JP2012077980A - Control method of refrigerating cycle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling a refrigerating cycle device that contributes to reduction of power consumption.SOLUTION: A first temperature condition and a first pressure condition which establish a constant pressure specific heat of a first value of a refrigerant in a circulation path 25 are set in a control circuit 72. The temperature and pressure in the circulation path 25 are adjusted by the operation of the control circuit 72 for the first temperature condition and the first pressure condition. If at least either the temperature or pressure deviates from the first temperature condition or the first pressure condition for a predetermined period during adjustment of temperature and pressure, a second temperature condition and a second pressure condition which establish a constant pressure specific heat of a second value, being smaller than the first value, are set in the control circuit 72. The temperature and pressure in the circulation path 25 are adjusted by the operation of the control circuit 72 for the second temperature condition and the second pressure condition.

Description

  The present invention relates to a method for controlling a refrigeration cycle apparatus such as an air conditioner.

  Even if the pressure is kept constant in the supercritical region, substances that change the constant-pressure specific heat greatly according to the temperature change are widely known. An example of such a substance is carbon dioxide (CO2). In air conditioners, the use of such substances as refrigerants in the supercritical region is sought. If the constant pressure specific heat is large, heat energy is efficiently transmitted to the indoor air with a small circulation flow rate. The power consumption can be reduced.

JP 2001-241800 A JP 2008-215717 A JP-A-5-231730

  On the other hand, since the constant-pressure specific heat changes remarkably according to the temperature change in such a supercritical substance, the operation state of the refrigeration circuit greatly varies depending on the environmental temperature, that is, the temperature of the outside air. Variations in operating conditions cause refrigerant temperature variations. Therefore, pressure adjustment is continuously performed in the refrigeration circuit. Since the control of various components and the control of each cycle must be used for the pressure adjustment of such an unstable cycle, the power consumption increases. If the temperature and pressure converge to the target temperature and target at an early stage, power consumption can be reduced.

  This invention is made | formed in view of the said actual condition, and it aims at providing the control method of the refrigerating-cycle apparatus which contributes to reduction of power consumption.

  In order to achieve the above object, according to one aspect of the present invention, the first change amount of the constant pressure specific heat per unit temperature change is shown in the first temperature range including the temperature establishing the first constant pressure specific heat in the supercritical state. The second change amount of the constant pressure specific heat is smaller than the first change amount per unit temperature change in the second temperature range including the temperature establishing the second constant pressure specific heat in the supercritical state lower than the first constant pressure specific heat. A refrigerant is circulated along a circulation path between the first heat exchanger and the second heat exchanger, and heat energy is conveyed from the first heat exchanger to the second heat exchanger according to the amount of heat of the refrigerant. A step of setting a first temperature condition in the first temperature range in the control circuit, and a step of adjusting the temperature and pressure in the circulation path by the action of the control circuit toward the first temperature condition; During the adjustment of the temperature and the pressure, the temperature is the first Deviating from the temperature condition over a predetermined period of time, setting the second temperature condition in the second temperature range in the control circuit, and the temperature in the circulation path by the action of the control circuit toward the second temperature condition And a step of adjusting the pressure. A method for controlling the refrigeration cycle apparatus is provided.

  When the first temperature condition is set in the control circuit, the temperature and pressure in the circulation path are adjusted toward the first temperature condition. When the first constant pressure specific heat in the supercritical state is established, the refrigeration cycle apparatus can be operated in a high constant pressure specific heat region. Efficient operation is realized. When the first temperature condition is switched to the second temperature condition in the control circuit, the refrigerant exhibits a second change amount of the constant pressure specific heat. Since the first change amount is reduced to the second change amount, the temperature and pressure of the refrigerant in the second temperature range are more easily stabilized than the refrigerant in the first temperature range. Therefore, the refrigerant is expected to satisfy the second temperature condition at an early stage. As a result, extra power consumption associated with control can be reduced.

  The method for controlling the refrigeration cycle includes the steps of adjusting the temperature and pressure of the refrigerant in the circulation path according to the storage amount of the refrigerant reservoir that is incorporated in the circulation path and partitions the space for storing the refrigerant, and heating The method may further include a step of separating the refrigerant reservoir from the circulation path when the pressure of the refrigerant reaches a predetermined pressure in the circulation path during operation. When the refrigerant pressure rises to a predetermined pressure, the refrigeration cycle apparatus shifts to steady operation. Therefore, even if the refrigerant reservoir is disconnected, the refrigerant pressure fluctuation is avoided in the circulation path. Since the refrigerant flow path is shortened in accordance with the separation of the refrigerant reservoir, the pressure loss of the refrigerant is reduced. The refrigerant can efficiently carry heat energy.

  The control method of the refrigeration cycle is such that the primary side refrigerant is circulated along the primary side circulation path between the first heat exchanger and the third heat exchanger, and the first heat is between the compressor and the expansion valve. A primary side refrigerant compressed to a high temperature and a high pressure by the compressor is supplied to the exchanger or the third heat exchanger, and heat energy is transferred from the primary side refrigerant to the refrigerant by the first heat exchanger. A step of transferring thermal energy by a fourth heat exchanger from the primary side refrigerant compressed to a high temperature and high pressure by the compressor to the refrigerant in the refrigerant reservoir, and the refrigerant reservoir from the circulation path. A step of separating the fourth heat exchanger from the primary-side circulation path when being separated. The first heat exchanger and the second heat exchanger form a secondary side transfer circuit. On the other hand, the first heat exchanger and the third heat exchanger form a primary side refrigeration circuit. In the transfer circuit, the primary side refrigerant is used for adjusting the pressure. Electric heating devices and cooling devices specific to the pressure adjustment can be omitted. In adjusting the pressure, an increase in power consumption of the air conditioner can be avoided. Since the flow path of the primary side refrigerant is shortened according to the disconnection of the fourth heat exchanger, the pressure loss of the primary side refrigerant is reduced. The primary refrigerant can carry heat energy efficiently.

  An example of the refrigerant is carbon dioxide. Carbon dioxide in the supercritical state greatly changes the constant pressure specific heat according to the temperature change even at a constant pressure. Therefore, the operating state of the refrigeration circuit varies greatly depending on the environmental temperature, that is, the temperature of the outside air. Variations in operating conditions cause refrigerant temperature variations. Even when such carbon dioxide is used as a refrigerant, according to the control method according to the present embodiment, heat energy can be efficiently used and power consumption can be reduced. The pressure in the circulation path only needs to be kept constant under the first temperature condition and the second temperature condition.

  As described above, according to one aspect of the present invention, a method for controlling a refrigeration cycle apparatus that contributes to a reduction in power consumption is provided.

