JP4407000B2 - Refrigeration system using CO2 refrigerant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is CO₂The present invention relates to a refrigeration system using a refrigerant.
[0002]
[Prior art]
CO₂Transcritical refrigeration cycle using refrigerant is CO₂Since the operating pressure is high as a characteristic of the refrigerant, there is a disadvantage that the efficiency (coefficient of performance: COP) is worse than that of a refrigeration cycle using a fluorocarbon refrigerant. As one method for improving this, FIG. As shown, an internal heat exchanger 8 is incorporated in a basic refrigerant circuit composed of a compressor 1, a four-way switching valve 5, an outdoor heat exchanger 2, an indoor heat exchanger 3, and an expansion valve 11. The high pressure side heat transfer section 8a and the low pressure side heat transfer section 8b of the heat exchanger 8 can be selectively connected to the outdoor heat exchanger 2 and the indoor heat exchanger 3 via the four-way switching valve 6, An internal heat exchanger built-in system has been proposed in which the efficiency of the entire refrigeration cycle is enhanced by internal heat exchange in the internal heat exchanger 8.
[0003]
[Problems to be solved by the invention]
However, in this way CO₂When an internal heat exchanger is incorporated in the refrigerant circuit for the purpose of improving the efficiency of the refrigeration cycle using refrigerant, the efficiency improvement objective is achieved, but as the compressor suction temperature rises due to internal heat exchange, Since the discharge temperature also rises, for example, the resin insulating material used in the compressor is rapidly deteriorated, and there is a disadvantage that reliability during long-term operation as a refrigeration system is impaired.
[0004]
Therefore, in the present invention, CO₂In a refrigeration system using a refrigerant, the efficiency improvement effect due to the incorporation of the internal heat exchanger in the refrigerant circuit is less than the drawbacks associated with the incorporation of the internal heat exchanger (that is, the reliability caused by the rise in the compressor discharge temperature). This was achieved for the purpose of achieving both high efficiency and high reliability.
[0005]
TECHNICAL BACKGROUND OF THE INVENTION
The inventors of the present application paid attention to the gas injection mechanism in the refrigerant circuit in the course of studying the means for solving the above problems. That is, this gas injection mechanism is similar to the above-described method of incorporating the internal heat exchanger into the refrigerant circuit, such as a fluorocarbon refrigerant or CO 2.₂7 has been proposed as an efficiency improvement measure for a refrigeration cycle using a refrigerant.₂An example of a refrigerant circuit in which a gas injection mechanism is incorporated in a transcritical refrigeration cycle using a refrigerant is shown. In this refrigerant circuit, the discharge port of the compressor 1 is switched to the outdoor heat exchanger 2 and the indoor heat exchanger 3 by the switching operation of the four-way switching valve 5, and the suction port of the compressor 1 is connected to the indoor heat exchanger 3. While being selectively connectable to the outdoor heat exchanger 2, the expansion valve 11, the receiver 7, and the expansion valve 12 are provided in the refrigerant path 31 that connects the outdoor heat exchanger 2 and the indoor heat exchanger 3. Are sequentially arranged, and the circuit is configured by connecting the air chamber of the receiver 7 and the compression chamber of the compressor 1 by the refrigerant path 32 provided with the control valve 10.
[0006]
FIG. 8 shows a PH diagram of a transcritical refrigeration cycle incorporating a gas injection mechanism. This will be briefly explained. For example, during cooling operation, CO in a supercritical state at the outlet point E of the outdoor heat exchanger 2 functioning as a gas cooler.₂The refrigerant is primarily expanded in the expansion valve 11 to produce gas-liquid two-phase CO.₂As a refrigerant, this gas-liquid two-phase CO₂The refrigerant is introduced into the receiver 7 and gas-liquid separation is performed here (point F). 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 injected as a saturated gas refrigerant (point G) through the refrigerant path 32 into the compression chamber in the middle of the compression stroke of the compressor 1.
