JP7460550B2 - Refrigeration cycle equipment - Google Patents

Description

The present invention relates to a refrigeration cycle device.

Conventionally, R32 refrigerant and R410A refrigerant have been used as refrigerants for refrigeration cycle devices. In order to reduce the impact on global warming, refrigeration cycle devices are known that use R290 (propane) refrigerant in the refrigerant circuit, which has a smaller global warming potential (GWP) than R32 refrigerant and R410A refrigerant. There is. Furthermore, refrigeration cycle devices equipped with internal heat exchangers for improving cooling capacity are known.

For example, Japanese Patent Application Laid-Open No. 2008-164245 (Patent Document 1) describes a refrigeration cycle device that uses propane as a refrigerant in the refrigerant circuit and is equipped with an internal heat exchanger. The refrigeration cycle device described in this publication includes a compressor, a condenser, a heat exchanger, and an evaporator. This heat exchanger corresponds to the internal heat exchanger. This internal heat exchanger has an inner tube and an outer tube into which the inner tube is inserted. The refrigerant sent from the compressor through the condenser to the internal heat exchanger is sent to the evaporator through the inner tube in the heat exchanger. The refrigerant sent to the evaporator returns to the compressor through the outer tube in the internal heat exchanger. In the internal heat exchanger, heat exchange occurs between the refrigerant flowing through the inner tube and the refrigerant flowing through the outer tube.

JP 2008-164245 A

In the refrigeration cycle device described in the above-mentioned publication, there is no mention that the refrigerant flowing outside the inner tube in the outer tube of the internal heat exchanger is entirely gas refrigerant. If the refrigerant flowing outside the inner tube in the outer tube of the internal heat exchanger contains liquid refrigerant, it is difficult to increase the degree of superheating of the refrigerant at the compressor inlet. It is difficult to improve the coefficient of performance (COP), which is the ratio of electric power. Furthermore, if the refrigerant flowing outside the inner tube in the outer tube of the internal heat exchanger contains liquid refrigerant, it is difficult to reduce the amount of refrigerant in the internal heat exchanger.

The present invention has been made in view of the above problems, and its purpose is to improve the coefficient of performance of a refrigeration cycle device by using a refrigerant with a small global warming potential, and to reduce the amount of refrigerant in an internal heat exchanger. An object of the present invention is to provide a refrigeration cycle device that can reduce

The refrigeration cycle device of the present invention includes a refrigerant circuit and a refrigerant. The refrigerant circuit includes a compressor, a condenser, an expansion valve, an evaporator, and an internal heat exchanger. The refrigerant flows through the refrigerant circuit in the order of the compressor, the condenser, the internal heat exchanger, the expansion valve, the evaporator, and the internal heat exchanger. The refrigerant is a hydrocarbon refrigerant. The internal heat exchanger includes an inner tube connected to the condenser and the expansion valve, and an outer tube into which the inner tube is inserted and which is connected to the evaporator and the compressor. The internal heat exchanger is configured to exchange heat between the refrigerant flowing through the inner tube from the condenser to the expansion valve and the refrigerant flowing outside the inner tube in the outer tube from the evaporator to the compressor. All of the refrigerants flowing outside the inner tube in the outer tube are gaseous. A groove is provided on the inner surface of the outer tube. No groove is provided on the inner surface and outer surface of the inner tube of the internal heat exchanger. The refrigerant flowing through the inner tube is a high-pressure side refrigerant and is a liquid refrigerant. The refrigerant flowing through the outer tube is a low-pressure side refrigerant and is a gaseous refrigerant. The grooves on the inner surface of the outer tube are configured to allow refrigeration oil to precipitate. The hydrocarbon refrigerant is propane. The refrigerant has zero superheat at the inlet on the low pressure side of the internal heat exchanger.

According to the refrigeration cycle device of the present invention, the refrigerant is a hydrocarbon refrigerant, and all of the refrigerant flowing outside the inner tube in the outer tube of the internal heat exchanger is gas. Therefore, a refrigerant with a small global warming potential can be used. Moreover, the coefficient of performance of the refrigeration cycle device can be improved. Furthermore, the amount of refrigerant in the internal heat exchanger can be reduced.

