JP2001296067A - Refrigerating system using co2 refrigerant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the improvement in efficiency to be compatible with securing of reliability in a refrigerating system using CO2 refrigerant. SOLUTION: A refrigerant circuit comprises a compressor 1, a gas cooler A, a primary expansion mechanism C, a receiver for gas-liquid separation 7, a secondary expansion mechanism D, an evaporator B, a gas injection mechanism E and an inside heat exchanger 8. Thereby, the rise in the discharge temperature of the compressor on the basis of the inside beat exchange is suppressed by the injection of gas refrigerant by the gas injection mechanism E, while the improvement in the efficiency of the inside heat exchange by the inside heat exchanger 8 is contrived. Moreover, a refrigerating capacity is improved on the basis of the increase in evaporation enthalpy due to introduction of liquid refrigerant after gas-liquid separation into the evaporator B, and the improvement in the refrigerating efficiency is made compatible with securing of the reliabilty of the compressor 1 as these synergistic effects.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a refrigeration system using a CO ₂ refrigerant.

[0002]

_2. Description of the Related Art A transcritical refrigeration cycle using a CO ₂ refrigerant has a higher efficiency (coefficient of performance: COP) than a refrigeration cycle using a chlorofluorocarbon-based refrigerant because of its high operating pressure as a characteristic of the CO ₂ refrigerant. There is a disadvantage that it is bad, and as one method of improving this, for example, as shown in FIG.
A basic refrigerant circuit including the compressor 1, the four-way switching valve 5, the outdoor heat exchanger 2, the indoor heat exchanger 3, and the expansion valve 11,
The internal heat exchanger 8 is incorporated, and the high-pressure side heat transfer portion 8a and the low-pressure side heat transfer portion 8b of the internal heat exchanger 8 are connected via the four-way switching valve 6 to the outdoor heat exchanger 2 and the indoor heat exchanger 3. An internal heat exchanger built-in system has been proposed in which the internal heat exchanger 8 can be connected to the internal heat exchanger 8 to increase the efficiency of the entire refrigeration cycle.

[0003]

However, when an internal heat exchanger is incorporated in a refrigerant circuit for the purpose of improving the efficiency of a refrigeration cycle using a CO ₂ refrigerant, although the purpose of improving the efficiency is achieved, Since the discharge temperature of the compressor rises as the suction temperature of the compressor rises due to internal heat exchange, for example, the deterioration of the resin insulation material used in the compressor accelerates, and the reliability of the refrigeration system during long-term operation However, there is a drawback that is deteriorated.

Therefore, in the present invention, in a refrigeration system using a CO ₂ refrigerant, the effect of improving the efficiency by incorporating an internal heat exchanger into the refrigerant circuit is improved by the disadvantages associated with the incorporation of the internal heat exchanger (ie, the compressor). It is intended to achieve both high efficiency and high reliability while preventing the reliability from being lowered due to the rise of the discharge temperature.

[0005]

BACKGROUND OF THE INVENTION In the course of studying means for solving the above problems, the present inventors paid attention to a gas injection mechanism in a refrigerant circuit. That is, this gas injection mechanism has been proposed as an efficiency improvement measure for a refrigeration cycle using a chlorofluorocarbon-based refrigerant or a CO ₂ refrigerant, similarly to the above-described method of incorporating an internal heat exchanger into a refrigerant circuit. FIG. 7 shows an example of a refrigerant circuit in which a gas injection mechanism is incorporated in a transcritical refrigeration cycle using a CO ₂ refrigerant. The refrigerant circuit is configured such that the discharge port of the compressor 1 is connected to the outdoor heat exchanger 2 and the indoor heat exchanger 3 and the suction port of the compressor 1 is connected to the indoor heat exchanger 3 by the switching operation of the four-way switching valve 5. Outdoor heat exchanger 2
The expansion valve 11, the receiver 7, and the expansion valve 12 are sequentially arranged in a refrigerant path 31 connecting the outdoor heat exchanger 2 and the indoor heat exchanger 3 while being selectively connectable. A circuit is configured by connecting the air chamber of the receiver 7 and the compression chamber of the compressor 1 by a refrigerant path 32 having a control valve 10.