[0007]
Thus, by injecting the gas refrigerant separated in the receiver 7 into the compression chamber of the compressor 1 in the middle of the compression process,₂Since the refrigerant and the injected gas refrigerant are mixed and the refrigerant temperature decreases from the temperature corresponding to the point B to the point C, the refrigerant temperature at the outlet of the compressor 1 (ie, “discharge temperature”) is Discharge temperature when gas injection is not performed (point D₀) (Temperature corresponding to point D).
[0008]
Further, by injecting the gas refrigerant separated into the gas and liquid into the compressor 1, the refrigerant circulation amount on the evaporator (indoor heat exchanger 3) side is the gas cooler (outdoor heat exchanger 2) by this injection amount. The refrigerant is less than the refrigerant circulation amount on the side, and the liquid refrigerant after gas-liquid separation is secondarily expanded in the expansion valve 12 and introduced into the evaporator, so that the evaporation enthalpy per unit weight in the evaporator (Fig. 8 shows "h₁The amount of enthalpy indicated by “)”, the cooling capacity increases accordingly. As a result, a refrigerating capacity equivalent to that before the refrigerant circulation amount is reduced can be obtained with a smaller refrigerant circulation amount.
[0009]
Inventors of the present application effectively use the advantages based on the incorporation of the gas injection mechanism in the refrigerant circuit, particularly the action of lowering the discharge temperature of the compressor. The idea is to eliminate as much as possible the rise in compressor discharge temperature.
[0010]
[Means for Solving the Problems]
In the present invention, based on such a technical background, the following configuration is adopted as specific means for solving the above-described problems.
[0011]
CO according to the first invention of the present application₂In refrigeration systems using refrigerants, CO₂A compressor 1 that compresses the refrigerant; a gas cooler A that dissipates heat in the supercritical region of the refrigerant discharged from the compressor 1; a primary expansion mechanism C that primarily expands the gas cooler A; and the primary A receiver 7 for gas-liquid separation of the refrigerant from the expansion mechanism C, a secondary expansion mechanism D for secondary expansion of the liquid refrigerant separated by the receiver 7, and an evaporation for evaporating the liquid refrigerant from the secondary expansion mechanism D A gas injection mechanism E for injecting the gas refrigerant separated by the receiver 7 into the compression chamber of the compressor 1, and the gas refrigerant from the evaporator B sucked into the compressor 1 and the system An internal heat exchanger 8 that exchanges heat with the liquid refrigerant is provided.
[0012]
In the second invention of the present application, the CO according to the first invention is provided.₂In the refrigeration system using the refrigerant, 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, and the gas cooling After the gas refrigerant is separated from the gas refrigerant from the evaporator B and the receiver 7 in both the operation when the evaporator A functions as a heat source side heat exchanger and the evaporator B functions as a utilization side heat exchanger. The heat exchanger is configured to exchange heat with the liquid refrigerant.
[0013]
In the third invention of the present application, the CO according to the first invention is provided.₂In the refrigeration system using the refrigerant, the internal heat exchanger 8 is separated from the evaporator B during 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. During 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, between the gas refrigerant and the liquid refrigerant on the outlet side of the gas cooler A It is characterized in that heat exchange is performed between the gas refrigerant from the evaporator B and the liquid refrigerant after gas-liquid separation by the receiver 7.
[0014]
【The invention's effect】
In the present invention, the following effects can be obtained by adopting such a configuration.
[0015]
(1) CO according to the first invention of the present application₂According to the refrigeration system using refrigerant, CO₂A compressor 1 that compresses the refrigerant, a gas cooler A that dissipates heat in the supercritical region of the refrigerant discharged from the compressor 1, a primary expansion mechanism C that primarily expands 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 expansion of the liquid refrigerant separated by the receiver 7, and a liquid refrigerant from the secondary expansion mechanism D are evaporated. An evaporator B, a gas injection mechanism E for injecting the gas refrigerant separated by the receiver 7 into the compression chamber of the compressor 1, and a gas refrigerant from the evaporator B sucked into the compressor 1 and the system The internal heat exchanger 8 that exchanges heat with the liquid refrigerant of the liquid refrigerant, the internal heat exchange in the internal heat exchanger 8 can improve the refrigeration efficiency, while the gas injection machine The rise of the discharge temperature of the compressor based on the internal heat exchange in the internal heat exchanger 8 is suppressed by the injection of the gas refrigerant to the compressor side by E, and the liquid refrigerant after gas-liquid separation is introduced into the evaporator B This increases the enthalpy of evaporation per unit weight and improves the refrigerating capacity. As a synergistic effect, high efficiency can be realized without impairing the reliability of the compressor.
