JP5990972B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner using a mixed refrigerant.

  Currently, R410A and R407C are mainly used as refrigerants in air conditioners. These refrigerants have an ozone depletion potential (ODP) of 0 but a high global warming potential (= GWP) (GWP of R410A = 2090, GWP = 1770 of R407C) and low GWP from the viewpoint of preventing global warming. A replacement with is being considered. Refrigerants listed as candidates for low GWP refrigerants include R32 (GWP = 675) and R1234yf (GWP = 4) in the HFC system, and propane (GWP = 3) in the natural refrigerant.

  Among these, R1234yf has a low pressure and has poor performance in stationary air conditioner applications, so it is necessary to increase the size of the product, and product design with the same specifications as conventional devices is difficult. Although natural refrigerants have good performance as refrigerants, the amount of refrigerant that can be enclosed in products is limited by the IEC standards due to their strong flammability, and can only be applied to some small air conditioners.

  On the other hand, R32 is a component that occupies 50 wt% of R410A, and has a better refrigerant performance than R410A. Although it is a slightly flammable refrigerant, there is a possibility that it can be applied if a predetermined explosion-proof measure is taken on the device side. However, the pressure at the same condensation temperature is slightly higher than that of R410A, and the discharge temperature tends to rise. Therefore, if it is intended to be applied alone to the conventional R410A device, some design changes such as a change in the design pressure and a response to a rise in the discharge temperature are required.

  Thus, there is no single low refrigerant candidate that can replace the conventional R410A device among the low GWP refrigerant candidates, so that several refrigerants are mixed at an appropriate ratio to solve each problem. A method has been proposed. For example, R32 having good performance but high pressure at the same condensation temperature and R1234yf having low performance but low pressure at the same condensation temperature, or a combination of this and R134a having similar pressure-temperature characteristics are known. . However, since the boiling points of R32 and R1234yf or R134a are greatly different (R32: −51.7 ° C., R1234yf: −29.5 ° C., R134a: −26.1 ° C.), a temperature gradient is generated when these refrigerants are mixed. There are problems such as difficulty in controlling and difficulty in performance.

  Regarding the air conditioner using such a mixed refrigerant, the present inventor has already proposed the air conditioners shown in Japanese Patent Application Nos. 2011-105556 and 2011-105557. As shown in FIG. 3, the refrigeration cycle circuit of the air conditioner includes a compressor 12, a condenser (outdoor unit) 14, a decompression unit 16, an evaporator (indoor unit) 18, and a four-way valve 20. Become. As the working refrigerant, a mixed refrigerant consisting of only R32 and R134a or only R32 and R1234yf is used.

  The mixed refrigerant from the compressor 12 enters the first condenser 14 a through the pipe 26 and is separated into gas and liquid by the gas-liquid separator 22. The R134a (or R1234yf) rich liquid refrigerant accumulated in the gas-liquid separator 22 is injected into the compressor 12 through the flow rate adjustment valve 24 and through the pipe 32. On the other hand, the saturated vapor refrigerant separated by the gas-liquid separator 22 enters the evaporator 18 from the second condenser 14 b through the pipe 28 and the decompression means 16. The ratio of R32 as the refrigerant entering the evaporator 18 is increased. The refrigerant from the evaporator 18 is sent to the compressor 12 through the pipe 30.

  Here, the gas-liquid separator 22 is attached at a position where the volume ratio A% :( 100−A)% of the condenser 14 is obtained, whereby the condenser 14 has a first volume ratio of A% with respect to the whole condenser. The condenser 14a and the (100-A)% second condenser 14b are configured. As the attachment position of the gas-liquid separator 22, it is necessary to select a position where the refrigerant is in the two-phase region under the assumed operation conditions. An example is a case where a mixed refrigerant composed of only R32 and R134a and the mixing ratio of R32 is 80 wt%. When operating at a condensing temperature of 68 ° C, the liquid injection is controlled so that the discharge temperature is 90 ° C, which is the same as the equipment using the conventional refrigerant R410A, and the degree of supercooling at the condenser outlet is a general refrigeration cycle. When the entire refrigeration cycle is controlled so as to be the same 5 deg, as shown in FIG. 4, the proportion of energy released by the refrigerant in the condenser is as follows: gas region: 24%, two-phase region: 69%, supercooling region: 7% It becomes. Since the heat exchange amount per unit volume of the condenser can be regarded as substantially uniform, when A is determined from the volume ratio of the heat exchanger described above, the value of A is in the range of 24 to 93%.

