0 ° C. When the amount of water is small, it begins to freeze from the stagnation part in the water flow path 4b. In order to reduce the heat exchange performance of the heat source side heat exchanger 4 even if the part is frozen, there is a case where the evaporation temperature is further lowered and the freezing is promoted as the low pressure is lowered. In order to prevent this freezing, if the compressor frequency is lowered or the heating operation is stopped, indoor comfort is deteriorated.

  Therefore, in the present embodiment, the bypass circuit 6 is operated during the heating operation so that freezing can be prevented while securing the heating capacity. The operation of the bypass circuit 6 will be specifically described below.

The pressure of the refrigerant flowing through the liquid pipe 14 is slightly lower than the high-pressure side pressure of the compressor 2, for sufficiently high compared to the pressure of the low-pressure pipe 15, open the bypass electric expansion valve 8, flows through the liquid piping 14 A part of the refrigerant flowing flows into the low-pressure pipe 15 through the bypass circuit 6, and the pressure of the low-pressure pipe 15 rises. Accordingly, the pressure of the refrigerant in the gas / liquid pipe 32 communicated with the low pressure pipe 15, the refrigerant side flow path 4 a of the heat source side heat exchanger 4 and the pipe to the heat source side electric expansion valve 5 is increased. As the refrigerant pressure rises, the refrigerant temperature also rises.

  In order to prevent the liquid refrigerant in the liquid pipe 14 from flowing into the low-pressure pipe 15 as it is and sucked into the compressor 2, a bypass heat exchanger 7 is installed in the bypass circuit 6. In the bypass heat exchanger 7, heat exchange is performed between the liquid refrigerant returned from the utilization unit 23 and the two-layer refrigerant decompressed through the bypass electric expansion valve 8. Since the refrigerant that has passed through the bypass electric expansion valve 8 has a lower temperature than the liquid refrigerant in the liquid pipe 14, it takes heat from the refrigerant in the liquid pipe 14 and evaporates. As a result, the liquid refrigerant does not return to the low pressure side of the compressor 2 and the heating capacity can be increased.

  Next, prevention of freezing when the compressor 2 is started in the heating operation will be described with reference to FIGS. 1 and 3. FIG. 3 is a diagram showing a change in low-pressure pressure when the compressor 2 is started up when the bypass circuit 6 of FIG. 1 is used and when it is not used.

  Depending on the opening degree of the heat source side electric expansion valve 5 and the installation conditions of the utilization unit 23, the low pressure of the low pressure pipe 15 may fall below the pressure in the steady operation state when the compressor 2 is started. In the air conditioner 50 provided with the heat source side heat exchanger 4 that uses water as a heat source, it is desirable to make the use range of water as large as possible, and the use range is a low water temperature that is barely established in a steady operation state.

Therefore, low pressure during startup when not using the bypass circuit 6, as shown in the characteristic curve 3 3 of Figure 3, may be less than the pressure P1. If the water is flowing, it will not freeze completely, so if the operation continues and the low pressure rises, the ice will melt, but during that time the evaporation capacity will decline and the heating capacity will remain lowered. Unable to make the room comfortable early.

  Therefore, in the present embodiment, the bypass electric expansion valve 8 is opened immediately after startup and the bypass circuit 6 is used to prevent the low pressure from dropping below the pressure P1. That is, by opening the bypass electric expansion valve 8 immediately after the start-up, the low-pressure pressure at the start-up is suppressed to drop to a pressure P2 higher than the pressure P1, as shown by the characteristic curve 34 in FIG. Thus, the heating capacity can be ensured without lowering the compressor frequency from the start to the steady operation, and the room can be comfortably brought to an early stage.

In addition, the temperature of the liquid pipe 14 does not rise so much immediately after the start-up, and the refrigerant in the bypass circuit 6 is separated from the refrigerant in the main circuit side flow path 7a even if it passes through the bypass side flow path 7b of the heat exchanger 7. there is a possibility to return to the low-pressure pipe 15 contains a liquid refrigerant can not sufficiently evaporated endotherm less. Therefore, in the present embodiment, the liquid receiver 9 is provided on the suction side of the compressor 2, and even if a refrigerant containing liquid refrigerant flows from the bypass circuit 6, the liquid refrigerant is accumulated in the liquid receiver 9 and the compressor 2. It is designed not to be inhaled.

  Next, specific operations of the bypass electric expansion valve 8 and the bypass heat exchanger 7 in the bypass circuit 6 will be described with reference to FIG.

  As a method of increasing the low-pressure pressure during the heating operation, it is conceivable to bypass the refrigerant directly from the high-pressure pipe 31 on the discharge side of the compressor 2 to the low-pressure pipe 15 on the suction side. However, in this bypass method, since the refrigerant that should flow to the use side heat exchanger 25 that is the high pressure side of the main circuit of the refrigeration cycle is directly flowed to the low pressure side, the refrigerant flowing through the use unit 23 is reduced, and the refrigeration cycle is effective. Will not be available.