[0016]
Moreover, since the efficiency can be increased by a relatively simple circuit change in which the internal heat exchanger 8 and the gas injection mechanism E are incorporated in the basic refrigerant circuit, both cost reduction and high efficiency of the refrigeration system can be achieved. Is easy.
[0017]
Furthermore, by introducing the liquid refrigerant after gas-liquid separation into the evaporator B, the CO flowing through the evaporator B₂Since the evaporation enthalpy per unit weight of the refrigerant can be increased, the refrigerant flow rate decreases and the refrigerant flow rate decreases under the same refrigeration capacity. As a result, a reduction in efficiency due to pressure loss in the evaporator B is suppressed and high refrigeration efficiency is ensured, and downsizing of the evaporator B is promoted by a smaller amount of refrigerant flow in the evaporator B.
[0018]
(2) CO according to the second invention of the present application₂According to the refrigeration system using the refrigerant, in addition to the effect described in the above item (1), the following specific effect can be obtained. That is, in 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, and the gas cooler A Functions as a heat source side heat exchanger and the evaporator B functions as a use side heat exchanger during operation, the gas refrigerant from the evaporator B and the liquid refrigerant after gas-liquid separation by the receiver 7 For example, in the internal heat exchanger 8, the CO before gas-liquid separation is used.₂Compared to the case where heat is exchanged with the refrigerant, the amount of refrigerant flowing through the internal heat exchanger 8 is reduced, and the internal heat exchanger 8 is thus made more compact.
[0019]
(3) CO according to the third invention of the present application₂According to the refrigeration system using the refrigerant, in addition to the effect described in the above item (1), the following specific effect can be obtained. That is, according to the present invention, the internal heat exchanger 8 is operated with the gas from the evaporator B during 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. During the operation in which the gas cooler A functions as a heat source side heat exchanger and the evaporator B functions as a utilization side heat exchanger between the refrigerant and the liquid refrigerant on the outlet side of the gas cooler A, the evaporator Heat exchange is performed between the gas refrigerant from B and the liquid refrigerant after gas-liquid separation by the receiver 7.
[0020]
Accordingly, particularly during the latter operation, heat exchange is performed with the liquid refrigerant after the gas-liquid separation by the receiver 7, so that, for example, before the gas-liquid separation in the internal heat exchanger 8. CO₂Compared with the case where heat is exchanged with the refrigerant, the amount of the refrigerant flowing through the internal heat exchanger 8 is small, and the downsizing of the internal heat exchanger 8 is promoted accordingly.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the CO according to the present invention₂A refrigeration system using a refrigerant will be specifically described based on a preferred embodiment.
[0022]
First embodiment
FIG. 1 shows CO according to the present invention.₂The refrigerant circuit in 1st Embodiment which applied the refrigeration system using a refrigerant | coolant to the air conditioner is shown, In the same figure, the code | symbol 1 is a compressor, 2 is an outdoor heat exchanger (the "heat source side of a claim" 3 corresponds to an indoor heat exchanger (corresponds to the “use side heat exchanger” in the claims), and 4 denotes a refrigerant path 24 connected to the suction port of the compressor 1. The accumulator 5 provided is a first four-way switching valve that selectively connects the outdoor heat exchanger 2 and the indoor heat exchanger 3 to the compressor 1 and the refrigerant path 23, and 6 is the outdoor heat exchanger. 2 is a second four-way switching valve that alternatively connects the indoor heat exchanger 3 to the refrigerant path 23 and the refrigerant path 24. In FIG. 1, the valve positions of the four-way switching valves 5 and 6 are indicated by a solid line during cooling operation and by a broken line during heating operation.
