JP2016121812A - Refrigeration cycle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration cycle device assuring reliability in operation of a compressor and restricting a reduction in efficiency of the compressor.SOLUTION: This invention relates to a refrigeration cycle in which a liquid injection compressor 1, a heat source side heat exchanger 2, a liquid side connection pipe 5, an expansion device 21, a use side heat exchanger 22 and a gas side connection pipe 6 are connected in sequence; and a refrigeration cycle device S comprising a bypass passage 31 for feeding refrigerant from between the heat source side heat exchanger 2 and the liquid side connection pipe 5 into an injection port of the liquid injection compressor 1 through a flow rate adjustment device 30 and a control device 50 for controlling a degree of opening of the flow rate adjustment device 30. R407E acting as refrigerant filled in the refrigeration cycle device S is employed, the control device 50 performs a controlling operation within a range of a temperature Td of refrigerant discharged from the liquid injection compressor 1 is 110°C or less and a super-heating degree TdSH of refrigerant discharged from the liquid injection compressor 1 is 10K or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to refrigeration cycle apparatuses such as air conditioners and refrigerators that use a refrigeration cycle, and more particularly to a refrigeration cycle apparatus that employs R407E as a refrigerant.

  From the viewpoint of preventing global warming, the global warming coefficient (GWP) is used as a refrigerant to be sealed in the refrigeration cycle device in order to minimize the impact on the global warming if the refrigerant leaks from the refrigeration cycle device. Adoption of a refrigerant having a low potential (low GWP refrigerant) has been studied. In particular, R404A (GWP = 3940) having a high GWP value is adopted in the refrigerator, and the adoption of a low GWP refrigerant is an urgent need.

  Currently, there are non-flammable refrigerants and slightly flammable refrigerants having combustibility as candidates for low GWP refrigerants employed in the refrigeration cycle apparatus. In a refrigeration cycle apparatus with a small amount of refrigerant, even if the refrigerant leaks, there is a possibility that the refrigerant concentration at the leakage destination can be set to be less than the flammable concentration, and therefore a slightly flammable refrigerant may be employed. However, when a slightly flammable refrigerant is employed in a refrigeration cycle apparatus having a large amount of refrigerant, it is necessary to take some safety measures, and it is inferior in terms of handling compared to a nonflammable refrigerant.

  For this reason, it is desirable to adopt a non-combustible low GWP refrigerant in a building multi-machine or refrigerator having a large amount of refrigerant. As an incombustible low GWP refrigerant, for example, there is an HFO mixed refrigerant in which an HFO refrigerant such as R32 or R125 is mixed with an HFO refrigerant having a double bond in the molecular structure of the refrigerant. However, since the HFO refrigerant has low chemical stability when mixed with air or moisture, the decomposition product of the HFO refrigerant raises the total acid value of the refrigeration oil, which may promote wear of the compressor sliding portion. For this reason, in the structure which employ | adopted the HFO refrigerant | coolant and the HFO mixed refrigerant | coolant as a refrigerant | coolant in a refrigerating-cycle apparatus, a device is needed for selection of refrigerating machine oil.

  Therefore, a refrigerant composed only of an HFC refrigerant not mixed with an HFO refrigerant is desirable, and a candidate thereof is R407E (R32: R125: R134a = 25: 15: 60 wt%). R407E is a refrigerant having GWP = 1425 (IPCC Fifth Assessment Report (AR5)) and a GWP value less than half of R404A and GWP 1500 or less, and is effective in reducing the GWP value.

  In the refrigerator, it is necessary to lower the evaporation temperature of the refrigerant in the use side heat exchanger to about −40 ° C., the pressure ratio in the compressor becomes large, and the temperature of the refrigerant discharged from the compressor may increase. is there. For this reason, in order to keep the temperature of the refrigerant discharged from the compressor low, a liquid injection compressor that introduces a refrigerant containing a liquid phase in the middle of the compression process of the compressor may be mounted. Also in the air conditioner, in a cold district specification where the outside air temperature is low, the pressure ratio in the compressor increases as in the case of the refrigerator, and the temperature of the refrigerant discharged from the compressor may increase. For this reason, there are products that employ liquid injection compressors.

  As a configuration in which R407E is used as a refrigerant in a refrigeration cycle apparatus equipped with a liquid injection compressor, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-106917) is disclosed.