FIG. 8 shows a PH diagram of a transcritical refrigeration cycle incorporating a gas injection mechanism. In brief, for example, during the cooling operation, the CO ₂ refrigerant in the supercritical state at the outlet point E of the outdoor heat exchanger 2 functioning as a gas cooler is primarily expanded in the expansion valve 11 to perform gas-liquid cooling. with the CO ₂ refrigerant phases, the CO ₂ refrigerant in the gas-liquid two-phase to gas-liquid separation here is introduced into the receiver 7 (point F). Then, the separated liquid refrigerant is secondarily expanded in the expansion valve 12 as a saturated liquid refrigerant (point H), and then sent to the indoor heat exchanger 3 functioning as an evaporator. On the other hand, the gas refrigerant separated in the receiver 7 is passed through the refrigerant path 32 as a saturated gas refrigerant (point G).
Is injected into the compression chamber in the middle of the compression stroke.

As described above, by injecting the gas refrigerant separated in the receiver 7 into the compression chamber of the compressor 1 in the middle of the compression stroke, CO _{2 in the} compression chamber is reduced.
Since the refrigerant and the injected gas refrigerant are mixed and the refrigerant temperature decreases from the temperature corresponding to the point B to the temperature corresponding to the point C, the refrigerant temperature at the outlet of the compressor 1 (that is, the “discharge temperature”) is: The temperature drops to a temperature (a temperature corresponding to the point D) lower than a discharge temperature (a temperature corresponding to the point D ₀ ) when the gas injection is not performed.

[0008] The gas refrigerant separated from the gas is separated into a compressor 1
By injecting into the side, the amount of refrigerant circulating on the side of the evaporator (indoor heat exchanger 3) is smaller than the amount of refrigerant circulating on the side of the gas cooler (outdoor heat exchanger 2) by this amount of injection, and Since the liquid refrigerant after the gas-liquid separation is secondarily expanded in the expansion valve 12 and introduced into the evaporator, the enthalpy of evaporation per unit weight in the evaporator increases (shown by “h ₁ ” in FIG. 8). Enthalpy amount), the cooling capacity increases accordingly. As a result, the same refrigeration capacity as before the decrease in the amount of circulating refrigerant can be obtained with a smaller amount of circulating refrigerant.

[0009] The inventors of the present invention have the advantages based on incorporating the gas injection mechanism into the refrigerant circuit as described above,
In particular, the present inventors have conceived to solve the drawback (i.e., increase in compressor discharge temperature) caused by the incorporation of the internal heat exchanger as much as possible by effectively utilizing the effect of lowering the compressor discharge temperature.

[0010]

The present invention is based on such technical background, and employs the following configuration as specific means for solving the above-mentioned problems.

In the refrigeration system using the CO ₂ refrigerant according to the first invention of the present application, the compressor 1 for compressing the CO ₂ refrigerant
A gas cooler A for releasing the refrigerant discharged from the compressor 1 in a supercritical region, a primary expansion mechanism C for primary expansion of the gas from the gas cooler A, and a refrigerant from the primary expansion mechanism C. A receiver 7 for gas-liquid separation, a secondary expansion mechanism D for secondary-expanding the liquid refrigerant separated by the receiver 7, an evaporator B for evaporating the liquid refrigerant from the secondary expansion mechanism D, and the receiver 7 A gas injection mechanism E for injecting the gas refrigerant separated in the compressor 1 into the compression chamber of the compressor 1 and heat between the gas refrigerant from the evaporator B sucked into the compressor 1 and the liquid refrigerant in the system. An internal heat exchanger 8 for performing exchange is provided.

According to a second invention of the present application, in the refrigeration system using the CO ₂ refrigerant according to the first invention, the internal heat exchanger 8 functions as the use side heat exchanger with the gas cooler A functioning. In both the operation in which the evaporator B functions as a heat source side heat exchanger and the operation in which the gas cooler A functions as a heat source side heat exchanger and the evaporator B functions as a use side heat exchanger, The heat exchanger is characterized in that heat exchange is performed between the gas refrigerant from the evaporator B and the liquid refrigerant after gas-liquid separation in the receiver 7.

According to a third aspect of the present invention, in the refrigeration system using the CO ₂ refrigerant according to the first aspect, the internal heat exchanger 8 functions as the gas-side cooler A as a use-side heat exchanger. During the operation in which the evaporator B functions as a heat source side heat exchanger, the gas cooler A operates between the gas refrigerant from the evaporator B and the liquid refrigerant at the outlet side of the gas cooler A. During operation in which the evaporator B functions as a heat exchanger and the evaporator B functions as a use side heat exchanger, heat exchange is performed between the gas refrigerant from the evaporator B and the liquid refrigerant after gas-liquid separation by the receiver 7. It is characterized in that it is configured to do so.

[0014]

According to the present invention, the following effects can be obtained by adopting such a configuration.