  Therefore, in the present embodiment, during the heating operation, the liquid refrigerant radiated and condensed to the indoor air by the use side heat exchanger 25 is diverted to the bypass circuit 6, decompressed by the bypass electric expansion valve 8, and the bypass side flow path 7b. So that the heat is absorbed from the bypass side flow path 7b (in other words, the heat of the refrigerant flowing through the main circuit side flow path 7a is dissipated to the refrigerant of the bypass side flow path 7b). The amount of heat can be used effectively. Thereby, the heating capacity of the refrigeration cycle can be improved.

  Next, the control operation during the heating operation of the air conditioner 50 will be specifically described with reference to FIGS. 4 to 6. FIG. 4 is a diagram showing changes in low-pressure pressure and compressor frequency during heating operation in the present embodiment, FIG. 5 is a diagram for explaining the upper limit and lower limit opening of the bypass electric expansion valve 8 in the present embodiment, and FIG. It is a control flowchart at the time of heating operation in an embodiment.

  When the bypass circuit 6 is used when the compressor 2 is started in the heating operation, as shown in FIGS. 3 and 4, the low pressure of the low pressure pipe 15 is the lowest low pressure P1 when the bypass circuit 6 is not used. Can be suppressed to a higher pressure P2.

  In the present embodiment, the compressor frequency is increased until the low-pressure pressure of the low-pressure pipe 15 reaches the freezing limit pressure P1 by utilizing the amount higher than the pressure P1 in the steady operation state of the heating operation. Thereby, heating capability can be raised, maintaining the low pressure same as the steady operation state in case the bypass circuit 6 is unused.

  Here, even if the bypass electric expansion valve 8 is opened more than a predetermined value, there is no effect in increasing the low pressure. Conversely, if the bypass electric expansion valve 8 is opened too much, the bypassed refrigerant cannot be completely evaporated in the heat exchanger 7 and flows into the low pressure side. It collects in the liquid receiver 2. If it becomes so, the fall of a bypass exit superheat will be caused and the reliability of the compressor 2 will be reduced. Further, the refrigerant accumulated in the liquid receiver 9 should be used to increase the condensation pressure by flowing through the main circuit of the refrigeration cycle, and since this is not done, the condensation pressure is reduced and blown out. The temperature is also lowered, adversely affecting comfort.

  Therefore, in this embodiment, the opening degree of the bypass electric expansion valve 8 is adjusted by the control unit 20 so that the discharge superheat degree and the bypass outlet superheat degree of the compressor 2 become predetermined values, and the refrigerant of the liquid receiver 9 is adjusted. The amount that accumulates can be controlled to ensure comfort. A specific description will be given along the control flowchart shown in FIG.

  Simultaneously with the start of the compressor 2, the bypass electric expansion valve 8 is opened by a predetermined amount (step S1). Next, it is determined whether the discharge superheat degree of the compressor 2 is higher or lower than the target value (step S2). In this determination, if it is higher than the target value, it is confirmed that the current opening degree is not the upper limit value (step S3). Is opened by a certain amount (step S4), and the process returns to step S2. The discharge superheat degree of the compressor 2 is calculated from the measured value of the high pressure sensor 10.

  If the discharge superheat degree of the compressor 2 is lower than the target value in step S2, it is determined whether the bypass outlet superheat degree is high or low (step S5). The bypass electric expansion valve 8 is controlled based on the determination result. Specifically, if the bypass outlet superheat degree is higher than a predetermined value, even if the bypass electric expansion valve 8 is opened, the discharge superheat degree of the compressor 2 is not lowered. S8). If the bypass outlet superheat degree is lower than the predetermined value, it is confirmed that the opening degree of the bypass electric expansion valve 8 is not the lower limit value (step S6), and if not, the bypass electric expansion valve 8 is closed by a predetermined amount ( Step S7). The bypass outlet superheat degree is calculated from the measured values of the low pressure sensor 11 and the temperature sensor 12.

  Here, an example of setting the upper limit value and the lower limit value of the bypass electric expansion valve 8 is shown in FIG. The upper limit is an opening at which the outlet temperature of the bypass-side flow path 7b of the bypass circuit 6 is equal to or lower than the saturation temperature of the refrigerant and the liquid refrigerant does not accumulate in the liquid receiver 9, and the lower-limit value is the bypass-side flow path of the bypass circuit 6. The opening degree which the 7b outlet superheat degree is more than a predetermined value and does not fully close is set.

  DESCRIPTION OF SYMBOLS 1 ... Heat source unit, 2 ... Compressor, 3 ... Switching valve, 4 ... Heat source side heat exchanger, 4a ... Refrigerant side flow path, 4b ... Water side flow path, 5 ... Heat source side electric expansion valve, 6 ... Bypass circuit, DESCRIPTION OF SYMBOLS 7 ... Bypass heat exchanger, 7a ... Main circuit side flow path, 7b ... Bypass side flow path, 8 ... Bypass electric expansion valve, 9 ... Liquid receiver, 10 ... High pressure sensor, 11 ... Low pressure sensor, 12 ... Temperature Sensor: 13 ... Temperature sensor, 14 ... Liquid pipe, 15 ... Low pressure pipe, 20 ... Control part, 21 ... Gas connection pipe, 22 ... Liquid connection pipe, 23 ... Use unit, 24 ... Use side electric expansion valve, 25 ... Use Side heat exchanger, 26 ... use side blower, 31 ... high pressure piping, 32 ... gas / liquid piping.