1 is a configuration diagram showing a refrigeration cycle device according to a first embodiment of the present invention; 1 is a perspective view schematically showing the configuration of an internal heat exchanger of a refrigeration cycle device according to Embodiment 1 of the present invention. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a graph showing the relationship between the intake SH and the theoretical COP of R290 refrigerant and R32 refrigerant. 3 is a cross-sectional view schematically showing the flow state of refrigerant in the internal heat exchanger of Comparative Example 1. FIG. 3 is a cross-sectional view schematically showing the flow state of refrigerant in an internal heat exchanger of Comparative Example 2. FIG. FIG. 2 is a cross-sectional view schematically showing the flow state of refrigerant in the internal heat exchanger of the refrigeration cycle device according to Embodiment 1 of the present invention. 8 is a partial cross-sectional view taken along line VIII-VIII in FIG. 7. 6 is a cross-sectional view illustrating a flow state of a refrigerant in an internal heat exchanger of a refrigeration cycle device according to a second embodiment of the present invention. FIG. 10 is a partial cross-sectional view taken along line XX in FIG. 9. FIG.

Embodiments of the present invention will be described below with reference to the drawings. In addition, in the following, the same reference numerals are given to the same or equivalent parts, and the description thereof will not be repeated in principle.

Embodiment 1.
The configuration of a refrigeration cycle apparatus 1 according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a configuration diagram showing a refrigeration cycle apparatus according to a first embodiment of the present invention. The refrigeration cycle apparatus according to the first embodiment of the present invention is, for example, an air conditioner. As shown in Fig. 1, the refrigeration cycle apparatus 1 according to the first embodiment of the present invention includes a refrigerant circuit 2, a control device 3, a condenser fan 10, an evaporator fan 11, and a refrigerant.

The refrigerant circuit 2 has a compressor 4, a condenser 5, an expansion valve 6, an evaporator 7, and an internal heat exchanger 8. The compressor 4, the condenser 5, the expansion valve 6, the evaporator 7, and the internal heat exchanger 8 are connected by piping 9. In this manner, the refrigerant circuit 2 is configured. The refrigerant circuit 2 is configured to be capable of circulating the refrigerant. The refrigerant circuit 2 is configured to perform a refrigeration cycle in which the refrigerant circulates while undergoing a phase change in the order of the compressor 4, the condenser 5, the internal heat exchanger 8, the expansion valve 6, the evaporator 7, and the internal heat exchanger 8.

The refrigerant flows through the refrigerant circuit 2 in the order of compressor 4, condenser 5, internal heat exchanger 8, expansion valve 6, evaporator 7, and internal heat exchanger 8. The refrigerant has a coefficient of performance that increases as the suction superheat (suction SH) of the compressor 4 increases. The refrigerant is, for example, a hydrocarbon refrigerant (HC refrigerant). Specifically, the refrigerant is, for example, propane (R290), isobutane (R600a), pentane (R601), butane (R600), ethane (R170), or propylene (R1270).

The control device 3 is configured to control the refrigerant circuit 2. The control device 3 is configured to perform calculations, instructions, etc. to control each means, device, etc. of the refrigeration cycle device 1. The control device 3 is electrically connected to the compressor 4, expansion valve 6, condenser fan 10, evaporator fan 11, etc., and is configured to control the operation of these.

The compressor 4 is configured to compress and discharge the sucked gaseous refrigerant. The compressor 4 is configured to have a variable capacity. The compressor 4 is configured so that the frequency is changed based on an instruction from the control device 3 to adjust the rotation speed, thereby changing the capacity. The compressor 4 uses refrigerating machine oil (lubricating oil). Refrigerating machine oils include, for example, polyalkylene glycol (PAG)-based oils having ether bonds, polyol ester (POE)-based oils having ester bonds, and the like.

The condenser 5 is configured to condense the refrigerant compressed by the compressor 4. Condenser 5 is connected to compressor 4 and internal heat exchanger 8 . The condenser 5 has heat transfer tubes through which a refrigerant flows. The condenser 5 is, for example, a fin-and-tube heat exchanger having a plurality of fins and a circular or flat heat exchanger tube passing through the plurality of fins.