  In addition, the mixed refrigerant passing through the condenser is liquefied first in the refrigerant having a higher boiling point. Here, FIG. 5 shows the composition of the liquid-phase refrigerant in the refrigerant in the two-phase region in FIG. 4, and the proportion of the high-boiling refrigerant increases in the two-phase region closer to the inlet side of the condenser. It is shown that. Therefore, when taking out the liquid of B section (refer FIG. 4) in a two-phase area | region, it is desirable to arrange | position said A to the inlet side of a condenser.

  Thus, by separating in advance the liquid refrigerant of R134a (or R1234yf) that is liable to liquefy first from the two-phase region, the ratio of R32 in the refrigerant that goes to the evaporator 18 becomes larger, and the temperature at the evaporator 18 The gradient can be reduced.

  On the other hand, since the refrigerant injected into the compressor 12 is in a liquid state, the temperature of the refrigerant finally discharged can be suppressed by the heat that it vaporizes. Furthermore, since this liquid refrigerant has a larger ratio of R134a (or R1234yf) having a smaller adiabatic compression index than R32, the liquid refrigerant has a larger discharge temperature suppression effect than injection of a liquid refrigerant having a smaller ratio of R134a (or R1234yf). For this reason, it is possible to reduce the influence of the disadvantages of the non-azeotropic refrigerant mixture and to reduce the influence of the disadvantages due to R32 as the main component.

  By the way, in the above-described conventional air conditioner using a mixed refrigerant, an operating temperature that can be used for both cooling and heating as well as preventing deterioration in the performance of the evaporator due to a temperature gradient and excessive discharge temperature during operation. The development of a wide range of air conditioners has been desired.

  The present invention has been made in view of the above, and in an air conditioner using a mixed refrigerant, prevents deterioration in the performance of the evaporator due to a temperature gradient and excessive discharge temperature during operation, and cooling and heating. An object is to provide an air conditioner with a wide operating temperature range that can be used together.

  In order to solve the above-described problems and achieve the object, an air conditioner according to claim 1 of the present invention includes a compressor, a first heat exchanger, a decompression unit, and a second heat exchanger connected by a refrigerant pipe. Air that can be switched between a cooling operation and a heating operation by circulating a two-type mixed refrigerant in which R32, which is the first refrigerant, is mixed at a mixing ratio larger than R134a or R1234yf, which is the second refrigerant. In the air conditioner, the refrigerant circuit includes a gas-liquid from the two-type mixed refrigerant branched from a position where the second refrigerant of the first heat exchanger functioning as a condenser is liquid-rich during cooling operation. While the liquid refrigerant separated through the separator is injected into the intermediate pressure of the compressor, the gas-liquid separation is performed between the second heat exchanger functioning as a condenser and the pressure reducing means during heating operation. Connected And having a switching valve for switching the sea urchin circuit.

  The air conditioner according to claim 2 of the present invention is characterized in that, in the above-described claim 1, the mixing ratio of the first refrigerant is 80 to 90 wt%.

  The air conditioner according to claim 3 of the present invention is the air conditioner according to claim 1 or 2, wherein the refrigerant in the first heat exchanger functioning as a condenser is in a gas-liquid two-phase state in the cooling operation. The liquid refrigerant is separated from the position.

  Moreover, the air conditioner which concerns on Claim 4 of this invention has the switching valve which switches use / non-use of the said gas-liquid separator in the cooling operation in any one of Claims 1-3 mentioned above. It is characterized by that.

  An air conditioner according to a fifth aspect of the present invention is the air conditioner according to any one of the first to fourth aspects, wherein during the heating operation, the pressure in the container of the gas-liquid separator is reduced to a condensation pressure and an evaporation pressure. A throttling mechanism for controlling to an arbitrary value between is provided between the container of the gas-liquid separator and the second heat exchanger functioning as a condenser.

  According to the present invention, R32 which is the first refrigerant is the second refrigerant in the refrigerant circuit formed by connecting the compressor, the first heat exchanger, the pressure reducing means, and the second heat exchanger with the refrigerant pipe. The air conditioner is capable of switching between a cooling operation and a heating operation by circulating a two-type mixed refrigerant mixed at a mixing ratio larger than R134a or R1234yf, and the refrigerant circuit functions as a condenser during the cooling operation. While the liquid refrigerant separated from the two-type mixed refrigerant branched from the position where the second refrigerant of the first heat exchanger is liquid-rich through a gas-liquid separator is injected into the intermediate pressure of the compressor And a switching valve for switching the circuit so that the gas-liquid separator is connected between the second heat exchanger functioning as a condenser and the pressure reducing means during heating operation.