It is a figure showing roughly the composition of the air harmony machine concerning a 1st embodiment of the present invention. It is a block diagram showing roughly the composition of the control system of the air harmony machine concerning a 1st embodiment. It is a figure which shows the flow of a 1st refrigerant | coolant and a 2nd refrigerant | coolant at the time of heating operation. It is a figure which shows the flow of a 1st refrigerant | coolant and a 2nd refrigerant | coolant when a refrigerant | coolant tank is cut away at the time of heating operation. It is a figure which shows the flow of a 1st refrigerant | coolant and a 2nd refrigerant | coolant at the time of air_conditionaing | cooling operation. It is a figure which shows the flow of a 1st refrigerant | coolant and a 2nd refrigerant | coolant when a refrigerant | coolant tank is cut off at the time of air_conditionaing | cooling operation. It is a flowchart which shows a specific example of the control at the time of heating operation. It is a graph which shows the constant-pressure specific heat of CO2 (carbon dioxide). It is a figure which shows roughly the structure of the air conditioner which concerns on 2nd Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 schematically shows the configuration of a refrigeration cycle apparatus, that is, an air conditioner 11 according to a first embodiment of the present invention. The air conditioner 11 includes a primary refrigerant circuit 12 and a secondary refrigerant circuit 13. The primary refrigerant circuit 12 constitutes a refrigeration circuit. In the primary refrigerant circuit 12, a natural refrigerant such as ammonia or propane is used as a refrigerant (hereinafter referred to as “first refrigerant”). However, substances other than ammonia and propane may be used for the first refrigerant. It is desirable that a natural substance that changes phase at a pressure as close to atmospheric pressure as possible is used for the first refrigerant. The first refrigerant exchanges heat energy with, for example, outdoor air.

  The secondary refrigerant circuit 13 constitutes a conveyance circuit. In the secondary refrigerant circuit 13, a natural refrigerant such as CO2 (oxygen dioxide) is used as a refrigerant (hereinafter referred to as "second refrigerant"). However, a substance other than CO2 may be used for the second refrigerant. As the second refrigerant, it is desirable to use a natural substance that has as little burden on living organisms as possible. The second refrigerant exchanges thermal energy with the first refrigerant, and at the same time exchanges thermal energy with the indoor air.

  The primary refrigerant circuit 12 includes a compressor 14. The compressor 14 is incorporated in the first circulation path 15. The first circulation path 15 connects the first port 16a and the second port 16b of the four-way valve 16 to each other. The suction port 14 a of the compressor 14 is connected to the first port 16 a of the four-way valve 16. The gas refrigerant is supplied from the first port 16 a to the suction port 14 a of the compressor 14. The compressor 14 compresses the low-pressure gas refrigerant to a prescribed high temperature and high pressure. The discharge port 14 b of the compressor 14 is connected to the second port 16 b of the four-way valve 16. The gas refrigerant is supplied from the discharge port 14 b of the compressor 14 to the second port 16 b of the four-way valve 16. The first circulation path 15 is formed of a refrigerant pipe such as a copper pipe. When ammonia is used as the first refrigerant, a pipe having corrosion resistance to ammonia, such as a stainless steel (SUS) pipe, is used as the refrigerant pipe.

  A second circulation path 17 is connected to the third port 16 c and the fourth port 16 d of the four-way valve 16. The second circulation path 17 connects the third port 16c and the fourth port 16d of the four-way valve 16 to each other. In the second circulation path 17, an outdoor heat exchanger 18, an expansion valve 19, and a refrigerant-refrigerant heat exchanger 21 are sequentially incorporated. The outdoor heat exchanger 18 has a first port 18a and a second port 18b. The refrigerant passes through the outdoor heat exchanger 18 between the first port 18a and the second port 18b. The outdoor heat exchanger 18 realizes heat energy exchange between the refrigerant passing therethrough and ambient air. The first port 18 a of the outdoor heat exchanger 18 is connected to the third port 16 c of the four-way valve 16. By the action of the four-way valve 16, the first port 18a of the outdoor heat exchanger 18 is switchably connected to either the suction port 14a of the compressor 14 or the discharge port 14b of the compressor 14. An expansion valve 19 is connected to the second port 18 b of the outdoor heat exchanger 18. The second circulation path 17 may be formed of a refrigerant pipe such as a copper pipe. When ammonia is used as the first refrigerant, a pipe having corrosion resistance to ammonia, such as a stainless steel (SUS) pipe, is used as the refrigerant pipe.

  A blower fan 22 is installed in association with the outdoor heat exchanger 18. The blower fan 22 generates an air flow according to the rotation of the impeller. The airflow passes through the outdoor heat exchanger 18. The flow rate of the airflow sent from the blower fan 22 is adjusted according to the number of revolutions per minute of the impeller. The amount of heat energy exchanged between the refrigerant and the air can be adjusted in the outdoor heat exchanger 18 according to the flow rate of the airflow. The temperature and pressure of the first refrigerant change according to the adjustment of the heat energy amount.

  The refrigerant-refrigerant heat exchanger 21 includes a first flow path 23 that provides the second circulation path 17 of the primary refrigerant circuit 12. The first flow passage 23 has a first port 23a and a second port 23b. The refrigerant passes through the first flow passage 23 between the first port 23a and the second port 23b. The first port 23 a of the first flow passage 23 is connected to the expansion valve 19. The second port 23 b of the first flow passage 23 is connected to the fourth port 16 d of the four-way valve 16. By the action of the four-way valve 16, the second port 23b of the first flow passage 23 is switchably connected to either the suction port 14a or the discharge port 14b of the compressor 14. In response to switching of the four-way valve 16, the first refrigerant compressed by the action of the compressor 14 is selectively supplied to the outdoor heat exchanger 18 or the refrigerant-refrigerant heat exchanger 21.

  At the same time, the refrigerant-refrigerant heat exchanger 21 includes a second flow passage 24. The second flow path 24 extends, for example, in parallel with the first flow path 23. The second flow passage 24 has a first port 24a and a second port 24b. The refrigerant passes through the second flow passage 24 between the first port 24a and the second port 24b. A circulation path 25 is connected to the first port 24 a and the second port 24 b of the second flow passage 24. The circulation path 25 connects the first port 24a and the second port 24b of the second flow passage 24 to each other. A pump 26 and an indoor heat exchanger 27 are incorporated in the circulation path 25. As described above, the refrigerant-refrigerant heat exchanger 21 is incorporated into the second circulation path 17 of the primary refrigerant circuit 12 and simultaneously into the circulation path 25 of the secondary refrigerant circuit 13. Exchange of thermal energy is realized between the second refrigerant in the second flow passage 24 and the first refrigerant in the first flow passage 23. In exchanging the heat energy, for example, the pipe of the first flow path 23 and the pipe of the second flow path 24 may be in contact with each other.

