JP5421717B2 - Refrigeration cycle apparatus and hot water heater - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus that supercools refrigerant that has flowed out of a condenser, and a hot water heater using the refrigeration cycle apparatus.

  2. Description of the Related Art Conventionally, there has been provided a refrigeration cycle apparatus in which a supercooling heat exchanger is provided on the downstream side of a condenser in a refrigerant circuit, and the refrigerant flowing out of the condenser is supercooled by allowing the expanded refrigerant to flow into the supercooling heat exchanger. Are known. For example, Patent Document 1 discloses a refrigeration cycle apparatus 100 as shown in FIG.

  The refrigeration cycle apparatus 100 includes a refrigerant circuit 110 that circulates refrigerant and a bypass passage 120. The refrigerant circuit 110 is configured by connecting a compressor 111, a condenser 112, a supercooling heat exchanger 113, a main expansion valve 114, and an evaporator 115 in an annular shape by piping. The bypass 120 is branched from the refrigerant circuit 110 between the condenser 112 and the supercooling heat exchanger 113 and connected to the refrigerant circuit 110 between the evaporator 115 and the compressor 111 via the supercooling heat exchanger 113. ing. The bypass passage 120 is provided with a bypass expansion valve 121 upstream of the supercooling heat exchanger 113.

  Further, the refrigeration cycle apparatus 100 includes a pressure sensor 131 that detects the pressure of the refrigerant sucked into the compressor 111, and a temperature sensor 141 that detects the temperature of the refrigerant flowing out of the evaporator 115 (evaporator outlet temperature) Teo. In addition, a temperature sensor 142 that detects the temperature (bypass side outlet temperature) Tbo of the refrigerant flowing out of the supercooling heat exchanger 113 in the bypass passage 120 is provided.

  In Patent Document 1, the saturation temperature Ts at the pressure is calculated from the pressure detected by the pressure sensor 131, and the superheat degree (Teo-Ts) at the outlet of the evaporator 115 is the target superheat degree. It is described that the expansion valve 114 is controlled and the bypass expansion valve 121 is controlled so that the degree of superheat (Tbo-Ts) at the outlet of the supercooling heat exchanger 113 becomes the target degree of superheat.

Japanese Patent Laid-Open No. 10-68553

  However, as described in Patent Document 1, when the bypass expansion valve 121 is controlled so that the degree of superheat (Tbo-Ts) at the outlet of the supercooling heat exchanger 113 becomes the target degree of superheating, the supercooling is performed. Since more refrigerant can be evaporated in the heat exchanger 113, the performance of the supercooling heat exchanger 113 cannot be utilized to the maximum extent. That is, the effect of increasing the enthalpy in the evaporator 115 by heat exchange between the mainstream refrigerant and the bypass refrigerant and the effect of reducing the pressure loss of the low-pressure refrigerant path by bypassing the refrigerant cannot be maximized. In addition, when the refrigerant bypassing the evaporator 115 is overheated (superheated), the specific volume of the refrigerant sucked into the compressor 111 is increased, the refrigerant circulation amount is decreased, and the discharge temperature of the compressor is also increased. For this reason, at the low outside air temperature in which a large heating capacity is required, the rotational speed of the compressor cannot be increased so much from the viewpoint of securing the reliability by suppressing the discharge temperature, and the heating capacity may be insufficient.

  In view of such circumstances, the present invention can maximize the effect of increasing the enthalpy in the evaporator and the effect of reducing the pressure loss of the low-pressure side refrigerant path, and can obtain sufficient heating capacity at a low outside air temperature. An object is to provide a refrigeration cycle apparatus and a hot water heating apparatus using the refrigeration cycle apparatus.

