JP5956839B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that can be operated by switching between a forced circulation cooling operation and a natural circulation cooling operation.

  The energy depletion problem and global warming problem in recent years have attracted attention, and the energy-saving performance of air conditioners has become more important. On the other hand, loads due to office automation equipment and the like are increasing in buildings and offices, and the number of cases where cooling is required even in spring and autumn when the outside air temperature is low.

  In such a situation, in order to improve the energy saving performance of the air conditioner, Japanese Patent No. 4167196 (Patent Document 1) proposes an air conditioner that combines natural circulation cooling operation and forced circulation cooling operation. ing. That is, in this patent document 1, when the outside air temperature is low, the compressor is stopped and the natural circulation cooling operation with less power using the circulation of the refrigerant by gravity is performed, and the outside air temperature is high and the load is high. Describes a natural circulation combined type air conditioner that performs a forced circulation cooling operation that operates a compressor.

Japanese Patent No. 4167196

  An air conditioner in which an outdoor unit having an outdoor heat exchanger and an indoor unit having an indoor heat exchanger are connected by a refrigerant pipe, and a refrigerant is circulated between the outdoor unit and the indoor unit to constitute a refrigeration cycle. In the above, the outdoor heat exchanger is installed above the indoor heat exchanger. When the outside air temperature is lower than the indoor temperature, cooling by natural circulation (natural circulation cooling operation) is performed. Is possible.

  That is, in the outdoor heat exchanger, the refrigerant condensed and liquefied by the outside air is introduced into the indoor heat exchanger via the refrigerant pipe (connecting liquid pipe) using gravity, and is evaporated here. It is possible to perform a natural circulation cooling operation in which the gaseous refrigerant (gas refrigerant) is raised through the refrigerant pipe (connecting gas pipe) and reintroduced into the outdoor heat exchanger installed in the upper part.

  In this natural circulation cooling operation, since the compressor is stopped, no power is required to drive the compressor. Therefore, the cooling operation with low energy consumption can be performed. However, in this natural circulation cooling operation, if the outside air temperature is not lower than the room temperature to some extent, the circulation amount of the refrigerant is reduced and the necessary cooling capacity cannot be obtained.

  In the air conditioner described in Patent Document 1, as described above, the forced circulation cooling operation by the compressor drive is performed when the outside air temperature is high, and the natural circulation cooling operation is performed when the outside air temperature is low. It is configured. And in this patent document 1, when switching from forced circulation cooling operation to natural circulation cooling operation, by performing a switching operation such that the refrigerant in the connection liquid pipe is always in a supercooled state, Natural circulation cooling operation after switching can be performed stably.

  In the air conditioner that switches from forced circulation cooling operation to natural circulation cooling operation as described above, transition to natural circulation cooling operation during forced circulation cooling operation is performed to ensure switching to natural circulation cooling operation. It is necessary to control. That is, at the time of transition to natural circulation cooling operation, the liquid refrigerant surely flows through the connection liquid pipe connecting the outdoor unit and the indoor unit, and the gas refrigerant flows through the connection gas pipe without fail. It is necessary to control the temperature of the refrigerant flowing through the connection liquid pipe and the connection gas pipe.

  However, although there is a description in the above-mentioned Patent Document 1 that the refrigerant in the connection liquid pipe is brought into a supercooled state during the transition, no consideration is given to the connection gas pipe. For this reason, there is a problem that the transition from the forced circulation cooling operation to the natural circulation cooling operation cannot be reliably performed.

  An object of the present invention is to obtain an air conditioner that can reliably shift from forced circulation cooling operation to natural circulation cooling operation.

  In order to achieve the above object, the present invention sequentially connects a compressor, an outdoor heat exchanger for exchanging heat with outdoor air, a decompression device, and an indoor heat exchanger for exchanging heat with indoor air through refrigerant piping, Connected liquid piping for forced circulation cooling operation for operating the compressor to forcibly circulate the refrigerant, the indoor heat exchanger, and the outdoor heat exchanger installed at a position higher than the indoor heat exchanger And an air conditioner that can be operated by switching between a natural circulation cooling operation in which the refrigerant is naturally circulated using gravity and is connected with a connecting gas pipe, when the forced circulation cooling operation is shifted to the natural circulation cooling operation. In addition, the temperature of the connection liquid pipe is decreased by increasing the amount of air for heat exchange with the outdoor heat exchanger so that the temperature of the connection liquid pipe is lower than the temperature of the connection gas pipe. The decompressor By increasing the pressure reduction amount, and controls to raise the temperature of the connection gas pipe.