  The indoor heat exchanger 27 has a first port 27a and a second port 27b. The refrigerant passes through the indoor heat exchanger 27 between the first port 27a and the second port 27b. The indoor heat exchanger 27 realizes heat energy exchange between the refrigerant passing therethrough and ambient air. A first port 27 a of the indoor heat exchanger 27 is connected to the pump 26. The second refrigerant circulates in the circulation path 25 by the action of the pump 26. The first port 24 a of the second flow passage 24 is connected to the second port 27 b of the indoor heat exchanger 27. The pump 26 is configured as a so-called bidirectional pump. That is, the pump 26 can circulate the second refrigerant along the circulation path 25 in the order of the outdoor heat exchanger 27 and the refrigerant-refrigerant heat exchanger 21, and conversely, the refrigerant-refrigerant heat exchanger 21 and the outdoor The second refrigerant can be circulated along the circulation path 25 in the order of the heat exchanger 27.

  A blower fan 28 is installed in association with the indoor heat exchanger 27. The blower fan 28 generates an air flow according to the rotation of the impeller. The airflow passes through the indoor heat exchanger 27. The flow rate of the airflow sent from the blower fan 28 is adjusted according to the number of revolutions per minute of the impeller. The amount of heat energy exchanged between the refrigerant and the air can be adjusted in the indoor heat exchanger 27 in accordance with the flow rate of the airflow. The temperature and pressure of the second refrigerant change according to the adjustment of the heat energy amount.

  A refrigerant reservoir, that is, a refrigerant tank 29 is connected to the circulation path 25 in a detachable manner. A branch path 31 is connected to the circulation path 25 between the refrigerant-refrigerant heat exchanger 21 and the indoor heat exchanger 27 when the refrigerant tank 29 is connected. The branch path 31 connects the first branch point 32 and the second branch point 33 to each other. The first branch point 32 and the second branch point 33 are disposed between the refrigerant-refrigerant heat exchanger 21 and the indoor heat exchanger 27. The refrigerant tank 29 is connected to the branch path 31.

  The refrigerant tank 29 defines an internal space 29a. The second refrigerant is stored in the internal space 29 a of the refrigerant tank 29. In the secondary refrigerant circuit 13, a supercritical pressure is established during heating operation. On the other hand, a pressure lower than the supercritical pressure is established in the secondary refrigerant circuit 13 during the cooling operation. As a result, the refrigerant amount required during the cooling operation is smaller than the refrigerant amount required during the heating operation. Excess refrigerant can be stored in the refrigerant tank 29 during the cooling operation. Thus, a sufficient amount of refrigerant is ensured during heating operation.

  A first auxiliary path 34 is connected to the refrigerant tank 29. One end of the first auxiliary path 34 is connected to the refrigerant tank 29. The other end of the first auxiliary path 34 is connected to the circulation path 25 between the pump 26 and the refrigerant-refrigerant heat exchanger 21. The second auxiliary path 35 branches from the first auxiliary path 34 at a third branch point 36. The second auxiliary path 35 is connected to the circulation path 25 between the pump 26 and the indoor heat exchanger 27.

  A first flow path control device 37 is incorporated in the secondary refrigerant circuit 13. The first flow path control device 37 includes a first flow rate adjustment valve 38, a second flow rate adjustment valve 39, a third flow rate adjustment valve 41, and a fourth flow rate adjustment valve 42. The first flow rate adjusting valve 38 is inserted into the first auxiliary path 34 between the third branch point 36 and the circulation path 25. The second flow rate adjustment valve 39 is inserted into the second auxiliary path 35. During the heating operation, the first flow rate adjustment valve 38 is closed. The first flow rate adjustment valve 38 prevents the second refrigerant from flowing. As a result, the second refrigerant having a predetermined flow rate is supplied from the refrigerant tank 29 to the suction side of the pump 26 in accordance with the opening degree of the second flow rate adjustment valve 39. During the cooling operation, the second flow rate adjustment valve 39 is closed. The second flow rate adjustment valve 39 prevents the second refrigerant from flowing. As a result, the second refrigerant having a predetermined flow rate is supplied from the refrigerant tank 29 to the suction side of the pump 26 in accordance with the opening degree of the first flow rate adjustment valve 38. The third flow rate adjustment valve 41 is inserted into the branch path 31 between the first branch point 32 and the second branch point 33. The fourth flow rate adjustment valve 42 is inserted into the circulation path 25 between the first branch point 32 and the second branch point 33.

  Here, the primary refrigerant circuit 12 includes a fourth heat exchanger 45. The fourth heat exchanger 45 is connected to the second circulation path 17. A first branch path 46 and a second branch path 47 are connected to the second circulation path 17. The first branch path 46 branches from the second circulation path 17 between the refrigerant-refrigerant heat exchanger 21 and the four-way valve 16. The first branch path 46 bypasses the second circulation path 17 between the fourth branch point 48 and the fifth branch point 49. The fourth heat exchanger 45 is incorporated in the first branch path 46. Thus, the first heat exchanger 45 and the expansion valve 19 flow through the fourth heat exchanger 45 between the compressor 14 and the expansion valve 19 during the heating operation. At this time, the fourth heat exchanger 45 moves thermal energy from the first refrigerant to the second refrigerant in the refrigerant tank 29. The second refrigerant evaporates and expands in the refrigerant tank 29 in accordance with the movement of thermal energy. The pressure in the refrigerant tank 29 is increased. As the pressure rises, the supercritical second refrigerant is discharged from the refrigerant tank 29. The 4th heat exchanger 45 should just be formed with piping shape | molded from the material of comparatively high heat conductivity, such as copper and aluminum, for example. For example, the pipe may be wound around a heat conductive wall surrounding the internal space 29 a of the refrigerant tank 29, or may be arranged in the internal space 29 a of the refrigerant tank 29. In the present embodiment, the fourth heat exchanger 45 is disposed upstream of the refrigerant-refrigerant heat exchanger 21 during the heating operation. Therefore, in the fourth heat exchanger 45, the second refrigerant can be efficiently heated prior to the heat radiation of the refrigerant-refrigerant heat exchanger 21. However, as long as the heating of the second refrigerant is sufficiently realized by the fourth heat exchanger 45, the fourth heat exchanger 45 may be incorporated at least between the second port 14b of the compressor 14 and the expansion valve 19. .