  For this reason, during the cooling operation, R32a (or R1234yf) rich liquid refrigerant, which is liable to be liquefied first from the two-phase region, is separated in advance, so that R32 out of the refrigerant circulating to the second heat exchanger functioning as an evaporator. And the temperature gradient in the evaporator can be reduced. Further, since the refrigerant injected into the compressor is in a liquid state, the temperature of the refrigerant finally discharged can be suppressed by the heat that it vaporizes. Further, since this liquid refrigerant contains a larger amount of R134a (or R1234yf) having a lower discharge temperature than R32, it has a larger discharge temperature suppression effect than injection of liquid refrigerant having a composition ratio at the time of encapsulation.

  Moreover, this air conditioner can also perform heating operation by connecting and disposing a gas-liquid separator between the second heat exchanger and the pressure reducing means by switching the switching valve. Therefore, it is possible to provide an air conditioner with a wide operating temperature range that can be used for both cooling and heating, while preventing a decrease in the performance of the evaporator due to a temperature gradient and an excessive increase in the discharge temperature during operation. Play.

FIG. 1 is a refrigerant circuit diagram during cooling operation of the air conditioner according to the present invention. FIG. 2 is a refrigerant circuit diagram during heating operation of the air conditioner according to the present invention. FIG. 3 is a refrigerant circuit diagram during cooling operation of a conventional air conditioner. FIG. 4 is a ph diagram for the circuits of FIGS. FIG. 5 is a diagram showing the composition of the liquid refrigerant (liquid phase) in the two-phase region in the condenser when a condensation temperature of 68 ° C. is assumed.

  Embodiments of an air conditioner according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  In the air conditioner according to the present invention, a two-component mixed refrigerant obtained by mixing R134a with R32 or R1234yf with R32 is used. At this time, the mixing ratio of R32 is assumed to be cooling operation in the tropical region, and is set to 80 to 90 wt% so that the pressure at the condensation temperature of 65 to 68 ° C. is less than the design pressure (4.15 MPaG) of R410A. In the following description, as an example, it is assumed that a refrigerant in which R32 and R134a are mixed at a ratio of 80 wt% and 20 wt%, respectively, is operated under the conditions of an evaporation temperature of 15 ° C./condensation temperature of 68 ° C. Here, since the two components of the mixed refrigerant have different boiling points, a temperature gradient is generated in the condensation and evaporation processes. The temperature gradient in the evaporator is 2.5 degrees.

  In addition, when the mixing ratio of R32 is 80 wt% or more, the temperature gradient becomes smaller when the mixing ratio of R134a decreases, so that the refrigerant flowing into the evaporator preferably has a smaller ratio of R134a. On the other hand, when the refrigerant in the condenser condenses, R134a having a higher boiling point condenses first. That is, the liquid refrigerant component while the mixed refrigerant is condensed (the entire dryness is between 0 and 1) includes the R134a component in a proportion larger than the composition ratio of the refrigerant composition when sealed in the refrigerant cycle circuit ( (See FIG. 5). By separating a part of the liquid refrigerant from the middle of the condenser, the ratio of the refrigerant R134a flowing into the evaporator can be reduced.

  R32 tends to have a higher discharge temperature than R410A. For example, assuming a case where the operation is performed under conditions of an evaporation temperature of 15 ° C./condensation temperature of 68 ° C. in a refrigeration cycle using only R32 as a refrigerant, the discharge temperature exceeds 104 ° C. (in the case of R410A, about 90 ° C.). Even in a mixed refrigerant containing 20 wt% of R134a, the discharge temperature under the same conditions exceeds 100 ° C. Therefore, in order to use this mixed refrigerant in the refrigerant cycle of the same design as the air conditioner using R410A, the discharge temperature is about 10 degrees. Need to lower.