JP 2002-106917 A

  As described above, in a refrigerator or an air conditioner for cold districts where the pressure on the suction side of the compressor decreases, the pressure ratio in the compressor increases and the temperature of the refrigerant discharged from the compressor increases. As a result, the temperature of the refrigerating machine oil that lubricates the sliding part of the compressor is increased, the deterioration of the refrigerating machine oil is promoted, and the total acid value of the refrigerating machine oil is increased by the carboxylic acid that is a degradation product. There is a risk of accelerating wear. For this reason, an appropriate value exists in the temperature of the refrigerant discharged from the compressor.

  In addition, when the refrigerant on the discharge side of the compressor is in a gas-liquid two-phase state, the liquid-phase refrigerant is present, so the viscosity of the refrigeration oil sealing the compression chamber is reduced, and the sealing performance is reduced. There is a possibility that the refrigerant leaks from the compression chamber and the efficiency of the compressor is lowered, or the lubricity of the compressor sliding portion is lowered. For this reason, the refrigerant on the discharge side of the compressor is preferably in an overheated state (a state where the temperature of the refrigerant is higher than the saturation temperature).

  Therefore, for the purpose of controlling the temperature of the refrigerant discharged from the compressor, a liquid injection compressor may be employed as the compressor of the refrigeration cycle apparatus. Further, the amount of liquid injection required for cooling the liquid injection compressor varies depending on the condensation temperature in the heat source side heat exchanger and the evaporation temperature in the use side heat exchanger. For this reason, in order to control the temperature of the refrigerant discharged from the compressor to an appropriate value, there is an appropriate range of the liquid injection amount according to the condensation temperature and the evaporation temperature. However, the refrigeration cycle apparatus disclosed in the cited document 1 has not been studied for the liquid injection amount.

  Then, this invention makes it a subject to provide the refrigerating-cycle apparatus which suppresses the efficiency fall of a compressor while ensuring the reliability of a compressor.

In order to solve such a problem, the refrigeration cycle apparatus according to the present invention sequentially includes a liquid injection compressor, a heat source side heat exchanger, a liquid side connection pipe, an expansion device, a use side heat exchanger, and a gas side connection pipe. A refrigeration cycle that is connected, a bypass path that introduces a refrigerant into the injection port of the liquid injection compressor from between the heat source side heat exchanger and the liquid side connection pipe via the flow rate adjustment device, and the flow rate adjustment device And a control device that controls the opening degree, wherein R407E is adopted as a refrigerant sealed in the refrigeration cycle device, and the control device uses a temperature Td of the refrigerant discharged from the liquid injection compressor. Is 110 ° C. or less, and the superheat degree TdSH of the refrigerant discharged from the liquid injection compressor is controlled in the range of 10K or more, Serial and flow rate of the refrigerant flowing in the bypass path, the ratio between the flow rate of the refrigerant flowing through the utilization-side heat exchanger, when the evaporating temperature in the utilization-side heat exchanger is -40 ℃, 8.11 × 10 ^{- When 3} × Tc + 1.28 × 10 ⁻¹ or more and 1.52 × 10 ⁻² × Tc + 4.81 × 10 ⁻¹ or less and the evaporation temperature in the use side heat exchanger is −20 ° C., 6. 60 × 10 ⁻³ × Tc + 2.14 × 10 ⁻¹ (provided that 0 if less than 0), and 7.86 × 10 ⁻³ × Tc + 1.99 × 10 ⁻¹ or less, the use side heat When the evaporation temperature in the exchanger is −10 ° C., it is 0 or more and 5.54 × 10 ⁻³ × Tc + 1.49 × 10 ⁻¹ or less (where Tc is the condensation temperature of the heat source side heat exchanger [ ° C]), the opening degree of the flow rate adjusting device is controlled.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring the reliability of a compressor, the refrigerating-cycle apparatus which suppresses the efficiency fall of a compressor can be provided.

It is a refrigerating cycle system diagram of the refrigerating cycle device concerning a 1st embodiment. It is a graph which shows the relationship between the injection flow rate ratio and condensation temperature in evaporating temperature -40 degreeC and the discharge side refrigerant | coolant superheat degree 10K. It is a graph which shows the relationship between the injection flow rate ratio and condensation temperature in evaporating temperature -40 degreeC and discharge side refrigerant | coolant temperature 110 degreeC. It is a graph which shows the relationship between the injection flow rate ratio and condensation temperature in evaporating temperature-20 degreeC and the discharge side refrigerant | coolant superheat degree 10K. It is a graph which shows the relationship between the injection flow rate ratio and condensation temperature in evaporating temperature-20 degreeC and discharge side refrigerant | coolant temperature 110 degreeC. It is a graph which shows the relationship between the injection flow rate ratio and condensation temperature in evaporating temperature -10 degreeC and discharge side refrigerant | coolant superheat degree 10K. It is a graph which shows the relationship between the injection flow rate ratio and condensation temperature in evaporating temperature -10 degreeC and discharge side refrigerant | coolant temperature 110 degreeC. It is a refrigerating cycle system diagram of the refrigerating cycle device concerning the modification of a 1st embodiment. It is a refrigeration cycle system diagram of the refrigeration cycle apparatus according to the second embodiment.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

