JP5990973B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner.

  Conventionally, in an air conditioner for a tropical region corresponding to a high outside air temperature environment with a maximum outside air temperature of about 52 ° C., R22 is used as a working refrigerant. As shown in the list of physical properties in FIG. 1, R22 is scheduled to be abolished in 2020 in developed countries because the ozone depletion potential (ODP) is not zero. For this reason, there is an urgent need to shift to an alternative refrigerant having zero ODP. As alternative refrigerants with zero ODP, mixed refrigerants such as R410A and R407C and single refrigerants such as R32 are generally known.

  R410A is generally used in a temperate region where the outside air temperature is not high. As shown in FIG. 1, this R410A has a relatively low critical temperature of 71.4 ° C., so the cooling capacity and coefficient of performance at high outside air temperature (high condensation temperature) are extremely reduced, and it is intended for the tropical region. When used in an air conditioner, there is a problem that the efficiency is remarkably deteriorated. In recent years, a refrigerant with a small global warming potential (GWP), which is an index for comparing the degree of impact of global warming due to greenhouse gases, has been desired from the consideration of the global environment, but the GWP of R410A is 2090. There is a disadvantage that it is larger than the G22 (= 1810) of R22.

  As shown in FIG. 1, R407C is a non-azeotropic refrigerant mixture having a high critical temperature of 86.0 ° C. and suitable for use in a high outside air temperature environment than R410A, but having a relatively large temperature gradient of about 6 deg. There are disadvantages that it is difficult to handle because of certain things and GWP is relatively high.

  As shown in FIG. 1, R32 is a single refrigerant that is also included in R410A, and generally has a performance equal to or higher than R22. However, since the condensing pressure and the discharge temperature are relatively high, it is difficult to use the conventional air conditioner using refrigerants such as R410A and R22.

  For this reason, it has been desired to develop a refrigerant having zero ODP and smaller GWP than the conventional R22. As such a refrigerant, when a mixed refrigerant mainly composed of R32 having a relatively high refrigerating capacity is considered, the condensation pressure and discharge temperature, which are disadvantages of R32, are reduced, and the temperature gradient is at least about 2.5 deg. It is necessary to keep it below.

  The present invention has been made in view of the above, and in an air conditioner using a mixed refrigerant having an ODP of zero and a small GWP, the discharge temperature is suppressed and the temperature gradient on the evaporator side is reduced. An object of the present invention is to provide an air conditioner that can be used.

  In order to solve the above-described problems and achieve the object, an air conditioner according to claim 1 of the present invention is a refrigerant circuit formed by connecting a compressor, a condenser, a decompression unit, and an evaporator with refrigerant piping. , An air conditioner that circulates a two-type mixed refrigerant obtained by mixing R32, which is a first refrigerant, at a mixing ratio greater than R134a or R1234yf, which is a second refrigerant, wherein the refrigerant circuit includes the first refrigerant of the condenser. A liquid refrigerant separated from the two-type mixed refrigerant branched from a position where the second refrigerant is rich in liquid is injected into an intermediate pressure of the compressor.

  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%.

  An air conditioner according to claim 3 of the present invention is characterized in that in claim 1 or 2 described above, the liquid refrigerant is separated from a position where the refrigerant in the condenser is in a gas-liquid two-phase state. To do.

  An air conditioner according to a fourth aspect of the present invention is the gas-liquid separator according to the third aspect, wherein the liquid refrigerant is separated from a position where the refrigerant in the condenser is in a gas-liquid two-phase state. And a switching valve for switching between use and non-use of the gas-liquid separator.

  According to the present invention, in the refrigerant circuit formed by connecting the compressor, the condenser, the pressure reducing means, and the evaporator with the refrigerant pipe, the first refrigerant R32 is mixed with the second refrigerant R134a or R1234yf. An air conditioner for circulating a two-type mixed refrigerant mixed at a ratio, wherein the refrigerant circuit is a liquid separated from the two-type mixed refrigerant branched from a position where the second refrigerant of the condenser is liquid-rich. Since the refrigerant is injected into the intermediate pressure of the compressor, R134a (or R1234yf) rich liquid refrigerant that tends to be liquefied first from the two-phase region is separated in advance, so that the ratio of R32 in the refrigerant that goes to the evaporator is As a result, 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. For this reason, it is possible to reduce the influence of the disadvantages of the non-azeotropic refrigerant mixture, and at the same time, it is possible to reduce the influence of the disadvantages due to the main component R32.