The expansion valve 6 is configured to expand and reduce the pressure of the liquid refrigerant condensed by the condenser 5. The liquid refrigerant condensed by the condenser 5 is expanded and depressurized by the expansion valve 6, so that at the outlet of the expansion valve 6, the state of the refrigerant becomes a gas-liquid two-phase state. The expansion valve 6 is connected to the condenser 5 and the evaporator 7. The expansion valve 6 is, for example, an electric expansion valve that can adjust the flow rate of the refrigerant based on instructions from the control device 3. The amount of refrigerant passing through the expansion valve 6 is adjusted by adjusting the opening degree of the expansion valve 6.

The evaporator 7 is configured to evaporate the refrigerant decompressed by the expansion valve 6. The evaporator 7 is connected to the expansion valve 6 and the internal heat exchanger 8. The evaporator 7 has a heat transfer tube through which the refrigerant flows. The evaporator 7 is, for example, a fin-and-tube type heat exchanger having a plurality of fins and a circular or flat heat transfer tube that passes through the plurality of fins.

The internal heat exchanger 8 is configured to exchange heat between the refrigerant on the outlet side of the condenser 5 and the refrigerant on the outlet side of the evaporator 7. In the internal heat exchanger 8, heat exchange takes place between the refrigerant condensed in the condenser 5 and the refrigerant evaporated in the evaporator 7.

Piping 9 connects compressor 4 , condenser 5 , expansion valve 6 , evaporator 7 and internal heat exchanger 8 . The piping 9 constitutes a gas side refrigerant path and a liquid side refrigerant path. The piping 9 includes a first piping section 9a, a second piping section 9b, a third piping section 9c, and a fourth piping section 9d. The first piping section 9a is connected to the condenser 5 and the internal heat exchanger 8. The second piping section 9b is connected to the internal heat exchanger 8 and the expansion valve 6. The third piping section 9c is connected to the evaporator 7 and the internal heat exchanger 8. The fourth piping section 9d is connected to the internal heat exchanger 8 and the compressor 4.

For cooling, the condenser fan 10 is provided in an outdoor unit (not shown). The condenser fan 10 is configured to forcefully send outdoor air to the condenser 5. The condenser fan 10 is attached to the condenser 5 and is configured to supply air as a heat exchange fluid to the condenser 5. The condenser fan 10 adjusts the amount of air flowing around the condenser 5 by adjusting the rotation speed of the condenser fan 10 based on an instruction from the control device 3, thereby increasing the amount of air between the air and the refrigerant. It is configured to adjust the amount of heat exchange.

The evaporator fan 11 is provided in an indoor unit (not shown). The evaporator fan 11 is configured to forcefully send indoor air to the evaporator 7. The evaporator fan 11 is attached to the evaporator 7 and is configured to supply air as a heat exchange fluid to the evaporator 7. The evaporator fan 11 adjusts the amount of air flowing around the evaporator 7 by adjusting the rotation speed of the evaporator fan 11 based on instructions from the control device 3, thereby increasing the amount of air between the air and the refrigerant. It is configured to adjust the amount of heat exchange.

The configuration of the internal heat exchanger 8 will be described in detail with reference to FIGS.
As shown in Figures 2 and 3, the internal heat exchanger 8 is a double-pipe heat exchanger. The internal heat exchanger 8 has an inner pipe 8a and an outer pipe 8b. The inner pipe 8a has a tubular shape. The outer pipe 8b has a tubular shape. The inner pipe 8a is inserted into the outer pipe 8b. That is, the inner pipe 8a is disposed inside the outer pipe 8b. A gap GP is provided between the outer peripheral surface of the inner pipe 8a and the inner peripheral surface of the outer pipe 8b. This gap GP may have a uniform dimension around the entire circumference in the outer peripheral direction of the inner pipe 8a.

As shown in Figures 1 to 3, the inner pipe 8a is connected to the condenser 5 and the expansion valve 6. The inner pipe 8a is connected to the condenser 5 via the first piping section 9a, and to the expansion valve 6 via the second piping section 9b. The inner pipe 8a is configured to allow a high-pressure side refrigerant to flow through it. The outer pipe 8b is connected to the evaporator 7 and the compressor 4. The outer pipe 8b is connected to the evaporator 7 via the third piping section 9c, and to the compressor 4 via the fourth piping section 9d. The outer pipe 8b is configured to allow a low-pressure side refrigerant to flow through it.