  The second branch path 47 branches from the second circulation path 17 between the expansion valve 19 and the first port 23 a of the first flow path 23. The second branch path 47 bypasses the second circulation path 17 between the sixth branch point 51 and the seventh branch point 52. The second branch path 47 shares the path of the first branch path 46 and the first refrigerant between the eighth branch point 53 and the ninth branch point 54. A fourth heat exchanger 45 is incorporated in the first branch 46 between the eighth branch point 53 and the ninth branch point 54. Thus, the expanded first refrigerant flows through the fourth heat exchanger 45 during the cooling operation. At this time, the fourth heat exchanger 45 moves thermal energy from the second refrigerant in the refrigerant tank 29 to the first refrigerant. The second refrigerant condenses in the refrigerant tank 29 based on the endothermic action of the first refrigerant. The pressure in the refrigerant tank 29 decreases. The second refrigerant is stored in the refrigerant tank 29 as the pressure decreases. Thus, the refrigerant tank 29 and the fourth heat exchanger 45 form a pressure adjustment unit. The pressure adjustment unit adjusts the pressure of the second refrigerant in the secondary refrigerant circuit 13 based on the thermal energy of the first refrigerant during the heating operation and the cooling operation. In the present embodiment, the fourth heat exchanger 45 is disposed upstream of the refrigerant-refrigerant heat exchanger 21 during the cooling operation. Therefore, in the fourth heat exchanger 45, the second refrigerant can be efficiently cooled prior to the heat absorption of the refrigerant-refrigerant heat exchanger 21. However, as long as the cooling of the second refrigerant is sufficiently realized by the fourth heat exchanger 45, the fourth heat exchanger 45 may be incorporated at least between the expansion valve 19 and the first port 14a of the compressor 14. .

  A second flow path control device 56 is incorporated in the primary refrigerant circuit 12. The second flow control device 56 includes a fifth flow rate adjustment valve 57, a sixth flow rate adjustment valve 58, a seventh flow rate adjustment valve 59, an eighth flow rate adjustment valve 61, a ninth flow rate adjustment valve 62, and a tenth flow rate adjustment valve 63. Prepare. The fifth flow rate adjusting valve 57 is inserted into the second circulation path 17 between the fourth branch point 48 and the fifth branch point 49. The fourth flow rate adjusting valve is inserted into the first branch path 46 between the fourth branch point 48 and the eighth branch point 53. The seventh flow rate adjusting valve 59 is inserted into the first branch path 46 between the ninth branch point 54 and the fifth branch point 49. The eighth flow regulating valve 61 is inserted into the second circulation path 17 between the sixth branch point 51 and the seventh branch point 52. The ninth flow rate adjustment valve 62 is inserted into the second branch path 47 between the sixth branch point 51 and the eighth branch point 53. The tenth flow rate adjusting valve 63 is inserted into the second branch path 47 between the ninth branch point 54 and the seventh branch point 52.

  In the secondary refrigerant circuit 13, a first thermometer 67 and a first pressure gauge 68 are inserted in the circulation path 25 between the second branch point 33 and the indoor heat exchanger 27. The first thermometer 67 measures the temperature of the second refrigerant at the inlet of the indoor heat exchanger 27 during heating operation. The first pressure gauge 68 measures the pressure of the second refrigerant at the inlet of the indoor heat exchanger 27 during heating operation. Similarly, a second thermometer 69 and a second pressure gauge 71 are inserted into the circulation path 25 between the pump 26 and the indoor heat exchanger 27. The second thermometer 69 measures the temperature of the second refrigerant at the inlet of the indoor heat exchanger 27 during the cooling operation. The second pressure gauge 71 measures the pressure of the second refrigerant at the inlet of the indoor heat exchanger 27 during the cooling operation.

  As shown in FIG. 2, the air conditioner 11 includes a control circuit 72. The control circuit 72 includes a room temperature meter 73, first and second thermometers 67 and 69, first and second pressure gauges 68 and 71, third to tenth flow rate adjusting valves 41, 42, 57 to 59, 61 to 63. The blower fans 22, 28, the expansion valve 19 and the compressor 14 are connected. The room temperature meter 73 measures the room temperature. Room temperature corresponds to the indoor temperature. At least an indoor heat exchanger 27 is installed in the room. The primary refrigerant circuit 12 including the refrigerant-refrigerant heat exchanger 21 and the fourth heat exchanger 45 is installed outdoors. Therefore, the intrusion of the first refrigerant is avoided indoors. The room temperature meter 73 supplies a room temperature signal to the control circuit 72. The room temperature signal specifies the room temperature. The room temperature signal is output at a predetermined time interval, for example.

  The first thermometer 67 supplies a first temperature signal to the control circuit 72. The first temperature signal specifies the temperature of the second refrigerant measured by the first thermometer 67. The first pressure gauge 68 supplies a first pressure signal to the control circuit 72. The first pressure signal specifies the pressure of the second refrigerant measured by the first pressure gauge 68. Similarly, the second thermometer 69 supplies a second temperature signal to the control circuit 72. The second temperature signal specifies the temperature of the second refrigerant measured by the second thermometer 69. The second pressure gauge 71 supplies a second pressure signal to the control circuit 72. The second pressure signal specifies the pressure of the second refrigerant measured by the second pressure gauge 71.

  The control circuit 72 supplies control signals to the third to tenth flow rate adjustment valves 41, 42, 57 to 59, 61 to 63, the blower fans 22 and 28, the expansion valve 19 and the compressor 14, respectively. The control signal describes the opening degree of the flow rate adjusting valve (including zero, ie, closing), the rotational speed of the fan per minute, the opening degree of the expansion valve 19, and the driving frequency of the compressor 14. The third to tenth flow control valves 41, 42, 57 to 59, 61 to 63 are opened or closed at the opening degree specified by the control signal. The blower fans 22 and 28 rotate at the number of rotations per minute specified by the control signal. The amount of air blown by the blower fans 22 and 28 is adjusted according to the number of rotations per minute. The expansion valve 19 opens at an opening specified by the control signal. The compressor 14 operates at a frequency specified by the control signal. The discharge pressure of the first refrigerant is adjusted according to the opening degree of the expansion valve 19 and the operating frequency of the compressor 14.

  Next, the operation of the air conditioner 11 will be briefly described. During the heating operation, in the primary refrigerant circuit 12, the eighth flow rate adjustment valve 61 is opened and the ninth and tenth flow rate adjustment valves 62, 63 are closed. At the same time, the seventh flow rate adjustment valve 59 is opened. As shown in FIG. 3, when the compressor 14 is operated, the first refrigerant compressed to high temperature and high pressure by the compressor is supplied to the refrigerant-refrigerant heat exchanger 21. Thermal energy is transferred from the first refrigerant in the first flow passage 23 to the second refrigerant in the second flow passage 24 in accordance with the phase change. The expanded first refrigerant reaches the outdoor heat exchanger 18. The first refrigerant absorbs heat from the outside air in the outdoor heat exchanger 18. The first refrigerant evaporates according to the heat absorption. The evaporated first refrigerant flows into the compressor 14.