<< First Embodiment >>
<Refrigeration cycle equipment>
The refrigeration cycle apparatus S according to the first embodiment will be described with reference to FIG. FIG. 1 is a refrigeration cycle system diagram of the refrigeration cycle apparatus S according to the first embodiment. In the following description, the refrigeration cycle apparatus S will be described as a refrigerator that employs R407E as a refrigerant.

  The refrigeration cycle apparatus S includes an outdoor unit 10 and a use side unit 20 and is configured to be connected by a liquid side connection pipe 5 and a gas side connection pipe 6. The outdoor unit 10 includes a liquid injection compressor (compressor) 1, a heat source side heat exchanger 2 acting as a condenser, a liquid pipe 3, a blocking valve 4, a blocking valve 7, a gas pipe 8, The accumulator 9, the injection flow rate adjusting device 30, the injection piping 31, and the control device 50 are provided. The use side unit 20 includes an expansion device 21 and a use side heat exchanger 22 that functions as an evaporator.

  Liquid injection compressor 1, heat source side heat exchanger 2, liquid pipe 3, blocking valve 4, liquid side connecting pipe 5, expansion device 21, use side heat exchanger 22, gas side connecting pipe 6, blocking valve 7, gas pipe 8 and a refrigeration cycle (refrigerant circulation path) is formed by sequentially connecting the accumulators 9.

  Further, a bypass path is formed which branches from the liquid pipe 3 and connects to the injection port of the liquid injection compressor 1 through the injection flow rate adjusting device 30 and the injection pipe 31. The control device 50 controls the flow rate of the refrigerant flowing through the injection pipe 31, that is, the flow rate of the refrigerant flowing into the injection port of the liquid injection compressor 1 by controlling the opening degree of the injection flow rate adjusting device 30. The injection flow rate adjusting device 30 may be composed of an electronic expansion valve capable of controlling the opening degree, and is composed of a combination of a plurality of capillaries and solenoid valves, and the opening degree can be controlled by opening and closing the solenoid valves. It may be done.

  In the case of the refrigeration operation of the refrigeration cycle apparatus S, the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 is discharged from the compressor 1 together with the refrigeration oil, and flows into the heat source side heat exchanger 2 acting as a condenser. Thus, heat exchange with the heat source side heat medium (outdoor air) condenses and liquefies to become a liquid refrigerant. Thereafter, the liquid refrigerant passes through the liquid pipe 3 and the blocking valve 4 and is sent to the use side unit 20 via the liquid side connection pipe 5. The liquid refrigerant sent to the use side unit 20 flows into the expansion device 21, where the liquid refrigerant is decompressed to a low pressure to become a low pressure two-phase state, and flows into the use side heat exchanger 22 acting as an evaporator, where air By exchanging heat with the use side heat medium such as, it is evaporated and gasified to become a gas refrigerant. Thereafter, the gas refrigerant is sent to the outdoor unit 10 through the gas side connection pipe 6. The gas refrigerant sent to the outdoor unit 10 passes through the blocking valve 7 and the gas pipe 8, is adjusted to an appropriate suction degree by the accumulator 9, and is sucked into the compressor 1 and compressed again. The surplus refrigerant is stored in the accumulator 9, and the operating pressure and temperature of the refrigeration cycle are maintained in a normal state.

  Here, the evaporation temperature ET in the use side heat exchanger 22 is set by the user according to the object to be cooled (not shown) (for example, −40 ° C., −20 ° C., −10 ° C., etc.). The control device 50 of the refrigeration cycle apparatus S controls the operating frequency of the compressor 1, the expansion device 21 and the like so that the set evaporation temperature ET is obtained. Further, the condensation temperature Tc in the heat source side heat exchanger 2 is the temperature (outside air temperature) of the heat source side heat medium (outdoor air), the refrigerant circulation amount, the heat source side heat medium (outdoor air) flowing through the heat source side heat exchanger 2. Varies depending on the flow rate.