The internal heat exchanger 8 exchanges refrigerant flowing in an inner tube 8a from the condenser 5 toward the expansion valve 6, and refrigerant flowing outside the inner tube 8a in an outer tube 8b from the evaporator 7 toward the compressor 4. It is configured to exchange heat. The internal heat exchanger 8 is configured so that the refrigerant flowing through the inner tube 8a and the refrigerant flowing outside the inner tube 8a in the outer tube 8b exchange heat via the wall surface of the inner tube 8a. The internal heat exchanger 8 is configured so that the refrigerant flowing through the inner tube 8a and the refrigerant flowing through the gap GP exchange heat via the wall surface of the inner tube 8a.

In the internal heat exchanger 8, all of the refrigerant flowing outside the inner tube 8a within the outer tube 8b is gas. All of the refrigerant flowing through the gap GP is gas. All of the refrigerant flowing outside the inner tube 8a within the outer tube 8b is in a dry state.

Next, the operation of the refrigeration cycle device 1 will be explained with reference to FIGS. 1 to 3. During refrigeration cycle operation, the gaseous refrigerant compressed by the compressor 4 is discharged from the compressor 4 and sent to the condenser 5 through a pipe 9 serving as a gas-side refrigerant path. In the condenser 5, heat is released from the refrigerant flowing through the heat transfer tubes to the air, thereby condensing the refrigerant. Thereafter, the refrigerant is sent to the internal heat exchanger 8 through the first piping section 9a as a liquid side refrigerant path. The refrigerant sent to the internal heat exchanger 8 through the first piping section 9a flows through the inner tube 8a of the internal heat exchanger 8, and then is sent to the expansion valve 6 through the second piping section 9b.

In the expansion valve 6, the liquid refrigerant is decompressed to become a gas-liquid two-phase refrigerant. The refrigerant decompressed in the expansion valve 6 is sent to the evaporator 7 through the pipe 9 as a liquid refrigerant path. After this, the refrigerant absorbs heat from the air in the evaporator 7 and evaporates, and is sent to the internal heat exchanger 8 through the third pipe section 9c as a gas refrigerant path. The refrigerant sent to the internal heat exchanger 8 through the third pipe section 9c flows through the outer pipe 8b of the internal heat exchanger 8 and then returns to the compressor 4 through the fourth pipe section 9d.

In the internal heat exchanger 8, heat is transferred between the refrigerant on the outlet side of the condenser 5 (high pressure side refrigerant) flowing through the inner tube 8a and the refrigerant on the outlet side of the evaporator 7 (low pressure side refrigerant) flowing through the outer tube 8b. An exchange takes place. The internal heat exchanger 8 can reduce the dryness of the refrigerant at the outlet of the evaporator 7, thereby improving the heat transfer performance of the evaporator 7. This improves the coefficient of performance (COP) of the refrigeration cycle device 1.

Next, the operational effect of the refrigeration cycle device 1 relating to embodiment 1 of the present invention will be explained in comparison with comparative example 1 and comparative example 2.

Here, R290 refrigerant is used as an example of a refrigerant in the refrigeration cycle device 1 according to Embodiment 1 of the present invention. Comparative Example 1 differs from refrigeration cycle device 1 according to Embodiment 1 of the present invention in that the refrigerant is R32. Note that R32 refrigerant has a higher global warming potential (GWP) than R290 refrigerant. Furthermore, Comparative Example 1 differs from the refrigeration cycle device according to Embodiment 1 of the present invention in that in the internal heat exchanger 8, the low-pressure refrigerant flows through the inner tube 8a, and the high-pressure refrigerant flows through the outer tube 8b. ing. That is, in Comparative Example 1, in the internal heat exchanger 8, the inner pipe 8a is connected to the evaporator 7 and the compressor 4, and the outer pipe 8b is connected to the condenser 5 and the expansion valve 6.