According to the refrigeration system using the CO ₂ refrigerant according to the first invention of the present application, the compressor 1 for compressing the CO ₂ refrigerant and the refrigerant discharged from the compressor 1 are radiated in the supercritical region. A gas cooler A, a primary expansion mechanism C for temporarily expanding the refrigerant from the gas cooler A, and a receiver 7 for gas-liquid separation of the refrigerant from the primary expansion mechanism C
A secondary expansion mechanism D for secondary-expanding the liquid refrigerant separated by the receiver 7, an evaporator B for evaporating the liquid refrigerant from the secondary expansion mechanism D, and a gas refrigerant separated by the receiver 7 A gas injection mechanism E for injecting the gas into the compression chamber of the compressor 1 and an internal heat for performing heat exchange between the gas refrigerant from the evaporator B sucked into the compressor 1 and the liquid refrigerant in the system. Since the internal heat exchanger 8 includes the heat exchanger 8, the internal heat exchange in the internal heat exchanger 8 improves the refrigeration efficiency. On the other hand, the gas injection mechanism E injects the gas refrigerant to the compressor side, thereby improving the internal heat. The increase in the compressor discharge temperature due to the internal heat exchange in the exchanger 8 is suppressed, and the liquid refrigerant after the gas-liquid separation is introduced into the evaporator B, whereby the evaporative energy per unit weight is increased. Rs is increased, which improves the refrigerating capacity, as these synergistic effects, without compromising the reliability of the compressor, in which it is possible to realize a high efficiency.

Further, since the efficiency can be increased by a relatively simple circuit change of incorporating the internal heat exchanger 8 and the gas injection mechanism E into the basic refrigerant circuit, the cost of the refrigeration system can be reduced and the efficiency can be increased. It is easy to achieve both.

Furthermore, by introducing the liquid refrigerant after gas-liquid separation into the evaporator B, the enthalpy of vaporization per unit weight of the CO ₂ refrigerant flowing through the evaporator B can be increased. The flow rate of the refrigerant decreases, and the flow velocity of the refrigerant decreases. As a result, a decrease in efficiency due to the pressure loss in the evaporator B is suppressed, a high refrigerating efficiency is secured, and the evaporator B is promoted to be more compact because the refrigerant flow rate in the evaporator B is small.

According to the refrigeration system using a CO ₂ refrigerant according to the second aspect of the present invention, the following specific effects can be obtained in addition to the effects described above. That is, according to the present invention, the internal heat exchanger 8 is operated during the operation in which the gas cooler A functions as a use side heat exchanger and the evaporator B functions as a heat source side heat exchanger. Functions as a heat source side heat exchanger and the evaporator B functions as a use side heat exchanger, both during operation and the gas refrigerant from the evaporator B and the liquid refrigerant after being gas-liquid separated by the receiver 7. And heat exchange with the CO ₂ refrigerant before gas-liquid separation in the internal heat exchanger 8, for example. The amount of the refrigerant is reduced, and the size of the internal heat exchanger 8 is reduced accordingly.

According to the refrigeration system using a CO ₂ refrigerant according to the third invention of the present application, the following specific effects can be obtained in addition to the effects described above. That is, according to the present invention, the gas from the evaporator B is used during the operation in which the gas cooler A functions as the use side heat exchanger and the evaporator B functions as the heat source side heat exchanger. During operation in which the gas cooler A functions as a heat source side heat exchanger and the evaporator B functions as a use side heat exchanger between the refrigerant and the liquid refrigerant at the outlet side of the gas cooler A, The heat exchange is performed between the gas refrigerant from B and the liquid refrigerant after gas-liquid separation by the receiver 7.

Therefore, particularly in the latter operation, the heat exchange is performed between the liquid refrigerant after the gas-liquid separation by the receiver 7, so that, for example, the gas exchange in the internal heat exchanger 8 is performed. The amount of refrigerant flowing through the internal heat exchanger 8 is smaller than when heat is exchanged with the CO ₂ refrigerant before liquid separation,
As a result, downsizing of the internal heat exchanger 8 is promoted.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a refrigeration system using a CO ₂ refrigerant according to the present invention will be described in detail based on a preferred embodiment.