  In order to solve the above-described problems, the present invention provides a compressor, a condenser, a supercooling heat exchanger, a refrigerant circuit in which a main expansion means and an evaporator are connected in an annular shape, the condenser and the supercooling heat exchanger. Or a bypass that branches from the refrigerant circuit between the supercooling heat exchanger and the main expansion means, and connects to the refrigerant circuit between the evaporator and the compressor via the supercooling heat exchanger A bypass expansion means provided upstream of the subcooling heat exchanger in the bypass passage, and a first temperature sensor for detecting the temperature of the refrigerant flowing out of the supercooling heat exchanger in the bypass passage A second temperature sensor for detecting a temperature of the refrigerant flowing out of the evaporator in the refrigerant circuit, and a temperature detected by the first temperature sensor becomes a saturation temperature at a pressure of the refrigerant sucked into the compressor, And the second A controller that controls the bypass expansion means so that the degree of superheat at the evaporator outlet calculated based on the temperature detected by the degree sensor is equal to or lower than a predetermined degree of superheat. A refrigeration cycle apparatus is provided.

  Moreover, this invention is a hot water heating apparatus which utilizes the warm water produced | generated by the heating means for heating, Comprising: The hot water heating apparatus provided with said refrigeration cycle apparatus as said heating means is provided.

  According to said structure, since the temperature of the refrigerant | coolant which flows out from a supercooling heat exchanger in a bypass channel is maintained at the saturation temperature in the pressure of the refrigerant | coolant suck | inhaled by a compressor, the refrigerant | coolant which flows out from a supercooling heat exchanger Can be kept wet or saturated. In addition, since the superheat degree at the evaporator outlet is suppressed to a predetermined superheat degree or less, the flow rate of the refrigerant flowing through the bypass passage becomes too large and the refrigerant sucked into the compressor (the refrigerant flowing through the bypass passage and the evaporator) It is possible to prevent the dryness of the refrigerant that has passed with the refrigerant that has passed through from being too low, and to set the dryness of the refrigerant sucked into the compressor within a desired range (for example, 0.8 to less than 1.0). ). Thereby, the enthalpy increase effect in the evaporator by heat exchange between the main flow refrigerant and the bypass flow refrigerant and the pressure loss reduction effect in the low pressure side refrigerant path by the refrigerant bypass can be maximized. Further, since the discharge temperature of the compressor can be suppressed, it is possible to increase the rotation speed of the compressor at a low outside air temperature, and a sufficient heating capacity can be obtained.

1 is a schematic configuration diagram of a refrigeration cycle apparatus according to a first embodiment of the present invention. Mollier diagram of the refrigeration cycle apparatus shown in FIG. Flowchart of control performed by the control device in the first embodiment Schematic block diagram of the refrigeration cycle apparatus according to the second embodiment of the present invention. Flowchart of control performed by the control device in the second embodiment Schematic configuration diagram of a conventional refrigeration cycle apparatus

(First embodiment)
FIG. 1 shows a refrigeration cycle apparatus 1A according to the first embodiment of the present invention. The refrigeration cycle apparatus 1 </ b> A includes a refrigerant circuit 2 that circulates refrigerant, a bypass path 3, and a control device 4. As the refrigerant, for example, a non-azeotropic refrigerant mixture such as R407C, a pseudo-azeotropic refrigerant mixture such as R410A, or a single refrigerant can be used.

  The refrigerant circuit 2 is configured by connecting a compressor 21, a condenser 22, a supercooling heat exchanger 23, a main expansion valve (main expansion means) 24, and an evaporator 25 in an annular shape by piping. In the present embodiment, a sub-accumulator 26 and a main accumulator 27 that perform gas-liquid separation are provided between the evaporator 25 and the compressor 21. The refrigerant circuit 2 is provided with a four-way valve 28 for switching between normal operation and defrost operation.

  In the present embodiment, the refrigeration cycle apparatus 1A constitutes a heating means of a hot water heating apparatus that uses hot water generated by the heating means for heating, and the condenser 22 exchanges heat between the refrigerant and water. It is a heat exchanger that heats water. Specifically, a supply pipe 71 and a recovery pipe 72 are connected to the condenser 22. Water is supplied to the condenser 22 through the supply pipe 71, and water (hot water) heated by the condenser 22 is recovered in the recovery pipe 72. It has come to be collected through. The hot water collected by the collection pipe 72 is sent to a heater such as a radiator directly or via a hot water storage tank, and thereby heating is performed.