Figure 4 is a graph showing the relationship between the theoretical coefficient of performance (hereinafter referred to as "theoretical COP") and the suction superheat (suction SH) of the compressor 4 when R290 refrigerant and R32 refrigerant are used as the refrigerant in the refrigerant circuit 2. The coefficient of performance (COP) is the ratio of power consumption to the capacity of the refrigeration cycle device 1.

Referring to FIG. 4, the theoretical COP of the R32 refrigerant decreases as the suction superheat degree (suction SH) of the compressor 4 increases. On the other hand, the theoretical COP of R290 refrigerant improves as the suction superheat degree (SH) of the compressor 4 increases. This is because the R290 refrigerant and the R32 refrigerant have different characteristics. That is, the coefficient of performance of the R290 refrigerant is superior to that of the R32 refrigerant when the suction superheat degree (suction SH) of the compressor 4 is increased.

With R32 refrigerant, due to the characteristics of the refrigerant, when the suction superheat degree (suction SH) of the compressor 4 is zero (0), it is higher than when the suction superheat degree (suction SH) of the compressor 4 is greater than zero (0). The coefficient of performance improves. Therefore, in order to improve the coefficient of performance, the refrigerant on the low pressure side of the internal heat exchanger 8 is made wet so that the suction superheat degree (suction SH) of the compressor 4 does not become greater than zero (0).

Figure 5 is a cross-sectional view showing the flow state of the refrigerant inside the internal heat exchanger 8 in Comparative Example 1. Referring to Figure 5, in the internal heat exchanger 8 in Comparative Example 1, the refrigerant R1 flowing through the inner tube 8a is a low-pressure refrigerant, and the refrigerant R2 flowing through the outer tube 8b is a high-pressure refrigerant. The low-pressure refrigerant R1 flowing through the inner tube 8a is in a gas-liquid two-phase state. The low-pressure refrigerant R1 flowing through this inner tube 8a becomes an annular flow. That is, in the low-pressure refrigerant flowing through this inner tube 8a, gas refrigerant Ra flows in the center of the inner tube 8a, and liquid refrigerant Rb flows in the outer part along the wall surface of the inner tube 8a. Since the liquid refrigerant Rb contacts the wall surface of the inner tube 8a, which is the heat transfer surface, the heat transfer performance is improved. However, since the refrigerant in Comparative Example 1 is an R32 refrigerant, the global warming potential is larger than that of the R290 refrigerant. Therefore, in Comparative Example 1, the global warming potential of the refrigerant cannot be reduced.

FIG. 6 is a cross-sectional view showing the flow state of the refrigerant inside the internal heat exchanger 8 in Comparative Example 2. Referring to FIG. 6, in the internal heat exchanger 8 in Comparative Example 2, the refrigerant R1 flowing through the inner tube 8a is a low-pressure side refrigerant, and the refrigerant R2 flowing through the outer tube 8b is a high-pressure side refrigerant. This is different from the refrigeration cycle device 1 according to the first embodiment of the invention. The refrigerant in Comparative Example 2 is propane (R290).

In theory, the performance of the evaporator 7 improves when the degree of superheat of the refrigerant at the outlet of the evaporator 7 is zero (SH = 0). On the other hand, due to the characteristics of propane (R290) refrigerant, the greater the degree of suction superheat (suction SH) of the compressor 4, the better the coefficient of performance. Therefore, in order to increase the degree of superheat of the refrigerant at the outlet of the evaporator 7 (SH = 0) while keeping the degree of superheat of the refrigerant at the outlet of the evaporator 7 at zero (SH = 0) and increasing the degree of suction superheat (suction SH) of the compressor 4, it is preferable that the degree of superheat of the refrigerant at the inlet of the low-pressure side of the internal heat exchanger 8 be zero.

When the refrigeration cycle device 1 using propane (R290) as the refrigerant is operated to improve the coefficient of performance, the degree of superheat of the refrigerant at the outlet of the evaporator 7 is close to zero. In this case, the degree of superheat at the outlet on the low pressure side of the internal heat exchanger 8, i.e., the inlet of the compressor 4, is zero or more. Also, the refrigerant at the inlet on the low pressure side of the internal heat exchanger 8 becomes gas. In this case, since there is no liquid refrigerant in the refrigerant R1 flowing through the inner tube 8a of the internal heat exchanger 8, the refrigeration oil 20 is likely to precipitate on the inner surface of the wall surface of the inner tube 8a. When the refrigeration oil 20 precipitates on the wall surface of the inner tube 8a of the internal heat exchanger 8, the refrigeration oil 20 precipitated on the wall surface of the inner tube 8a of the internal heat exchanger 8 becomes a thermal resistance, and the heat transfer performance of the internal heat exchanger 8 decreases.