FIG. 1 is a list illustrating physical properties of a mixed refrigerant and a conventional refrigerant used in the present invention. FIG. 2 is a diagram illustrating an example of the relationship between the saturated vapor pressure and the condensation temperature. FIG. 3 is a comparison diagram of the discharge temperature when a condensation temperature of 68 ° C. is assumed. FIG. 4 is a comparison diagram of refrigerating capacity when a condensation temperature of 68 ° C. is assumed. FIG. 5 is a comparison chart of coefficient of performance when a condensation temperature of 68 ° C. is assumed. FIG. 6 is a refrigerant circuit diagram showing an embodiment of an air conditioner according to the present invention. FIG. 7 is a ph diagram for the circuit of FIG. FIG. 8 is a diagram showing the composition of the liquid refrigerant in the two-phase region in the condenser when a condensation temperature of 68 ° C. is assumed. FIG. 9 is a refrigerant circuit diagram showing another embodiment of the air conditioner according to the present invention.

  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.

[Mixed refrigerant]
First, the mixed refrigerant used in the air conditioner of the present invention will be described.
The mixed refrigerant used in the air conditioner of the present invention is a mixed refrigerant composed of two kinds of refrigerants, that is, the first refrigerant R32 and the second refrigerant R134a or R1234yf, and is a mixture of the first refrigerant. The ratio is larger than the mixing ratio of the second refrigerant. Below, the case of the mixed refrigerant which consists only of R32 and R134a will be described as an example.

  In the column of “R32 + R134a” in FIG. 1, the physical property values of the mixed refrigerant composed only of R32 and R134a are shown for each content ratio of R32. The content ratio of R32 is three types of 90, 80, and 70 wt%. As shown in FIG. 1, the ODP of these three mixed refrigerants is zero. Moreover, GWP is 751-902, and it turns out that it becomes smaller than GWP (= 1810) of R22. Here, SL in FIG. 1 indicates standard conditions and assumes a condensation temperature of 48 ° C. OL shows the conditions for the tropical region and assumes a condensation temperature of 68 ° C.

FIG. 2 is a diagram illustrating an example of the relationship between the saturated vapor pressure and the condensation temperature of each refrigerant.
When considering the use of the above mixed refrigerant in an existing air conditioner for R410A for tropical regions, as shown in FIG. It can be seen that in order to keep the pressure below the design pressure (4.15 MPa), it is necessary to mix R134a (or R1234yf) with R32 in an amount of 10 wt% or more.

  In this case, for example, if a mixed refrigerant containing 80 to 90 wt% of R32 is used and the air conditioner is operated at a condensation temperature of about 65 to 68 ° C., the pressure is about the design pressure of R410A compared to the case where R32 is used alone. Can be lowered to Moreover, as shown in FIG. 1, the high condensing pressure and discharge temperature, which are weak points of R32, can be reduced, and the temperature gradient in the evaporator can be suppressed to at least about 2.5 deg or less. That is, if the upper limit of the usable condensing temperature is up to about 68 ° C., the above mixed refrigerant containing 80 to 90 wt% R32 can be used for existing products for tropical regions.

  FIG. 3 is a diagram comparing the discharge temperature at the time of high condensation temperature. In the figure, the notation such as R32 + R134a (90/10) indicates that R32 is a mixed refrigerant of 90 wt% and R134a is 10 wt%. As shown in FIG. 3, it can be seen that mixing R134a (or R1234yf) with R32 suppresses the discharge temperature. Note that FIG. 3 is obtained assuming a method that does not use the liquid injection method described later.

  FIG. 4 is a diagram comparing the refrigeration capacity at high condensing temperature (theoretical value: when the compressor displacement volume / rotation speed is the same), and is represented by the capacity when R22 is 100%. As shown in FIGS. 4 and 1, it can be seen that the refrigerant having a higher refrigeration capacity than R22 (the refrigerant having R410A, R32 and R32 + R134a of 20 wt% or less) has a higher pressure than R22. In addition, in the mixed refrigerant of the present invention consisting only of R32 and R134a, it can be seen that the content ratio of R32 needs to be at least 80 wt% in order to obtain a refrigerating capacity equal to or higher than R410A.

  FIG. 5 is a diagram comparing the coefficient of performance (theoretical value) at a high condensation temperature. As shown in FIG. 5, among the refrigerants having higher refrigerating capacity than R22, it can be seen that the coefficient of performance of R410A is particularly low and the operation efficiency is poor. The coefficient of performance of the mixed refrigerant of the present invention consisting only of R32 and R134a is almost the same as the coefficient of performance of R32.

[Air conditioner]
Next, the air conditioner according to the present invention will be described with reference to FIGS.

  FIG. 6 is a refrigerant circuit diagram during cooling operation. As shown in FIG. 6, the refrigeration cycle circuit of the air conditioner 10 according to the present invention includes a compressor 12, a condenser (outdoor unit) 14, a decompression means 16, an evaporator (indoor unit) 18, and a four-way system. It consists of a valve 20. As the working refrigerant, the above mixed refrigerant consisting of only R32 and R134a or only R32 and R1234yf is used.