  Further, there is an appropriate value for the temperature (discharge-side refrigerant temperature) Td of the refrigerant discharged from the compressor 1. When the evaporation temperature ET in the use side heat exchanger 22 is lowered, the evaporation pressure is lowered and the pressure on the suction side of the compressor 1 is lowered. If the condensation temperature Tc in the heat source side heat exchanger 2 is constant as the pressure on the suction side of the compressor 1 decreases, the discharge side refrigerant temperature Td of the compressor 1 increases. When the discharge side refrigerant temperature Td of the compressor 1 rises, the temperature of the refrigerating machine oil that lubricates the sliding portion (not shown) of the compressor 1 rises, so that the deterioration of the refrigerating machine oil is promoted and is a deteriorated product. Carboxylic acid may increase the total acid value of the refrigerating machine oil and promote wear of the sliding portion of the compressor 1. In addition, deterioration of refrigerating machine oil is accelerated as the temperature increases, and when the temperature rises by about 10 ° C., the deterioration is accelerated twice.

  Therefore, it is desirable that the discharge-side refrigerant temperature Td of the compressor 1 be controlled to 110 ° C. or less, which is a set temperature when designing the chemical stability of the refrigeration oil.

  Furthermore, when the refrigerant on the discharge side of the compressor 1 is in a gas-liquid two-phase state, the viscosity of the refrigerating machine oil sealing the compression chamber (not shown) of the compressor 1 is present because liquid-phase refrigerant is present. When the sealing performance of the compression chamber is lowered, the refrigerant leaks from the compression chamber and the efficiency of the compressor 1 may be reduced, or the lubricity of the sliding portion of the compressor 1 may be reduced.

  Therefore, it is desirable that the refrigerant on the discharge side of the compressor 1 is in an overheated state (a state where the temperature of the refrigerant is higher than the saturation temperature). Since the discharge-side refrigerant superheat degree (discharge-side refrigerant superheat degree) TdSH exceeds 0K, it is desirable to set the minimum value of the target value of the discharge-side refrigerant superheat degree TdSH during steady operation to 10K or more. The degree of superheat is a value indicating how many times [K] the refrigerant temperature is higher than the saturation temperature.

  In order to perform control so that the discharge-side refrigerant temperature Td (Td ≦ 110 [° C.]) and the discharge-side refrigerant superheat degree TdSH (TdSH ≧ 10 [K]) set as described above are satisfied, the first embodiment The refrigeration cycle apparatus S according to FIG. 1 employs a liquid injection compressor 1 having an injection port for introducing a refrigerant containing a liquid phase in the middle of a compression process as a compressor. The control device 50 controls the opening of the injection flow rate adjusting device 30 so that the discharge side refrigerant temperature Td ≦ 110 [° C.] and the discharge side refrigerant superheat degree TdSH ≧ 10 [K]. To do.

  Further, the liquid injection flow rate of the refrigerant flowing through the injection piping 31 necessary for cooling the liquid injection compressor 1 is determined by the condensation temperature Tc in the heat source side heat exchanger 2 and the evaporation temperature ET in the use side heat exchanger 22. And changes. Here, the higher the condensation temperature Tc in the heat source side heat exchanger 2 and the lower the evaporation temperature ET in the use side heat exchanger 22, the higher the discharge side refrigerant temperature Td of the compressor 1 tends to be. . For this reason, the injection flow rate required for cooling the compressor 1 increases. Therefore, in order to control the discharge side refrigerant temperature Td of the liquid injection compressor 1 to an appropriate value, there is an appropriate range of the liquid injection amount according to the condensation temperature Tc and the evaporation temperature ET.

  2 to 7, the evaporation temperature ET in the use side heat exchanger 22 is −40 ° C. (see FIGS. 2 and 3), −20 ° C. (see FIGS. 4 and 5), −10 ° C. (FIG. 6, The condensation temperature Tc [° C. in the heat source side heat exchanger 2, which is the horizontal axis x, when the refrigerant superheat degree (suction side refrigerant superheat degree) TsSH of the liquid injection compressor 1 in FIG. ] Is a graph showing the relationship of the injection flow rate ratio [−], which is the vertical axis y. 2, 4, and 6 show the case where the target superheat degree of the discharge-side refrigerant superheat degree TdSH of the liquid injection compressor 1 is 10 K, and FIGS. 3, 5, and 7 show the liquid injection compressor. The case where the target temperature of 1 discharge side refrigerant temperature Td is 110 degreeC is shown. Here, the injection flow rate ratio represents the ratio of the mass flow rate of the refrigerant flowing through the injection pipe 31 to the mass flow rate of the refrigerant flowing through the use-side heat exchanger 22. The graphs of FIGS. 2 to 7 are the results calculated by theoretical cycle calculation.