  The bypass path 3 branches from the refrigerant circuit 2 between the supercooling heat exchanger 23 and the main expansion valve 24, and enters the refrigerant circuit 2 between the evaporator 25 and the compressor 21 via the supercooling heat exchanger 23. linked. In the present embodiment, the bypass 3 is connected to the refrigerant circuit 2 between the sub accumulator 26 and the main accumulator 27. The bypass passage 3 is provided with a bypass expansion valve (bypass expansion means) 31 on the upstream side of the supercooling heat exchanger 23.

  In the normal operation, the refrigerant discharged from the compressor 21 is sent to the condenser 22 via the four-way valve 28, and in the defrost operation, the refrigerant discharged from the compressor 21 is sent to the evaporator 25 via the four-way valve 28. It is done. In FIG. 1, the direction of refrigerant flow during normal operation is indicated by arrows. Hereinafter, the state change of the refrigerant in the normal operation will be described.

  The high-pressure refrigerant discharged from the compressor 21 flows into the condenser 22 and radiates heat to the water passing through the condenser 22. The high-pressure refrigerant flowing out of the condenser 22 flows into the supercooling heat exchanger 23 and is supercooled by the low-pressure refrigerant decompressed by the bypass expansion valve 31. The high-pressure refrigerant that has flowed out of the supercooling heat exchanger 23 is divided into the main expansion valve 24 side and the bypass expansion valve 31 side.

  The high-pressure refrigerant branched to the main expansion valve 24 side is decompressed and expanded by the main expansion valve 24 and then flows into the evaporator 25. Here, the low-pressure refrigerant flowing into the evaporator 25 absorbs heat from the air. On the other hand, the high-pressure refrigerant branched to the bypass expansion valve 31 side is decompressed and expanded by the bypass expansion valve 31 and then flows into the supercooling heat exchanger 23. The low-pressure refrigerant that has flowed into the supercooling heat exchanger 23 is heated by the high-pressure refrigerant that has flowed out of the condenser 22. Thereafter, the low-pressure refrigerant that has flowed out of the supercooling heat exchanger 23 merges with the low-pressure refrigerant that has flowed out of the evaporator 25, and is sucked into the compressor 21 again.

  The configuration of the refrigeration cycle apparatus 1A of the present embodiment is that the pressure of the refrigerant sucked into the compressor 21 at the low outside air temperature decreases and the refrigerant circulation amount decreases, thereby reducing the heating capacity of the condenser 22. It is for preventing. In order to realize this, the amount of gas-phase refrigerant having a small endothermic effect that flows through the low pressure side portion of the refrigerant circuit 2 by increasing the enthalpy difference in the evaporator 25 by supercooling and bypassing the refrigerant by the bypass passage 3. It is important to reduce the pressure loss at the low pressure side portion of the refrigerant circuit 2. If the pressure loss in the low pressure side portion of the refrigerant circuit 2 is reduced, the pressure of the refrigerant sucked into the compressor 21 is increased by that amount, and the specific volume is reduced, so that the refrigerant circulation amount is increased. Moreover, if the enthalpy difference in the evaporator 25 is increased, even if the mass flow rate of the refrigerant passing through the evaporator 25 is reduced by bypass, the heat absorption amount in the evaporator 25 can be secured. That is, if the degree of supercooling of the refrigerant and the amount of bypass are maximized, the maximum heating capacity improvement effect of the condenser 22 and the COP (Coefficient of Performance) improvement effect of the refrigeration cycle apparatus 1A can be obtained.

  In this embodiment, as will be described in detail later, the bypass expansion valve 31 is controlled so that the refrigerant flowing through the bypass passage 3 is not superheated (superheated) by the supercooling heat exchanger 23. Therefore, the state of the refrigerant that has flowed out of the supercooling heat exchanger 23 in the bypass passage 3 is saturated as shown by point a in FIG. On the other hand, since the refrigerant is superheated in the evaporator 25, the state of the refrigerant flowing out of the evaporator 25 is a point b in FIG. And since the refrigerant | coolant suck | inhaled by the compressor 21 is what those refrigerant | coolants merged, it will be in the state of the c point between the point a and b point.