7 and 8 are cross-sectional views showing the flow state of the refrigerant inside the internal heat exchanger 8 of the refrigeration cycle device 1 according to Embodiment 1 of the present invention. Referring to FIGS. 7 and 8, in the internal heat exchanger 8 of the refrigeration cycle device 1 according to the first embodiment of the present invention, the refrigerant R1 flowing through the inner tube 8a is a high-pressure side refrigerant, and the outer tube 8b is The flowing refrigerant R2 is a low-pressure refrigerant.

Inside the internal heat exchanger 8, the heat transfer surface where the high-pressure side refrigerant R1 flowing through the inner tube 8a and the low-pressure side refrigerant R2 flowing through the outer tube 8b exchange heat is the wall surface of the inner tube 8a. In addition to the wall surface of the inner tube 8a as a heat transfer surface that exchanges heat with the high-pressure side refrigerant flowing through the inner tube 8a, the low-pressure side refrigerant flowing through the outer tube 8b has the wall surface of the outer tube 8b as a heat transfer surface that exchanges heat with the air outside the outer tube 8b. Therefore, in the refrigeration cycle device 1 according to embodiment 1 of the present invention, the area of the wall surface on which the refrigerating machine oil 20 precipitates is increased compared to comparative example 2. Therefore, the amount of refrigerating machine oil precipitated on the wall surface of the inner tube 8a as a heat transfer surface is reduced. Therefore, the refrigerating machine oil precipitated on the wall surface of the inner tube 8a becomes a thermal resistance, and the heat transfer performance of the internal heat exchanger 8 can be suppressed from being reduced.

That is, in the refrigeration cycle device 1 according to the first embodiment of the present invention, propane (R290) refrigerant is used, and high-pressure refrigerant is flowed through the inner tube 8a of the internal heat exchanger 8, and low-pressure refrigerant is flowed through the outer tube 8b. The refrigerant on the side is flushed away. Furthermore, the refrigerant at the low-pressure side inlet of the internal heat exchanger 8 becomes dry. In other words, the degree of superheating of the refrigerant at the low-pressure side inlet of the internal heat exchanger 8 becomes zero. This suppresses a decrease in heat transfer performance due to precipitation of refrigerating machine oil in the internal heat exchanger 8. Therefore, operation with a good coefficient of performance can be realized in the refrigeration cycle apparatus 1.

According to the refrigeration cycle device 1 according to the first embodiment of the present invention, since the refrigerant is a hydrocarbon refrigerant (HC refrigerant), a refrigerant with a small global warming potential (GWP) can be used. Furthermore, all of the refrigerant flowing outside the inner tube 8a within the outer tube 8b of the internal heat exchanger 8 is gas. Therefore, the degree of superheating of the refrigerant at the inlet of the compressor 4 can be increased compared to the case where the refrigerant flowing outside the inner tube 8a in the outer tube 8b of the internal heat exchanger 8 contains liquid refrigerant. Therefore, the coefficient of performance (COP) of the refrigeration cycle device 1 can be improved. Furthermore, the degree of superheating of the refrigerant at the outlet of the outer tube 8b of the internal heat exchanger 8 is increased compared to the case where the refrigerant flowing outside the inner tube 8a in the outer tube 8b of the internal heat exchanger 8 contains liquid refrigerant. can do. Therefore, the amount of refrigerant in the internal heat exchanger 8 can be reduced.

According to the refrigeration cycle device 1 of the first embodiment of the present invention, the refrigerant is an HC refrigerant. Therefore, the global warming potential (GWP) of the refrigerant can be reduced.

According to the refrigeration cycle device 1 of the first embodiment of the present invention, the expansion valve 6 is an electric expansion valve capable of adjusting the flow rate of the refrigerant. Therefore, it is possible to adjust the flow rate of the refrigerant by the electric expansion valve.