  Next, consider a case where the heating operation is performed with the same refrigerant. Assuming a heating operation in a cold region and assuming an evaporation temperature of −25 ° C./condensation temperature of 37 ° C., when the mixing ratio of R32 is 80 wt% with a mixed refrigerant consisting only of R32 and R134a, the theoretical discharge temperature is about 86 (In the case of R410A, about 67 ° C.). However, this is a value ignoring the loss in the compressor, and the discharge temperature may exceed 100 ° C. in an actual operation state. Therefore, even when this refrigerant is used for heating operation, it is necessary to devise a technique for lowering the discharge temperature as in the case of cooling.

  Therefore, the refrigeration cycle circuit of the air conditioner according to the present invention is configured to be switchable between the circuit during the cooling operation of FIG. 1 and the circuit during the heating operation of FIG. Hereinafter, the air conditioner of the present invention will be described separately for cooling operation and heating operation.

[During cooling operation]
As shown in the refrigerant circuit diagram of FIG. 1 and the ph diagram of FIG. 4, the air conditioner 10 according to the present invention includes a compressor 12, a first heat exchanger 14, a decompression means 16, a second The heat exchanger 18, the four-way valve 20, the gas-liquid separator 22, and the switching valves 44, 46, 36, and 38 are included. During the cooling operation, the first heat exchanger 14 functions as a condenser (outdoor unit), and the second heat exchanger 18 functions as an evaporator (indoor unit).

  Here, the liquid refrigerant separated from the condenser (first heat exchanger 14) is used to suppress the discharge temperature. Specifically, liquid refrigerant is injected into the intermediate pressure portion of the compressor 12. R134a tends to have a lower discharge temperature than R410A. Therefore, the final discharge temperature can be suppressed by injecting the liquid refrigerant rich in R134a containing a large amount of R134a into the intermediate pressure of the compressor 12.

  In addition, it is known as a prior art that liquid refrigerant is injected into a compressor. However, in those techniques, the refrigerant is completely condensed and supercooled (from the outlet of the condenser (first heat exchanger 14)). The refrigerant in front of the decompression means 16 is separated and injected. However, in the present invention, when all the components of the mixed refrigerant are condensed (the overall dryness is 0 or less), the composition ratio of R32 and R134a becomes the same as the composition ratio of the refrigerant composition when sealed in the refrigerant cycle circuit, The composition ratio of the refrigerant flowing into the evaporator (second heat exchanger 18) cannot be changed. Therefore, the liquid refrigerant for injection into the compressor 12 is separated from the two-phase region of the condenser (first heat exchanger 14). By taking out the saturated liquid refrigerant using the gas-liquid separator 22, a larger amount of refrigerant having a high boiling point (R134a) can be used for liquid injection.

  More specifically, the gas-liquid separator 22 is attached via piping 40 and 42 at a position where the volume ratio A% :( 100-A)% of the condenser (first heat exchanger 14) is obtained. Thus, the condenser (first heat exchanger 14) is composed of a first condenser 14a having a volume ratio of A% with respect to the whole condenser and a second condenser 14b having (100-A)%. As the attachment position of the gas-liquid separator 22, it is necessary to select a position where the refrigerant is in the two-phase region under the assumed operation conditions.

  When the mixed ratio of R32 and R134a is Rwt and the mixing ratio of R32 is 80 wt%, liquid injection is performed so that the discharge temperature is 90 ° C, which is the same as the equipment using the conventional refrigerant R410A when operating at a condensation temperature of 68 ° C. If the overall refrigeration cycle is controlled so that the degree of supercooling at the outlet of the condenser is 5 degrees, which is the same as that of a typical refrigeration cycle, as shown in FIG. The ratio is 24% for the gas region, 69% for the two-phase region, and 7% for the supercooling region. Since the heat exchange amount per unit volume of the condenser can be regarded as almost uniform, if A is determined from the ratio of the heat radiation amount, the value of A is in the range of 24 to 93%. In addition, since the physical property of the refrigerant (the ratio of the heat release amount) varies depending on the mixing ratio, it is desirable to select a position corresponding to the mixing ratio.

  As for the mixed refrigerant passing through the condenser (first heat exchanger 14), the refrigerant having a higher boiling point is liquefied first. Here, FIG. 5 shows the composition of the liquid-phase refrigerant in the refrigerant in the two-phase region in FIG. 4, and the proportion of the high-boiling refrigerant increases in the two-phase region closer to the inlet side of the condenser. It is shown that. Therefore, when taking out the liquid of B section (refer FIG. 4) in a two-phase area | region, it is desirable to arrange | position said A to the inlet side of a condenser.