  In the primary refrigerant circuit 12, the refrigerant is distributed from the fourth branch point 48 to the second circulation path 17 and the first branch path 46 according to the opening degrees of the fifth flow rate adjustment valve 57 and the sixth flow rate adjustment valve 58. The first refrigerant flows through the fourth heat exchanger 45 of the pressure adjustment unit. The fourth heat exchanger 45 transfers thermal energy from the high temperature and pressure first refrigerant to the second refrigerant in the refrigerant tank 29. The second refrigerant is overheated. The second refrigerant expands. As a result, the pressure of the second refrigerant is increased in the secondary refrigerant circuit 13 based on the thermal energy of the first refrigerant. In the refrigerant tank 29, the density of the second refrigerant decreases. The amount of the second refrigerant stored in the refrigerant tank 29 decreases. Thus, a supercritical pressure is established in the secondary refrigerant circuit 13.

  In the secondary refrigerant circuit 13, the third flow rate adjustment valve 41 is opened and the fourth flow rate adjustment valve 42 is closed. Therefore, the refrigerant tank 29 is connected to the circulation path 25. When the pump 26 operates, the supercritical second refrigerant circulates in the order of the refrigerant-refrigerant heat exchanger 21, the refrigerant tank 29, and the indoor heat exchanger 27. The second refrigerant receives heat energy from the first refrigerant in the refrigerant-refrigerant heat exchanger 21. The second refrigerant is sent into the indoor heat exchanger 27. The heat energy is transferred from the second refrigerant to the indoor air by the indoor heat exchanger 27. The indoor air is warmed.

  In the control circuit 72, a target temperature and a target pressure are set. The control circuit 72 acquires the first temperature signal and the first pressure signal from the first thermometer 67 and the first pressure gauge 68. The signal acquisition may be performed periodically at predetermined time intervals, for example. Since the pressure change is faster than the temperature change, the time interval for acquiring the first pressure signal may be set shorter than the time interval for acquiring the first temperature signal. The control circuit 72 compares the inlet temperature of the indoor heat exchanger 27 with the target temperature so that the inlet temperature of the indoor heat exchanger 27 matches the target temperature and the inlet pressure of the indoor heat exchanger 27 matches the target pressure. In addition, the number of revolutions per minute of the blower fan 28 is controlled based on the comparison between the inlet pressure of the indoor heat exchanger 27 and the target pressure. In such control, a control signal is supplied from the control circuit 72 to the blower fan 28.

  Instead of controlling the number of revolutions per minute, the opening degree of the expansion valve 19 of the primary refrigerant circuit 12 and the operating frequency of the compressor 14 may be controlled. The control circuit 72 compares the inlet temperature of the indoor heat exchanger 27 with the target temperature so that the inlet temperature of the indoor heat exchanger 27 matches the target temperature and the inlet pressure of the indoor heat exchanger 27 matches the target pressure. In addition, the opening degree of the expansion valve 19 and the operation of the compressor 14 are controlled based on the comparison between the inlet pressure of the indoor heat exchanger 27 and the target pressure. In such control, control signals are supplied from the control circuit 72 to the expansion valve 19 and the compressor 14. The control of the blower fan 28 and the control of the expansion valve 19 and the compressor 14 may be performed simultaneously or alternately in order.

  Thereafter, the inlet temperature specified by the first temperature signal enters a specific temperature range (for example, ± 1 degree of the target temperature), and the inlet pressure specified by the first pressure signal changes to the specific pressure range (for example, ±± of the target pressure). (0.1 MPa), the control circuit 72 disconnects the refrigerant tank 29 from the circulation path 25 as shown in FIG. The third flow rate adjustment valve 41 is closed and the fourth flow rate adjustment valve 42 is opened. At this time, the air conditioner 11 operates in a stable steady operation unless exposed to load fluctuations (for example, room temperature fluctuations). Therefore, the inlet temperature of the indoor heat exchanger 27 is maintained in a specific temperature range, and the inlet pressure of the indoor heat exchanger 27 is maintained in a specific pressure range. Even if the refrigerant tank 29 is disconnected, the pressure fluctuation of the second refrigerant is avoided in the circulation path 25. Since the flow path of the second refrigerant is shortened in accordance with the separation of the refrigerant tank 29, the pressure loss of the second refrigerant is reduced. The second refrigerant can carry heat energy efficiently.

  Simultaneously with the disconnection of the refrigerant tank 29, the control circuit 72 disconnects the fourth heat exchanger 45 from the second circulation path 17 in the primary refrigerant circuit 12. At least one of the sixth flow rate adjustment valve 58 and the seventh flow rate adjustment valve 59 is closed. Both may be closed. Since the flow path of the first refrigerant is shortened according to the disconnection of the first branch path 46, the pressure loss of the first refrigerant is reduced. The first refrigerant can carry heat energy efficiently.

  During the cooling operation, in the primary refrigerant circuit 12, the fifth flow rate adjusting valve 57 is opened and the sixth and seventh flow rate adjusting valves 58, 59 are closed. At the same time, the tenth flow rate adjustment valve 63 is opened. As shown in FIG. 5, when the compressor 14 operates, the first refrigerant compressed to a high temperature and high pressure by the compressor is supplied to the outdoor heat exchanger 18. In the outdoor heat exchanger 18, the first refrigerant releases heat to the outside air. The first refrigerant condenses as the heat is released. The condensed first refrigerant is supplied to the refrigerant-refrigerant heat exchanger 21. The first refrigerant in the first flow passage 23 absorbs heat from the second refrigerant in the second flow passage 24 according to the phase change. The first refrigerant evaporates according to the heat absorption. The evaporated first refrigerant flows into the compressor 14.

  In the primary refrigerant circuit 12, the refrigerant is distributed from the sixth branch point 51 to the second circulation path 17 and the second branch path 47 in accordance with the opening degrees of the eighth flow rate adjustment valve 61 and the ninth flow rate adjustment valve 62. The first refrigerant flows through the fourth heat exchanger 45 of the pressure adjustment unit. The first refrigerant expanded in the fourth heat exchanger 45 absorbs heat from the second refrigerant in the refrigerant tank 29. The second refrigerant is supercooled. As a result, the pressure of the second refrigerant decreases in the secondary refrigerant circuit 13 based on the endothermic action of the first refrigerant. The density of the second refrigerant is increased in the refrigerant tank 29. The amount of the second refrigerant stored in the refrigerant tank 29 increases. In this way, a pressure lower than the supercritical pressure is established in the secondary refrigerant circuit 13.

  In the secondary refrigerant circuit 13, the third flow rate adjustment valve 41 is opened and the fourth flow rate adjustment valve 42 is closed. Therefore, the refrigerant tank 29 is connected to the circulation path 25. When the pump 26 is operated, as shown in FIG. 5, the pump 26 circulates the second refrigerant in the opposite direction to that during the heating operation. That is, the second refrigerant having a pressure lower than the supercritical pressure circulates in the order of the indoor heat exchanger 27, the refrigerant tank 29, and the refrigerant-refrigerant heat exchanger 21. The first refrigerant absorbs heat from the second refrigerant in the refrigerant-refrigerant heat exchanger 21 and is sent to the indoor heat exchanger 27. In the indoor heat exchanger 27, the second refrigerant takes heat energy from the indoor air. Indoor air is cooled.