First Embodiment FIG. 1 shows a refrigerant circuit according to a first embodiment in which a refrigeration system using a CO ₂ refrigerant according to the present invention is applied to an air conditioner. Is a compressor,
2 is an outdoor heat exchanger (corresponding to the “heat source side heat exchanger” in the claims), 3 is an indoor heat exchanger (corresponds to the “use side heat exchanger” in the claims), 4 is The above compressor 1
The accumulator 5 provided in the refrigerant passage 24 connected to the suction port of the first unit selectively connects the outdoor heat exchanger 2 and the indoor heat exchanger 3 to the compressor 1 and the refrigerant passage 23. The four-way switching valve 6 includes the outdoor heat exchanger 2 and the indoor heat exchanger 3
And a second four-way switching valve for alternatively connecting the refrigerant passage 23 and the refrigerant passage 24 to each other. In FIG. 1, the positions of the four-way switching valves 5 and 6 are indicated by solid lines during the cooling operation and by broken lines during the heating operation.

Reference numeral 7 denotes a first expansion valve 11 and a second expansion valve 11.
And a gas-liquid separation receiver provided at an intermediate position between the expansion valves 11 and 12 in the refrigerant path 23 in which the expansion valve 12 is provided in series. The compressor 1 is connected to a compression chamber of the compressor 1 through a refrigerant passage 26. The receiver 7, the refrigerant passage 26, and the control valve 10 constitute a "gas injection mechanism E" in the claims.

Further, reference numeral 8 denotes an internal heat exchanger provided with a high-pressure side heat transfer section 8a and a low-pressure side heat transfer section 8b. 2 is provided at an intermediate position of the expansion valve 12 and the low-pressure side heat transfer section 8.
b is provided in the refrigerant passage 24.

Subsequently, the operation of the refrigerant circuit of the air conditioner is performed during a cooling operation (ie, the outdoor heat exchanger 2 functions as a "gas cooler A" in the claims, and the indoor heat exchanger 3 An operation state that functions as the “evaporator B” in the claims will be described as an example, together with the “PH diagram” shown in FIG. 2.

During the cooling operation, the CO ₂ refrigerant (gas refrigerant) discharged from the compressor 1 is introduced into the outdoor heat exchanger 2 via the first four-way switching valve 5, The heat is dissipated in the critical region (the region between points D and E in FIG. 2). Supercritical CO ₂ flowing out of the outdoor heat exchanger ₂
The refrigerant reaches the first expansion valve 11 (corresponding to the “primary expansion mechanism C” in the claims) from the second four-way switching valve 6 and is primarily expanded in the first expansion valve 11 (FIG. 2). (Areas from point E to point F), the gas is introduced into the receiver 7 in a gas-liquid two-phase state, where it is separated into gas and liquid (points G and H in FIG. 2).

The liquid refrigerant separated by the receiver 7 flows into the high-pressure heat transfer section 8a of the internal heat exchanger 8, and from its inlet (point H in FIG. 2) to its outlet (point I in FIG. 2). During the flow, the internal heat exchange between the low-pressure side heat transfer portion 8b and the gas refrigerant flowing from the inlet (point K in FIG. 2) to the outlet (point A in FIG. 2) is performed. Second expansion valve 12
(Corresponding to the “secondary expansion mechanism D” in the claims), where it is secondarily expanded (in the region of points I to J in FIG. 2) and then sent to the indoor heat exchanger 3. The gas evaporates while flowing from the inlet (point J in FIG. 2) to the outlet (point K in FIG. 2) to be a gas refrigerant. The gas refrigerant is sucked into the compressor 1 again and compressed. The suction temperature of the refrigerant is higher than the outlet temperature of the indoor heat exchanger 3 (the temperature corresponding to the point K in FIG. 2). The temperature is set to be higher (that is, the temperature corresponding to the point A in FIG. 2) by the temperature rise (indicated by “d” in FIG. 2) due to the internal heat exchange in FIG.

On the other hand, the gas refrigerant separated by the receiver 7 is injected via the refrigerant passage 26 into the compression chamber in the middle of the compression stroke of the compressor 1 (see point G in FIG. 2).
As described above, since the gas refrigerant is injected into the compression chamber of the compressor 1 and mixed with the gas refrigerant in the compression chamber, the cooling and the densification of the gas refrigerant in the compression chamber are promoted. Meanwhile, the temperature of the gas refrigerant in the compression chamber corresponds to the point B at the time of the gas injection, despite the fact that the suction temperature of the compressor 1 has risen due to internal heat exchange, and the compression is started from this high suction temperature. The temperature temporarily decreases from the temperature corresponding to the point C to the temperature corresponding to the point C, and the temperature is increased again from the lowered temperature, and finally, the temperature corresponding to the point D becomes the discharge temperature. Therefore, since the discharge temperature is affected by the temperature drop accompanying the gas injection, the discharge temperature is lower than the temperature when the gas is compressed from the point A to the point D ₀ without performing the gas injection (the temperature corresponding to the point D ₀ ). Low temperature.