[0023]
Reference numeral 7 denotes a gas-liquid separation receiver provided at an intermediate position between the expansion valves 11 and 12 of the refrigerant passage 23 in which the first expansion valve 11 and the second expansion valve 12 are provided in series. Yes, the gas phase part of the receiver 7 is connected to the compression chamber of the compressor 1 via a refrigerant path 26 provided with a control valve 10. The receiver 7, the refrigerant path 26, and the control valve 10 constitute a “gas injection mechanism E” recited in the claims.
[0024]
Reference numeral 8 denotes an internal heat exchanger including a high-pressure side heat transfer unit 8a and a low-pressure side heat transfer unit 8b. The high-pressure side heat transfer unit 8a is connected to the receiver 7 and the second expansion of the refrigerant path 23. The intermediate position of the valve 12 is interposed, and the low-pressure side heat transfer section 8 b is interposed in the refrigerant path 24.
[0025]
Subsequently, the operation of the refrigerant circuit of the air conditioner is performed during a cooling operation (that is, the outdoor heat exchanger 2 functions as the “gas cooler A” in the claims, and the indoor heat exchanger 3 is in the claims). A description will be given with reference to the “PH diagram” shown in FIG.
[0026]
During cooling operation, the CO discharged from the compressor 1₂The refrigerant (gas refrigerant) is introduced into the outdoor heat exchanger 2 through the first four-way switching valve 5, and is radiated in the supercritical region in the outdoor heat exchanger 2 (from point D to point E in FIG. 2). region). CO in supercritical state flowing out of the outdoor heat exchanger 2₂The refrigerant reaches the first expansion valve 11 (corresponding to “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). In the gas-liquid two-phase state, it is introduced into the receiver 7 where it is gas-liquid separated (points G and H in FIG. 2).
[0027]
The liquid refrigerant separated by the receiver 7 flows into the high-pressure side heat transfer section 8a of the internal heat exchanger 8 and flows from the inlet (point H in FIG. 2) toward the outlet (point I in FIG. 2). In the meantime, after the internal heat exchange between the low-pressure side heat transfer section 8b and the gas refrigerant flowing from the inlet (point K in FIG. 2) toward the outlet (point A in FIG. 2), After flowing into the expansion valve 12 (corresponding to “secondary expansion mechanism D” in the scope of claims) and subjected to secondary expansion (region of points I to J in FIG. 2), the indoor heat exchanger 3 And evaporates while flowing from the inlet (point J in FIG. 2) to the outlet (point K in FIG. 2) to be a gas refrigerant. This gas refrigerant is again sucked into the compressor 1 and compressed, but the suction temperature is higher than the outlet temperature of the indoor heat exchanger 3 (the temperature corresponding to the point K in FIG. 2). 8, the temperature is increased by the temperature rise (indicated by “d” in FIG. 2) due to the internal heat exchange (that is, the temperature corresponding to the point A in FIG. 2).
[0028]
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 path 26 (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, cooling and densification of the gas refrigerant in the compression chamber are promoted. In addition, the suction temperature of the compressor 1 has increased due to the internal heat exchange, and the temperature of the gas refrigerant in the compression chamber corresponds to the point B at the time of gas injection, although the compression starts from this high suction temperature. The temperature is once lowered from the temperature to the temperature corresponding to the point C, and the pressure is raised again from the lowered temperature. Finally, the temperature corresponding to the point D becomes the discharge temperature. Therefore, since this discharge temperature is affected by the temperature drop caused by the gas injection, the point A to the point D without performing the gas injection.₀Temperature when compressed to (point D₀Temperature).
[0029]
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, but the refrigerant in the internal heat exchanger 8 The flow direction is the same during cooling operation and heating operation. That is, the internal heat exchanger 8 always exchanges heat with the liquid refrigerant after the gas-liquid separation by the receiver 7.