  As described above, the target temperature and the target pressure are set in the control circuit 72. The control circuit 72 acquires the second temperature signal and the second pressure signal from the second thermometer 69 and the second pressure gauge 71. The signal acquisition may be performed periodically at predetermined time intervals, for example. Since the pressure change is faster than the temperature change, the time interval for acquiring the second pressure signal may be set shorter than the time interval for acquiring the second temperature signal. As in the heating operation, the control circuit 72 matches the inlet temperature of the indoor heat exchanger 27 with the target temperature, and matches the inlet pressure of the indoor heat exchanger 27 with the target pressure. Based on the comparison between the temperature and the target temperature, and the comparison between the inlet pressure of the indoor heat exchanger 27 and the target pressure, the number of revolutions per minute of the blower fan 28 is controlled. Similarly to the above, instead of controlling the number of revolutions per minute, the opening degree of the expansion valve 19 of the primary refrigerant circuit 12 and the operating frequency of the compressor 14 may be controlled. The control of the blower fan 28 and the control of the expansion valve 19 and the compressor 14 may be performed simultaneously or alternately in order.

  Thereafter, the inlet temperature specified by the second temperature signal enters a specific temperature range (for example, ± 1 degree of the target temperature), and the inlet pressure specified by the second pressure signal changes to the specific pressure range (for example, ±± of the target pressure). (0.1 MPa), the control circuit 72 disconnects the refrigerant tank 29 from the circulation path 25 as shown in FIG. The third flow rate adjustment valve 41 is closed and the fourth flow rate adjustment valve 42 is opened. At this time, the air conditioner 11 operates in a stable steady operation unless exposed to load fluctuations (for example, room temperature fluctuations). Therefore, the inlet temperature of the indoor heat exchanger 27 is maintained in a specific temperature range, and the inlet pressure of the indoor heat exchanger 27 is maintained in a specific pressure range. Even if the refrigerant tank 29 is disconnected, the pressure fluctuation of the second refrigerant is avoided in the circulation path 25. Since the flow path of the second refrigerant is shortened in accordance with the separation of the refrigerant tank 29, the pressure loss of the second refrigerant is reduced. The second refrigerant can carry heat energy efficiently.

  Simultaneously with the disconnection of the refrigerant tank 29, the control circuit 72 disconnects the fourth heat exchanger 45 from the second circulation path 17 in the primary refrigerant circuit 12. At least one of the ninth flow rate adjustment valve 62 and the tenth flow rate adjustment valve 63 is closed. Both may be closed. Since the flow path of the first refrigerant is shortened according to the disconnection of the first branch path 46, the pressure loss of the first refrigerant is reduced. The first refrigerant can carry heat energy efficiently.

  In this embodiment, the target temperature and the target pressure may be changed according to the temperature change in the room. That is, in the control circuit 72, first, a first temperature condition and a first pressure condition that establish a constant pressure specific heat of the first value of the second refrigerant in the circulation path 25 are set. The first temperature condition and the first pressure condition are stored in a data table in the control circuit 72 in advance. The temperature and pressure in the circulation path 25 are adjusted toward the first temperature condition and the first pressure condition by the action of the control circuit 72. As described above, in adjusting the temperature and pressure in the circulation path 25, the rotational speed per minute of the blower fan 28 may be controlled, and the opening degree of the expansion valve 19 and the operating frequency of the compressor 14 may be controlled. When the temperature and pressure in the circulation path 25 enter the first temperature condition and the first pressure condition during the adjustment of the temperature and pressure, respectively, the control circuit 72 disconnects the refrigerant tank 29 from the circulation path 25 as described above. At this time, the first branch path 46 is simultaneously disconnected from the second circulation path 17 in the primary refrigerant circuit 12. If at least one of temperature and pressure deviates from the first temperature condition or the first pressure condition for a predetermined period during the adjustment of the temperature and pressure, the control circuit 72 changes the first temperature condition and the first pressure condition to each other. Instead, a second temperature condition and a second pressure condition that establish a constant-pressure specific heat having a second value smaller than the first value are set. The second temperature condition and the second pressure condition are stored in advance in a data table in the control circuit 72. Again, the temperature and pressure in the circulation path 25 are adjusted toward the second temperature condition and the second pressure condition by the action of the control circuit 72. As described above, in adjusting the temperature and pressure in the circulation path 25, the rotational speed per minute of the blower fan 28 may be controlled, and the opening degree of the expansion valve 19 and the operating frequency of the compressor 14 may be controlled. When the temperature and pressure in the circulation path 25 enter the second temperature condition and the second pressure condition, respectively, the control circuit 72 disconnects the refrigerant tank 29 from the circulation path 25 and the first branch path from the second circulation path 17 as described above. 46 is cut off.

  Specifically, as shown in FIG. 7, the control circuit 72 initializes various variables in step S1. In step S2, the control circuit 72 sets the first set temperature value Tset1 as the target temperature Tset. In step S3, the control circuit 72 sets the first set pressure value Pset1 as the target pressure Pset. Details of the first set temperature value Tset1 and the first set pressure value Pset1 will be described later. In step S4, the control circuit 72 sets a value “0 (zero)” to the variable n and sets an arbitrary value “5” to the variable H.

  In step S5, the control circuit 72 acquires the first temperature signal and the first pressure signal. The control circuit 72 specifies the inlet temperature T [° C.] and the inlet pressure P [MPa] of the indoor heat exchanger 27 based on the first temperature signal and the first pressure signal. In subsequent step S6, the control circuit 72 compares the inlet temperature T with the first temperature condition and the inlet pressure P with the first pressure condition. For example, the first temperature condition is set to a temperature range of ± 1 degree of the first set temperature value Tset1. The first pressure condition is set, for example, within a pressure range of ± 0.1 MPa of the first set pressure value Pset1. A pressure range as low as possible is set as the first pressure condition. If the pressure is low, the wall thickness of, for example, piping can be reduced. The reduction in wall thickness contributes to reducing the weight of the air conditioner 11 and reducing the manufacturing cost. The first temperature condition is set to a temperature range in which as high a constant pressure specific heat as possible can be obtained. A high constant pressure specific heat contributes to a reduction in the refrigerant flow rate. The room can be efficiently warmed with a small refrigerant flow rate. When the inlet temperature T is specified within the temperature range of the first temperature condition and the inlet pressure P is specified within the pressure range of the first pressure condition, in step S7, the control circuit 72 causes the refrigerant tank from the circulation path 25 as described above. 29 is cut off. Thereafter, as long as the load of the indoor heat exchanger 27 does not vary, the inlet temperature T and the inlet pressure P continue to satisfy the first temperature condition and the first pressure condition. The air conditioner 11 realizes stable heating operation.