In the heating operation, contrary to the cooling operation, the outdoor heat exchanger 2 functions as an evaporator and the indoor heat exchanger 3 functions as a gas cooler. The flow direction of the refrigerant at 8 is the same in both the cooling operation and the heating operation. That is, the internal heat exchanger 8 always exchanges heat with the liquid refrigerant that has been gas-liquid separated by the receiver 7.

As described above, by incorporating the internal heat exchanger 8 and the gas injection mechanism E into the refrigerant circuit of the transcritical refrigeration cycle using the CO ₂ refrigerant, the internal heat exchange in the internal heat exchanger 8 The rise in compressor discharge temperature
Since the cooling effect is suppressed by the gas injection, the effect of improving the efficiency by increasing the refrigerating capacity by the internal heat exchange (the enthalpy amount “c ₁ ” in FIG. 2) can be realized while securing the reliability of the compressor 1. Furthermore, as a result of injecting the gas refrigerant separated into gas and liquid by the receiver 7 into the compressor 1, the refrigerant circulation amount of the evaporator (that is, the indoor heat exchanger 3 during the cooling operation) is reduced by an amount corresponding to the injection amount. Although the amount of refrigerant circulating on the gas cooler (ie, the outdoor heat exchanger 2 during the cooling operation) side is reduced, the enthalpy of evaporation per unit weight is increased by that amount (the enthalpy amount “c” in FIG. ₂ )), refrigeration capacity does not change. As these synergistic effects, high efficiency can be realized without impairing the reliability of the compressor 1, and both high efficiency and high reliability can be achieved.

The liquid refrigerant after gas-liquid separation by the receiver 7 is introduced into an evaporator (ie, the indoor heat exchanger 3 during the cooling operation and the outdoor heat exchanger 2 during the heating operation). Accordingly, the enthalpy of evaporation per unit weight of the CO ₂ refrigerant flowing through the evaporator can be increased, and the refrigerant flow rate decreases and the refrigerant flow rate decreases under the same refrigeration capacity. As a result, a decrease in efficiency due to a pressure loss in the evaporator is suppressed, a high refrigerating efficiency is ensured, and the evaporator is downsized by the small amount of the refrigerant flow.

Further, as in this embodiment, during both the cooling operation and the heating operation, heat is generated between the gas refrigerant discharged from the evaporator and the liquid refrigerant after gas-liquid separation by the receiver 7. By performing the exchange, the amount of refrigerant flowing through the internal heat exchanger 8 is reduced, for example, as compared with the case where the internal heat exchanger 8 exchanges heat with the CO ₂ refrigerant before gas-liquid separation, As a result, downsizing of the internal heat exchanger 8 is promoted.

On the other hand, by appropriately controlling the degree of opening of the expansion valves 10 and 11 and adjusting the amount of gas injection to the compressor 1 side, the compressor input is reduced and energy saving operation is realized. be able to.

Second Embodiment FIG. 3 shows a refrigerant circuit in a second embodiment in which a refrigeration system using a CO ₂ refrigerant according to the present invention is applied to an air conditioner, and FIGS. 5 shows a “PH diagram” during the cooling operation and the heating operation, respectively.

First, the refrigerant circuit of FIG. 3 will be described. In FIG. 3, reference numeral 1 denotes a compressor, 2 denotes an outdoor heat exchanger (corresponding to a “heat source side heat exchanger” in the claims),
Reference numeral 3 denotes an indoor heat exchanger (corresponding to the "use-side heat exchanger" in the claims). Reference numeral 4 denotes an accumulator provided in a refrigerant passage 25 connected to a suction port of the compressor 1. Reference numeral 5 denotes an outdoor heat exchanger. This is a four-way switching valve that selectively connects the heat exchanger 2 and the indoor heat exchanger 3 to the compressor 1 and the refrigerant passage 24. The outdoor heat exchanger 2 and the indoor heat exchanger 3 are connected to the refrigerant passage 2
1, the refrigerant passage 21 is connected to the first
An expansion valve 11, a second expansion valve 12, and a third expansion valve 13 are interposed in series, and a gas-liquid separation is provided at an intermediate position between the first expansion valve 11 and the second expansion valve 12. Receiver 7 for
However, at the intermediate position between the second expansion valve 12 and the third expansion valve 13, the high pressure side heat transfer portion 8a of the internal heat exchanger 8 having the high pressure side heat transfer portion 8a and the low pressure side heat transfer portion 8b. Is interposed.
Further, one end of the low-pressure side heat transfer portion 8b of the internal heat exchanger 8 is connected to the refrigerant passage 24, and the other end is connected to the refrigerant passage 25.
Connected to each other. Further, the gas phase portion of the receiver 7 is connected to a compression chamber of the compressor 1 via a refrigerant passage 26 having a control valve 10. In this embodiment, the "gas injection mechanism E" in the claims is constituted by the receiver 7, the refrigerant passage 26, and the control valve 10.