  Another feature of the present invention is a forced circulation cooling operation in which a compressor, an outdoor heat exchanger, a pressure reducing device, and an indoor heat exchanger are sequentially connected by a refrigerant pipe, and the compressor is operated to forcibly circulate the refrigerant. The indoor heat exchanger and an outdoor heat exchanger installed at a position higher than the indoor heat exchanger are connected by a connecting liquid pipe and a connecting gas pipe, and the refrigerant is removed using gravity. In an air conditioner that can be operated by switching between natural circulation cooling operation for natural circulation, when the forced circulation cooling operation is shifted to the natural circulation cooling operation, the temperature of the connection liquid pipe is higher than the temperature of the connection gas pipe. Control to lower the temperature of the connecting liquid piping by lowering the rotational speed of the compressor and increase the pressure reduction amount of the decompressing device to increase the temperature of the connecting gas piping so that the temperature of the connecting gas piping is increased. There is to do.

  According to the present invention, it is possible to obtain an air conditioner that can reliably perform a transition from forced circulation cooling operation to natural circulation cooling operation.

The refrigeration cycle block diagram which shows Example 1 of the air conditioner of this invention. The refrigeration cycle block diagram which shows Example 2 of the air conditioner of this invention.

  Hereinafter, specific embodiments of the air conditioner of the present invention will be described with reference to the drawings. Note that, in each drawing, the portions denoted by the same reference numerals indicate the same or corresponding portions.

  FIG. 1 is a refrigeration cycle configuration diagram showing Embodiment 1 of an air conditioner of the present invention. In FIG. 1, 1 is a compressor constituted by a scroll compressor and the like, 2 is an outdoor heat exchanger for exchanging heat with outdoor air, and 3 is an indoor expansion valve (pressure reducing device) constituted by an electronic expansion valve and the like. Reference numeral 4 denotes an indoor heat exchanger for exchanging heat with room air. These devices are sequentially connected by refrigerant pipes (connection liquid pipe 5, connection gas pipe 6 and the like). The refrigerant pipe on the suction side and the refrigerant pipe on the discharge side of the compressor 1 are connected by a bypass pipe 7 so as to bypass the compressor 1, and the outdoor heat exchange is connected to the bypass pipe 7. A check valve 8 is provided that allows the refrigerant to flow only to the side of the vessel 2.

  9 is an outdoor fan that blows outdoor air to the outdoor heat exchanger 2, 10 is an indoor fan that blows indoor air to the indoor heat exchanger 4, and 11 is a refrigerant on the outlet side of the outdoor heat exchanger 2. A temperature sensor (temperature detection means) 12 for detecting the temperature of the pipe, and 12 is a temperature sensor (temperature detection means) for detecting the temperature of the refrigerant pipe on the outlet side of the indoor heat exchanger 2.

  The compressor 1, the outdoor heat exchanger 2, the bypass pipe 7, the check valve 8, the outdoor fan 9, the temperature sensor 11, and the like described above are provided in the outdoor unit 100 installed outdoors, and the indoor expansion described above. The valve 3, the indoor heat exchanger 4, the indoor fan 10, the temperature sensor 12, and the like are provided in an indoor unit 200 installed indoors. The outdoor unit 100 and the indoor unit 200 are connected by the connection liquid pipe 5 and the connection gas pipe 6, and the outdoor unit 100 is installed at a position higher than the indoor unit 200, for example, on the roof of a building. Yes.

  That is, the air conditioner of this embodiment was installed not only in the forced circulation cooling operation in which the compressor 1 is operated to forcibly circulate the refrigerant, but also in the indoor heat exchanger 4 and a position higher than this. The outdoor heat exchanger 2 is connected by the connection liquid pipe 5 and the connection gas pipe 6, and a natural circulation cooling operation in which the refrigerant is naturally circulated using gravity is possible. The air conditioner can be operated by switching between the forced circulation cooling operation and the natural circulation cooling operation.

  During the forced circulation cooling operation, the refrigerant flows as indicated by the solid black arrows in FIG. That is, the refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 2 installed above, where it is liquefied by exchanging heat with the air blown by the outdoor fan 9. Thereafter, the liquefied liquid refrigerant flows through the connecting liquid pipe 5, is depressurized by the indoor expansion valve 3, and enters the indoor heat exchanger 4. Here, the refrigerant exchanges heat with the air sent by the indoor fan 10 to cool the air, and also increases (vaporizes) the vapor itself, flows through the connecting gas pipe 6 and is sucked into the compressor 1 again. Repeat the refrigeration cycle.