The operation of the above configuration will be described.
The mixed refrigerant from the compressor 12 enters the first condenser 14 a through the pipe 26 and is separated into gas and liquid by the gas-liquid separator 22. The R134a rich liquid refrigerant accumulated in the gas-liquid separator 22 is injected into the compressor 12 through the flow rate adjusting valve 24 and through the pipe 32. As described above, the flow rate adjusting valve 24 is controlled in accordance with the temperature of the refrigerant discharged from the compressor 12, and thereby liquid injection is controlled. On the other hand, the saturated vapor refrigerant separated by the gas-liquid separator 22 enters the evaporator (second heat exchanger 18) from the second condenser 14b through the decompression means 16 and the pipes 54 and 28. As a refrigerant entering this evaporator, the ratio of R32 increases. The refrigerant from the evaporator is sent to the compressor 12 through the pipe 30.

  In this way, by separating the R134a liquid refrigerant that is liable to be liquefied first from the two-phase region in advance, the ratio of R32 in the refrigerant that goes to the evaporator (second heat exchanger 18) becomes larger. The temperature gradient can be reduced.

  On the other hand, since the refrigerant injected into the compressor 12 is in a liquid state, the temperature of the refrigerant finally discharged can be suppressed by the heat that it vaporizes. Further, since this liquid refrigerant contains a larger amount of R134a having a smaller adiabatic compression index than R32, it has a greater discharge temperature suppression effect than injection of a liquid refrigerant that does not contain much R134a. For this reason, according to the air conditioner 10 of the present invention, the influence of the disadvantages of the non-azeotropic refrigerant mixture can be reduced, and at the same time, the influence of the disadvantages caused by the main component R32 can be reduced.

  Here, of the refrigerant (two phases) flowing into the gas-liquid separator 22, the saturated vapor refrigerant flows out of the gas-liquid separator, but the saturated liquid refrigerant is not gasified because the outside air temperature is lower than the refrigerant temperature. . Therefore, when the refrigerant circulation amount is constant, the saturated liquid refrigerant is accumulated in the gas-liquid separator 22 with time. In this case, the liquid level in the container 22a of the gas-liquid separator 22 increases, and if the saturated vapor state refrigerant cannot be taken out, the condensing performance deteriorates. Therefore, the liquid level is inserted into the container 22a. It is necessary to control so as to keep the position lower than the lower end of the outlet pipe.

  Therefore, as shown in FIG. 1, a bypass 34 and switching valves 36 and 38 are provided on the refrigerant circuit connecting the condenser 14 and the gas-liquid separator 22, and pipes 40 and 42 having different lengths are provided in the container 22a. It is inserted so that the use / nonuse of the gas-liquid separator 22 can be switched as necessary during operation of the air conditioner. As a condition for this switching, for example, a liquid level detection sensor (not shown) is provided at a position lower than the communication port 42a at the lower end of the short pipe 42, and whether the liquid level in the container 22a detected by this sensor exceeds a predetermined height. It may be determined depending on whether or not.

  In this case, at a normal time when the detected liquid level is lower than a predetermined height, the amount of liquid refrigerant stored is within an allowable range, so that the state of the switching valves 36 and 38 is changed to the first condenser 14a, the piping 40, the first The two condensers 14b and the pipe 42 are communicated with each other so that the bypass 34 is shut off. As a result, the gas-liquid separator 22 is in use, the two-phase refrigerant from the first condenser 14a flows into the gas-liquid separator 22 via the pipe 40, and the refrigerant accumulated in the container 22a is liquid-injected through the pipe 32. Used for.

  On the other hand, when the detected liquid level exceeds a predetermined height, the storage amount of the liquid refrigerant is excessive, so that the first condenser 14a, the bypass 34, and the second condenser 14b are communicated with each other. The switching valves 36 and 38 are switched so that the communication between the pipe 14a and the pipe 40, and the communication between the second condenser 14b and the pipe 42 are cut off. As a result, the gas-liquid separator 22 is not used, and the two-phase refrigerant from the first condenser 14a does not flow into the gas-liquid separator 22 but flows directly into the second condenser 14b through the bypass. Thereby, since only a liquid refrigerant does not distribute | circulate through the 2nd condenser 14b, compared with this case, the fall of the condensing capability as the whole condenser 14 can be avoided. The switching control of the switching valves 36 and 38 based on the detection by the liquid level detection sensor can be performed by a control means (not shown).