The first to third expansion valves 11 to 13 are used.
Is different in the operation mode between the cooling operation and the heating operation. That is, during the cooling operation in which the outdoor heat exchanger 2 functions as a gas cooler, the first expansion valve 11 functions as a “primary expansion mechanism C” in claims to perform primary expansion of the refrigerant, and The third expansion valve 13 functions as a “secondary expansion mechanism D” in the claims to perform secondary expansion of the refrigerant. On the other hand, during the heating operation, the first expansion valve 11 functions as a “secondary expansion mechanism D” in the claims to perform secondary expansion of the refrigerant, and the second expansion valve 12 is a “secondary expansion mechanism” in the claims. The third expansion valve 13 functions as a “primary expansion mechanism C” to perform a primary expansion of the refrigerant, and the third expansion valve 13 is fully opened and does not perform an expansion action.

In FIG. 3, the four-way switching valve 5
Are indicated by a solid line during the cooling operation and by a broken line during the heating operation.

Next, the operation of the refrigerant circuit of the air conditioner during the cooling operation and the heating operation will be described with reference to the “PH diagram” during the cooling operation shown in FIG. 4 and the “PH diagram” during the heating operation shown in FIG. The description will be made using the “PH diagram” together.

Operation During Cooling Operation During cooling operation (ie, the outdoor heat exchanger 2 functions as the "gas cooler A" in the claims, and the indoor heat exchanger 3 operates in the "evaporator B" in the claims. ), The CO ₂ refrigerant (gas refrigerant) discharged from the compressor 1
Is introduced into the outdoor heat exchanger 2 via the four-way switching valve 5,
The heat is radiated in the supercritical region in the outdoor heat exchanger 2 (regions D to E in FIG. 4). The supercritical CO ₂ refrigerant flowing out of the outdoor heat exchanger 2 is primarily expanded in the first expansion valve 11 (the area between points E to F in FIG. 4) and introduced into the receiver 7 in a gas-liquid two-phase state. Here, gas-liquid separation is performed (points G and H in FIG. 4).

Then, the liquid refrigerant separated by the receiver 7 flows into the high-pressure side heat transfer portion 8a of the internal heat exchanger 8 through the second expansion valve 12 which is in a fully opened state, and its inlet (see FIG. 4). While flowing from point H) to the exit (point I in FIG. 4),
After performing internal heat exchange between the low pressure side heat transfer portion 8b and the gas refrigerant flowing from the inlet (point K in FIG. 4) to the outlet (point A in FIG. 4), the third expansion valve 13 Is subjected to secondary expansion (regions I to J in FIG. 4), and then sent to the indoor heat exchanger 3 while flowing from the inlet (point J in FIG. 4) to the outlet (point K in FIG. 4). And evaporates into gas refrigerant. This gas refrigerant is sucked into the compressor 1 again and compressed. The suction temperature is determined by the outlet temperature of the indoor heat exchanger 3 (point K in FIG. 4).
(A temperature corresponding to the point A in FIG. 4) higher than the temperature corresponding to the point A in FIG. .

On the other hand, the gas refrigerant separated by the receiver 7
Is in the middle of the compression stroke of the compressor 1 via the refrigerant passage 26.
It is injected into the compression chamber (see point G in FIG. 4).
Thus, the gas refrigerant is injected into the compression chamber of the compressor 1 by injection.
This is mixed with the gas refrigerant in the compression chamber.
As a result, cooling and densification of the gas refrigerant in the compression chamber are promoted.
As described above, the internal heat exchange
The suction temperature of the compressor 1 is rising, and this high suction temperature
Gas compression inside the compression chamber
The temperature of the medium corresponds to point B at the time of gas injection.
Once lowers to the temperature corresponding to point C,
The temperature is raised again from the lowered temperature, and the temperature corresponding to point D
Is the discharge temperature. Therefore, this discharge temperature is
Gas injection is affected by the temperature drop accompanying the injection.
Point A to point D without injection ₀Compressed to
Case temperature (point D₀Lower than the temperature corresponding to
You.