  The bypass passage 3 is provided with a first temperature sensor 61 that detects the temperature (bypass side outlet temperature) Tbo of the refrigerant flowing out from the supercooling heat exchanger 23. On the other hand, the refrigerant circuit 2 includes a pressure sensor 51 that detects the pressure (suction pressure) Ps of the refrigerant sucked into the compressor 21 and a discharge that detects the temperature (discharge temperature) Td of the refrigerant discharged from the compressor 21. A temperature sensor 65 and a second temperature sensor 62 for detecting the temperature (evaporator outlet temperature) Teo of the refrigerant flowing out of the evaporator 25 are provided.

  Based on the detection values detected by the various sensors 51, 61, 62 and 65, the control device 4 switches the rotational speed of the compressor 21, the four-way valve 28, and the main expansion valve 24 and the bypass expansion valve 31. Control the opening. In the present embodiment, during normal operation, the control device 4 determines that the bypass-side outlet temperature Tbo detected by the first temperature sensor 61 becomes the saturation temperature STs at the pressure of the refrigerant sucked into the compressor 21, and the second The bypass expansion means 31 is controlled so that the degree of superheat SHe at the outlet of the evaporator 25 calculated based on the evaporator outlet temperature Teo detected by the temperature sensor 62 is equal to or lower than a predetermined degree of superheat.

  Next, the control of the control device 4 during normal operation will be described in detail with reference to the flowchart shown in FIG.

  First, the control device 4 detects the discharge temperature Td with the discharge temperature sensor 65 (step S1), and adjusts the opening of the main expansion valve 24 so that the discharge temperature Td becomes a target value (step S2).

  Next, the control device 4 detects the suction pressure Ps with the pressure sensor 51 and detects the bypass side outlet temperature Tbo with the first temperature sensor 61 (step S3). Further, the control device 4 calculates the saturation temperature STs at the refrigerant pressure sucked into the compressor 21 from the detected suction pressure Ps (step S4). The calculation of the saturation temperature STs is performed using a refrigerant physical property formula. Thereafter, the control device 4 determines whether or not the bypass side outlet temperature Tbo is equal to the saturation temperature STs (step S5).

  When the bypass-side outlet temperature Tbo is not equal to the saturation temperature STs (NO in step S5), it is considered that more refrigerant can be evaporated in the supercooling heat exchanger 23. The opening degree of the expansion valve 31 is increased by a predetermined amount (step S6), and the process returns to step S1.

  On the other hand, when the bypass-side outlet temperature Tbo is equal to the saturation temperature STs (YES in step S5), it is considered that the performance of the supercooling heat exchanger 23 can be fully utilized for the evaporation of the refrigerant. 4 shifts to control for correcting the opening degree of the bypass expansion valve 31.

That is, the control device 4 detects the evaporator outlet temperature Teo with the second temperature sensor 62 (step S7), and calculates the superheat degree SHe at the outlet of the evaporator 25 by the following equation (step S8).
SHe = Teo-STs

  Thereafter, the control device 4 determines whether or not the calculated degree of superheat SHe at the outlet of the evaporator 25 is equal to or lower than a predetermined degree of superheat (step S9). In the case of NO in step S9, it is considered that the point c shown in FIG. 2 has gone too far to the right (overheating due to insufficient flow), that is, the point a has gone too far to the left (too wet due to excessive flow). Therefore, the opening degree of the bypass expansion valve 31 is lowered by a predetermined amount (step S10), and the process returns to step S1. On the other hand, if YES in step S10, it is considered that the opening degree of the bypass expansion valve 31 is appropriate, and therefore the control device 4 directly returns to step S1.

  As described above, in the present embodiment, the bypass-side outlet temperature Tbo is maintained at the saturation temperature STs at the pressure of the refrigerant sucked into the compressor 21, so that the refrigerant flowing out of the supercooling heat exchanger 23 is moistened. State or saturated gas state. Moreover, since the degree of superheat SHe at the outlet of the evaporator 25 is suppressed to a predetermined degree of superheat or less, the flow rate of the refrigerant flowing through the bypass passage 3 becomes too large and the refrigerant sucked into the compressor 21 (flowed through the bypass passage 3). It is possible to prevent the dryness of the refrigerant after the refrigerant and the refrigerant that has passed through the evaporator 25 from joining together, and to prevent the dryness of the refrigerant sucked into the compressor 21 from being in a desired range (for example, 0). .8 or more and less than 1.0). Thereby, the enthalpy increasing effect in the evaporator 25 due to heat exchange between the mainstream refrigerant and the bypass flow refrigerant and the pressure loss reducing effect in the low-pressure side refrigerant path due to the refrigerant bypass can be maximized. In addition, since the discharge temperature Td of the compressor 21 is suppressed, the rotation speed of the compressor 21 can be increased at a low outside air temperature, and sufficient heating capability can be obtained.