Claims (2)

A compressor, a switching valve, a heat source side electric expansion valve, a heat source side heat exchanger using water as a heat source, a liquid receiver, and a water side flow path through which a refrigerant flows and a water side flow path through which water flows . A heat source unit having a high pressure sensor and a low pressure sensor, a use unit having a use side heat exchanger and a use side electric expansion valve, a gas connection pipe and a liquid connection pipe connecting the heat source unit and the use unit, A control device,
The compressor, the switching valve, the gas connection pipe, the use side heat exchanger, the use side electric expansion valve, the liquid connection pipe, the heat source side electric expansion valve, and the refrigerant side flow path of the heat source side heat exchanger The refrigeration cycle is configured by sequentially connecting the liquid receiver, the switching valve, and the compressor,
In an air conditioner capable of heating operation and cooling operation,
The refrigeration cycle includes a bypass circuit that communicates a liquid pipe on the liquid connection pipe side of the heat source side electric expansion valve and a low pressure pipe on the suction side of the receiver.
The bypass circuit includes a bypass electric expansion valve,
The main circuit side flow path provided in the liquid piping and the bypass side flow path provided on the downstream side of the bypass circuit of the bypass electric expansion valve, the refrigerant flowing in the main circuit side flow path and the bypass side flow It is equipped with a bypass heat exchanger that can exchange heat with the refrigerant flowing through the path,
The controller is
The part of the refrigerant said bypass electric expansion valve opening have been at compressor start heating operation through the liquid pipe flowing into the low-pressure pipe through the bypass circuit, the refrigerant pressure in the low-pressure pipe of the heat source-side heat exchanger Control so that the temperature of the refrigerant flowing in the side flow path becomes higher than the freezing limit pressure at which it becomes negative ,
Even if the heating operation starts from the start of the compressor to the steady operation, the bypass electric expansion valve is kept open, and the operating frequency of the compressor is increased until the low pressure of the low pressure pipe reaches the freezing limit pressure. The air conditioner is characterized by being controlled so as to enhance the pressure . Heat source unit having compressor, switching valve, heat source side electric expansion valve, heat source side heat exchanger using water as heat source, liquid receiver, high pressure sensor and low pressure sensor, user side heat exchanger and user side electric expansion A use unit having a valve, a gas connection pipe and a liquid connection pipe for connecting the heat source unit and the use unit, and a control device,
The compressor, the switching valve, the gas connection pipe, the use side heat exchanger, the use side electric expansion valve, the liquid connection pipe, the heat source side electric expansion valve, the heat source side heat exchanger, the liquid receiver The refrigeration cycle is configured by sequentially connecting the switching valve and the compressor,
In an air conditioner capable of heating operation and cooling operation,
The refrigeration cycle includes a bypass circuit that communicates a liquid pipe on the liquid connection pipe side of the heat source side electric expansion valve and a low pressure pipe on the suction side of the receiver.
The bypass circuit includes a bypass electric expansion valve,
The main circuit side flow path provided in the liquid piping and the bypass side flow path provided on the downstream side of the bypass circuit of the bypass electric expansion valve, the refrigerant flowing in the main circuit side flow path and the bypass side flow It is equipped with a bypass heat exchanger that can exchange heat with the refrigerant flowing through the path,
The control device opens the bypass electric expansion valve when the compressor for heating operation is started, and increases the pressure of the low-pressure pipe to flow through the heat source side heat exchanger as compared with the case where the bypass electric expansion valve is not opened. Control is performed so that the temperature of the refrigerant rises, and even if the compressor is switched from the start-up of the heating operation to the steady operation, the bypass electric expansion valve is kept open and the operating frequency of the compressor is increased to increase the heating capacity. Control to enhance,
The heat source unit includes the high pressure sensor that detects a discharge superheat degree of the compressor, and a temperature sensor that detects an outlet superheat degree on the low pressure piping side of the bypass circuit,
Further, the control device sets the upper limit of the opening degree of the bypass electric expansion valve based on the high pressure sensor and the temperature sensor so that the outlet temperature on the low pressure piping side of the bypass circuit is equal to or lower than the saturation temperature of the refrigerant. The opening is controlled so that the liquid refrigerant does not accumulate too much in the liquidator, and the lower limit of the opening degree of the bypass electric expansion valve is set to an opening degree at which the outlet superheat degree on the low pressure piping side of the bypass circuit is not less than a predetermined value and is not fully closed. An air conditioner that is controlled at a time .

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