  Here, the higher the suction-side refrigerant superheat degree TsSH, the higher the suction-side refrigerant temperature (suction-side refrigerant temperature) Ts of the compressor 1, and thus the discharge-side refrigerant temperature Td. Further, the suction side refrigerant superheat degree TsSH can be set by the expansion device 21 mounted on the use side unit 20. However, when the expansion device 21 is a temperature type expansion valve, or the outdoor unit 10 and the use side unit 20 are manufactured by different equipment manufacturers, and the expansion device 21 is an electronic expansion valve, the expansion device 21 is not opened. The degree may not be controlled by the control device 50 of the outdoor unit 10.

  For this reason, as shown in FIGS. 3, 5, and 7, when the target temperature of the discharge-side refrigerant temperature Td is 110 ° C., the above-described setting conditions (Td ≦ 110 [° C.] and TdSH ≧ 10 [ K]), the discharge side refrigerant temperature Td is high, the cooling amount of the liquid injection compressor 1 is small, and the amount of refrigerant introduced into the injection port of the liquid injection compressor 1 is the smallest. The smallest injection flow rate ratio was adopted in the refrigerant superheat degree TsSH.

  As shown in FIGS. 2, 4, and 6, when the target superheat degree of the discharge-side refrigerant superheat degree TdSH is 10 K, the above-described setting conditions (Td ≦ 110 [° C.] and TdSH ≧ 10 [ K]), the discharge side refrigerant temperature Td is low, the amount of cooling of the liquid injection compressor 1 is large, and the amount of refrigerant introduced into the injection port of the liquid injection compressor 1 is the largest. The maximum injection flow rate ratio was adopted in the refrigerant superheat degree TsSH.

  Further, the lower limit value of the set value of the suction side refrigerant superheating degree TsSH studied in FIGS. 2 to 7 is the suction side refrigerant superheat degree TsSH in which the state of the refrigerant on the suction side of the liquid injection compressor 1 becomes a saturated gas state = 0 [K] was set as the lower limit.

  Further, the gas refrigerant evaporated in the use side heat exchanger 22 of the use side unit 20 is sent to the outdoor unit 10 through the gas side connection pipe 6 and is sucked into the liquid injection compressor 1. At this time, when the temperature around the gas side connection pipe 6 is higher than the temperature of the gas refrigerant flowing through the gas side connection pipe 6, heat is transferred from the ambient temperature and the temperature of the gas refrigerant rises. For this reason, the ambient temperature of the gas side connection pipe 6 is set to 30 ° C., and the upper limit value of the set value of the suction side refrigerant superheat TsSH examined in FIGS. 2 to 7 is about 30 at the suction side refrigerant temperature Ts. The upper limit of the suction side refrigerant superheating degree TsSH that is equal to or lower than ° C. was used. 2 to 7, the suction side refrigerant superheating degree TsSH was calculated every 20K.

As a result, as shown in FIGS. 2 and 3, when the evaporation temperature ET in the use side heat exchanger 22 is −40 ° C., the condensation temperature Tc [° C.] in the heat source side heat exchanger 2 is The injection flow rate adjusting device 30 has an injection flow rate ratio of 8.11 × 10 ⁻³ × Tc + 1.28 × 10 ⁻¹ or more and 1.52 × 10 ⁻² × Tc + 4.81 × 10 ⁻¹ or less. What is necessary is just to adjust an opening degree.

As shown in FIGS. 4 and 5, when the evaporation temperature ET in the use side heat exchanger 22 is −20 ° C., the injection is performed with respect to the condensation temperature Tc [° C.] in the heat source side heat exchanger 2. The flow rate ratio is 6.60 × 10 ⁻³ × Tc + 2.14 × 10 ⁻¹ (however, it is 0 when less than 0), and 7.86 × 10 ⁻³ × Tc + 1.99 × 10 ^−1. What is necessary is just to adjust the opening degree of the injection flow control apparatus 30 so that it may become the following.

Further, as shown in FIGS. 6 and 7, when the evaporation temperature ET in the use side heat exchanger 22 is −10 ° C., the injection is performed with respect to the condensation temperature Tc [° C.] in the heat source side heat exchanger 2. The opening degree of the injection flow rate adjusting device 30 may be adjusted so that the flow rate ratio is 0 or more and 5.54 × 10 ⁻³ × Tc + 1.49 × 10 ⁻¹ or less.