Here, the “predetermined superheat degree” used in step S9 is preferably a superheat degree at which the dryness of the refrigerant sucked into the compressor 21 becomes 0.8 or more and less than 1.0. If it has become like this, it will become possible to operate refrigeration cycle device 1A in the most efficient state. The dryness of the refrigerant sucked into the compressor 21 is calculated by the following equation.
X = (ha−hl) / (hv−hl)
X: dryness of refrigerant sucked into the compressor 21 ha: enthalpy of refrigerant sucked into the compressor 21 hl: saturated gas enthalpy at the pressure of refrigerant sucked into the compressor 21 hv: sucked into the compressor 21 Saturated liquid enthalpy at the refrigerant pressure

  Further, the “predetermined degree of superheat” is preferably determined according to the outside air temperature so that the dryness of the refrigerant sucked into the compressor 21 decreases as the outside air temperature decreases. If it becomes like this, the rotation speed of the compressor 21 can be raised while suppressing that the discharge temperature rises beyond the appropriate range due to the decrease in the evaporation pressure accompanying the decrease in the outside air temperature, and the heating capacity is sufficient. Can get to. In this case, the control may be performed while the outside temperature is detected by the outside temperature sensor.

  Alternatively, the “predetermined degree of superheat” is determined according to the compression ratio of the refrigerant so that the degree of dryness of the refrigerant sucked into the compressor 21 decreases as the compression ratio of the refrigerant by the compressor 21 increases. Is preferred. If it becomes like this, the rotation speed of the compressor 21 can be raised, suppressing the discharge temperature rise accompanying the compression ratio raise, and heating capability can fully be acquired. In this case, the control may be performed while detecting the discharge pressure and the suction pressure of the compressor 21 with a pressure sensor.

  From another viewpoint, the “predetermined degree of superheat” depends on the rotational speed of the compressor 21 so that the higher the rotational speed of the compressor 21 is, the smaller the dryness of the refrigerant sucked into the compressor 21 is. It is preferable that it is defined. If it becomes like this, the rotation speed of the compressor 21 can be raised, suppressing the discharge temperature rise accompanying the rotation speed rise, and heating capability can fully be acquired.

<Modification>
In FIG. 1, the pressure sensor 51 is provided between the position where the bypass path 3 in the refrigerant circuit 2 is connected and the main accumulator 27, but the pressure sensor 51 is between the evaporator 25 and the compressor 21. It may be provided at any position in the refrigerant circuit 2. Alternatively, the pressure sensor 51 may be provided on the downstream side of the subcooling heat exchanger 23 in the bypass passage 3.

(Second Embodiment)
FIG. 4 shows a refrigeration cycle apparatus 1B according to the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Also in this embodiment, as in the first embodiment, the control device 4 saturates the bypass-side outlet temperature Tbo detected by the first temperature sensor 61 with the pressure of the refrigerant sucked into the compressor 21 during normal operation. The degree of superheat SHe at the outlet of the evaporator 25 calculated based on the evaporator outlet temperature Teo detected by the second temperature sensor 62 is equal to or lower than a predetermined predetermined degree of superheat. The bypass expansion means 31 is controlled. However, in the present embodiment, the controller 4 determines that the bypass side outlet temperature Tbo detected by the first temperature sensor 61 becomes the saturation temperature STs at the pressure of the refrigerant sucked into the compressor 21. This differs from the first embodiment in that the bypass-side outlet temperature Tbo detected by the sensor 61 is detected by being substantially equal to the temperature detected by the third temperature sensor 63.