  If the inlet temperature T deviates from the temperature range of the first temperature condition or the inlet pressure P deviates from the pressure range of the first pressure condition in step S6, the control circuit 72 determines the number n of pressure adjustments in step S8. . If the number n of pressure adjustments does not reach the predetermined number H (here, “5 times”), the control circuit 72 adjusts the pressure of the secondary refrigerant circuit 13 in step S9. As described above, for example, the number of rotations per minute of the blower fan 28 is adjusted. In subsequent step S10, the number n of pressure adjustments is counted. Thereafter, the process of the control circuit 72 returns to step S5. Thus, the inlet temperature T and the inlet pressure P of the indoor heat exchanger 27 are adjusted. A first value of constant pressure specific heat is established with the second refrigerant.

  If the inlet temperature T continues to deviate from the temperature range of the first temperature condition in step S6 or the inlet pressure P continues to deviate from the pressure range of the first pressure condition, the number n of pressure adjustments becomes the default value H in step S8. Reach. At this time, the control circuit 72 proceeds to step S11. In step S11, the control circuit 72 sets the second set temperature value Tset2 to the target temperature Tset. In subsequent step S12, the control circuit 72 sets the second set pressure value Pset2 to the target pressure Pset. Details of the second set temperature value Tset2 and the second set pressure value Pset2 will be described later.

  In step S13, the control circuit 72 acquires the first temperature signal and the first pressure signal. The control circuit 72 specifies the inlet temperature T and the inlet pressure P of the indoor heat exchanger 27 based on the first temperature signal and the first pressure signal. In subsequent step S14, the control circuit 72 compares the inlet temperature T with the second temperature condition and the inlet pressure P with the second pressure condition. For example, the second temperature condition is set to a temperature range of ± 1 degree of the second set temperature value Tset2. The second pressure condition is set, for example, within a pressure range of ± 0.1 MPa of the second set pressure value Pset2. Here, the first pressure condition and the second pressure condition may coincide or overlap. A temperature range in which a constant pressure specific heat lower than that of the first temperature condition can be obtained is set as the second temperature condition. When the inlet temperature T is specified within the temperature range of the second temperature condition and the inlet pressure P is specified within the pressure range of the second pressure condition, in step S15, the control circuit 72 causes the refrigerant tank from the circulation path 25 as described above. 29 is cut off. Thereafter, as long as the load of the indoor heat exchanger 27 does not fluctuate, the inlet temperature T and the inlet pressure P continue to satisfy the second temperature condition and the second pressure condition. The air conditioner 11 realizes stable heating operation.

  When the inlet temperature T deviates from the temperature range of the second temperature condition in step S14 or the inlet pressure P deviates from the pressure range of the second pressure condition, the control circuit 72 adjusts the pressure of the secondary refrigerant circuit 13 in step S16. To implement. As described above, for example, the number of rotations per minute of the blower fan 28 is adjusted. Thereafter, the process of the control circuit 72 returns to step S13. Thus, the inlet temperature T and the inlet pressure P of the indoor heat exchanger 27 are adjusted. A second value of constant pressure specific heat is established with the second refrigerant.

  As shown in FIG. 8, the constant-pressure specific heat of supercritical CO2 increases the temperature dependence as the pressure decreases. In other words, when the pressure decreases, the constant pressure specific heat greatly fluctuates according to a change in temperature. When the pressure is kept constant, the temperature dependence of the constant pressure specific heat increases as the temperature approaches the temperature at which the maximum value of the constant pressure specific heat is established. If the constant pressure specific heat is large, the room can be efficiently warmed with a small refrigerant flow rate. On the other hand, if the temperature dependence of the constant pressure specific heat is high, the temperature and pressure of CO2 are likely to fluctuate according to the fluctuation of the load. The temperature and pressure of CO2 are difficult to converge to the target temperature and target pressure.

  For example, when CO2 is used as the second refrigerant in the air conditioner 11 described above, the first setting is set when 8.5 [MPa] is set in the first set pressure value Pset1 and the second set pressure value Pset2. In the temperature value Tset1, a temperature (= about 37.5 degrees Celsius) that establishes the maximum value of constant pressure specific heat is set. Therefore, if the inlet temperature T remains in the temperature range of the first temperature condition, an efficient and stable heating operation can be realized based on the high constant pressure specific heat. However, when the load fluctuation of the indoor heat exchanger 27 increases, the pressure adjustment of the secondary refrigerant circuit 13 is continuously performed. In this case, the second set temperature value Tset2 is used instead of the first set temperature value Tset1. In the second set temperature value Tset2, for example, a temperature (for example, 44 degrees Celsius) that establishes a constant pressure specific heat lower than the maximum value is set. As a result, the temperature dependence of the constant pressure specific heat is reduced with respect to the load fluctuation of the indoor heat exchanger 27. Accordingly, the inlet temperature T can be kept within the temperature range of the second temperature condition relatively easily. The pressure adjustment operation, that is, the control of the number of revolutions per minute of the blower fan 28, the control of the opening degree of the expansion valve 19, and the control of the operating frequency of the compressor 14 can be suppressed. As a result, power consumption is suppressed. In addition, since the inlet temperature T and the inlet pressure P converge on the target temperature and the target pressure relatively early in the second temperature condition as compared with the first temperature condition, the refrigerant tank 29 is disconnected from the circulation path 25 at an early stage. The first branch path 46 can be disconnected from the second circulation path 17 at an early stage. Such early separation contributes to further reduction of power consumption.

  As described above, when the inlet temperature T and the inlet pressure P satisfy the second temperature condition and the second pressure condition and the operation of the air conditioner 11 is stabilized, the second temperature condition is again obtained after a predetermined period. Instead of the second pressure condition, the first temperature condition and the first pressure condition may be used. In this case, for example, the room temperature may be measured when determining the period. If fluctuations in the room temperature are suppressed, the load on the indoor heat exchanger 27 is stabilized. Therefore, even if the first temperature condition and the first pressure condition are restored, the temperature and pressure of the second refrigerant are expected to converge to the target temperature and the target pressure at an early stage.

  In the air conditioner 11 as described above, the pressure of the second refrigerant is adjusted in the secondary refrigerant circuit 13 based on the thermal energy of the first refrigerant in the primary refrigerant circuit 12 by the action of the pressure adjustment unit. The first refrigerant is used for adjusting the pressure. Electric heating devices and cooling devices specific to the pressure adjustment can be omitted. In adjusting the pressure, an increase in power consumption of the air conditioner can be avoided.