<Effect>
The effects of the refrigeration cycle apparatus S according to the first embodiment will be described.

  According to the refrigeration cycle apparatus S according to the first embodiment, as a refrigerant, R407E that is a low GWP refrigerant, is a non-flammable refrigerant, and includes only an HFC refrigerant that is not mixed with an HFO refrigerant can be employed. .

  And the control apparatus 50 of the refrigerating-cycle apparatus S which concerns on 1st Embodiment is defined by the function according to the condensation temperature Tc in the heat source side heat exchanger 2 for every evaporation temperature ET in the utilization side heat exchanger 22. FIG. The injection flow rate adjusting device 30 is controlled so that the injection flow rate ratio is within a predetermined range. Thereby, the temperature of the refrigerant discharged from the liquid injection compressor 1 can be controlled to an appropriate value (the discharge-side refrigerant temperature Td is 110 ° C. or less and the discharge-side refrigerant superheat degree TdSH is 10 K or more). .

  By controlling the discharge side refrigerant temperature Td of the compressor 1 to be 110 ° C. or lower, it is possible to suppress deterioration of the refrigerating machine oil due to heat, and to suppress wear of the compressor sliding portion due to the deteriorated refrigerating machine oil. The reliability of the refrigeration cycle apparatus S can be improved.

  Further, by controlling the discharge side refrigerant superheat degree TdSH of the compressor 1 to be 10K or more, the discharge side refrigerant can be made only of the gas refrigerant. That is, the gas-liquid two-phase state is prevented, the sealing property of the compression chamber of the compressor 1 is improved, the efficiency reduction of the compressor 1 is suppressed, and the operation efficiency of the refrigeration cycle apparatus S is improved. be able to.

  As described above, in the refrigeration cycle apparatus S that employs R407E as the refrigerant and is equipped with the liquid injection compressor 1, it is possible to ensure reliability and suppress a reduction in efficiency of the compressor 1.

<< Modification of First Embodiment >>
FIG. 8 is a refrigeration cycle system diagram of the refrigeration cycle apparatus S according to a modification of the first embodiment. As shown in FIG. 8, the refrigeration cycle apparatus S includes a supercooling heat exchanger 32 that exchanges heat between the refrigerant flowing through the liquid pipe 3 and the refrigerant flowing through the injection pipe 31 (downstream of the injection flow rate adjusting device 30). It may be.

  The liquid refrigerant branched from the liquid pipe 3 to the bypass path passes through the injection flow control device 30 and is depressurized to become a low-pressure and low-temperature refrigerant. The low-pressure and low-temperature refrigerant flowing through the injection pipe 31 and the relatively high-temperature and high-pressure refrigerant flowing through the liquid pipe 3 are heat-exchanged by the supercooling heat exchanger 32, so that the refrigerant flowing through the liquid-side connection pipe 5 is excessively passed. Set to cool.

  With such a configuration, the specific enthalpy of the refrigerant before being introduced into the use side heat exchanger 22 can be reduced, so that the specific enthalpy difference between the refrigerant at the inlet and the outlet of the use side heat exchanger 22 is increased, and the use side If the mass flow rate of the refrigerant flowing through the heat exchanger 22 is constant, the refrigerating capacity in the use side heat exchanger 22 is improved.

  Further, if the refrigerating capacity may be a constant value, the mass flow rate of the refrigerant flowing through the use side heat exchanger 22 can be reduced, so the mass flow rate of the refrigerant flowing through the gas side connection pipe 6 is reduced and the gas side connection is made. The refrigerant side pressure loss in the pipe 6 is reduced. Thereby, the pipe diameter of the gas side connection pipe 6 can be set thin, and it is possible to improve workability.

<< Second Embodiment >>
Next, the refrigeration cycle apparatus S according to the second embodiment will be described. In addition, since the structure of the refrigerating-cycle apparatus S which concerns on 2nd Embodiment is the same as that of the above-mentioned (refer FIG. 1, FIG. 8), the overlapping description is abbreviate | omitted.

  R407E has a lower refrigerant gas density on the low pressure side than R404A. That is, the density of the refrigerant sucked into the compressor 1 is small. For this reason, when R407E is adopted as the refrigerant of the refrigeration cycle apparatus, it is necessary to set a larger volume flow rate of the refrigerant discharged from the compressor 1 than when R404A is adopted. Specifically, it is necessary to increase the volume of the compression chamber of the compressor 1. As a result, in the refrigeration cycle apparatus that employs R407E as the refrigerant, the compressor 1 needs to be enlarged, so that the refrigeration cycle apparatus becomes large and the workability deteriorates.