  During the natural circulation cooling operation, the refrigerant flows as indicated by solid white arrows in the figure. In the natural circulation cooling operation, the compressor 1 is stopped. For this reason, the refrigerant does not flow through the compressor 1, and the gas refrigerant (gaseous refrigerant) from the indoor heat exchanger 4 passes through the bypass pipe 7 and the check valve 8 and the outdoor heat exchanger 2. Flowing into. Further, the indoor expansion valve 3 is fully opened to reduce the flow resistance through which the refrigerant flows as much as possible.

  This natural circulation cooling operation enables efficient operation when the temperature of outdoor air is low and the temperature of indoor air is high. In order to reliably perform this natural circulation cooling operation, it is necessary to ensure that liquid refrigerant flows through the connection liquid pipe 5 and gas refrigerant (gas refrigerant) flows through the connection gas pipe 6 reliably. However, during the forced circulation cooling operation, since the compressor is operated, the condensation temperature in the outdoor heat exchanger 2 is normally higher than the evaporation temperature in the indoor heat exchanger 4. For this reason, in most cases, the temperature of the connection liquid pipe 5 is higher than the temperature of the connection gas pipe 6, and immediately after shifting to the natural circulation cooling operation, In some cases, a part of the gas refrigerant is vaporized, or a part of the gas refrigerant is liquefied in the connection gas pipe 6, and natural circulation of the refrigerant is hindered, and the natural circulation cooling operation cannot be performed.

  If the temperature condition of the connection liquid pipe 5 is lower than the temperature of the connection gas pipe 6 before shifting to the natural circulation cooling operation, one of the liquid refrigerants in the connection liquid pipe 5 can be obtained. Since it is possible to prevent the portion from being vaporized and liquefying a part of the gas refrigerant in the connection gas pipe 6, it is possible to smoothly shift to the natural circulation cooling operation.

Therefore, in the present embodiment, when the forced circulation cooling operation is shifted to the natural circulation cooling operation, the rotational speed of the outdoor fan 9 is increased so as to satisfy the temperature condition, and the outdoor heat exchanger 2 is increased. Control to increase the amount of heat exchange. If it does in this way, it will become possible to cool the temperature of the said connection liquid piping 5 to near outdoor temperature.
Further, the amount of superheat of the gas refrigerant flowing out of the indoor heat exchanger 4 is controlled by increasing the amount of pressure reduction of the indoor expansion valve 3. As a result, the temperature of the connecting gas pipe 6 can be heated to near the room temperature.

  In this way, the temperature of the connection liquid pipe 5 can be made lower than the temperature of the connection gas pipe 6. Although not shown, the air conditioner of FIG. 1 is provided with a control device, which takes in the temperature signal detected by the temperature sensors 11 and 12, and connects the connection liquid pipe 5. After confirming that the temperature is lower than the temperature of the connecting gas pipe 6, the compressor 1 is then stopped and shifted to a natural circulation cooling operation.

  Thus, the control device controls the outdoor fan 9 and the indoor expansion valve 3 as described above, and confirms that the temperature of the connection liquid pipe 5 is lower than the temperature of the connection gas pipe 6. After that, by controlling the compressor 1 to stop and shift to the natural circulation cooling operation, a part of the liquid refrigerant is vaporized in the connection liquid pipe 5 or in the connection gas pipe 6. A part of the gas refrigerant can be prevented from being liquefied, and the transition to the natural circulation cooling operation can be performed smoothly and reliably.

  In the above-described example, the temperature of the connection liquid pipe 5 is decreased by increasing the number of rotations of the outdoor fan 9, but instead of increasing the number of rotations of the outdoor fan 9, the compressor Even if it controls so that the rotation speed of 1 may be reduced, it is possible to reduce the temperature of the said connection liquid piping 5. FIG. Therefore, the temperature of the connection liquid pipe 5 can be lowered by performing at least one control of increasing the rotational speed of the outdoor fan 9 and decreasing the rotational speed of the compressor 1. . Preferably, if both the increase of the rotation speed of the outdoor fan 9 and the decrease of the rotation speed of the compressor 1 are performed, the effect of lowering the temperature of the connection liquid pipe 5 is achieved. Can be larger.