Embodiment 2.
The refrigeration cycle device 1 according to the second embodiment of the present invention has the same configuration, operation, and effect as the refrigeration cycle device 1 according to the first embodiment of the present invention described above, unless otherwise described.

Referring to FIGS. 9 and 10, the refrigeration cycle device 1 according to the second embodiment of the present invention has a configuration of the outer tube 8b of the internal heat exchanger 8 according to the first embodiment of the present invention. It is different from

In the refrigeration cycle device 1 according to the second embodiment of the present invention, a groove 30 is provided on the inner surface of the outer tube 8b of the internal heat exchanger 8. The groove 30 may be provided around the entire circumference of the inner surface of the outer tube 8b of the internal heat exchanger 8. The groove 30 may be configured in a sawtooth shape. The groove 30 is not provided on the inner tube 8a of the internal heat exchanger 8. In other words, no groove is provided on the inner and outer surfaces of the inner tube 8a of the internal heat exchanger 8.

Since the groove 30 is provided only in the outer tube 8b of the internal heat exchanger 8, it is a portion that does not contribute to heat transfer between the refrigerant flowing through the inner tube 8a and the refrigerant flowing through the outer tube 8b in the internal heat exchanger 8. Refrigerating machine oil 20 tends to precipitate in certain grooves 30. This makes it possible to suppress a decrease in heat transfer performance due to refrigerating machine oil deposited on the wall surface of the inner tube 8a more than in the first embodiment.

According to the refrigeration cycle device 1 according to the present embodiment, the groove 30 is provided on the inner surface of the outer tube 8b of the internal heat exchanger 8. Since the heat transfer area of the outer tube 8b is increased by the grooves 30, the refrigerating machine oil 20 is likely to be deposited in the grooves 30. Therefore, it is possible to suppress a decrease in heat transfer performance due to refrigerating machine oil deposited on the wall surface of the inner tube 8a.

According to the refrigeration cycle device 1 of this embodiment, the grooves 30 are configured in a sawtooth shape. This makes it easier for refrigeration oil to precipitate at the bottom of the sawtooth shape.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Refrigeration cycle device, 2 Refrigerant circuit, 3 Control device, 4 Compressor, 5 Condenser, 6 Expansion valve, 7 Evaporator, 8 Internal heat exchanger, 8a Inner tube, 8b Outer tube, 9 Piping, 10 Condenser fan , 11 evaporator fan, 20 refrigeration oil, 30 groove.

Claims (3)

a refrigerant circuit having a compressor, a condenser, an expansion valve, an evaporator and an internal heat exchanger;
the refrigerant circuit includes a refrigerant that flows through the compressor, the condenser, the internal heat exchanger, the expansion valve, the evaporator, and the internal heat exchanger in this order;
The refrigerant is a hydrocarbon refrigerant,
the internal heat exchanger has an inner pipe connected to the condenser and the expansion valve, and an outer pipe into which the inner pipe is inserted and which is connected to the evaporator and the compressor;
the internal heat exchanger is configured to exchange heat between the refrigerant flowing inside the inner tube from the condenser toward the expansion valve and the refrigerant flowing outside the inner tube in the outer tube from the evaporator toward the compressor,
The refrigerant flowing in the outer tube and outside the inner tube is entirely gas,
A groove is provided on the inner surface of the outer tube,
The inner and outer surfaces of the inner tube of the internal heat exchanger are not provided with grooves,
The refrigerant flowing through the inner tube is a high-pressure side refrigerant and is a liquid refrigerant,
The refrigerant flowing through the outer tube is a low-pressure refrigerant and is a gaseous refrigerant,
The groove provided on the inner surface of the outer pipe is configured to allow refrigeration oil to precipitate ,
the hydrocarbon refrigerant is propane;
A refrigeration cycle device , wherein a degree of superheat of the refrigerant at an inlet on a low pressure side of the internal heat exchanger is zero . The refrigeration cycle device according to claim 1, wherein the grooves are configured in a sawtooth shape. The refrigeration cycle device according to claim 1 or 2 , wherein the expansion valve is an electric expansion valve that can adjust the flow rate of the refrigerant.

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