  Here, R407E is a non-azeotropic refrigerant mixture in which R32, R125, and R134a are mixed. For this reason, when R407E is present in a gas-liquid two-phase state at a low pressure site such as the accumulator 9, since R32 and R125 have a lower boiling point than R134a, there are a large amount of R32 and R125 in the gas phase. In this state, a large amount of R134a is present.

  Further, since the accumulator 9 has a structure for deriving a larger amount of gas-phase refrigerant than liquid-phase refrigerant, the accumulator 9 derives refrigerant having a high ratio of R32 and R125.

  In this way, by storing a part of the refrigerant in the accumulator 9, a refrigerant having a ratio of R32 and R125 larger than the mixing ratio of R407E is supplied to the compressor 1 and circulates in the refrigeration cycle.

  Here, R32 and R125 are refrigerants having higher pressures than R134a and R407E, and are refrigerants having a high density of low pressures. With such a configuration, since the density of the refrigerant supplied to the suction side of the compressor 1 can be increased, an increase in size of the compressor 1 can be suppressed and a compact refrigeration cycle apparatus S can be obtained.

  As a method for storing the refrigerant in the accumulator 9, it is necessary to introduce into the accumulator 9 a refrigerant having a degree of conductivity smaller than the set degree of refrigerant derived from the accumulator 9.

  Specifically, in the configuration of the refrigeration cycle apparatus S shown in FIGS. 1 and 8, the flow rate of the refrigerant flowing through the use side heat exchanger 22 is increased by setting the opening degree of the expansion device 21 to be large, and the use side heat exchange is performed. If the heat exchange amount in the heat exchanger 22 is constant, the specific enthalpy of the refrigerant at the outlet of the use side heat exchanger 22 is lowered, that is, the degree of refrigerant of the refrigerant at the outlet of the use side heat exchanger 22 is set small. Can do.

  Alternatively, as shown in FIG. 9, by introducing a part of the liquid-phase refrigerant flowing through the liquid pipe 3 to the inlet of the accumulator 9 via the liquid bypass pipe 41 and the liquid bypass flow rate adjustment device 40, It is possible to set the degree of cooling of the refrigerant at the inlet of the accumulator 9 to be small. The liquid bypass flow rate adjusting device 40 may be configured by an electronic expansion valve capable of controlling the opening degree, and is configured by a combination of a plurality of capillaries and electromagnetic valves, and the opening degree can be controlled by opening and closing the electromagnetic valves. It may be configured.

  On the other hand, when the ratio of R32 and R125 in the refrigerant circulating in the refrigeration cycle increases, the operating pressure of the refrigeration cycle increases because R32 and R125 are high-pressure refrigerants. For this reason, it is necessary to set the design pressure of the refrigeration cycle apparatus S high according to the operating pressure on the high pressure side of the refrigeration cycle.

  For example, the refrigerant (R407E) is added to the refrigeration cycle apparatus S so that the refrigerant in which the ratio of R32, R125, and R134a in the refrigerant circulating through the refrigeration cycle apparatus S is 33:33:34 wt% is stored in the accumulator 9. By enclosing, there is a possibility that the volume of the compression chamber of the compressor 1 can be set to the same level as R404A.

  At this time, the saturation pressure is 3.0 MPa when the set temperature is 60 ° C., 3.4 Pa when the set temperature is 65 ° C., and 3.8 MPa when the set temperature is 70 ° C.

  Therefore, the design pressure on the high pressure side of the refrigeration cycle apparatus S is set to 3.0 MPa or more when the set temperature is 60 ° C., 3.4 Pa or more when the set temperature is 65 ° C., and when the set temperature is 70 ° C. It is desirable to set it to 3.8 MPa or more. The pressure is a gauge pressure.

  Furthermore, when the evaporation temperature ET in the use side heat exchanger 22 is −40 ° C., the evaporation pressure of R407E is lower than the atmospheric pressure (negative pressure). For this reason, if there is a refrigerant leakage point on the low temperature side of the refrigeration cycle apparatus S, air in the atmosphere enters the refrigeration cycle. Thereby, the discharge pressure in the compressor 1 increases, the refrigeration oil is oxidized and deteriorated, and the wear of the sliding portion of the compressor 1 is promoted by the carboxylic acid that is the deterioration product. There is a risk of reducing the performance.