  Moreover, in the air conditioner 11, the pressure adjustment unit can reduce the pressure of the second refrigerant based on the endothermic action of the first refrigerant. In the secondary refrigerant circuit 13, a pressure lower than the supercritical pressure can be reliably established regardless of the ambient environmental temperature. In the secondary refrigerant circuit 13, the pressure of the second refrigerant can be reliably adjusted for the cooling operation. An efficient cooling operation can be realized.

  FIG. 9 schematically shows a configuration of a refrigeration cycle apparatus, that is, an air conditioner 11a according to the second embodiment of the present invention. In the drawing, the same reference numerals are given to the equivalent components to those of the first embodiment described above, and their detailed description is omitted. In the second embodiment, a first internal heat exchanger 74 and a second internal heat exchanger 75 are incorporated in the primary refrigerant circuit 12. A third branch path 76 is connected to the first circulation path 15 when incorporating the first and second internal heat exchangers 74 and 75. The third branch path 76 forms a detour in the first circulation path 15 from the branch point 77 to the branch point 78 between the first port 16 a of the four-way valve 16 and the suction port 14 a of the compressor 14.

  The first internal heat exchanger 74 includes a first passage 74a and a second passage 74b. The first passage 74 a is incorporated into the third branch path 76 between the branch point 77 and the branch point 78. The first refrigerant passes from the first port 16 a of the four-way valve 16 through the first passage 74 a and reaches the compressor 14. The second passage 74 b is incorporated in the second circulation path 17 between the refrigerant-refrigerant heat exchanger 21 and the expansion valve 19. Here, the second passage 74 b is disposed between the sixth branch point 51 and the expansion valve 19. Thermal energy is exchanged between the refrigerant in the first passage 74a and the refrigerant in the second passage 74b. For example, the piping of the first passage 74a and the piping of the second passage 74b may be in contact with each other when exchanging thermal energy.

  The second internal heat exchanger 75 includes a first passage 75a and a second passage 75b. The first passage 75 a is incorporated in the first circulation path 15 between the branch point 77 and the branch point 78. The first refrigerant passes from the first port 16 a of the four-way valve 16 through the first passage 75 a and reaches the compressor 14. The second passage 75 b is incorporated in the second circulation path 17 between the expansion valve 19 and the outdoor heat exchanger 18. Thus, heat energy is exchanged between the refrigerant in the first passage 75a and the refrigerant in the second passage 75b. In exchanging the heat energy, for example, the pipe of the first passage 75a and the pipe of the second passage 75b may be in contact with each other.

  A first on-off valve 81 is inserted into the third branch path 76 between the branch point 77 and the branch point 78. A second on-off valve 82 is inserted in the first circulation path 15 between the branch point 77 and the branch point 78. The first opening / closing valve 81 and the second opening / closing valve 82 switch between the flow and blocking of the first refrigerant in accordance with the opening / closing of the valve element.

  During the heating operation, the first on-off valve 81 is opened and the second on-off valve 82 is closed. As a result, the first refrigerant flows from the first port 16 a of the four-way valve 16 into the third branch path 76. Thermal energy moves from the refrigerant in the second passage 74b to the refrigerant in the first passage 74a. The first refrigerant that has received the heat energy is supplied to the suction side of the compressor 14. The temperature of the 1st refrigerant | coolant supplied to the 4th heat exchanger 45 rises. In the refrigerant tank 29, the pressure of the second refrigerant rises with good responsiveness. On the other hand, during the cooling operation, the first on-off valve 81 is closed and the second on-off valve 82 is opened. As a result, the first refrigerant flows through the first circulation path 15 between the branch point 77 and the branch point 78. Thermal energy moves from the refrigerant in the second passage 75b to the refrigerant in the first passage 75a. As a result, the first refrigerant that has received the thermal energy is supplied to the suction side of the compressor 14. The temperature of the 1st refrigerant | coolant supplied to the 4th heat exchanger 45 falls. In the refrigerant tank 29, the pressure of the second refrigerant falls with good responsiveness.

  DESCRIPTION OF SYMBOLS 11 Air conditioner as refrigeration cycle apparatus, 17 Primary side circulation path (second circulation path), 18 Outdoor heat exchanger as third heat exchanger, 19 Expansion valve, 21 Refrigerant as first heat exchanger Refrigerant heat exchanger, 25 circulation path, 27 indoor heat exchanger as second heat exchanger, 29 refrigerant tank as refrigerant reservoir, 45 fourth heat exchanger, 72 control circuit.

Claims (4)

The first constant pressure specific heat per unit temperature change in the first temperature range including the temperature that establishes the first constant pressure specific heat in the supercritical state, and the second constant pressure specific heat in the supercritical state lower than the first constant pressure specific heat. A refrigerant that exhibits a second change amount of constant pressure specific heat that is smaller than the first change amount per unit temperature change in a second temperature range including a temperature that establishes the temperature is circulated between the first heat exchanger and the second heat exchanger. Circulating along the path and conveying thermal energy from the first heat exchanger to the second heat exchanger according to the amount of heat of the refrigerant;
Setting a first temperature condition in the first temperature range in the control circuit;
Adjusting the temperature and pressure in the circulation path by the action of the control circuit toward the first temperature condition;
Setting the second temperature condition within the second temperature range in the control circuit when the temperature deviates from the first temperature condition for a predetermined period during the adjustment of the temperature and the pressure;
And a step of adjusting the temperature and pressure in the circulation path by the action of the control circuit toward the second temperature condition. In the control method of the refrigerating cycle device according to claim 1,
Adjusting the temperature and pressure of the refrigerant in the circulation path according to the storage amount of the refrigerant reservoir that is incorporated in the circulation path and partitions the space for storing the refrigerant;
A control method for a refrigeration cycle apparatus, further comprising a step of separating the refrigerant reservoir from the circulation path when the pressure of the refrigerant reaches a predetermined pressure in the circulation path during heating operation. In the control method of the refrigerating cycle device according to claim 2,
A primary-side refrigerant is circulated along the primary-side circulation path between the first heat exchanger and the third heat exchanger, and the first heat exchanger or the second heat is interposed between the compressor and the expansion valve. Supplying a primary side refrigerant compressed to a high temperature and high pressure by the compressor to the exchanger, and transferring thermal energy from the primary side refrigerant to the refrigerant in the first heat exchanger;
A step of transferring thermal energy by a fourth heat exchanger from the primary side refrigerant compressed to high temperature and high pressure by the compressor to the refrigerant in the refrigerant reservoir;
And a step of separating the fourth heat exchanger from the primary circulation path when the refrigerant reservoir is separated from the circulation path. The control method of the refrigerating cycle device according to any one of claims 1 to 3, wherein the pressure in the circulation path is maintained constant under the first temperature condition and the second temperature condition. Control method of refrigeration cycle apparatus.

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