[0030]
As mentioned above, CO₂By incorporating the internal heat exchanger 8 and the gas injection mechanism E in the refrigerant circuit of the transcritical refrigeration cycle using the refrigerant, the rise in the compressor discharge temperature accompanying the internal heat exchange in the internal heat exchanger 8 is increased by the gas injection. Therefore, the increase in refrigeration capacity due to internal heat exchange (enthalpy amount “c” in FIG. 2)₁)) Can be achieved while ensuring the reliability of the compressor 1. Furthermore, as a result of the gas refrigerant separated by the receiver 7 being injected into the compressor 1, the refrigerant circulation amount of the evaporator (that is, the indoor heat exchanger 3 during the cooling operation) is increased by an amount corresponding to the injection amount. Although the refrigerant circulation amount on the side of the gas cooler (that is, the outdoor heat exchanger 2 during the cooling operation) decreases, the enthalpy of evaporation per unit weight increases by that amount (the enthalpy amount “c” in FIG. 2).₂"), Refrigeration capacity does not change. As a synergistic effect, high efficiency can be realized without impairing the reliability of the compressor 1, and both high efficiency and high reliability can be achieved.
[0031]
Further, since the liquid refrigerant after the gas-liquid separation by the receiver 7 is introduced into the evaporator (that is, the indoor heat exchanger 3 during the cooling operation and the outdoor heat exchanger 2 during the heating operation), CO flowing through the evaporator₂The enthalpy of evaporation per unit weight of the refrigerant is large, and the refrigerant flow rate decreases and the refrigerant flow rate decreases under the same refrigeration capacity. As a result, a reduction in efficiency due to pressure loss in the evaporator is suppressed, high refrigeration efficiency is ensured, and downsizing of the evaporator is promoted by a smaller refrigerant flow rate.
[0032]
Further, as in this embodiment, heat exchange is performed between the gas refrigerant that has exited the evaporator and the liquid refrigerant that has been gas-liquid separated by the receiver 7 during both the cooling operation and the heating operation. By configuring in this way, for example, the CO before gas-liquid separation in the internal heat exchanger 8₂Compared to the case where heat is exchanged with the refrigerant, the amount of refrigerant flowing through the internal heat exchanger 8 is reduced, and the internal heat exchanger 8 is thus made more compact.
[0033]
On the other hand, by appropriately controlling the opening degree of the expansion valve 10 and the expansion valve 11 and adjusting the gas injection amount to the compressor 1, the compressor input can be reduced to realize an energy saving operation. .
[0034]
Second embodiment
FIG. 3 shows CO according to the present invention.₂The refrigerant circuit in 2nd Embodiment which applied the refrigeration system using a refrigerant | coolant to the air conditioner is shown, and also the "PH diagram" at the time of air_conditionaing | cooling operation and heating operation is shown in FIG.4 and FIG.5. Each is shown.
[0035]
First, the refrigerant circuit of FIG. 3 will be described. In FIG. 3, reference numeral 1 is a compressor, 2 is an outdoor heat exchanger (corresponding to the “heat source side heat exchanger” in the claims), and 3 is indoor heat exchange. 4 (according to the “use side heat exchanger” in the claims), 4 is an accumulator provided in the refrigerant passage 25 connected to the suction port of the compressor 1, and 5 is the outdoor heat exchanger 2 This is a four-way switching valve that alternatively connects the indoor heat exchanger 3 to the compressor 1 and the refrigerant path 24. The outdoor heat exchanger 2 and the indoor heat exchanger 3 are connected via a refrigerant path 21, and the refrigerant path 21 includes a first expansion valve 11, a second expansion valve 12, and a third one. The expansion valve 13 is connected in series, and a receiver 7 for gas-liquid separation is provided at an intermediate position between the first expansion valve 11 and the second expansion valve 12, and the second expansion valve 12. A high pressure side heat transfer portion 8a of the internal heat exchanger 8 having a high pressure side heat transfer portion 8a and a low pressure side heat transfer portion 8b is interposed at an intermediate position with respect to the third expansion valve 13. Further, one end of the low-pressure side heat transfer section 8b of the internal heat exchanger 8 is connected to the refrigerant path 24 and the other end is connected to the refrigerant path 25. The gas phase portion of the receiver 7 is connected to the compression chamber of the compressor 1 through a refrigerant path 26 provided with a control valve 10. In this embodiment, the receiver 7, the refrigerant path 26, and the control valve 10 constitute a “gas injection mechanism E” in the claims.