In the example described above, the amount of pressure reduction of the indoor expansion valve 3 is increased in order to increase the temperature of the connection gas pipe 6, but it is also effective to increase the rotational speed of the indoor fan 10. There is. Therefore, preferably, when the pressure reduction amount of the indoor expansion valve 3 is increased and the rotational speed of the indoor fan 10 is also increased, the effect of increasing the temperature of the connection gas pipe 6 can be increased. it can.
Control for decreasing the rotational speed of the compressor 1 and control for increasing the rotational speed of the indoor fan 10 are also performed by the control device.

  As described above, in this embodiment, when the forced circulation cooling operation is shifted to the natural circulation cooling operation, the temperature of the connection liquid pipe 5 that connects the outdoor unit 100 and the indoor unit 200 is the temperature of the connection gas pipe 6. Air conditioning that can make a transition from forced circulation cooling operation to high-efficiency natural circulation cooling operation with certainty. Machine can be realized.

  In the above embodiment, the case where the pressure reducing device is the indoor expansion valve 3 provided in the indoor unit 200 has been described. However, the pressure reducing device is not limited to the indoor expansion valve 3, and the chamber What is necessary is just the decompression device provided in the refrigerant | coolant piping which has connected the exit side of the outer side heat exchanger 2, and the entrance side of the said indoor heat exchanger 4. FIG.

  In the example described above, the temperature of the connection liquid pipe 5 is lowered by increasing the rotational speed of the outdoor fan 9 or decreasing the rotational speed of the compressor 1, and the indoor expansion valve 3 is decompressed. The temperature of the connecting gas pipe 6 is increased by increasing the amount. However, if the rotational speed of the outdoor fan 9 is increased or the rotational speed of the compressor 1 is decreased, the temperature of the connection liquid pipe 5 can be lowered. If the temperature condition can be made lower than the temperature of the connecting gas pipe 6, the transition to the natural circulation cooling operation is possible. Therefore, it is preferable to perform the control for increasing the pressure reduction amount of the indoor expansion valve 3 together. However, when the temperature of the connection liquid pipe 5 can be lower than the temperature of the connection gas pipe 6 without performing this control. In some cases, transition to natural circulation cooling operation is possible.

  FIG. 2 is a refrigeration cycle configuration diagram showing Embodiment 2 of the air conditioner of the present invention. 2, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and the description of the same parts is omitted. Hereinafter, the difference between the second embodiment and the first embodiment will be mainly described.

In the first embodiment, the case where the decompression device is the indoor expansion valve 3 provided in the indoor unit 200 has been described as an example. However, in the present embodiment, the indoor expansion valve 3 provided in the indoor unit 200 is described. In addition, the outdoor unit 100 is also provided with an outdoor expansion valve 13 as a pressure reducing device. That is, in the present embodiment, the outdoor expansion valve 13 is also provided in the refrigerant pipe on the outlet side of the outdoor heat exchanger 2 in the outdoor unit 100. In this embodiment, the temperature sensor 11 for detecting the temperature of the refrigerant pipe on the outlet side of the outdoor heat exchanger 2 is provided on the outlet side of the outdoor expansion valve 13 in the outdoor unit 100. . Other configurations are the same as those shown in FIG.
In the air conditioner of this embodiment, during the normal forced circulation cooling operation, the outdoor expansion valve 13 is fully opened, and the pressure reduction level is kept to a minimum state. During the forced circulation cooling operation, the operations other than the outdoor expansion valve 13 are the same as those described with reference to FIG.

  Next, the operation when shifting from the forced circulation cooling operation to the natural circulation cooling operation will be described. At the time of this transition, first, while the operation of the compressor 1 is continued, the opening of the outdoor expansion valve 13 is reduced to reduce the pressure. As a result, the refrigerant in the connection liquid pipe 5 becomes a low-pressure two-phase flow, and the temperature of the refrigerant can be greatly reduced. Therefore, the temperature of the connection liquid pipe 5 can be sufficiently reduced. In the operation at the time of this transition, since it is necessary to lower the temperature by lowering the pressure of the connection liquid pipe 5, is the pressure reduction amount of the indoor expansion valve 3 provided in the indoor unit 200 reduced? , Fully open. The refrigerant decompressed by the outdoor expansion valve 13 (and the indoor expansion valve 3) evaporates by exchanging heat with indoor air in the indoor heat exchanger 4, but the outdoor expansion valve 13 (and the indoor expansion valve 3). ) Can be increased, the degree of superheat of the refrigerant in the indoor heat exchanger 4 can be increased, so that the temperature of the connecting gas pipe 6 can be increased.