[During heating operation]
As shown in FIG. 2, when heating operation is performed with the same air conditioner 10, the first heat exchanger 14 functions as an evaporator (outdoor unit), and the second heat exchanger 18 serves as a condenser (indoor unit). Function. If a gas-liquid separator is present during the evaporation process, gas-liquid separation is performed in the same way as during cooling. However, since the refrigerant temperature in the container is lower than the ambient temperature, a part of the separated liquid is contained in the container. Evaporate at. On the other hand, when gas and liquid are separated and only the gas flows through the evaporator, the performance is significantly reduced, so it is desired to take out the liquid refrigerant from the container, but only the liquid refrigerant is sent to the downstream evaporator under the condition that the refrigerant circulation amount is constant. If it tries to flow, the saturated liquid refrigerant in a gas-liquid separator will decrease with time. Therefore, during the heating operation, the gap between the evaporator (first heat exchanger 14) and the gas-liquid separator 22 is blocked by the aforementioned switching valves 36 and 38 so that the refrigerant always passes the bypass 34.

  Here, the refrigeration cycle circuit is configured so that the gas-liquid separator 22 is inserted into a supercooling region (between the outlet of the second heat exchanger 18 and the decompression means 16) during heating operation. As a result, the liquid refrigerant exiting the condenser (second heat exchanger 18) can be stored in the container 22a of the gas-liquid separator 22 and used for liquid injection in the same manner as before. However, since the circuit (condenser (second heat exchanger 18) to gas-liquid separator 22 to decompression means 16) connecting these portions needs to prevent refrigerant from passing during the cooling operation, the switching valve 44, 46, the refrigerant circuit is switched between the cooling operation and the heating operation.

  At this time, in addition to the decompression means 16 for the entire refrigeration cycle, a throttle mechanism 48 having a variable opening is provided between the condenser (second heat exchanger 18) and the gas-liquid separator 22. By the combination of these two decompression means 16 and the throttle mechanism 48, the pressure in the container 22a of the gas-liquid separator 22 can be adjusted between the evaporation pressure and the condensation pressure. The ratio of the liquid refrigerant in the container 22a increases when the pressure in the gas-liquid separator 22 is high, and decreases when the pressure is low. Therefore, adjusting the pressure in the gas-liquid separator 22 can control the refrigerant distribution of the entire refrigeration cycle as a result.

The operation of the above configuration will be described.
The mixed refrigerant from the compressor 12 enters the condenser (second heat exchanger 18) through the pipe 30 and enters the gas-liquid separator 22 from the pipe 42 through the pipes 28 and 50 and the throttle mechanism 48. Separated into liquid. The liquid refrigerant accumulated in the gas-liquid separator 22 is injected into the compressor 12 through the flow rate adjusting valve 24 and through the pipe 32, while passing through the pipes 40 and 52 and the decompression means 16 to the evaporator (first heat exchange). 14), passes through the bypass 34 inside thereof, and is sent to the compressor 12 via the pipe 26.

  Here, the pressure in the gas-liquid separator 22 is adjusted by setting the degree of supercooling at the outlet of the condenser (second heat exchanger 18) and the degree of superheating at the outlet of the evaporator (first heat exchanger 14). It aims to keep the value of. Since the optimum degree of supercooling and superheat varies depending on the operating conditions (air temperature and ability to output), the opening degree of the throttle mechanism 48 is adjusted so that the target supercooling degree according to the operating conditions is obtained. Moreover, the opening degree of the decompression means 16 is adjusted so that the target superheat degree according to the operating conditions is obtained.

  In addition, since the liquid-phase refrigerant has a composition with a little higher boiling point refrigerant (R134a) by gas-liquid separation in the container 22a, the refrigerant having a high effect of suppressing the discharge temperature is injected into the compressor 12. become. Note that the refrigerant entering the evaporator (first heat exchanger 14) from the gas-liquid separator 22 is also taken out of the liquid phase and has a slightly larger composition of R134a. However, heating is performed by increasing the refrigerant circulation rate by liquid injection. A decrease in ability (heat of condensation) can be suppressed. Thus, according to the present invention, an air conditioner having a wide operating temperature range can be provided by using the same gas-liquid separator 22 not only for cooling operation but also for heating operation.