[0036]
The operation modes of the first to third expansion valves 11 to 13 are different 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 the claims to perform primary expansion of the refrigerant, The expansion valve 12 is fully opened and does not perform the expansion action, and the third expansion valve 13 functions as the “secondary expansion mechanism D” in the claims and performs the secondary expansion of the refrigerant. On the other hand, during the heating operation, the first expansion valve 11 functions as the “secondary expansion mechanism D” in the claims to perform secondary expansion of the refrigerant, and the second expansion valve 12 is in the claims “ It functions as a primary expansion mechanism C ”to perform primary expansion of the refrigerant, and the third expansion valve 13 is fully opened and does not perform expansion.
[0037]
In FIG. 3, the valve position of the four-way switching valve 5 is indicated by a solid line during the cooling operation and by a broken line during the heating operation.
[0038]
Subsequently, the operation during the cooling operation and the heating operation of the refrigerant circuit of the air conditioner is described as “PH diagram” during the cooling operation shown in FIG. 4 and “PH” during the heating operation shown in FIG. The explanation will be made with reference to the “line diagram”.
[0039]
Operation during cooling operation
During the cooling operation (that is, the outdoor heat exchanger 2 functions as the “gas cooler A” in the claims, and the indoor heat exchanger 3 functions as the “evaporator B” in the claims). Is the CO discharged from the compressor 1₂The refrigerant (gas refrigerant) is introduced into the outdoor heat exchanger 2 through the four-way switching valve 5, and is radiated in the supercritical region in the outdoor heat exchanger 2 (regions from point D to point E in FIG. 4). CO in supercritical state flowing out of the outdoor heat exchanger 2₂The refrigerant is primarily expanded in the first expansion valve 11 (region from point E to point F in FIG. 4), introduced into the receiver 7 in a gas-liquid two-phase state, and gas-liquid separation is performed here (point in FIG. 4). G and point H).
[0040]
Then, the liquid refrigerant separated by the receiver 7 flows into the high-pressure side heat transfer section 8a of the internal heat exchanger 8 through the second expansion valve 12 in the fully opened state, and the inlet (point H in FIG. 4). Gas refrigerant flowing through the low pressure side heat transfer section 8b from the inlet (point K in FIG. 4) to the outlet (point A in FIG. 4) while flowing from the outlet to the outlet (point I in FIG. 4). After the internal heat exchange between them, the secondary expansion is performed in the third expansion valve 13 (the region from the point I to the point J in FIG. 4), and then sent to the indoor heat exchanger 3 and the inlet (FIG. 4). Evaporates while flowing from the point J) to the outlet (point K in FIG. 4) to be a gas refrigerant. This gas refrigerant is again sucked into the compressor 1 and compressed, but the suction temperature is higher than the outlet temperature of the indoor heat exchanger 3 (the temperature corresponding to the point K in FIG. 4). 8, the temperature is increased by the temperature rise (indicated by “d” in FIG. 4) due to internal heat exchange (that is, the temperature corresponding to point A in FIG. 4).
[0041]
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 through the refrigerant path 26 (see point G in FIG. 4). 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, cooling and densification of the gas refrigerant in the compression chamber are promoted. In addition, the suction temperature of the compressor 1 has increased due to the internal heat exchange, and the temperature of the gas refrigerant in the compression chamber corresponds to the point B at the time of gas injection, although the compression starts from this high suction temperature. The temperature is once lowered from the temperature to the temperature corresponding to the point C, and the pressure is raised again from the lowered temperature, and the temperature corresponding to the point D becomes the discharge temperature. Therefore, this discharge temperature is affected by the temperature drop caused by gas injection, and gas injection is not performed.₀Temperature when compressed to (point D₀Temperature).