Operation During Heating Operation During the heating operation (ie, the outdoor heat exchanger 2 functions as the "evaporator B" in the claims, and the indoor heat exchanger 3 operates in the "gas cooler A" in the claims. ), The CO ₂ refrigerant (gas refrigerant) discharged from the compressor 1
Is introduced into the indoor heat exchanger 3 via the four-way switching valve 5,
The heat is radiated in the supercritical region in the indoor heat exchanger 3 (regions D to E in FIG. 5). The supercritical CO ₂ refrigerant flowing out of the indoor heat exchanger 3 is supplied to the third expansion valve 1 in the fully opened state.
3, flows into the high-pressure side heat transfer portion 8a of the internal heat exchanger 8 and flows from the inlet (point E in FIG. 5) to the outlet (point F in FIG. 5). The internal heat exchange is performed between the portion 8b and the gas refrigerant flowing from the inlet (point K in FIG. 5) to the outlet (point A in FIG. 5). Further, the refrigerant flowing out of the high-pressure side heat transfer portion 8a of the internal heat exchanger 8 undergoes primary expansion (the area between points F and G in FIG. 5) in the second expansion valve 12, and then has a gas-liquid two-phase state. Is introduced into the receiver 7,
Here, gas-liquid separation is performed (points H and I in FIG. 4).

The liquid refrigerant separated by the receiver 7 flows into the first expansion valve 11, where it undergoes secondary expansion (FIG. 5).
After that, it is sent to the outdoor heat exchanger 2 and evaporates while flowing from the inlet (point J in FIG. 5) to the outlet (point K in FIG. 5) to be a gas refrigerant. You. The gas refrigerant is sucked into the compressor 1 again and compressed. The suction temperature of the gas refrigerant is higher than the outlet temperature of the outdoor heat exchanger 2 (the temperature corresponding to the point K in FIG. 5). The temperature is set to be higher (that is, the temperature corresponding to the point A in FIG. 5) by the temperature rise (indicated by “d” in FIG. 5) due to the internal heat exchange in FIG.

On the other hand, the gas refrigerant separated by the receiver 7 is injected into the compression chamber in the middle of the compression stroke of the compressor 1 via the refrigerant passage 26 (see point H in FIG. 5).
As described above, since the gas refrigerant is injected into the compression chamber of the compressor 1 and mixed with the gas refrigerant in the compression chamber, the cooling and the densification of the gas refrigerant in the compression chamber are promoted. Meanwhile, the temperature of the gas refrigerant in the compression chamber corresponds to the point B at the time of the gas injection, despite the fact that the suction temperature of the compressor 1 has risen due to internal heat exchange, and the compression is started from this high suction temperature. The temperature once decreases from the temperature to the temperature corresponding to the point C, and the temperature is increased again from the lowered temperature, and the temperature corresponding to the point D becomes the discharge temperature. Accordingly, the discharge temperature is lower than the temperature (the temperature corresponding to the point D ₀ ) when the gas is not injected and is compressed from the point A to the point D ₀ due to the influence of the temperature drop accompanying the gas injection. Is done.

As described above, by incorporating the internal heat exchanger 8 and the gas injection mechanism E into the refrigerant circuit of the transcritical refrigeration cycle using the CO ₂ refrigerant, the internal heat exchanger 8 The rise in compressor discharge temperature
Since the cooling effect by the gas injection is suppressed, the effect of improving the efficiency due to the increase in the refrigerating capacity due to the internal heat exchange (the enthalpy amount “c ₁ ” in FIGS. 4 and 5) is obtained while securing the reliability of the compressor 1. realizable. Further, as a result of injecting the gas refrigerant separated into gas and liquid by the receiver 7 into the compressor 1 side, the evaporator (that is, the indoor heat exchanger 3 during the cooling operation and the outdoor The amount of circulating refrigerant in the heat exchanger 2) is smaller on the gas cooler side (that is, the outdoor heat exchanger 2 during the cooling operation and the indoor heat exchanger 3 during the heating operation), but the refrigerant circulation amount is correspondingly smaller. However, since the enthalpy of evaporation per unit weight is increased only (the enthalpy amount “c ₂ ” in FIGS. 4 and 5), the refrigerating capacity does not change. As these synergistic effects, high efficiency can be realized without impairing the reliability of the compressor 1, and both high efficiency and high reliability can be achieved.

The liquid refrigerant after gas-liquid separation by the receiver 7 is introduced into an evaporator (that is, the indoor heat exchanger 3 during the cooling operation and the outdoor heat exchanger 2 during the heating operation). Therefore, the enthalpy of evaporation per unit weight of the CO ₂ refrigerant flowing through the evaporator can be increased, and the flow rate of the refrigerant decreases and the flow velocity of the refrigerant decreases under the same refrigeration capacity. As a result, a decrease in efficiency due to a pressure loss in the evaporator is suppressed, a high refrigerating efficiency is ensured, and the evaporator is downsized by the small amount of the refrigerant flow.