By operating in this way, the temperature of the connection liquid pipe 5 connecting the outdoor unit 100 and the indoor unit 200 can be controlled to be lower than the temperature of the connection gas pipe 6. Therefore, the subsequent transition to the natural circulation cooling operation can be performed reliably.
When shifting from the forced circulation cooling operation to the natural circulation cooling operation, the rotational speed of the compressor 1 is decreased or the rotational speed of the outdoor fan 9 is increased as in the first embodiment. Increasing the degree of supercooling of the refrigerant coming out of the outdoor heat exchanger, increasing the pressure reduction amount of the outdoor expansion valve 13 (and the indoor expansion valve 3), and increasing the rotational speed of the outdoor fan 10, It is preferable to increase the degree of superheat of the refrigerant coming out of the indoor heat exchanger 4.

  According to the present embodiment, the outdoor expansion valve 13 provided in the outdoor unit 100 allows the decompressed two-phase flow refrigerant to flow through the connection liquid pipe 5, so that the temperature of the connection liquid pipe 5 can be easily increased. It is possible to achieve an air conditioner that can be reduced and that can more reliably shift from forced circulation cooling operation to highly efficient natural circulation cooling operation.

1: compressor,
2: outdoor heat exchanger,
3, 13: decompression device (3: indoor expansion valve, 13: outdoor expansion valve),
4: Indoor heat exchanger,
5, 6: Refrigerant piping (5: Connection liquid piping, 6: Connection gas piping),
7: Bypass piping, 8: Check valve,
9: Outdoor fan, 10: Indoor fan,
11, 12: Temperature sensor (temperature detection means).

Claims (10)