[0042]
Operation during heating operation
During heating operation (that is, the outdoor heat exchanger 2 functions as the “evaporator B” in the claims, and the indoor heat exchanger 3 functions as the “gas cooler A” in the claims). Is the CO discharged from the compressor 1₂The refrigerant (gas refrigerant) is introduced into the indoor heat exchanger 3 through the four-way switching valve 5, and is radiated in the supercritical region in the indoor heat exchanger 3 (regions from point D to point E in FIG. 5). CO in supercritical state flowing out of the indoor heat exchanger 3₂The refrigerant flows into the high-pressure side heat transfer section 8a of the internal heat exchanger 8 through the fully opened third expansion valve 13, and from the inlet (point E in FIG. 5) to the outlet (point F in FIG. 5). While flowing in the direction, internal heat exchange is performed between the low-pressure side heat transfer section 8b and the gas refrigerant flowing from the inlet (point K in FIG. 5) toward the outlet (point A in FIG. 5). Furthermore, after the refrigerant | coolant which exits from the high pressure side heat-transfer part 8a of the internal heat exchanger 8 is primary-expanded in the 2nd expansion valve 12 (area | region of the point F-point G of FIG. 5), a gas-liquid two-phase state Then, it is introduced into the receiver 7 where it is gas-liquid separated (point H and point I in FIG. 4).
[0043]
Then, the liquid refrigerant separated by the receiver 7 flows into the first expansion valve 11, where it is subjected to secondary expansion (regions from point I to point J in FIG. 5) and then sent to the outdoor heat exchanger 2. Then, it evaporates while flowing from the inlet (point J in FIG. 5) to the outlet (point K in FIG. 5), and becomes a gas refrigerant. This gas refrigerant is again sucked into the compressor 1 and compressed, but the suction temperature is higher than the outlet temperature of the outdoor heat exchanger 2 (the temperature corresponding to the point K in FIG. 5). 8, the temperature is increased by the temperature rise (indicated by “d” in FIG. 5) due to the internal heat exchange (that is, the temperature corresponding to the point A in FIG. 5).
[0044]
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 path 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, cooling and densification of the gas refrigerant in the compression chamber are promoted. In addition, the suction temperature of the compressor 1 has increased due to the internal heat exchange, and the temperature of the gas refrigerant in the compression chamber corresponds to the point B at the time of gas injection, although the compression starts from this high suction temperature. The temperature is once lowered from the temperature to the temperature corresponding to the point C, and the temperature is raised again from the lowered temperature, and the temperature corresponding to the point D becomes the discharge temperature. Therefore, this discharge temperature is affected by the temperature drop caused by gas injection, and gas injection is not performed.₀Temperature when compressed to (point D₀Temperature).
[0045]
As mentioned above, CO₂By incorporating the internal heat exchanger 8 and the gas injection mechanism E in the refrigerant circuit of the transcritical refrigeration cycle using the refrigerant, the rise in the compressor discharge temperature accompanying the internal heat exchange in the internal heat exchanger 8 is increased by the gas injection. Therefore, the increase in the refrigeration capacity due to the internal heat exchange (the enthalpy amount “c” in FIGS. 4 and 5).₁)) Can be achieved while ensuring the reliability of the compressor 1. Furthermore, as a result of injecting the gas refrigerant separated into gas and liquid by the receiver 7 to the compressor 1 side, the evaporator (that is, the indoor heat exchanger 3 during the cooling operation and the outdoor during the heating operation) corresponding to the injection amount. Although the refrigerant circulation amount of the heat exchanger 2) is smaller in the gas cooler (that is, the outdoor heat exchanger 2 during the cooling operation and the indoor heat exchanger 3 during the heating operation), the refrigerant circulation amount is reduced. As the evaporation enthalpy per unit weight increases only (the enthalpy amount “c” in FIGS. 4 and 5).₂"), Refrigeration capacity does not change. As a synergistic effect, high efficiency can be realized without impairing the reliability of the compressor 1, and both high efficiency and high reliability can be achieved.