Further, as in this embodiment, during the cooling operation, heat exchange is performed between the gas refrigerant discharged from the evaporator and the liquid refrigerant after gas-liquid separation by the receiver 7. For example, the amount of refrigerant flowing through the internal heat exchanger 8 is smaller than in the case where heat is exchanged with the CO ₂ refrigerant before gas-liquid separation in the internal heat exchanger 8, and the internal heat exchanger 8 is more compact. Will be promoted.

On the other hand, by appropriately controlling the degree of opening of the expansion valves 10 and 11 and adjusting the amount of gas injection to the compressor 1 side, the compressor input is reduced and energy saving operation is realized. be able to.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of an air conditioner that is a first embodiment of a refrigeration system according to the present invention.

FIG. 2 is a graph showing P during cooling and heating in the air conditioner shown in FIG. 1;
FIG.

FIG. 3 is a refrigerant circuit diagram of an air conditioner that is a second embodiment of the refrigeration system according to the present invention.

FIG. 4 is a PH diagram of the air conditioner shown in FIG. 3 during a cooling operation.

FIG. 5 is a PH diagram during a heating operation of the air conditioner shown in FIG. 3;

FIG. 6 is a refrigerant circuit diagram of a conventional air conditioner including an internal heat exchanger.

FIG. 7 is a refrigerant circuit diagram of a conventional air conditioner provided with an injection mechanism.

FIG. 8 is a diagram showing a PH of the conventional air conditioner shown in FIG. 7;
FIG.

[Explanation of symbols]

1 is a compressor, 2 is an outdoor heat exchanger, 3 is an indoor heat exchanger, 4
The accumulator 5 and 6 the four-way switching valve, 7 a receiver, 8 internal heat exchanger, 10 a control valve, 11 to 13 expansion valve, 21 to 26 refrigerant passages, Z ₁ and Z ₂ are an air conditioner It is.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Kazuyuki Nishikawa, 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries Inside the Kanaoka Plant of Sakai Seisakusho Co., Ltd. (72) Katsumi Hokoya 1304, Kanaokacho, Sakai-shi, Osaka Daikin Industries Sakai Factory Kanaoka Factory

Claims (3)

[Claims] 1. A compressor (1) for compressing a CO ₂ refrigerant, a gas cooler (A) for radiating a refrigerant discharged from the compressor (1) in a supercritical region, and a gas cooler (A) ), A primary expansion mechanism (C) for primary expansion of the refrigerant from the above, a receiver (7) for gas-liquid separation of the refrigerant from the primary expansion mechanism (C), and a liquid refrigerant separated by the receiver (7). A secondary expansion mechanism (D) for performing secondary expansion, an evaporator (B) for evaporating the liquid refrigerant from the secondary expansion mechanism (D), and a gas refrigerant separated by the receiver (7). 1) heat exchange between a gas injection mechanism (E) for injecting into the compression chamber and a gas refrigerant from the evaporator (B) sucked into the compressor (1) and a liquid refrigerant in the system. And an internal heat exchanger (8) Refrigeration system using CO ₂ refrigerant. 2. The heat exchanger according to claim 1, wherein the internal heat exchanger (8) has the gas cooler (A) functioning as a use side heat exchanger, and the evaporator (B) functions as a heat source side heat exchanger. Operation and the above gas cooler (A)
Functions as a heat-source-side heat exchanger and the evaporator (B) functions as a use-side heat exchanger, during both operation, the gas refrigerant from the evaporator (B) and the gas-liquid separation by the receiver (7). A refrigeration system using a CO ₂ refrigerant, wherein the refrigeration system is configured to perform heat exchange with the liquid refrigerant after the cooling. 3. The internal heat exchanger (8) according to claim 1, wherein the gas cooler (A) functions as a use side heat exchanger, and the evaporator (B) functions as a heat source side heat exchanger. During operation, between the gas refrigerant from the evaporator (B) and the liquid refrigerant at the outlet side of the gas cooler (A), the gas cooler (A) functions as a heat source side heat exchanger to perform the evaporation. During operation in which the heat exchanger (B) functions as a use side heat exchanger, heat exchange is performed between the gas refrigerant from the evaporator (B) and the liquid refrigerant after gas-liquid separation by the receiver (7). And a refrigeration system using a CO ₂ refrigerant.