A compressor, an outdoor heat exchanger that exchanges heat with outdoor air, a decompression device, and an indoor heat exchanger that exchanges heat with indoor air are connected in order by refrigerant piping, and the compressor is operated to forcibly circulate the refrigerant. The forced circulation cooling operation, the indoor heat exchanger, and the outdoor heat exchanger installed at a position higher than the indoor heat exchanger are connected by connection liquid piping and connection gas piping, and gravity is In an air conditioner that can be operated by switching between natural cooling and cooling operation for natural circulation of the refrigerant,
Temperature detection means for detecting the temperature of the connection liquid pipe on the outlet side of the outdoor heat exchanger, and temperature detection means for detecting the temperature of the connection gas pipe on the outlet side of the indoor heat exchanger And
When shifting from the forced circulation cooling operation to the natural circulation cooling operation, the temperature of the air that exchanges heat with the outdoor heat exchanger is set so that the temperature of the connection liquid piping is lower than the temperature of the connection gas piping. Increasing the amount to lower the temperature of the connection liquid piping, increasing the pressure reduction amount of the decompression device, and controlling to increase the temperature of the connection gas piping,
Due to the temperature detected by the temperature detecting means for detecting the temperature of the connecting liquid pipe and the temperature detecting means for detecting the temperature of the connecting gas pipe, the temperature of the connecting liquid pipe becomes lower than the temperature of the connecting gas pipe. After confirming that the natural circulation cooling operation ,
The indoor heat exchanger is provided in an indoor unit, a decompression device is provided on the indoor heat exchanger inlet side in the indoor unit, and the outdoor heat exchanger is provided in an outdoor unit. an air conditioner, wherein the chamber pressure reducing device on the outside heat exchanger outlet side that provided.   2. The air conditioner according to claim 1, wherein the rotational speed of the compressor is also reduced when the forced circulation cooling operation is shifted to the natural circulation cooling operation. 3. A compressor, an outdoor heat exchanger, a decompression device, and an indoor heat exchanger are sequentially connected by refrigerant piping, and the forced circulation cooling operation in which the compressor is operated to forcibly circulate the refrigerant; and the indoor heat exchanger; A natural circulation cooling operation in which an outdoor heat exchanger installed at a position higher than the indoor heat exchanger is connected by a connecting liquid pipe and a connecting gas pipe, and the refrigerant is naturally circulated using gravity. In an air conditioner that can be operated by switching
Temperature detection means for detecting the temperature of the connection liquid pipe on the outlet side of the outdoor heat exchanger, and temperature detection means for detecting the temperature of the connection gas pipe on the outlet side of the indoor heat exchanger And
When shifting from the forced circulation cooling operation to the natural circulation cooling operation, the connection liquid is reduced by reducing the rotation speed of the compressor so that the temperature of the connection liquid pipe is lower than the temperature of the connection gas pipe. While reducing the temperature of the piping, increasing the amount of decompression of the decompression device, and controlling to increase the temperature of the connection gas piping,
Due to the temperature detected by the temperature detecting means for detecting the temperature of the connecting liquid pipe and the temperature detecting means for detecting the temperature of the connecting gas pipe, the temperature of the connecting liquid pipe becomes lower than the temperature of the connecting gas pipe. After confirming that the natural circulation cooling operation ,
The indoor heat exchanger is provided in an indoor unit, a decompression device is provided on the indoor heat exchanger inlet side in the indoor unit, and the outdoor heat exchanger is provided in an outdoor unit. an air conditioner, wherein the chamber pressure reducing device on the outside heat exchanger outlet side that provided.   The air conditioner according to claim 3, wherein the outdoor heat exchanger is provided with an outdoor fan that blows outdoor air, and the outdoor fan is accelerated at the time of transition from forced circulation cooling operation to natural circulation cooling operation. An air conditioner that increases the amount of air that exchanges heat with the outdoor heat exchanger.   In the air conditioner according to any one of claims 1 to 4, the indoor heat exchanger is provided with an indoor fan that blows indoor air, and when shifting from forced circulation cooling operation to natural circulation cooling operation, An air conditioner characterized in that the indoor fan is accelerated to increase the amount of air exchanging heat with the indoor heat exchanger. In the air conditioner according to any one of claims 1 to 4 ,
During forced circulation cooling operation, the opening of the decompression device provided in the outdoor unit is fully opened or set to a predetermined opening, and the opening of the decompression device provided in the indoor unit is controlled to reduce the pressure. With that, air conditioning operation
When the forced circulation cooling operation is shifted to the natural circulation cooling operation, the connection liquid pipe is configured such that the refrigerant flowing in the connection liquid pipe is increased in the amount of pressure reduction of the pressure reducing device in the outdoor unit to be a gas-liquid two-phase flow. The air conditioner is characterized in that the temperature of the air-conditioner is lowered and then the operation is shifted to the natural circulation cooling operation. The air conditioner according to claim 6 , wherein when the forced circulation cooling operation is shifted to the natural circulation cooling operation, the amount of pressure reduction of the decompression device in the indoor unit is reduced. In the air conditioner according to claim 6 , after shifting to the natural circulation cooling operation, both the decompression device in the outdoor unit and the decompression device in the indoor unit are fully opened or set to a predetermined opening degree. A featured air conditioner. A compressor, an outdoor heat exchanger that exchanges heat with outdoor air, a decompression device, and an indoor heat exchanger that exchanges heat with indoor air are connected in order by refrigerant piping, and the compressor is operated to forcibly circulate the refrigerant. The forced circulation cooling operation, the indoor heat exchanger, and the outdoor heat exchanger installed at a position higher than the indoor heat exchanger are connected by connection liquid piping and connection gas piping, and gravity is In an air conditioner that can be operated by switching between natural cooling and cooling operation for natural circulation of the refrigerant,
The outdoor heat exchanger is provided in an outdoor unit, and the decompression device is provided on the outdoor heat exchanger outlet side in the outdoor unit,
When shifting from the forced circulation cooling operation to the natural circulation cooling operation, the temperature of the air that exchanges heat with the outdoor heat exchanger is set so that the temperature of the connection liquid piping is lower than the temperature of the connection gas piping. The air conditioner is controlled to increase the amount to lower the temperature of the connection liquid piping and to increase the pressure reduction amount of the decompression device to increase the temperature of the connection gas piping. A compressor, an outdoor heat exchanger, a decompression device, and an indoor heat exchanger are sequentially connected by refrigerant piping, and the forced circulation cooling operation in which the compressor is operated to forcibly circulate the refrigerant; and the indoor heat exchanger; A natural circulation cooling operation in which an outdoor heat exchanger installed at a position higher than the indoor heat exchanger is connected by a connecting liquid pipe and a connecting gas pipe, and the refrigerant is naturally circulated using gravity. In an air conditioner that can be operated by switching
The outdoor heat exchanger is provided in an outdoor unit, and the decompression device is provided on the outdoor heat exchanger outlet side in the outdoor unit,
When shifting from the forced circulation cooling operation to the natural circulation cooling operation, the connection liquid is reduced by reducing the rotation speed of the compressor so that the temperature of the connection liquid pipe is lower than the temperature of the connection gas pipe. An air conditioner characterized by controlling the temperature of the connecting gas pipe to be increased by lowering the temperature of the pipe and increasing the amount of pressure reduction of the pressure reducing device.

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