  Specifically, as shown in FIG. 4, in the present embodiment, the refrigerant circuit 2 is not provided with the pressure sensor 51 (see FIG. 1). Instead, the bypass circuit 3 is connected to the supercooling heat exchanger 23. A third temperature sensor 63 for detecting the temperature of the refrigerant flowing in (the bypass side inlet temperature) Tbi is provided.

  Next, the control of the control device 4 during normal operation will be described in detail with reference to the flowchart shown in FIG.

  First, similarly to the first embodiment, the control device 4 detects the discharge temperature Td by the discharge temperature sensor 65 (step S21), and the opening degree of the main expansion valve 24 is adjusted so that the discharge temperature Td becomes a target value. Adjust (step S22).

  Next, the control device 4 detects the bypass side outlet temperature Tbo with the first temperature sensor 61 and also detects the bypass side inlet temperature Tbi with the third temperature sensor 63 (step S23). Thereafter, the control device 4 determines whether or not the bypass side outlet temperature Tbo is substantially equal to the bypass side inlet temperature Tbi (step S24). Here, “substantially equal” is a concept considering the phenomenon because the bypass side outlet temperature Tbo is not completely equal to the bypass side inlet temperature Tbi due to the effect of pressure loss. For example, if the temperature difference between the bypass side outlet temperature Tbo and the bypass side inlet temperature Tbi is 3K or less, they may be substantially equal.

  When the bypass-side outlet temperature Tbo is not substantially equal to the bypass-side inlet temperature Tbi (NO in step S24), it is considered that more refrigerant can be evaporated in the supercooling heat exchanger 23. Therefore, the control device 4 Increases the opening of the bypass expansion valve 31 by a predetermined amount (step S25), and returns to step S21.

  On the other hand, when the bypass side outlet temperature Tbo is substantially equal to the bypass side inlet temperature Tbi (YES in step S24), it is considered that the performance of the supercooling heat exchanger 23 can be utilized to the maximum for the evaporation of the refrigerant. The control device 4 proceeds to control for correcting the opening degree of the bypass expansion valve 31.

That is, the control device 4 detects the evaporator outlet temperature Teo with the second temperature sensor 62 (Step S26), and calculates the degree of superheat SHe at the outlet of the evaporator 25 by the following equation (Step S27).
SHe = Teo-Tbi

  Thereafter, the control device 4 determines whether or not the calculated degree of superheat SHe at the outlet of the evaporator 25 is equal to or lower than a predetermined degree of superheat (step S28). In the case of NO in step S28, it is considered that the point c shown in FIG. 2 has gone too far to the right, that is, the point a has gone too far to the left, so the opening degree of the bypass expansion valve 31 is lowered by a predetermined amount ( Step S29), the process returns to step S21. On the other hand, if YES in step S28, the opening degree of the bypass expansion valve 31 is considered to be appropriate, and the control device 4 directly returns to step S21.

  Even if the control as in this embodiment is performed, the same effect as in the first embodiment can be obtained.

<Modification>
In the present embodiment, the third temperature sensor 63 that detects the bypass side inlet temperature Tbi is used. However, the third temperature sensor of the present invention uses the temperature of the refrigerant flowing into the evaporator 25 in the refrigerant circuit 2 ( An evaporator inlet temperature) Tei may be detected. The flowchart in this case is obtained by changing the bypass side inlet temperature Tbi of the flowchart shown in FIG. 5 to the evaporator inlet temperature Tei. In step S27, the superheat degree SHe at the outlet of the evaporator 25 is calculated by the following equation. Good.
SHe = Teo-Tei

(Other embodiments)
In the first and second embodiments, the main expansion valve 24 is controlled so that the discharge temperature Td becomes the target value, but the method for controlling the main control valve 24 is not limited to this. For example, the main expansion valve 24 may be controlled so that the pressure of the refrigerant discharged from the compressor 21 becomes a target value. Alternatively, the main expansion valve 24 can be controlled based on the degree of superheat at the outlet of the compressor 21 or the degree of supercooling at the outlet of the condenser 22.

  Further, the bypass passage 3 does not necessarily have to branch from the refrigerant circuit 2 between the supercooling heat exchanger 23 and the main expansion valve 24, and the refrigerant circuit 2 is between the condenser 22 and the supercooling heat exchanger 23. You may branch from.