[0046]
Further, since the liquid refrigerant after the gas-liquid separation by the receiver 7 is introduced into the evaporator (that is, the indoor heat exchanger 3 during the cooling operation and the outdoor heat exchanger 2 during the heating operation) CO flowing through the evaporator₂The enthalpy of evaporation per unit weight of the refrigerant is large, and the refrigerant flow rate decreases and the refrigerant flow rate decreases under the same refrigeration capacity. As a result, a reduction in efficiency due to pressure loss in the evaporator is suppressed, high refrigeration efficiency is ensured, and downsizing of the evaporator is promoted by a smaller refrigerant flow rate.
[0047]
Further, as in this embodiment, during the cooling operation, by configuring the heat exchange between the gas refrigerant that has come out of the evaporator and the liquid refrigerant that has been gas-liquid separated by the receiver 7, for example, CO before gas-liquid separation in the internal heat exchanger 8₂Compared to the case where heat is exchanged with the refrigerant, the amount of refrigerant flowing through the internal heat exchanger 8 is reduced, and the internal heat exchanger 8 is thus made more compact.
[0048]
On the other hand, by appropriately controlling the opening degree of the expansion valve 10 and the expansion valve 11 and adjusting the gas injection amount to the compressor 1, the compressor input can be reduced to realize an energy saving operation. .
[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 PH diagram at the time of cooling and heating in the air conditioner shown in 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.
4 is a PH diagram at the time of cooling operation in the air conditioner shown in FIG. 3; FIG.
5 is a PH diagram at the time of heating operation in the air conditioner shown in FIG. 3. FIG.
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.
8 is a PH diagram of the conventional air conditioner shown in FIG.
[Explanation of symbols]
1 is a compressor, 2 is an outdoor heat exchanger, 3 is an indoor heat exchanger, 4 is an accumulator, 5 and 6 are four-way switching valves, 7 is a receiver, 8 is an internal heat exchanger, 10 is a control valve, 11-13 Is an expansion valve, 21 to 26 are refrigerant passages, Z₁And Z₂Is an air conditioner.

Claims (3)

A compressor (1) for compressing the CO ₂ refrigerant;
A gas cooler (A) that dissipates heat in the supercritical region of the refrigerant discharged from the compressor (1);
A primary expansion mechanism (C) for primarily expanding the refrigerant from the gas cooler (A);
A receiver (7) for gas-liquid separation of the refrigerant from the primary expansion mechanism (C);
A secondary expansion mechanism (D) for secondary expansion of the liquid refrigerant separated by the receiver (7);
An evaporator (B) for evaporating liquid refrigerant from the secondary expansion mechanism (D);
A gas injection mechanism (E) for injecting the gas refrigerant separated by the receiver (7) into the compression chamber of the compressor (1);
An internal heat exchanger (8) for exchanging heat between the gas refrigerant from the evaporator (B) sucked into the compressor (1) and the liquid refrigerant in the system. A refrigeration system using CO ₂ refrigerant. In claim 1,
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, and the gas cooler ( A) functions as a heat source side heat exchanger and the evaporator (B) functions as a use side heat exchanger, and the gas refrigerant from the evaporator (B) and the receiver (7) A refrigeration system using a CO ₂ refrigerant, wherein heat exchange is performed with the liquid refrigerant after liquid separation. In claim 1,
The internal heat exchanger (8) is operated from the evaporator (B) during 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. The gas cooler (A) functions as a heat source side heat exchanger and the evaporator (B) is a use side heat exchanger between the gas refrigerant of the gas cooler and the liquid refrigerant on the outlet side of the gas cooler (A). In the operation that functions as, the gas refrigerant from the evaporator (B) and the liquid refrigerant after gas-liquid separation by the receiver (7) are each configured to perform heat exchange. A refrigeration system using CO ₂ refrigerant.

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