  As described above, according to the air conditioner according to the present invention, the refrigerant circuit formed by connecting the compressor, the first heat exchanger, the pressure reducing means, and the second heat exchanger with the refrigerant pipes has the first An air conditioner capable of switching between a cooling operation and a heating operation by circulating a two-type mixed refrigerant obtained by mixing R32 as a refrigerant at a mixing ratio larger than R134a or R1234yf as a second refrigerant, wherein the refrigerant circuit includes: In the cooling operation, the liquid refrigerant separated from the two-type mixed refrigerant branched from the position where the second refrigerant of the first heat exchanger functioning as a condenser is liquid-rich through a gas-liquid separator. The circuit is arranged such that the gas-liquid separator is connected between the second heat exchanger functioning as a condenser and the pressure reducing means during the heating operation while injecting the intermediate pressure of the compressor. Switching to switch Having.

  For this reason, during cooling operation, the R134a (or R1234yf) rich liquid refrigerant that is liable to liquefy first from the two-phase region is included in the refrigerant circulating in the second heat exchanger that functions as an evaporator by separating in advance. The ratio of R32 to be increased increases, and the temperature gradient in the evaporator can be reduced. Further, since the refrigerant injected into the compressor is in a liquid state, the temperature of the refrigerant finally discharged can be suppressed by the heat that it vaporizes. Further, since this liquid refrigerant contains a larger amount of R134a (or R1234yf) having a physical property with a smaller adiabatic compression index than R32, it has a larger discharge temperature suppression effect than injection of liquid refrigerant having a composition ratio at the time of encapsulation. For this reason, the influence of the disadvantages of the non-azeotropic refrigerant mixture can be reduced, and at the same time, the influence of the disadvantages caused by R32 as the main component can be reduced.

  Moreover, this air conditioner can also perform heating operation by connecting and disposing a gas-liquid separator between the second heat exchanger and the pressure reducing means by switching the switching valve. Therefore, it is possible to provide an air conditioner with a wide operating temperature range that can be used for both cooling and heating, while preventing a decrease in the performance of the evaporator due to a temperature gradient and an excessive increase in the discharge temperature during operation. Play.

  As described above, the air conditioner according to the present invention is useful for an air conditioner using a mixed refrigerant, and in particular, prevents deterioration in the performance of the evaporator due to a temperature gradient and excessive discharge temperature during operation. It is suitable for providing an air conditioner with a wide operating temperature range that can be used for both cooling and heating.

10 Air Conditioner 12 Compressor 14 First Heat Exchanger (Outdoor Unit)
16 Pressure reducing means 18 Second heat exchanger (indoor unit)
20 Four-way valve 22 Gas-liquid separator 22a Container 24 Flow rate adjustment valve 26, 28, 30, 32, 40, 42, 50, 52, 54 Piping 34 Bypass 36, 38, 44, 46 Switching valve 48 Throttle mechanism

Claims (5)

In the refrigerant circuit formed by connecting the compressor, the first heat exchanger, the decompression means, and the second heat exchanger with the refrigerant pipe, the first refrigerant R32 is mixed with the second refrigerant R134a or R1234yf. An air conditioner capable of switching between a cooling operation and a heating operation by circulating a two-type mixed refrigerant mixed at a ratio,
The refrigerant circuit is
During the cooling operation, the liquid refrigerant separated from the two-type mixed refrigerant branched from the position where the second refrigerant of the first heat exchanger functioning as a condenser is liquid rich via a gas-liquid separator, While injecting into the intermediate pressure of the compressor,
An air conditioner comprising a switching valve for switching a circuit so that the gas-liquid separator is connected and disposed between the second heat exchanger functioning as a condenser and the pressure reducing means during heating operation. Machine.   The air conditioner according to claim 1, wherein a mixing ratio of the first refrigerant is 80 to 90 wt%.   3. The air conditioning according to claim 1, wherein during the cooling operation, the liquid refrigerant is separated from a position where the refrigerant in the first heat exchanger functioning as a condenser is in a gas-liquid two-phase state. Machine.   The air conditioner according to any one of claims 1 to 3, further comprising a switching valve that switches use / nonuse of the gas-liquid separator during cooling operation.   In the heating operation, the throttle mechanism for controlling the pressure in the gas-liquid separator container to an arbitrary value between the condensing pressure and the evaporation pressure functions as the gas-liquid separator container and the condenser. It provided between 2nd heat exchangers, The air conditioner as described in any one of Claims 1-4 characterized by the above-mentioned.

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