  Furthermore, the main expansion means and bypass expansion means of the present invention are not necessarily expansion valves, and may be an expander that recovers power from the expanding refrigerant. In this case, for example, the rotational speed of the expander may be controlled by changing the load with a generator connected to the expander.

  INDUSTRIAL APPLICABILITY The present invention is particularly useful for a hot water heater that generates hot water using a refrigeration cycle apparatus and uses the hot water for heating.

1A, 1B Refrigeration cycle apparatus 2 Refrigerant circuit 21 Compressor 22 Condenser 23 Supercooling heat exchanger 24 Main expansion valve (main expansion means)
25 Evaporator 3 Bypass path 31 Bypass expansion valve (bypass expansion means)
4 Control Device 51 Pressure Sensor 61 First Temperature Sensor 62 Second Temperature Sensor 63 Third Temperature Sensor

Claims (9)

A refrigerant circuit in which a compressor, a condenser, a supercooling heat exchanger, a main expansion valve capable of opening adjustment, and an evaporator are connected in an annular shape;
Branching from the refrigerant circuit between the condenser and the supercooling heat exchanger or between the supercooling heat exchanger and the main expansion valve , the evaporator and the compression via the supercooling heat exchanger A bypass that leads to the refrigerant circuit between the machines,
A bypass expansion valve capable of adjusting the opening provided upstream of the supercooling heat exchanger of the bypass passage;
A first temperature sensor for detecting a temperature of the refrigerant flowing out of the supercooling heat exchanger in the bypass path;
A second temperature sensor for detecting a temperature of refrigerant flowing out of the evaporator in the refrigerant circuit;
The temperature detected by the first temperature sensor becomes a saturation temperature at the pressure of the refrigerant sucked into the compressor, and the evaporator outlet is calculated based on the temperature detected by the second temperature sensor. A control device for controlling the degree of opening of the bypass expansion valve so that the degree of superheat is equal to or less than a predetermined degree of superheat,
The said control apparatus is a refrigerating-cycle apparatus which makes the opening degree of the said bypass expansion valve small, when the superheat degree in the said evaporator exit is larger than the said predetermined superheat degree . A pressure sensor for detecting the pressure of the refrigerant sucked into the compressor;
2. The refrigeration cycle apparatus according to claim 1, wherein the control device calculates a saturation temperature at a pressure of a refrigerant sucked into the compressor from a pressure detected by the pressure sensor. A third temperature sensor for detecting the temperature of the refrigerant flowing into the supercooling heat exchanger in the bypass passage or the temperature of the refrigerant flowing into the evaporator in the refrigerant circuit;
The controller determines that the temperature detected by the first temperature sensor is a saturation temperature at the pressure of the refrigerant sucked into the compressor, and the temperature detected by the first temperature sensor is the third temperature. The refrigeration cycle apparatus according to claim 1, wherein the refrigeration cycle apparatus is detected by being substantially equal to a temperature detected by a sensor.   The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the predetermined degree of superheat is a degree of superheat at which a dryness of the refrigerant sucked into the compressor is 0.8 or more and less than 1.0. .   The refrigeration cycle apparatus according to claim 4, wherein the predetermined degree of superheat is determined according to the outside air temperature so that the degree of dryness of the refrigerant sucked into the compressor decreases as the outside air temperature decreases.   5. The predetermined degree of superheat is determined according to the compression ratio of the refrigerant such that the higher the compression ratio of the refrigerant by the compressor, the smaller the dryness of the refrigerant sucked into the compressor. The refrigeration cycle apparatus described in 1.   The predetermined degree of superheat is determined according to the rotational speed of the compressor so that the higher the rotational speed of the compressor, the smaller the dryness of the refrigerant sucked into the compressor. The refrigeration cycle apparatus described.   The refrigeration cycle apparatus according to any one of claims 1 to 7, wherein the condenser is a heat exchanger that heats water by performing heat exchange between a refrigerant and water. A hot water heater that uses hot water generated by a heating means for heating,
A hot water heating apparatus comprising the refrigeration cycle apparatus according to claim 8 as the heating means.

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