  This refrigeration cycle circuit separates R134a (or R1234yf) rich liquid refrigerant from a predetermined position of the condenser 14 and injects the separated liquid refrigerant into the intermediate pressure of the compressor 12.

  Specifically, 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 volume ratio of A% with respect to the whole condenser. The first 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 to be the same 5 deg, as shown in FIG. 7, the ratio 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, 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.

  In addition, the mixed refrigerant passing through the condenser is liquefied first in the refrigerant having a higher boiling point. Here, FIG. 8 shows the composition of the liquid-phase refrigerant in the refrigerant in the two-phase region in FIG. 7, 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. 7) 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 (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.

  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. Further, since this liquid refrigerant contains a larger amount of R134a (or R1234yf) having a lower discharge temperature than R32, the liquid refrigerant has a greater discharge temperature suppression effect than injection of a liquid refrigerant that does not contain much R134a (or R1234yf). 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.

  By the way, 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, when the liquid level in the container 22a of the gas-liquid separator 22 increases and the saturated vapor state refrigerant cannot be taken out, only the liquid refrigerant flows through the second condenser 14b. Since the condensation performance is deteriorated, it is necessary to control the liquid level so as to keep a position lower than the lower end portion of the outlet pipe inserted into the container 22a.

  Therefore, as shown in FIG. 9, 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. Accordingly, the gas-liquid separator 22 is not used, and the two-phase refrigerant from the first condenser 14a flows directly to the second condenser 14b and does not flow into the gas-liquid separator 22. 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).

  In the above-described embodiment, the case of the mixed refrigerant mainly composed of only R32 and R134a has been described. However, using R1234yf having similar physical properties to R134a as shown in FIGS. 1 and 2, R32 is used. Even if it is a mixed refrigerant consisting only of R32 and R1234yf, the present invention has the same effect as the mixed refrigerant consisting only of R32 and R134a, such as ODP being zero and GWP being smaller than R22. Note that the inventors have confirmed.

  As described above, 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 condenser, the pressure reducing means, and the evaporator with the refrigerant pipe. An air conditioner that circulates a two-type mixed refrigerant mixed at a mixing ratio greater than R134a or R1234yf, wherein the refrigerant circuit branches from the position where the second refrigerant of the condenser is liquid-rich. Since the liquid refrigerant separated from the mixed refrigerant is injected into the intermediate pressure of the compressor, the refrigerant circulating in the evaporator is separated in advance from the R134a (or R1234yf) rich liquid refrigerant that is liable to be liquefied first from the two-phase region. Of these, the ratio of R32 is increased, 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, the liquid refrigerant has a larger discharge temperature suppression effect than injection of liquid refrigerant having a composition ratio at the time of encapsulation. 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.

  In addition, since the condensing pressure and the discharge temperature can be reduced, operation is performed at a pressure equal to or lower than that of the refrigerant (R410A) conventionally used even at a high outside temperature where the outside temperature is 52 ° C. or higher. As a result, it is not necessary to change the design pressure of the expansion valve, piping, etc., and parts can be shared to reduce costs.

  As described above, the air conditioner according to the present invention is useful for an air conditioner for a tropical region, and is particularly suitable for suppressing the discharge temperature and reducing the temperature gradient on the evaporator side.

10 Air Conditioner 12 Compressor 14 Condenser (Outdoor Unit)
16 Pressure reducing means 18 Evaporator (indoor unit)
20 Four-way valve 22 Gas-liquid separator 24 Flow control valve 26, 28, 30, 32, 40, 42 Piping 34 Bypass 36, 38 Switching valve

Claims (4)

Two types of refrigerant circuit formed by connecting a compressor, a condenser, a pressure reducing means, and an evaporator with refrigerant piping and mixing R32 as the first refrigerant at a mixing ratio larger than R134a or R1234yf as the second refrigerant An air conditioner for circulating a mixed refrigerant,
The refrigerant circuit injects liquid refrigerant separated from the two-type mixed refrigerant branched from a position where the second refrigerant of the condenser is liquid-rich into an intermediate pressure of the compressor. Harmony machine.   The air conditioner according to claim 1, wherein a mixing ratio of the first refrigerant is 80 to 90 wt%.   The air conditioner according to claim 1 or 2, wherein the liquid refrigerant is separated from a position where the refrigerant in the condenser is in a gas-liquid two-phase state. A gas-liquid separator that separates the liquid refrigerant from a position where the refrigerant in the condenser is in a gas-liquid two-phase state, and a switching valve that switches use / non-use of the gas-liquid separator. The air conditioner according to claim 3.

Images