  On the other hand, by storing the refrigerant in the accumulator 9 and setting the circulation composition of the refrigerant circulating in the refrigeration cycle to a state where the ratio of R32 and R125 is large, the evaporation pressure in the use side heat exchanger 22 is set to atmospheric pressure. It is possible to maintain a higher state.

≪Modification≫
The refrigeration cycle apparatus S according to this embodiment is not limited to the configuration of the above embodiment, and various modifications can be made without departing from the spirit of the invention.

  The refrigeration cycle apparatus S according to the present embodiment has been described as being a refrigerator, but is not limited thereto. For example, you may apply to the air conditioner for cold districts where evaporation temperature becomes low. In this case, the refrigeration cycle apparatus S includes a four-way valve (not shown) and an outdoor unit side expansion device (not shown) in the liquid pipe 3, and the flow path is switched by the four-way valve (not shown). The heat source side heat exchanger 2 acts as an evaporator, and the use side heat exchanger 22 acts as a condenser.

S Refrigeration cycle apparatus 10 Outdoor unit 1 Liquid injection compressor (compressor)
2 Heat source side heat exchanger (condenser)
3 Liquid piping 4 Stop valve 5 Liquid side connection piping 6 Gas side connection piping 7 Stop valve 8 Gas piping 9 Accumulator 20 User side unit 21 Expansion device 22 User side heat exchanger (evaporator)
30 Injection flow control device (flow control device)
31 Injection piping (bypass route)
32 Supercooling heat exchanger 40 Liquid bypass flow rate adjustment device 41 Liquid bypass piping 50 Control device Tc Condensing temperature ET Evaporating temperature Ts Suction side refrigerant temperature Td Discharge side refrigerant temperature TsSH Suction side refrigerant superheat degree TdSH Discharge side refrigerant superheat degree

Claims (4)

A refrigeration cycle in which a liquid injection compressor, a heat source side heat exchanger, a liquid side connection pipe, an expansion device, a use side heat exchanger, and a gas side connection pipe are sequentially connected;
A bypass path for introducing a refrigerant into the injection port of the liquid injection compressor from between the heat source side heat exchanger and the liquid side connection pipe via a flow rate adjustment device;
A refrigeration cycle apparatus comprising a control device for controlling the opening degree of the flow rate adjusting device,
Adopting R407E as a refrigerant sealed in the refrigeration cycle apparatus,
The controller is
When the temperature Td of the refrigerant discharged from the liquid injection compressor is 110 ° C. or less and the superheat degree TdSH of the refrigerant discharged from the liquid injection compressor is controlled in the range of 10K or more,
The ratio of the flow rate of the refrigerant flowing through the bypass path and the flow rate of the refrigerant flowing through the use side heat exchanger is:
When the evaporation temperature in the use side heat exchanger is −40 ° C.,
8.11 × 10 ⁻³ × Tc + 1.28 × 10 ⁻¹ or more and 1.52 × 10 ⁻² × Tc + 4.81 × 10 ⁻¹ or less,
When the evaporation temperature in the use side heat exchanger is −20 ° C.,
6.60 × 10 ⁻³ × Tc + 2.14 × 10 ⁻¹ (provided that 0 if less than 0), and 7.86 × 10 ⁻³ × Tc + 1.99 × 10 ⁻¹ or less,
When the evaporation temperature in the use side heat exchanger is −10 ° C.,
0 or more and 5.54 × 10 ⁻³ × Tc + 1.49 × 10 ⁻¹ or less (where Tc is the condensation temperature [° C.] of the heat source side heat exchanger)
The refrigeration cycle apparatus is characterized in that the opening degree of the flow rate adjusting device is controlled so as to become. And further comprising a supercooling heat exchanger that exchanges heat between the refrigerant flowing through the liquid pipe between the heat source side heat exchanger and the liquid side connection pipe and the refrigerant after the flow rate adjusting device installed in the bypass path. The refrigeration cycle apparatus according to claim 1, wherein: An accumulator coupled to the refrigeration cycle;
The refrigeration cycle apparatus according to claim 1, further comprising: a control unit that stores liquid refrigerant in the accumulator. The design pressure on the high temperature side of the refrigeration cycle,
When the set temperature is 60 ° C., 3.0 MPa or more,
When the set temperature is 65 ° C., 3.4 Pa or more,
The refrigeration cycle apparatus according to claim 3, wherein when the set temperature is 70 ° C, the temperature is set to 3.8 MPa or more.

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